CURRENT ASSISTED PHOTONIC DEMODULATOR TYPE INDIRECT TIME OF FLIGHT PIXEL FOR III-V MATERIALS, IMAGING SENSOR, AND METHOD OF PRODUCTION
TECHNICAL FIELD
The present disclosure generally pertains to a current assisted photo demodulator type indirect Time of Flight pixel for III-V semiconductor materials, an imaging sensor and a method of production.
TECHNICAL BACKGROUND
Generally, time-of-flight (ToF) image sensors are known. For example, in the field of indirect time-of-flight (iToF), a depth may be measured indirectly by measuring a phase-shift of modulated light which is reflected at a scene (e.g., an object) and which is then incident on the image sensor.
The modulated light is typically in the infrared range, such that an interference with visible light is minimized.
On a material-level, iToF sensors are typically based on silicon technology and may contain pixels based on current-assisted photonic demodulator (CAPD) technology, which modulate taps storing photoelectric charges generated by the incident light.
Although there exist techniques for producing a time-of-flight measurement apparatuses, it is generally desirable to provide a method of producing a current assisted photonic demodulator type indirect Time of Flight pixel for III-V semiconductor materials.
SUMMARY
According to a first aspect the disclosure provides a device for photoelectric conversion and current assisted demodulation of electromagnetic radiation, comprising: a semiconductor layer including III-V-materials and configured for photoelectric conversion in the infrared spectrum as a substrate; at least two control regions comprising one of a region of n-type doped III-V semiconductor material with electrons as a majority of charge carriers or a region of p-type doped III-V semiconductor material with holes as a majority of charge carriers; at least one detection region comprising the other one of a region of p-type doped III-V semiconductor material with holes as a majority of charge carriers or a region of n-type doped III-V semiconductor material with electrons as a majority of charge carriers. Further aspects are set forth in the dependent claims, the following description and the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments are explained by way of example with respect to the accompanying drawings, in which:
Fig. la - Ij schematically illustrate cross-sections exemplifying production stages and use of an embodiment of a current assisted photo demodulator of the present disclosure;
Fig. 2a - 2h schematically illustrate cross-sections exemplifying production stages and use of an embodiment of a current assisted photo demodulator of the present disclosure;
Fig. 3a - 3j schematically illustrate cross-sections exemplifying production stages and use of an embodiment of a current assisted photo demodulator of the present disclosure;
Fig. 4a - 4j schematically illustrate cross-sections exemplifying production stages and use of an embodiment of a current assisted photo demodulator of the present disclosure;
Fig. 5a - 5i schematically illustrate cross-sections exemplifying production stages and use of an embodiment of a current assisted photo demodulator of the present disclosure;
Fig. 6a - 6h schematically illustrate a top view of the n- and p- type diffusions of an embodiment of a current assisted photo demodulator of the present disclosure;
Fig. 7a - 7h schematically illustrate a top view of the n- and p- type diffusions of an embodiment of a current assisted photo demodulators of the present disclosure.
Fig. 8 schematically illustrate a top view of the n- and p- type diffusions of an embodiment of a current assisted photo demodulators of the present disclosure; and
Fig. 9 illustrates an embodiment of a time-of-flight imaging apparatus, which can be used for depth sensing or providing a distance measurement.
DETAILED DESCRIPTION OF EMBODIMENTS
Before a detailed description of the embodiments under reference to Fig. 1, general explanations are made.
As mentioned at the outset, known time-of-flight (ToF) sensors such as current assisted photonic demodulators are typically based on silicon technology.
However, it has been recognized that silicon-based semiconductors may only be suitable for optical sensing of light with a wavelength up to roughly a thousand nanometers in the near infrared (NIR). Silicon-based materials may become transparent for wavelengths longer than a thousand nanometers.
As also mentioned at the outset, ToF measurements are typically carried out in the infrared wavelength range, such that it is desirable to provide ToF for longer wavelengths since a measurement accuracy may increase due to less ambient light (or radiation) in such wavelength ranges.
It has been recognized that III-V materials, such as InGaAs, may have light absorption properties which make them suitable to be used for imaging (or optical sensing) of radiation with a wavelength of up to roughly one-thousand seven-hundred nanometers (or more).
However, transferring silicon based iToF technology to III-V materials (e.g., CAPD, gate-type, etc.) may be difficult and/or costly because processing options (e.g., diffusion, ion implantation, etc.) for III-V materials may be more limited than those for silicon. Furthermore, available device options may be limited and/or may require significant research and development to optimize (e.g., with respect to device isolation, low leakage, MOS (metal oxide semiconductor) gates, or the like) to achieve a performance similar to silicon-based technology.
Some embodiments pertain to a device for photoelectric conversion and current assisted demodulation of electromagnetic radiation, comprising: a semiconductor layer including III-V- materials and configured for photoelectric conversion in the infrared spectrum as a substrate; at least two control regions comprising one of a region of n-type doped III-V semiconductor material with electrons as a majority of charge carriers or a region of p-type doped III-V semiconductor material with holes as a majority of charge carriers; at least one detection region comprising the other one of a region of p-type doped III-V semiconductor material with holes as a majority of charge carriers or a region of n-type doped III-V semiconductor material with electrons as a majority of charge carriers. A III-V semiconductor material may include (but is not limited to) elements of the third and fifth main group of the periodic table. The present disclosure is not limited to any element or any number of different elements which are used in a III-V semiconductor material. For example, the semiconductor material may include or be based on Indium (In), Gallium (Ga), and Arsenic (As). For example, a III-V semiconductor may be based on InGaAs (indium gallium arsenide).
However, as mentioned above, the present disclosure is not limited to any specific III-V semiconductor material. Hence, materials which are used may be based on any phosphide, arsenide, antimonide, or the like, such as GaN (gallium nitride), AIN (aluminum nitride), InN (indium nitride), BN (boron nitride), GaP (gallium phosphide), A1P (aluminum phosphide), InP (indium phosphide), InGaP (indium gallium phosphide), BP (boron phosphide), GaAs (gallium arsenide), AlAs (aluminum arsenide), InAs (indium arsenide), BAs (boron arsenide), GaSb (gallium antimonide), AlSb (aluminum antimoinde), InSb (indium antimonide), or the like.
The at least one detection region and the at least two control regions may be connectable to circuitry (e.g., readout circuitry, such as an ROIC (read-out integrated circuit) or applicationspecific integrated circuit (ASIC)) and which may be provided into the III-V semiconductor material based on a doping of the III-V semiconductor material.
Hence, the at least two control regions may be adapted such that a voltage can be applied to them.
For example, the III-V semiconductor layer may correspond to an undoped substrate with a predetermined concentration of electric carriers (to which it is referred to as n/i (n-type/intrinsic) substrate, in some embodiments). The at least one detection region may then correspond to a region which is p (p-type) doped. The at least two control regions may also be an n doped (n- type) region.
The III-V semiconductor material may further be doped in another region than the at least one detection region and the at least two control regions, and a doping may be different. Electric carriers (e.g., electron-hole-pairs) may be generated inside the semiconductor in response to light being incident on an illumination region, to which it may be referred to as light sensitive region.
The light sensitive region may additionally be n or p doped or undoped without limiting the present disclosure in that regard. The incident light may be provided on any surface of the III-V semiconductor material (substrate), such as a back-surface (e.g., the opposite surface than the surface in which the at least one detection region and the at least two control regions are provided) or the front-surface (e.g., the same surface as the at least one detection region and the at least two control regions).
The doping may depend on what should be collected and measured. In the case of a collection and measurement of holes as electric carriers, the at least two control regions and the substrate may be n doped, while the at least one detection region may be p doped, whereas in the case of electrons as electric carriers, the at least two control regions and the substrate may be p doped, while the at least one detection region is n doped.
However, the present disclosure is also not limited to the case that the diffusion regions are provided in or on the same surface, as they may be provided on opposite surfaces as well. As discussed above, it may be possible to apply a voltage to the at least two control regions (i.e., at least to one of them). The voltage may be based on a demodulation signal, as it is generally known in the field of time-of-flight, such that an unnecessary description thereof is omitted.
Circuitry may pertain to any entity or multitude of entities, which is adapted to control electric signals, such as a CPU (central processing unit), FPGA (field-programmable gate array), microcontroller, IC (integrated circuit), or the like.
In some embodiments, the region of p-type doped III-V semiconductor material is formed in a capping layer of the semiconductor layer
In some embodiments the region of p-type doped III-V semiconductor material is formed in a trench region extending through the capping layer into the semiconductor layer.
Therefore, the charges, either electrons or holes depending on the dopant (see above), intended to be accumulated in the at least one detection region travel a shorter distance from a light sensitive region where photons are converted into electron hole pairs to the at least one detection region. Thus, the current assisted photonic demodulator can collect the detected signals faster.
In some embodiments, the region of n-type doped III-V semiconductor material is formed as a raised diffusion on a capping layer of the semiconductor layer.
This can be achieved by epitaxial growth of an n-type doped III-V semiconductor material onto the capping layer of the semiconductor layer and a following step of masking by a masking layer, partially removing the masking layer according to a mask by means of lithography and developing and etching the n-type doped III-V semiconductor under the removed masking layer portions. This makes it possible to achieve an n-type diffusion in III-V semiconductor material, as well as easily and cheaply fabricate a current assisted photo demodulator in III-V semiconductor material that can operate in wavelengths longer than a thousand manometers.
In some embodiments, the region of n-type doped III-V semiconductor material is formed in a capping layer of the semiconductor layer and regions of n-type doped III-V semiconductor material are further insulated from one another via insulating means in the capping layer and semiconductor layer.
The capping layer can be epitaxially grown, ion-implanted or diffused as a n-type doped III-V semiconductor material and the insulation means may be formed through the capping layer (and/or a mix layer) into the semiconductor layer, e.g., by etching. This makes it possible to achieve an n-type diffusion in III-V semiconductor material, as well as easily and cheaply fabricate a current assisted photo demodulator in III-V semiconductor material that can operate in wavelengths longer than a thousand manometers.
In some embodiments, the insulation means is formed as a trench region, which may be formed by an etching method.
In some embodiments, the region of n-type doped III-V semiconductor material is formed as a raised diffusion on a capping layer of the semiconductor layer.
The region of p-type doped III-V semiconductor material (p type diffusions) are described as being formed by ion diffusion in a planar surface such as a mix or capping layer or a trench. However, this could also be done for the region of n-type doped III-V semiconductor material (n type diffusions).
Similarly, the region of n-type doped III-V semiconductor material (n type diffusions) are described as being formed by raised diffusion. However, this could also be done for the region of p-type doped III-V semiconductor material (p type diffusions).
The raised diffusion can be epitaxially grown, ion -implanted or diffused as an n-type doped III- V semiconductor material.
This makes it possible to achieve an n type diffusion in III-V semiconductor material, as well as easily and cheaply fabricate a current assisted photo demodulator in III-V semiconductor material that can operate in wavelengths higher than a thousand manometers.
Further, forming the raised diffusion on a capping layer that comprises less n-type dopant or no n-type dopant may improve the electrical performance of a p-type doped III-V semiconductor material in the capping layer.
In some embodiments, the raised diffusions are further isolated from one another via trench regions formed in the capping layer and semiconductor layer.
The trench region may for instance be etched through the capping layer into the semiconductor layer, while the raised diffusion mitigates a rise in dark current that may be caused by the trench region in the capping layer and semiconductor layer.
This makes it possible to achieve an n-type diffusion in III-V semiconductor material, as well as easily and cheaply fabricate a current assisted photo demodulator in III-V semiconductor material that can operate in wavelengths longer than a thousand manometers. In some embodiments, the at least two control regions are formed comprising a region of n-type doped III-V semiconductor material, respectively, with electrons as majority carriers, the current assisting the demodulation is a current of electrons and the carrier that are detected in the at least one detection region are positively charged holes.
It is therefore possible to use the current of electrons flowing between the at least two control regions to better collect the holes as the measurement signal in the at least one detection region.
In some embodiments, the at least one detection region is formed comprising the region of n- type doped III-V semiconductor material with electrons as majority carriers when the carriers of the current assisting the demodulation flowing between the at least two control regions are positively charged holes.
It is therefore possible to use the current of holes flowing between the at least two control regions to better collect the electrons as the measurement signal in the at least one detection region.
In some embodiments, a control region of the at least two control regions and the at least one detection region are formed in a predetermined pattern.
Generally, the shape of the pattern of the at least two control regions and the at least one detection region influences the modulated electric field in the semiconductor layer (i.e., light sensitive region) and may improve a depth and shape of a volume from where the at least two control regions can draw the charges of the current, they are inducing and a depth and shape of a volume from which the charges to be collected as the measurement signal travel to the at least one detection region. The predetermined pattern may thus influence the efficiency of the current assisted photo demodulator. A similar effect may be achieved by implementing the at least two control regions with more than two control regions.
In some embodiments, a control region of the at least two control regions or the at least one detection region are formed surrounding the other of the control region or the at least one detection region.
In some embodiments, an overflow node is formed in proximity to a control region of the at least two control regions and the at least one detection region.
The overflow node can collect charges away from the at least one detection region at times when the at least one detection region is not intended to collect those charges (inactive pixel or not in the integration time). The overflow node may be formed of the same material as the at least two control regions or the at least one detection region and may have a potential applied to it, when it is supposed to collect the charges away from the at least one detection region.
In some embodiments, an intermediate bias is formed further separating the at least two control regions.
Generally, a potential applied to the intermediate bias influences the modulated electric field in the semiconductor layer and may improve a depth and shape of a volume from where the least two control regions can draw the charges of the current, they are inducing and a depth and shape of a volume from which the charges to be collected as the measurement signal travel to the at least one detection region. The intermediate bias may thus influence the efficiency and modulation contrast of the current assisted photo demodulator.
In some embodiments, an image or depth sensor comprises a pixel array of the device for photoelectric conversion and current assisted demodulation of electromagnetic radiation as described above.
Further, a method for producing a device for photoelectric conversion and current assisted demodulation of electromagnetic radiation as described above, comprises: using a semiconductor layer comprising III-V-materials and configured for photoelectric conversion in the infrared spectrum as a substrate; forming at least two control regions comprising one of a region of n- type doped III-V semiconductor material with electrons as a majority of charge carriers or a region of p-type doped III-V semiconductor material with holes as a majority of charge carriers; forming at least one detection region comprising the other one of a region of p-type doped III-V semiconductor material with holes as a majority of charge carriers or a region of n-type doped III-V semiconductor material with electrons as a majority of charge carriers.
Returning to Fig. 1, in Fig. la-j there is schematically illustrated cross-sections exemplifying production stages and use of an embodiment of a current assisted photonic demodulator 100 of the present disclosure.
Fig. la illustrates a first production stage beginning with growing a mix layer 106 and a capping layer 108 on a III-V semiconductor material wafer 102 and depositing a masking layer 104 on top of the grown layers. The mix layer 106 is a layer of III-V semiconductor material comprising an n-type dopant which can be epitaxially grown with a III-V semiconductor material or be added later through e.g., diffusion or ion-implementation. The caping layer 108 is a layer of III- V semiconductor material also comprising a n-type dopant which can be epitaxially grown with a III-V semiconductor material or be added later through e.g., diffusion or ion-implementation. Fig. lb illustrates a production stage of the current assisted photonic demodulator 100 after parts of the masking layer 104 are exposed to light during a lithography step and a developing step wherein a developer dissolves away the masking layer 104 except for the areas 112.
Fig. 1c illustrates a production stage of the current assisted photonic demodulator 100 after parts of the mix layer 106 which are not covered by the areas 112 of the masking layer 104 are etched away, so that of the mix layer 106 only the raised diffusions 114 remain.
Fig. Id illustrates a production stage of the current assisted photonic demodulator 100 after the areas 112 of the masking layer are etched away and only the raised diffusions 114 of the mix layer 106 remain on the capping layer 108 and the wafer 102.
Fig. le illustrates a production stage of the current assisted photonic demodulator 100 after a passivation layer 110 is applied to the top surface and in Fig. If areas 116 are etched into the passivation layer 110 reaching to the capping layer 108. The areas 116 can be etched using lithography steps similar to those depicted in and described with reference to Fig. la - 1c. The areas 116 are formed on the inside of the raised diffusions 114.
Fig. 1g illustrates a production stage of the current assisted photonic demodulator 100 after diffusion or ion-implementation is used to created p-type diffusions 118 in the capping layer 108 at the bottom of the areas 116. The areas 116 and thus the p-type diffusions 118 are formed in the inside of the raised diffusions 114. However, the form of the areas 116 and the p-type diffusions 118 is not limited to this. The areas 116 and the p-type diffusions 118 may also be formed as the layout options of Fig. 6a - 6h. The capping layer 108 is n-type doped in its entirety prior to this step.
Fig. Ih illustrates a production stage of the current assisted photonic demodulator 100 after further areas 120 are etched into the passivation layer 110 reaching the raised diffusions 114. The areas 120 can be etched using lithography steps similar to those depicted in and described with reference to Fig. la - 1c. Fig. li illustrates the current assisted photonic demodulator 100 wherein the raised diffusion 114 of n-type doped III-V semiconductor materials are contacted by the contacts 124 and the p-type diffusion 118 of p-type doped III-V semiconductor materials are contacted by contacts 122, thus constituting a functioning current assisted photonic demodulator 100 with an n-type diffusion in III-V semiconductor material and formed as a raised diffusion 114.
The III-V semiconductor material are advantageous over silicon-based semiconductors in converting infrared photons into electron hole pairs and thus electrical signals, particularly for photons of a wavelength over 1000 nm. This raised diffusion approach offers an architecture to implement a current assisted photonic demodulator 100 in III-V semiconductor materials, since a current assisted photonic demodulator 100 comprises p-type and n-type diffusions so that between the diffusions of one type a voltage (143 in Fig. Ij) can be applied, wherein the voltage (143 in Fig. Ij) induces the current of either electrons (141 in Fig. Ij) or hole (142 in Fig. Ij) that assists the demodulation, while the other of the diffusion types collects the other of either electrons (141 in Fig. Ij) or holes (142 in Fig. Ij) as the measurement signal.
Fig. Ij illustrates a modulating electric field 140 at a fixed time in the current assisted photonic demodulator 100 with an n-type doped raised diffusion 114. A modulated voltage 143, shown at a fixed time, is applied to the raised diffusions 114 via the contacts 124 thus creating a modulated electric field that guides the charges intended to be collected as measurement signals to one of the p-type diffusions 118. The modulated electric field may alternate in the direction of the field lines. Thus, which of the p-type diffusions 118 collects the charges also alternates. Therefore, a current is induced, wherein the electrons 141 flow against the direction of the electric field lines 140 to one of the raised diffusions 114 while the holes 142 flow with the electric field lines 140 and are collected by the p-type diffusion 118 as the measurement signal.
This current separates the electrons 141 to the n-type raised diffusion 114 on one side, e.g., left or right, of the current assisted photo demodulator 100 and the holes 142 to the p-type diffusion 118 on the other side of the current assisted photonic demodulator 100. The electron current is part photocurrent and part current generated by the n-type diffusions 114 and assists the demodulation. The hole current is only the photocurrent and is the measurement signal. In this case, the n-type raised diffusions 114 are an example of the least two control regions and the p- type diffusion 118 is an example of the at least one detection region, while the wafer and the capping layer are an example of the semiconductor layer which is n-type doped in this case.
The voltage 143 can also be applied to the p-type diffusion 118 via the contacts 122. In this case, the resulting current separates the electrons 141 to the raised diffusion 114 on one side of the current assisted photonic demodulator 100 and the holes 142 to the p-type diffusion 118 on the other side of the current assisted photo demodulator 100. The hole current is part photocurrent and part current generated by the p-type diffusions 118 and assists the demodulation. The electron current is only the photocurrent and is the measurement signal. In this case, the n-type raised diffusion 114 is an example of at least one detection region and the p-type diffusions 118 are an example of the least two control regions, while the wafer and the capping layer are an example of the semiconductor layer. In such a case the semiconductor layer needs to be p-type doped, to form a pn-junction at the then n-type doped raised diffusion 114. Fig. 2a - 2h schematically illustrate cross-sections exemplifying production stages and use of an embodiment of a current assisted photonic demodulator 200 of the present disclosure.
Fig. 2a illustrates s first production stage, beginning with growing a mix layer 206 on a III-V semiconductor material wafer 202 and depositing a masking layer 204 on top of the grown layers. The mix layer 206 is a layer of III-V semiconductor material comprising an n-type dopant which can be epitaxially grown with a III-V semiconductor material or be added later through, e.g., diffusion or ion-implementation.
Fig. 2b illustrates a production stage of the current assisted photonic demodulator 200 after parts of the masking layer 204 are exposed to light during a lithography step and a developing step wherein a developer dissolves away areas 216a of the masking layer 204, so that the areas 216a reach the mix layer 206.
Fig. 2c illustrates a production stage of the current assisted photonic demodulator 200 after the mix layer 206 under the area 216a of the masking layer 204 are further etched away so that the etched trenches 230 under the area 216a reach into the wafer 202. The trenches 230 insulate regions of the n-type doped mix layer 206 from one another, thus forming the n-type diffusions 214.
Fig. 2d illustrates a production stage of the current assisted photonic demodulator 200 after the masking layer 204 is removed and a dielectric layer 260 is deposited on top of the remaining mix layer 206. The dielectric layer 260 also fills the trenches 230.
In Fig. 2e areas 216b of the dielectric layer are etched away down to the mix layer 206. These areas 216b can be produced utilizing the lithography, development and etching steps depicted in and discussed with reference to Fig. 2a - 2c. Further, a p-type diffusion 218 is produced in the mix layer 206 at the bottom of the areas 216b e.g., by ion diffusion or ion implantation methods. The n-type diffusions 214 are depicted both on the outside and on the inside of the p-type diffusions 218. However, the form of the n-type diffusions 214 and the p-type diffusions 218 is not limited to this. The n-type diffusions 214 and the p-type diffusions 218 may also be formed as the layout options of Fig. 7a - 7h.
Fig. 2f illustrates a production stage of the current assisted photonic demodulator 200 after a further dielectric layer 270 is deposited on top of the dielectric layer 260. The areas 216c and 228 of the dielectric layers 260 and 270 are etched away utilizing lithography and development steps similar to those depicted in and described with reference to Fig. 2a - 2c. Fig. 2g illustrates the current assisted photonic demodulator 200 wherein the n-type diffusion 214 of n-type doped III-V semiconductor materials are contacted by the contacts 224 and the p- type diffusion 218 of p-type doped III-V semiconductor materials are contacted by contacts 222, thus constituting a functioning current assisted photo demodulator 200 with an n-type diffusion 214 in III-V semiconductor material and trenches 230. The dielectric layer 260 and 270 insulate the contacts 222 and 224.
The III-V semiconductor material are advantageous over silicon-based semiconductors in converting infrared photons into electron hole pairs and thus electrical signals, particularly for photons of a wavelength over 1000 nm. This trench approach offers an architecture to implement a current assisted photonic demodulator 200 in III-V semiconductor materials, since a current assisted photonic demodulator 200 comprises p-type and n-type diffusions so that between the diffusions of one type a voltage (243 in Fig. 2h) can be applied, wherein the voltage (243 in Fig. 2h) induces the current of either electrons (241 in Fig. 2h) or hole (242 in Fig. 2h) that assists the demodulation, while the other of the diffusion types collects the other of either electrons (241 in Fig. 2h) or holes (242 in Fig. 2h) as the measurement signal.
Fig. 2h illustrates a modulating electric field 240 at a fixed time in the current assisted photonic demodulator 200 with an n-type doped diffusion 214. A modulated voltage 243, shown at a fixed time, is applied to the n-type doped diffusions 214 via the contacts 224 thus creating a modulated electric field that guides the charges intended to be collected as measurement signals to one of the p-type doped diffusions 218. Depicted is a high potential applied to the left contact 224 and the low potential applied to the right contact 224. The modulated electric field alternates in the direction of the field lines. Thus, which one of the p-type diffusions 218 collects the charges also alternates. Therefore, a current is induced, wherein the electrons 241 flow against the direction of the electric field lines 240 to one of the n-type diffusions 214 while the holes 242 flow with the electric field lines 240 and are collected by the p-type diffusions 218 as the measurement signal.
This current separates the electrons 241 to the n-type diffusion 214 on one side, e.g., left or right, of the current assisted photonic demodulator 200 and the holes 242 to the p-type diffusion 218 on the other side of the current assisted photonic demodulator 200. The electron current is part photocurrent and part current generated by the n-type diffusions 214 and assists the demodulation. The hole current is only the photocurrent and is the measurement signal. In this case, the n-type diffusions 214 are an example of the least two control regions and the p-type diffusion 218 is an example of the at least one detection region, while the wafer 202 and the mix layer 206 are an example of the semiconductor layer, which is n-type doped in this case. The voltage 243 can also be applied to the p-type diffusion 218 via the contacts 222. In this case, the resulting current separates the electrons 241 to the diffusion 214 on one side of the current assisted photonic demodulator 200 and the holes 242 to the p-type diffusion 218 on the other side of the current assisted photonic demodulator 200. The hole current is part photocurrent and part current generated by the p-type diffusions 218 and assists the demodulation. The electron current is only the photocurrent and is the measurement signal. In this case, the n-type diffusion 214 is an example of at least one detection region and the p-type diffusions 218 are an example of the least two control regions, while the wafer is an example of the semiconductor layer. In such a case the semiconductor layer needs to be p-type doped, to form a pn-junction at the then n-type doped raised diffusion 214.
Usually, regions 224 can be used to selectively implant the capping layer 214 with n-type before contact formation to improve contact performance.
Fig. 3 a-3j schematically illustrates cross-sections exemplifying production stages and use of an embodiment of a current assisted photonic demodulator 300 of the present disclosure.
Fig. 3a illustrates a first production stage beginning with growing a mix layer 306 and a capping layer 308 on a III-V semiconductor material wafer 302 and depositing a masking layer 304 on top of the grown layers. The mix layer 306 is a layer of III-V semiconductor material comprising an n-type dopant which can be epitaxially grown with a III-V semiconductor material or be added later through e.g., diffusion or ion-implementation. The capping layer 308 is a layer of III- V semiconductor material also comprising a n-type dopant which can be epitaxially grown with a III-V semiconductor material or be added later through e.g., diffusion or ion-implementation.
Fig. 3b illustrates a production stage of the current assisted photonic demodulator 300 after parts of the masking layer 304 are exposed to light during a lithography step and a developing step wherein a developer dissolves away areas 316a and 316b of the masking layer 304 so that the areas 316a and 316b reach the mix layer 306.
Fig. 3c illustrates a production stage of the current assisted photonic demodulator 300 after the mix layer 306 under the areas 316a and 316b of the masking layer 304 are further etched away so that the etched regions under the area 316a and 316b reach the capping layer 308. The regions under areas 316a and 316b insulate regions of the n-type doped mix layer 306 from one another, thus forming the n-type diffusions 314
Fig. 3d illustrates a production stage of the current assisted photonic demodulator 300 after the masking layer 304 is etched away of the mix layer 306 and a new masking layer 326 is applied. The areas 316a of the masking layer 326 are etched away utilizing lithography and development steps similar to those depicted in and described with reference to Fig. 3a - 3c . In Fig. 3e trenches 330 are etched at the bottom of the areas 316a. The etched trenches 330 reach trough the capping layer 308 into the wafer 302. The trenches 330 further insulate regions of the n-type diffusions 314 from one another.
Fig. 3f illustrates a production stage of the current assisted photonic demodulator 300 after the masking layer 326 is removed and a dielectric layer 360 is deposited on top of the remaining mix layer 306 and the remaining capping layer 308. The dielectric layer 360 also fills the trenches 330.
Fig. 3g illustrates a production stage of the current assisted photonic demodulator 300 after areas 316c of the dielectric layer 360 have been etched away. The areas 316b of the masking layer 326 are etched away utilizing lithography and development steps similar to those depicted in and described with reference to Fig. 3a - 3c. Further, a p-type diffusion 318 is produced in the capping layer 308 at the bottom of the areas 316b e.g., by ion diffusion or ion implantation methods. The n-type diffusions 314 and the p-type diffusions 318 are produced while being separated by a gap. The n-type diffusions 314 are depicted on the outside of the p-type diffusions 318. However, the form of the n-type diffusions 314 and the p-type diffusions 318 is not limited to this. The n-type diffusions 314 and the p-type diffusions 318 may also be formed as the layout options of Fig. 7a - 7h.
Fig. 3h illustrates the current assisted photonic demodulator 300 wherein a further dielectric layer 370 is deposited on top of the dielectric layer 360. The areas 316d and 328 of the dielectric layer 360 are etched away utilizing lithography and development steps similar to those depicted in and described with reference to Fig. 3a - 3c.
Fig. 3i illustrates the current assisted photonic demodulator 300 wherein the n-type diffusion 314 of n-type doped III-V semiconductor materials are contacted by the contacts 324 and the p-type diffusion 318 of p-type doped III-V semiconductor materials are contacted by contacts 322, thus constituting a functioning current assisted photonic demodulator 300 with an n-type raised diffusion 314 in III-V semiconductor material and trenches 330. The dielectric layer 360 and 370 insulate the contacts 322 and 324 as well as the n type diffusion 314 and the p type diffusion 318.
The III-V semiconductor material are advantageous over silicon-based semiconductors in converting infrared photons into electron hole pairs and thus electrical signals, particularly for photons of a wavelength over 1000 nm. This combined raised diffusion and trench approach offers an architecture to implement current assisted photonic demodulator 300 in III-V semiconductor materials, since current assisted photonic demodulator 300 comprise p-type and n-type diffusions so that between the diffusions of one type a voltage (343 in Fig. 3j) can be applied, wherein the voltage (343 in Fig. 3j) induces the current of either electrons (341 in Fig. 3j) or hole (342 in Fig. 3j) that assists the demodulation, while the other of the diffusion types collects the other of either electrons (341 in Fig. 3j) or holes (342 in Fig. 3j) as the measurement signal.
Fig. 3j illustrates a modulating electric field 340 at a fixed time in the current assisted photonic demodulator 300 with an n-type raised diffusion 314. A modulated voltage 343, shown at a fixed time, is applied to the raised diffusions 314 via the contacts 324 thus creating a modulated electric field that guides the charges intended to be collected as measurement signals to one of the p-type diffusions 318. Depicted is a high potential applied to the left contact 324 and the low potential applied to the right contact 324. The modulated electric field alternates in the direction of its field lines. Thus, which one of the p-type diffusions 318 collects the charges also alternates. Therefore, a current is induced, wherein the electrons 341 flow against the direction of the electric field lines 340 to one of the n-type diffusions 314 while the holes 342 flow with the electric field lines 340 and are collected by the p-type diffusions 318 as the measurement signal.
This current separates the electrons 341 to the n-type diffusion 314 on one side of the current assisted photonic demodulator 300 and the holes 342 to the p-type diffusion 318 on the other side of the current assisted photonic demodulator 300. The electron current is part photocurrent and part current generated by the n-type diffusions 314 and assists the demodulation. The hole current is only the photocurrent and is the measurement signal. In this case, the n-type raised diffusions 314 are an example of the least two control regions and the p-type diffusion 318 is an example of the at least one detection region, while the wafer and the capping layer are an example of the semiconductor layer, which is n-type doped in this case.
The voltage 343 can also be applied to the p-type diffusion 318 via the contacts 322. In this case, the resulting current separates the electrons 341 to the raised diffusion 314 on one side of the current assisted photonic demodulator 300 and the holes 342 to the p-type diffusion 318 on the other side of the current assisted photonic demodulator 300. The hole current is part photocurrent and part current generated by the p-type diffusions 318 and assists the demodulation. The electron current is only the photocurrent and is the measurement signal. In this case, the n-type raised diffusion 314 is an example of at least one detection region and the p-type diffusions 318 are an example of the least two control regions, while the wafer and the capping layer are an example of the semiconductor layer. In such a case the semiconductor layer needs to be p-type doped, to form a pn-junction at the then n-type doped raised diffusion 314.
In the raised diffusion approach (Fig. 1), an epitaxial mix layer was deposited and etched to create the isolated n-type regions, which would serve as modulator for a 2-tap CAPD-like pixel. In the proposed trench approach (Fig. 2), similar isolation is achieved instead by utilizing specially designed trench regions. A benefit of the “raised diffusion” approach over the “trench approach” is that the surface for the p-type diffusion does not need to be highly n-doped, allowing for better collector properties, e.g., stronger depletion fields. On the other hand, the “trench approach” would exhibit lower currents due to the non-conductive trench separating the least two control regions. A combination of both previous approaches (Fig. 3), wherein the least two control regions are realized by a raised diffusion, further separated by trenches, results in a pixel structure having both good collector node properties and low current.
Fig. 4a - 4j schematically illustrates cross-sections exemplifying production stages and use of an embodiment of a current assisted photonic demodulator 400 of the present disclosure.
Fig. 4a illustrates a first production stage, beginning with growing a mix layer 406 on a III-V semiconductor material wafer 402 and depositing a masking layer 404 on top of the grown layers. The mix layer 406 is a layer of III-V semiconductor material comprising an n-type dopant which can be epitaxially grown with a III-V semiconductor material or be added later through, e.g., diffusion or ion-implementation.
Fig. 4b illustrates a production stage of the current assisted photonic demodulator 400 after parts of the masking layer 404 are exposed to light during a lithography step and a developing step wherein a developer dissolves away areas 416 of the masking layer 404 e.g., five areas 416, so that the areas 416 reach the mix layer 406. The outer areas 416 can also be shared between neighboring current assisted photonic demodulators 400.
Fig. 4c illustrates a production stage of the current assisted photonic demodulator 400 after areas 416 are etched through the mix layer 406 to the top of the wafer 402. The areas 416 insulate regions of the n type doped mix layer 406 from one another, thus also forming n type diffusions 414 to be connected later
Fig. 4d illustrates a production stage of the current assisted photonic demodulator 400 after the masking layer 404 is etched away of the mix layer 406 and another masking layer 426 is applied. Areas 416 and 416a are etched into the masking layer 426 using lithography and development steps similar to those depicted in and described with reference to Fig. 4a - 4c. The areas 416a are in this case narrower than the areas 416 previously at the same position. This ensures a gap between the n type diffusions 414 and p type diffusions to be formed later.
Fig. 4e illustrates a production stage of the current assisted photonic demodulator 400 after trenches 430 are etched from the bottom of the areas 416 and 416a into the wafer 402. The trenches 430 further insulate regions of the n type diffusions 414 from one another.
Fig. 4f illustrates a production stage of the current assisted photonic demodulator 400 after the masking layer 426 is etched away and a dielectric layer 460 is applied, which covers the mix layer 406 and the trenches 430.
In Fig. 4g areas 416b of the dielectric layer 460 are etched away utilizing a lithography step and a developing step similar to those depicted in and described with reference to Fig. 4a - 4c. The dielectric layer 460 is removed of part of the mix layer 406 as well as two of the trenches 430. In the case of Fig. 4g for example the two trenches 430 without the dielectric layer 460 are separated by trenches 430 with the dielectric layer 460 but this is only one layout option, Fig. 7a - 7h depict further layout options. Further, a p-type diffusion 418 is produced in the trenches 430 without the dielectric layer 460 at the bottom of the areas 416a e.g., by ion diffusion or ion implantation methods. The n-type diffusions 414 and the p-type diffusions 418 are produced while being separated by a gap. The n-type diffusions 414 are depicted on the outside of the p- type diffusions 418. However, the form of the n-type diffusions 414 and the p-type diffusions 418 is not limited to this. The n-type diffusions 414 and the p-type diffusions 418 may also be formed as the layout options of Fig. 7a - 7h.
Fig. 4h illustrates a production stage of the current assisted photo demodulator 400 after a further dielectric layer 470 is deposited on top of the dielectric layer 460. The dielectric layer 470 also fills the trenches 430 not filled by the dielectric 460. The areas 416c and 428 of the dielectric layers 460 and 470 are etched away utilizing lithography and development steps similar to those depicted in and described with reference to Fig. 4a - 4c.
Fig. 4i illustrates the current assisted photonic demodulator 400 wherein the n-type diffusion 414 of n-type doped III-V semiconductor materials are contacted by the contacts 424 and the p-type diffusion 418 of p-type doped III-V semiconductor materials are contacted by contacts 422, thus constituting a functioning current assisted photonic demodulator 400 with an n-type diffusion 414 in III-V semiconductor material and trenches 430, wherein two of those trenches form the p- type diffusions 418 so that the p-type diffusions 418 reach deeper into the wafer 402 than a diffusion or ion-implementation process would be able to achieve without a trench 430. This makes it easier for the p-type diffusions 428 to collect holes 442 which are collected as the measurement signal. If electrons 441 are collected as the measurement signal, the n-type diffusion 414 can collect the electrons as a measurement signal and the p-type diffusion 418 in the trenches 430 cause a hole current assisting the demodulation.
The III-V semiconductor material are advantageous over silicon-based semiconductors in converting infrared photons into electron hole pairs and thus electrical signals, particularly for photons of a wavelength over 1000 nm. This trench approach offers an architecture to implement current assisted photo demodulator 400 in III-V semiconductor materials, since current assisted photonic demodulator 400 comprise p-type and n-type diffusions so that between the diffusions of one type a voltage (443 in Fig. 4j) can be applied, wherein the voltage (443 in Fig. 4j) induces the current of either electrons (441 in Fig. 4j) or hole (442 in Fig. 4j) that assists the demodulation, while the other of the diffusion types collects the other of either electrons (441 in Fig. 4j) or holes (442 in Fig. 4j) as the measurement signal.
Fig. 4j illustrates a modulating electric field 440 at a fixed time in the current assisted photonic demodulator 400 with an n-type diffusion 414. A modulated voltage 443, shown at a fixed time, is applied to the n-type diffusions 414 via the contacts 424 thus creating a modulated electric field that guides the charges intended to be collected as measurement signals to one of the p-type diffusions 418. Depicted is a high potential applied to the left contact 424 and the low potential applied to the right contact 424. The modulated electric field alternates in the direction of the field lines. Thus, which one of the p-type diffusions 418 collects the charges also alternates. Therefore, a current is induced, wherein the electrons 441 flow against the direction of the electric field lines 440 to one of the n-type diffusions 414 while the holes 442 flow with the electric field lines 440 and are collected by the p-type diffusions 418 as the measurement signal.
This current separates the electrons 441 to the n-type diffusion 414 on one side, e.g., left or right, of the current assisted photonic demodulator 400 and the holes 442 to the p-type diffusion 418 on the other side of the current assisted photonic demodulator 400. The electron current is part photocurrent and part current generated by the n-type diffusions 414 and assists the demodulation. The hole current is only the photocurrent and is the measurement signal. In this case, the n-type diffusions 414 are an example of the least two control regions and the p-type diffusion 418 is an example of the at least one detection region, while the wafer and the capping layer are an example of the semiconductor layer, which is n-type doped in this case.
Usually, regions 424 can be used to selectively implant the capping layer 414 with n-type before contact formation to improve contact performance. The voltage 443 can also be applied to the p-type diffusion 418 via the contacts 422. In this case, the resulting current separates the electrons 441 to the n-type diffusion 414 on one side of the current assisted photonic demodulator 400 and the holes 442 to the p-type diffusion 418 on the other side of the current assisted photonic demodulator 400. The hole current is part photocurrent and part current generated by the p-type diffusions 418 and assists the demodulation. The electron current is only the photocurrent and is the measurement signal. In this case, the n-type diffusion 414 is an example of at least one detection region and the p-type diffusions 418 are an example of the at least two control regions, while the wafer is an example of the semiconductor layer. In such a case the semiconductor layer needs to be p-type doped, to form a pn-junction at the then n-type doped raised diffusion 414.
Fig. 5a-i schematically illustrates cross-sections exemplifying production stages and use of an embodiment of a current assisted photonic demodulator 500 of the present disclosure.
Fig. 5a illustrates a first production stage beginning with growing a mix layer 506 and a capping layer 508 on a III-V semiconductor material wafer 502 and depositing a masking layer 504 on top of the grown layers. The mix layer 506 is a layer of III-V semiconductor material comprising an n-type dopant which can be epitaxially grown with a III-V semiconductor material or be added later through e.g., diffusion or ion-implementation. The caping layer 508 is a layer of III-
V semiconductor material comprising a n-type dopant which can be epitaxially grown with a III-
V semiconductor material or be added later through e.g., diffusion or ion-implementation.
Fig. 5b illustrates a production stage of the current assisted photonic demodulator 500 after parts of the masking layer 504 are exposed to light during a lithography step and a developing step wherein a developer dissolves away areas 516 of the masking layer 504 e.g., five areas 516, so that the areas 516 reach the mix layer 506. Fig. 5c illustrates a production stage of the current assisted photonic demodulator 500 after the mix layer 506 in the areas 516 is etched away. Therefore, regions of the n-type doped mix layer 506 are insulated from one another, thus also forming n-type raised diffusions 514 to be contacted later.
Fig. 5d illustrates a production stage of the current assisted photonic demodulator 500 after a further mask layer 526 is deposited and the areas 516 and 516a are removed utilizing lithography and development steps similar to those depicted in and described in reference to Fig. 5a - 5c. The areas 516a a narrower than the areas 516 previously at the same spot. This difference leads to a portion of the capping layer 508 outside the area 516a exposed from under the mix layer 506 that can be contacted later as well as provide a gap between the n type diffusion 512 and a p type diffusion to be formed later. Fig. 5e illustrates a production stage of the current assisted photonic demodulator 500 after trenches 530 are etched from the bottom of the areas 516 through the capping layer 508 into the wafer 502.
Fig. 5f illustrates a production stage of the current assisted photonic demodulator 500 after the masking layer 526 is etched away of the mix layer 506 and a dielectric layer 560 is applied. The areas 516b are removed utilizing lithography and development steps similar to those depicted in and described in reference to Fig. 5a - 5c. Further, p-type diffusions 518 are produced in the trenches 530 without the dielectric layer 560 at the bottom of the areas 516b e.g., by ion diffusion or ion implantation methods. The n-type diffusions 514 and the p-type diffusions 518 are produced while being separated by a gap. The n-type diffusions 514 are depicted on the outside of the p-type diffusions 518. However, the form of the n-type diffusions 514 and the p- type diffusions 518 is not limited to this. The n-type diffusions 514 and the p-type diffusions 518 may also be formed as the layout options of Fig. 7a - 7h.
In Fig. 5g illustrates a production stage of the current assisted photonic demodulator 500 after a further dielectric layer 570 is deposited onto the dielectric layer 560 while also filling the trenches 530 not filled with the dielectric layer 560. The areas 516c and 528 of the dielectric layers 560 and 570 are etched away utilizing lithography and development steps similar to those depicted in and described with reference to Fig. 5a - 5c.
Fig. 5h illustrates the current assisted photonic demodulator 500 wherein the n-type diffusion 514 of n-type doped III-V semiconductor materials are contacted by the contacts 524 and the p- type diffusion 518 of p-type doped III-V semiconductor materials are contacted by contacts 522, thus constituting a functional current assisted photo demodulator 500 with an n-type diffusion 514 in III-V semiconductor material and trenches 530, wherein e.g., two of those trenches are formed as p-type diffusions 518 so that the p-type diffusions 518 reach deeper into the wafer 502 than a diffusion or ion-implementation process would be able to produce without a trench 530. This makes it easier for the p-type diffusions 518 to collect holes 542 which are collected as the measurement signal. The contacts 524 and 522 as well as the n type diffusion 514 and the p type diffusion 518 are insulated by the dielectric layers 560 and 570.
The III-V semiconductor material are advantageous over silicon-based semiconductors in converting infrared photons into electron hole pairs and thus electrical signals, particularly for photons of a wavelength over 1000 nm. This combined raised diffusion and trench approach offers an architecture to implement current assisted photonic demodulator 500 in III-V semiconductor materials, since current assisted photonic demodulator 500 comprise p-type and n-type diffusions so that between the diffusions of one type a voltage (543 in Fig. 5i) can be applied, wherein the voltage (543 in Fig. 5i) induces the current of either electrons (541 in Fig. 5i) or hole (542 in Fig. 5i) that assists the demodulation, while the other of the diffusion types collects the other of either electrons (541 in Fig. 5i) or holes (542 in Fig. 5i) as the measurement signal.
Fig. 5i illustrates a modulating electric field 540 at a fixed time in the current assisted photonic demodulator 500 with an n-type diffusion 514. A modulated voltage 543, shown at a fixed time, is applied to the raised diffusions 514 via the contacts 524 thus creating a modulated electric field that guides the charges intended to be collected as measurement signals to one of the p-type diffusions 518. Depicted is a high potential applied to the left contact 524 and the low potential applied to the right contact 524. The modulated electric field alternates in the direction of the field lines. Thus, which one of the p-type diffusions 518 collects the charges also alternates. Therefore, a current is induced, wherein the electrons 541 flow against the direction of the electric field lines 540 to one of the n-type diffusions 514 while the holes 542 flow with the electric field lines 540 and are collected by the p-type diffusions 518 as the measurement signal.
This current separates the electrons 541 to the n-type diffusion 514 on one side of the current assisted photonic demodulator 500 and the holes 542 to the p-type diffusion 518 on the other side of the current assisted photonic demodulator 500. The electron current is part photocurrent and part current generated by the n-type diffusions 514 and assists the demodulation. The hole current is only the photocurrent and is the measurement signal. In this case, the n-type raised diffusions 514 are an example of the least two control regions and the p-type diffusion 518 is an example of the at least one detection region, while the wafer and the capping layer are an example of the semiconductor layer, which is n-type doped in this case.
The voltage 543 can also be applied to the p-type diffusion 518 via the contacts 522. In this case, the resulting current separates the electrons 541 to the raised diffusion 514 on one side of the current assisted photonic demodulator 500 and the holes 542 to the p-type diffusion 518 on the other side of the current assisted photonic demodulator 500. The hole current is part photocurrent and part current generated by the p-type diffusions 518 and assists the demodulation. The electron current is only the photocurrent and is the measurement signal. In this case, the n-type raised diffusion 514 is an example of the at least one detection region and the p-type diffusions 518 are an example of the least two control regions, while the wafer and the capping layer are an example of the semiconductor layer. In such a case the semiconductor layer needs to be p-type doped, to form a pn-junction at the then n-type doped raised diffusion 514. Fig. 6a-h schematically illustrates a top view, without the depiction of the dielectrics and metallization (contacts), of the n- and p- type diffusions of an embodiment of a current assisted photonic demodulator 100 of the present disclosure.
The floating diffusions FDO and FD1 represent the p-type diffusions of the current assisted photonic demodulator 100, while the mix contacts MIX0 and MIX1 represent the n-type diffusions of the current assisted photonic demodulator 100. The mix contacts MIX0 and MIX1 have a voltage of a control signal applied to them, while the floating diffusions FDO and FD1 collect the holes as the measurement signal. In this case, the mix contacts MIX0 and MIX1 forming the n-type diffusions are an example of the least two control regions and the p-type diffusion forming the floating diffusions FDO or FD1 is an example of the at least one detection region.
However, it is also possible to apply the voltage of a control signal to the p-type diffusions of the current assisted photo demodulator 100, which makes the n-type diffusions of the current assisted photo demodulator 100 function as floating diffusions that collect electrons instead of holes.
Fig. 6a schematically illustrates the floating diffusions FDO and FD1 positioned on the outside of the mix contacts MIX0 and MIX1, which are formed further towards the center of the top surface.
Fig. 6b schematically illustrates the floating diffusions FDO and FD1 positioned on the outside of the mix contacts MIX0 and MIX1, which are formed further towards the center of the top surface. The mix contacts MIX0 and MIX1 are further separated by an intermediate bias 601.
Fig. 6c schematically illustrates the mix contacts MIX0 and MIX1 formed further towards the center of the top surface (e.g., the capping layer 608). The floating diffusions FDO and FD1 are positioned on the outside of these mix contacts MIX0 and MIX1. Further, mix contacts MIX0 and MIX1 are formed to the outside of the floating diffusions FDO and FD1. Every floating diffusion FDO or FD1 is therefore formed in between two mix contacts MIX0 or MIX1, respectively.
Fig. 6d schematically illustrates the mix contacts MIX0 and MIX1 positioned on the outside of the floating diffusions FDO and FD1, which are formed further towards the center of the top surface. The order illustrated in Fig. 6d is inverted from the order of Fig. 6a. Fig. 6e schematically illustrates the mix contacts MIXO and MIX1 surrounding the floating diffusions FDO and FD1. Both the mix contacts MIXO and MIX1 and the floating diffusions FDO and FD1 are located on the capping layer 608.
Fig. 6f schematically illustrates the floating diffusions FDO and FD1 surrounding the mix contacts MIXO and MIX1. Both the mix contacts MIXO and MIX1 and the floating diffusions FDO and FD1 are located on the capping layer 608.
Fig. 6g schematically illustrates the floating diffusions FDO and FD1 positioned on the outside of the mix contacts MIXO and MIX1, which area formed further towards the center of the top surface. The floating diffusions FDO and FD1 and the mix contacts MIXO and MIX1 are further surrounded by an overflow node OF. This overflow node OF may be useful to include for times when it is not intended to collect charges on the floating diffusions FDO and FD1. If this overflow node OF is pulled to a low voltage outside an integration period, holes will preferably be collected on the overflow node OF instead of being collected on the DET nodes. This overflow node OF function can be realized both by means of a metal electrode, or by means of a p-type or n-type diffusions based on the polarity of the floating diffusions. The overflow node does not have to surround the floating diffusions FDO and FD1 and the mix contacts MIXO and MIX1
Fig. 6h schematically illustrates the positioned mix contacts MIXO and MIX1 on the outside of the floating diffusions FDO and FD1, which are formed further towards the center of the top surface. The floating diffusions FDO and FD1 are further separated by an isolation 601.
The top surface as depicted in Figs. 6a-h is a capping layer 608, thus illustrating the top surface of the current assisted photonic demodulator 100 in Fig. 1. Further, the top surface is not necessarily arranged in the same plane. Either floating diffusions FDO and FD1 and/or mix contacts MIXO and MIX1 can also be arranged as trench regions of varying depth or raised diffusions. The floating diffusions FDO and FD1 can also be arranged in the position where the mix contacts MIXO and MIX1 are illustrated in Figs. 6a - 6h, while the mix contacts MIXO and MIX1 take the positions of the floating diffusions FDO and FD1. The polarity (n-type or p-type) of the floating diffusions FD and mix contacts MIX can also be switched.
Fig. 7a -7h schematically illustrates a top view, without the depiction of the dielectrics and metallization (contacts), of the n- and p- type diffusions of an embodiment of current assisted photonic demodulators 200, 300, 400 and 500 of the present disclosure.
The floating diffusions FDO and FD1 represent the p-type diffusions of the current assisted photonic demodulators 200, 300, 400 and 500, while the mix contacts MIXO and MIX1 represent the n-type diffusions of the current assisted photonic demodulators 200, 300, 400 and 500. The mix contacts MIX0 and MIX1 have a voltage of a control signal applied to them, while the floating diffusions FD0 and FD1 collect the holes as the measurement signal. In this case, the mix contacts MIX0 and MIX1 forming the n-type diffusions are an example of the least two control regions and the p-type diffusion forming the floating diffusions FD0 or FD1 is an example of the at least one detection region. The floating diffusions can thus be produced in a capping layer or a wafer substrate while the mix contacts can be produced in the capping layer or the mix layer of the current assisted photonic demodulators 200, 300, 400 and 500.
However, it is also possible to apply the voltage of a control signal to the p-type diffusions of the current assisted photonic demodulators 200, 300, 400 and 500, which makes the n-type diffusions of the current assisted photonic demodulators 200, 300, 400 and 500 function as floating diffusions FD0 and FD1.
Fig. 7a-h depict the same pattern of mix contacts MIX0 and MIX1 and floating diffusions FD0 and FD1 as depicted in Fig. 6a-h, and thus a detailed description is omitted here. The top surface as depicted in Figs. 7a-h is a trench region 708, thus illustrating the top surface of the current assisted photo demodulators 200, 300, 400 and 500 in Figs. 2-5. Further the top surface is not necessarily arranged in the same plane since the region surrounding the mix contacts MIX0 and MIX1 and the floating diffusions FD0 and FD1 is a trench region 708 and either floating diffusions FD0 and FD1 or mix contacts MIX0 and MIX1 can also be arranges as trench regions of varying depth or raised diffusions. The floating diffusions FD0 and FD1 can also be arranged in the position where the mix contacts MIX0 and MIX1 are illustrated in Figs. 7a - 7h, while the mix contacts MIX0 and MIX1 take the positions of the floating diffusions FD0 and FD1. The polarity (n-type or p-type) of the floating diffusions FD and mix contacts MIX can also be switched.
Fig. 8 schematically illustrates a top view, without the depiction of the dielectrics and metallization (contacts), of the n- and p- type diffusions of an embodiment of current assisted photonic demodulators 200, 300, 400 and 500 of the present disclosure.
The floating diffusions FD0 and FD1 represent the p-type diffusions of the current assisted photonic demodulators 200, 300, 400 and 500, while the mix contacts MIX0 and MIX1 represent the n-type diffusions of the current assisted photo demodulators 200, 300, 400 and 500. The mix contacts MIX0 and MIX1 have a voltage of a control signal applied to them, while the floating diffusions FD0 and FD1 collect the holes as the measurement signal. The floating diffusions can thus be produced in a capping layer or a wafer substrate while the mix contacts can be produced in the capping layer or the mix layer of the current assisted photonic demodulators 200, 300, 400 and 500.
The illustrated order of the floating diffusions FD0 and FD1 and the mix contacts MIX0 and MIX1 is similar to the order illustrated in Fig. 7e. One of the mix contacts MIX0 or MIX1 surrounds one of the floating diffusions FD0 or FD1. The one of the mix contacts MIX0 or MIX1 and the one of the floating diffusions FD0 or FD1 do not have a gap in between them.
The floating diffusions FD0 and FD1 and the mix contacts MIX0 and MIX1 are further contacted by contacts 822 and 824 to apply a voltage of a control signal to e.g., the mix contacts MIX0 and MIX1, and read accumulated charges e.g., holes, of the measurement signal from the floating diffusions FD0 and FD1.
Fig. 9 illustrates an embodiment of a time-of-flight (ToF) imaging apparatus 900, which can be used for depth sensing or providing a distance measurement, in particular for the technology as discussed herein, wherein the ToF imaging apparatus 900 is configured as an i ToF camera. The ToF imaging apparatus 900 has image sensor circuitry 907, which is configured to carry out a iToF depth measurement and which forms a control of the ToF imaging apparatus 900 (and it includes, not shown, corresponding processors, memory and storage, as it is generally known to the skilled person).
The ToF imaging apparatus 900 has a modulated light source 901, and it includes light-emitting elements which, for example can be based on laser diodes. The light source 901 emits light, i.e., modulated light, as discussed herein, to a scene 902 (region of interest or object), which reflects the light. The reflected light is focused by an optical stack 903 to a light detector 904.
The light detector 904 is implemented based on multiple ToF portions according to the present disclosure and based on a micro lens array 906 which focuses the light reflected from the scene 902 to an imaging portion 905 (to each pixel of the image sensor circuitry 907), which may comprise a current assisted photonic demodulator according to any of the previous embodiments.
The light emission time and modulation information is fed to the image sensor circuitry or control 907 including a time-of-flight measurement unit 908 (which includes time-of-flight demodulation circuitry according to the present disclosure), which also receives respective information from the imaging portion 905, when the light is detected which is reflected from the scene 902. The respective information from the imaging portion 905 may be based on the control signal applying a modulated voltage (modulated like the light source 901) to alternate the floating diffusions collecting the measurement signal. On the basis of the modulated light received from the light source 901, the time-of-flight measurement unit 908 computes a phase shift of the received modulated light which has been emitted from the light source 901 and reflected by the scene 902 and on the basis thereon it computes a distance d (depth information) between the imaging portion 905 and the scene 902.
The depth information can be fed from the time-of-flight measurement unit 908 to a 3D image reconstruction unit 909 of the image sensor circuitry 907, which can reconstruct (generate) a 3D image of the scene 902.
It should be recognized that the embodiments describe methods with an exemplary ordering of method steps and production stages. The specific ordering of method steps and production stages is, however, given for illustration purposes only and should not be construed as binding. For example, the p-type diffusion 118 in Fig. 1g could be formed before the raised diffusion 114 in Fig. 1c. Further, the p-type diffusions 218 in Fig. 2e could be formed before the trenches in Fig. 2c. Similarly, the p-type diffusions 318 in Fig. 3g could be formed before the trenches 330 in Fig. 3e. Furthermore, the trenches 530 in Fig. 5e could be formed before the n-type raised diffusion 514 in Fig. 5c.
Please note that the division of the control 907 into units 908 and 909 is only made for illustration purposes and that the present disclosure is not limited to any specific division of functions in specific units. For instance, the control 907 could be implemented by a respective programmed processor, field programmable gate array (FPGA) and the like.
All units and entities described in this specification and claimed in the appended claims can, if not stated otherwise, be implemented as integrated circuit logic, for example on a chip, and functionality provided by such units and entities can, if not stated otherwise, be implemented by software.
In so far as the embodiments of the disclosure described above are implemented, at least in part, using software-controlled data processing apparatus, it will be appreciated that a computer program providing such software control and a transmission, storage or other medium by which such a computer program is provided are envisaged as aspects of the present disclosure.
Note that the present technology can also be configured as described below.
(1) A device for photoelectric conversion and current assisted demodulation of electromagnetic radiation, comprising: a semiconductor layer including III-V-materials and configured for photoelectric conversion in the infrared spectrum as a substrate; at least two control regions comprising one of a region of n-type doped III-V semiconductor material with electrons as a majority of charge carriers or a region of p-type doped III-V semiconductor material with holes as a majority of charge carriers; at least one detection region comprising the other one of a region of p-type doped III-V semiconductor material with holes as a majority of charge carriers or a region of n-type doped III-V semiconductor material with electrons as a majority of charge carriers.
(2) The device of (1), wherein the region of p-type doped III-V semiconductor material is provided in a capping layer of the semiconductor layer.
(3) The device of (1) or (2), wherein the region of p-type doped III-V semiconductor material is provided in a trench region extending through the capping layer into the semiconductor layer.
(4) The device of (1) to (3), wherein the region of n-type doped III-V semiconductor material is provided as a raised diffusion on a capping layer of the semiconductor layer.
(5) The device of (1) to (4), wherein the region of n-type doped III-V semiconductor material is provided in a capping layer of the semiconductor layer and regions of n-type doped III-V semiconductor material are further insulated from one another via insulating means in the capping layer and semiconductor layer.
(6) The device of (5), wherein the insulation means is provided as a trench region.
(7) The device of (4), wherein the raised diffusions are further isolated from one another via trench regions provided in the capping layer and semiconductor layer.
(8) The device of (1) to (7), wherein the at least two control regions are provided comprising a region of n-type doped III-V semiconductor material, respectively, with electrons as majority carriers, wherein the current assisting the demodulation is a current of electrons and the carrier that are detected in the at least one detection region are positively charged holes.
(9) The device of (1) to (8), wherein the at least one detection region is provided comprising the region of n-type doped III-V semiconductor material with electrons as majority carriers, wherein the carriers, of the current assisting the demodulation flowing between the at least two control regions are positively charged holes.
(10) The device of (1) to (9), wherein a control region of the at least two control regions and the at least one detection region are provided in predetermined pattern. (11) The device of (1) to (10), wherein a control region of the at least two control regions and the at least one detection region are provided surrounding the other of the control region and the at least one detection region.
(12) The device of (1) to (11), wherein an overflow node is provided in proximity to a control region of the at least two control regions and the at least one detection region.
(13) The device of (1), wherein an intermediate bias is formed separating the at least two control regions.
(14) An image or depth sensor comprising a pixel array of the devices of any one of (1) to (13).
(15) A method for producing the device of any one of (1) to (13).