Disclosure of Invention
The application aims to provide an interband cascade laser and a manufacturing method thereof, which are used for simplifying the manufacturing process of a grating, reducing the manufacturing difficulty of the grating and improving the yield of the laser.
In order to solve the technical problems, the present application provides a method for manufacturing an interband cascade laser, including:
preparing a laser prefabricated structure body, wherein the laser prefabricated structure body comprises a substrate, a ridge structure and a dielectric layer, and the ridge structure comprises a ridge stripe;
Coating negative photoresist on the surface of the laser prefabricated structure body to form a negative photoresist layer;
exposing and developing the negative photoresist layer, and removing the unexposed negative photoresist layer to form a grating;
Manufacturing an electrode window in the dielectric layer on the ridge;
Manufacturing a first electrode on the surface of the laser prefabricated structure body with the grating;
And manufacturing a second electrode on the lower surface of the substrate to obtain the interband cascade laser.
Optionally, exposing and developing the negative photoresist layer to remove the unexposed negative photoresist layer, and before forming the grating, further including:
determining the period length of the grating according to the output wavelength of the interband cascade laser and the effective refractive index of the active region in the ridge structure;
determining the width of the grating according to the period length and the grating duty ratio;
Correspondingly, exposing and developing the negative photoresist layer comprises:
exposing the negative photoresist layer, wherein the width of an unexposed area between adjacent exposure areas is equal to the width of the grating;
and developing to remove the negative photoresist layer in the exposed area.
Optionally, determining the period length of the grating according to the output wavelength of the interband cascade laser and the effective refractive index of the active region in the ridge structure includes:
Determining the period length of the grating according to a first preset formula by the output wavelength of the interband cascade laser and the effective refractive index of the active region in the ridge structure, wherein the first preset formula is as follows:
L=λ/2n;
where L is the period length of the grating, λ is the output wavelength of the interband cascade laser, and n is the effective refractive index of the active region.
Optionally, determining the width of the grating according to the period length and the grating duty cycle includes:
determining the width of the grating according to a second preset formula through the period length and the grating duty ratio, wherein the second preset formula is as follows:
W=l/L×100%;
where W is the grating duty cycle, L is the grating width, and L is the grating period length.
Optionally, before preparing the laser prefabricated structure, the method further comprises:
manufacturing an epitaxial structure layer on the upper surface of the substrate, wherein the epitaxial structure layer comprises an active layer;
etching the epitaxial structure layer to form the ridge structure, wherein the etching exceeds the active layer;
and depositing the dielectric layer on the surface of the ridge structure to form the laser prefabricated structure.
Optionally, fabricating an epitaxial structure layer on the substrate includes:
And sequentially depositing a first limiting layer, a first waveguide layer, an active layer, a second waveguide layer and a second limiting layer which are stacked on the upper surface of the substrate to form the epitaxial structure layer.
The present application also provides an interband cascade laser comprising:
a substrate;
The ridge structure is positioned on the upper surface of the substrate and comprises ridge bars;
The dielectric layer is provided with an electrode window, and the electrode window is positioned on the ridge;
The gratings are positioned at two sides of the ridge, and the gratings are negative photoresist after exposure;
The first electrode is positioned between the gratings, on the upper surface of the gratings and on the surface of the dielectric layer;
and a second electrode positioned on the lower surface of the substrate.
Optionally, the ridge structure includes a first confinement layer, a first waveguide layer, an active layer, a second waveguide layer, and a second confinement layer sequentially stacked in a direction away from the substrate.
Optionally, the dielectric layer includes any one or any combination of a silicon nitride layer, a silicon oxide layer, and a silicon oxynitride layer.
Optionally, the duty cycle of the grating is greater than or equal to 50% and less than 100%.
The manufacturing method of the interband cascade laser comprises the steps of preparing a laser prefabricated structure body, wherein the laser prefabricated structure body comprises a substrate, a ridge structure and a dielectric layer, the ridge structure comprises a ridge bar, negative photoresist is coated on the surface of the laser prefabricated structure body to form a negative photoresist layer, the negative photoresist layer is exposed and developed to remove the non-exposed negative photoresist layer to form a grating, an electrode window is manufactured in the dielectric layer on the ridge bar, a first electrode is manufactured on the surface of the laser prefabricated structure body with the grating, and a second electrode is manufactured on the lower surface of the substrate to obtain the interband cascade laser.
Therefore, in the process of manufacturing the interband cascade laser, the negative photoresist layer is formed on the laser prefabricated structure body, then the negative photoresist layer is exposed, the negative photoresist property of an exposed area is changed to become the property of a medium, and after the negative photoresist layer of an unexposed area is developed and removed, the rest of the exposed negative photoresist layer forms a grating. The grating can be manufactured by coating the negative photoresist, exposing and developing, the manufacturing process is simple, the difficulty is low, the influence of the manufactured grating on the yield of the laser can be reduced, and the manufacturing yield of the interband cascade laser is improved. And after the grating is manufactured, the first electrode is manufactured, and the first electrode and the grating which are positioned between the gratings form an alternating conductive/dielectric structure, so that the wavelength emitted by the laser can be effectively screened.
In addition, the application also provides an interband cascade laser with the advantages.
Detailed Description
In order to better understand the aspects of the present application, the present application will be described in further detail with reference to the accompanying drawings and detailed description. It will be apparent that the described embodiments are only some, but not all, embodiments of the application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, but the present invention may be practiced in other ways other than those described herein, and persons skilled in the art will readily appreciate that the present invention is not limited to the specific embodiments disclosed below.
As described in the background art, the existing grating manufacturing process has the defects of complex process flow and high process difficulty, so that the yield of the laser is lower.
In view of this, the present application provides a method for manufacturing an interband cascade laser, please refer to fig. 1, which includes:
Step S101, preparing a laser prefabricated structure body, wherein the laser prefabricated structure body comprises a substrate, a ridge structure and a dielectric layer, and the ridge structure comprises a ridge stripe.
As shown in fig. 2, the schematic structure of the laser pre-fabricated structure 100 is shown, where the ridge structure 101 is located on the upper surface of the substrate 1, and the dielectric layer 7 is located on the surface of the ridge structure 101, i.e. the dielectric layer 7 is located on the surface of the laser pre-fabricated structure. The ridge structure 101 includes a ridge stripe 102 and two side portions connected to the ridge stripe 102, the ridge stripe 102 protrudes from the two side portions, and the ridge stripe 102 includes the active layer 4.
The material of the substrate 1 may be GaSb or the like, and is not particularly limited in the present application.
The ridge structure 101 includes a first confinement layer 2, a first waveguide layer 3, an active layer 4, a second waveguide layer 5, and a second confinement layer 6, which are sequentially stacked in a direction away from the substrate 1. The materials of the first confinement layer 2, the first waveguide layer 3, the active layer 4, the second waveguide layer 5, and the second confinement layer 6 may be set according to actual needs, and are not particularly limited in the present application.
The dielectric layer 7 has the function of protecting the side wall of the ridge structure formed by etching on the one hand and isolating the first electrode and the second electrode on the other hand, so as to avoid electric leakage.
Dielectric layer 7 includes, but is not limited to, any one or any combination of a silicon nitride layer, a silicon oxide layer, a silicon oxynitride layer.
When the dielectric layer 7 is any combination of a silicon nitride layer, a silicon oxide layer, and a silicon oxynitride layer, the layers of any combination are laminated to form the dielectric layer, for example, when the dielectric layer 7 includes a silicon nitride layer and a silicon oxide layer, the dielectric layer 7 is a laminated silicon nitride layer and silicon oxide layer.
And step S102, coating negative photoresist on the surface of the laser prefabricated structure body to form a negative photoresist layer.
As shown in fig. 3, a negative photoresist layer 8 covers the surface of the dielectric layer.
The negative photoresist may be coated by spin coating to improve the thickness uniformity of the negative photoresist layer 8.
The negative photoresist, also called photoresist, is a light sensitive mixed liquid composed of three main components of photosensitive resin, sensitizer (visible spectrum sensitization dye) and solvent. After exposure to electron beam, the negative photoresist changes its properties to become a dielectric material like silicon dioxide with a refractive index of 1.4.
The negative photoresist used in this embodiment may be directly purchased, and specific types of the negative photoresist are not limited in this embodiment, and for example, HSQ series negative photoresist may be used.
And step 103, exposing and developing the negative photoresist layer, and removing the unexposed negative photoresist layer to form a grating.
Referring to fig. 4 to 6, a mask 9 is placed over the negative photoresist layer 8, and then the pattern on the mask is exposed using an electron beam, and the properties of the negative photoresist layer 8 in the exposed area are changed to form a dielectric material similar to SiO2. After development, the areas of the negative photoresist layer 8 that were not exposed are rinsed away by the developer, leaving only the negative photoresist layer 8 in the exposed areas, forming a grating 10. The grating 10 is distributed on both sides of the ridge stripe 102 in the ridge structure and is perpendicular to the ridge stripe 102.
Each grating 10 is the same size and the distance between adjacent gratings 10 may be equal.
And step S104, manufacturing an electrode window in the dielectric layer on the ridge stripe.
The dielectric layer on top of the ridge structure may be processed by etching to form an electrode window.
The electrode window 11 extends through the dielectric layer as shown in fig. 7. The electrode window 11 is made in order to bring the subsequently made first electrode into contact with the ridge structure, forming an electrode.
And step S105, manufacturing a first electrode on the surface of the laser prefabricated structure body on which the grating is formed.
The material of the first electrode may be a metal material, such as gold, platinum, or the like.
Referring to fig. 8, a first electrode 12 is deposited on the upper surface of the laser preform structure on which the grating 10 is formed. The first electrode 12 is also deposited in the gap region between adjacent gratings 10, and the first electrode 12 in the gap region between adjacent gratings 10 and the gratings 10 form an alternating structure of metal and medium that effectively screens the interband cascade laser wavelength.
And S106, manufacturing a second electrode on the lower surface of the substrate to obtain the interband cascade laser.
The material of the second electrode may be a metal material.
The first electrode and the second electrode can be manufactured and formed by magnetron sputtering, evaporation plating or the like.
In this embodiment, during the process of manufacturing the interband cascade laser, a negative photoresist layer is formed on the laser prefabricated structure, then the negative photoresist layer is exposed, the negative photoresist property of the exposed area is changed to become the property of a medium, and after the negative photoresist layer of the unexposed area is developed and removed, the remaining exposed negative photoresist layer forms a grating. The grating can be manufactured by coating the negative photoresist, exposing and developing, the manufacturing process is simple, the difficulty is low, the influence of the manufactured grating on the yield of the laser can be reduced, and the manufacturing yield of the interband cascade laser is improved. And after the grating is manufactured, the first electrode is manufactured, and the first electrode and the grating which are positioned between the gratings form an alternating conductive/dielectric structure, so that the wavelength emitted by the laser can be effectively screened.
Based on the above embodiments, in one embodiment of the present application, referring to fig. 9, a method for manufacturing an interband cascade laser includes:
Step S201, preparing a laser prefabricated structure body, wherein the laser prefabricated structure body comprises a substrate, a ridge structure and a dielectric layer, and the ridge structure comprises a ridge stripe.
And step S202, coating negative photoresist on the surface of the laser prefabricated structure body to form a negative photoresist layer.
Step S203, determining the period length of the grating according to the output wavelength of the interband cascade laser and the effective refractive index of the active region in the ridge structure.
As an embodiment, determining the period length of the grating based on the output wavelength of the interband cascade laser and the effective refractive index of the active region in the ridge structure comprises:
Determining the period length of the grating according to a first preset formula by the output wavelength of the interband cascade laser and the effective refractive index of the active region in the ridge structure, wherein the first preset formula is as follows:
L=λ/2n; (1)
where L is the period length of the grating, λ is the output wavelength of the interband cascade laser, and n is the effective refractive index of the active region.
The output wavelength of the interband cascade laser is known, the material of the active region is known, the effective refractive index of the active region is also known, and the period length of the grating can be obtained according to formula (1).
The period length L of the grating is equal to the sum of the width L of the grating and the distance between adjacent gratings, as shown in fig. 10.
And step S204, determining the width of the grating according to the period length and the grating duty ratio.
As an embodiment, determining the width of the grating according to the period length and the grating duty cycle comprises:
determining the width of the grating according to a second preset formula through the period length and the grating duty ratio, wherein the second preset formula is as follows:
W=l/L×100%; (2)
where W is the grating duty cycle, L is the grating width, and L is the grating period length.
When the grating duty cycle and the period length of the grating are known, the width of the grating can be determined according to formula (2).
The grating duty cycle is the ratio of the grating width to the period length of the grating.
And step S205, exposing the negative photoresist layer, wherein the width of the unexposed area between the adjacent exposed areas is equal to the width of the grating.
And S206, developing and removing the negative photoresist layer of the exposure area to form a grating.
And S207, manufacturing an electrode window in the dielectric layer on the ridge.
And step S208, manufacturing a first electrode on the surface of the laser prefabricated structure body on which the grating is formed.
And step S209, manufacturing a second electrode on the lower surface of the substrate to obtain the interband cascade laser.
On the basis of any of the above embodiments, in one embodiment of the present application, a process of fabricating the laser preform structure may be further included before preparing the laser preform structure. Referring to fig. 11, the process for fabricating the laser preformed structure includes:
Step S301, an epitaxial structure layer is manufactured on the upper surface of the substrate, wherein the epitaxial structure layer comprises an active layer.
In one embodiment of the application, fabricating an epitaxial structure layer on the substrate comprises:
And sequentially depositing a first limiting layer, a first waveguide layer, an active layer, a second waveguide layer and a second limiting layer which are stacked on the upper surface of the substrate to form the epitaxial structure layer.
The first confinement layer, the first waveguide layer, the active layer, the second waveguide layer, and the second confinement layer may be fabricated by magnetron sputtering, plasma enhanced chemical vapor deposition, or the like.
As shown in fig. 12, the upper surface of the substrate 1 is sequentially deposited with a first confinement layer 2, a first waveguide layer 3, an active layer 4, a second waveguide layer 5, and a second confinement layer 6, which are laminated.
And step S302, etching the epitaxial structure layer to form the ridge structure, wherein the etching is performed beyond the active layer.
As shown in fig. 13, the ridge structure 101 is formed by etching over the active layer 4 and stopping on the first waveguide layer 3.
And step S303, depositing the dielectric layer on the surface of the ridge structure to form the laser prefabricated structure body.
The dielectric layer can be manufactured by adopting plasma enhanced chemical vapor deposition and the like.
After the dielectric layer is manufactured, the dielectric layer is shown in fig. 2.
The present application also provides an interband cascade laser, please refer to fig. 14, comprising:
A substrate 1;
A ridge structure on the upper surface of the substrate 1, wherein the ridge structure comprises a ridge stripe;
the dielectric layer 7 is positioned on the surface of the ridge structure, an electrode window is arranged in the dielectric layer 7, and the electrode window is positioned on the ridge;
the grating 10 is positioned at two sides of the ridge, and the grating 10 is negative photoresist after exposure;
A first electrode 12 located between the gratings 10, on the upper surface of the gratings 10, and on the surface of the dielectric layer 7;
a second electrode 13 located on the lower surface of the substrate 1.
Wherein the ridge structure comprises a first confinement layer 2, a first waveguide layer 3, an active layer 4, a second waveguide layer 5 and a second confinement layer 6, which are laminated in this order in a direction away from the substrate 1.
The substrate 1 includes, but is not limited to, a GaSb substrate 1.
As an embodiment, the dielectric layer 7 includes any one or any combination of a silicon nitride layer, a silicon oxide layer, and a silicon oxynitride layer.
The material of the grating 10 is a negative photoresist after exposure, the property of the negative photoresist is changed after exposure, and the negative photoresist becomes a dielectric material similar to silicon dioxide, and the refractive index is 1.4.
The grating 10 is located on both sides of the ridge and perpendicular to the ridge. Gaps exist between adjacent gratings 10, first electrodes 12 are distributed in the gaps between the adjacent gratings 10, the first electrodes 12 are made of metal, the gratings 10 are made of dielectric materials, namely, an alternating structure of the metal and the dielectric is formed, and the alternating structure can effectively screen wavelengths emitted by a laser.
In one embodiment of the application, the duty cycle of the grating 10 is greater than or equal to 50% and less than 100%. For example, the grating 10 duty cycle may be 50%, 60%, 70%, 75%, 80%, 90%, 95%, etc.
The duty ratio of the grating 10 ranges from 50% to 100%, the grating 10 is relatively more, and the metal between the adjacent gratings 10 is relatively less, so that the absorption of the metal to the laser can be reduced.
In the interband cascade laser of the embodiment, the grating 10 is a negative photoresist after exposure, that is, the manufacturing of the grating 10 can be completed by coating the negative photoresist, exposing and developing, the manufacturing process is simple, the difficulty is low, the influence of the manufacturing of the grating 10 on the yield of the laser can be reduced, and the manufacturing yield of the interband cascade laser is improved. The gaps between adjacent gratings 10 are distributed with first electrodes 12, and the first electrodes 12 between the gratings 10 and the gratings 10 form an alternating conductive/dielectric structure, so that the wavelength emitted by the laser can be effectively screened.
In this specification, each embodiment is described in a progressive manner, and each embodiment is mainly described in a different point from other embodiments, so that the same or similar parts between the embodiments are referred to each other.
The interband cascade laser and the manufacturing method thereof provided by the application are described in detail. The principles and embodiments of the present application have been described herein with reference to specific examples, the description of which is intended only to facilitate an understanding of the inventive arrangements and their core ideas. It should be noted that it will be apparent to those skilled in the art that the present application may be modified and practiced without departing from the spirit of the present application.