Detailed Description
Other advantages and effects of the present invention will become apparent to those skilled in the art from the following disclosure, which describes the embodiments of the present invention with reference to specific examples. The invention may be practiced or carried out in other embodiments that depart from the specific details, and the details of the present description may be modified or varied from the spirit and scope of the present invention.
It should be noted that, the illustrations provided in the present embodiment only illustrate the basic concept of the present invention by way of illustration, but only the components related to the present invention are shown in the illustrations, rather than being drawn according to the number, shape and size of the components in actual implementation, and the form, number, positional relationship and proportion of each component in actual implementation may be changed at will on the premise of implementing the present technical solution, and the layout of the components may be more complex.
Example 1
Example 1
The present embodiment provides a light emitting diode, as shown in fig. 1, which includes a semiconductor stack 200, an insulating reflective layer 300 disposed over the semiconductor stack 200, and an electrode structure disposed over the insulating reflective layer 300. In an alternative embodiment, the light emitting diode further comprises a substrate 100, and the material of the substrate 100 may be sapphire, silicon carbide, silicon or gallium nitride. In this embodiment, the substrate 100 is exemplified as a sapphire substrate.
Referring also to fig. 1, the above-described semiconductor stack 200 is located above the substrate 100 and includes a first semiconductor layer 201, an active layer 202, and a second semiconductor layer 203 stacked in this order from bottom to top. The first semiconductor layer 201, the active layer 202 and the second semiconductor layer 203 may include a iii-V nitride semiconductor, for example, may include a nitride semiconductor such as (A1, ga, in). The first semiconductor layer 201 may include n-type impurities (e.g., si, ge, sn), and the second semiconductor layer 203 may include p-type impurities (e.g., mg, sr, ba). It is understood that the dopants of the first semiconductor layer 201 and the second semiconductor layer 203 may also be reversed from those described above. The active layer 202 may include a multiple quantum well structure (MQW), and the active layer 202 may emit a desired wavelength by adjusting a composition ratio of the nitride-based semiconductor.
The semiconductor stack 200 is formed with a mesa structure to expose a portion of the surface of the first semiconductor layer 201 for subsequent formation of an electrode structure. The shape of a portion of the surface of the first semiconductor layer 201 exposed by the mesa structure of the semiconductor stack 200 may be arbitrary, and the mesa structure may be an open mesa structure or a closed mesa structure of a hole type structure.
Referring also to fig. 1, the insulating reflective layer 300 is located above the semiconductor stack 200, i.e. on the side of the second semiconductor layer 203 of the semiconductor stack 200, and covers at least the surface of the semiconductor stack 200. In this embodiment, the insulating reflective layer 300 covers the surface and sidewalls of the semiconductor stack 200, and further covers the exposed substrate 100 surface from the sidewalls of the semiconductor stack 200. The insulating reflective layer 300 protects the semiconductor stack 200 from external moisture or contaminants to ensure good optical and electrical performance of the light emitting diode. Alternatively, the insulating reflective layer 300 may be a single-layer structure, whose refractive index is lower than that of the semiconductor stack 200, and may reflect light emitted from the semiconductor stack 200, for example, a SiO2 layer, a SiNx layer, or the like, or the insulating reflective layer 300 may be a multi-layer structure, for example, two layers formed by combining a SiO2 layer and a SiNx layer, or may be a DBR structure formed by alternately stacking two material layers with different refractive indexes, for example, any one of TiO2、Nb2O5、Ta2O5、HfO2、ZrO2 and ZnO, and any one of SiO2、MgF2、A12O3 and SiON, and in an alternative embodiment, the thickness of the DBR structure is 1 μm to 10 μm, further, 0.3 μm to 5 μm,1 μm to 2 μm, or 4 μm to 5 μm, or 2 μm to 6 μm.
As shown in fig. 1, a first opening 301 and a second opening 302 are formed in the insulating reflective layer 300, the first opening 301 is located above the exposed first semiconductor layer 201 in the semiconductor stack 200, and the second opening 302 is located above the second semiconductor layer 203. An electrode structure of the light emitting diode is located above the insulating reflective layer 300, and includes a first electrode 400 connected to the first semiconductor layer 201 and a second electrode 500 connected to the second semiconductor layer 203. In this embodiment, as shown in fig. 1, the first electrode 400 includes a first contact electrode 401 and a first connection electrode 402, and the first contact electrode 401 is formed over the first semiconductor layer 201 with the mesa structure exposed. The first contact electrode 401 may be a single metal material layer or a plurality of metal material layers, for example, one or a combination of any of nickel, gold, chromium, titanium, platinum, palladium, chromium, aluminum, tin, indium, but copper, diamond, iron, nail, error, tungsten, molybdenum. In alternative embodiments, al, cr/Al or Ni/Al structures may be used. The first contact electrode 401 forms a good ohmic contact with the first semiconductor layer 201, thereby ensuring good electrical performance of the light emitting diode. In addition, in the process of etching the insulating reflective layer 300 to form the first opening, the first contact electrode 401 may serve as an etching stop layer, thereby ensuring etching accuracy of the first opening 301 and preventing damage to the first semiconductor layer 201 due to over-etching. As shown in fig. 1, the first opening 301 is formed over the first semiconductor layer 201 and the bottom thereof exposes the first contact electrode 401, and the first connection electrode 402 is filled to the point that the first opening 301 is connected to the first contact electrode 401 at the bottom of the first opening 301 and extends over the insulating reflective layer 300 at the periphery of the first opening 301.
Referring also to fig. 1, the second electrode 500 includes a second connection electrode 501, the second connection electrode 501 including a contact layer 5011 and a connection layer 5012, wherein the contact layer 5011 is filled to the second opening 302 to be electrically connected with the second semiconductor layer 203, and the connection layer 5012 is formed over the contact layer 5011 to be connected with the contact layer 5011. Optionally, a current diffusion layer 204 is further formed between the second semiconductor layer 203 and the insulating reflective layer 300, where the current diffusion layer 204 is a transparent conductive material layer, for example, may be Indium Tin Oxide (ITO), indium Zinc Oxide (IZO), aluminum doped zinc oxide transparent conductive glass (AZO), and the like, and the bottom of the second opening 302 exposes the current diffusion layer 204. The current diffusion layer 204 covers at least a portion of the surface of the second semiconductor layer 203 to diffuse the current as uniformly as possible to the surface of the second semiconductor layer 203, thereby improving the light emitting effect.
Meanwhile, in order to prevent concentration of current at the second semiconductor layer 203 under the second opening 302, a current blocking layer 205 is disposed between the second semiconductor layer 203 and the current diffusion layer 204, and the current blocking layer 205 is a layer of insulating material, such as SiO2 and/or SiN material, or the like. In order to ensure the electrical connection between the current diffusion layer 204 and the second semiconductor layer 203 and the current diffusion effect of the current diffusion layer 204, the current blocking layer 205 is formed as a patterned structure, i.e. not entirely covering the second semiconductor layer 203, for example, the current blocking layer 205 is located under the second opening 302, and is formed as an island-like or block-like structure, and the current diffusion layer 204 covers the surface and the sidewalls of the current blocking layer 205. When the current blocking layer 205 is located below the second opening 302 and is formed in an island-like or block-like structure, the projected area of the contact layer 5011 is larger than the projected area of the current blocking layer 205 below the second opening 302 on the plane where the surface of the semiconductor stack 200 is located, and the projected area of the current blocking layer 205 below the second opening 302 is located within the projected range of the contact layer 5011. Thereby facilitating lateral diffusion of current from the contact layer 5011 along the current spreading layer.
As described above, the current diffusion layer 204 is formed between the second semiconductor layer 203 and the insulating reflective layer 300, and thus the bottom of the second opening 302 includes the current diffusion layer 204, i.e., the bottom of the second opening 302 is located on the surface of the current diffusion layer 204, or the bottom of the second opening 302 is located inside the current diffusion layer 204, but does not penetrate the current diffusion layer 204. In an alternative embodiment, the thickness of the current diffusion layer 204 is betweenFurther, betweenOr is betweenWhen the bottom of the second opening 302 is located inside the current diffusion layer 204, i.e., when the second opening 302 extends inside the current diffusion layer 204, the second opening 302 extends to a depth in the current diffusion layer 204 that is less than or equal toFurther, betweenAnd ensures that the current spreading layer 204 is not penetrated. The contact layer 5011 fills the second opening 302 to be connected with the current spreading layer 204 exposed at the bottom of the second opening 302 to realize electrical connection with the second semiconductor layer 203.
In this embodiment, the contact layer 5011 of the second connection electrode 501 is formed as a multilayer structure containing an Al layer, such as a Ni/Al/Ti/Pt stacked structure or a Cr/Al/Ti/Pt stacked structure. As described above, the contact layer 5011 is filled in the second opening 302, wherein the Ni layer or the Cr layer can increase the adhesion between the contact layer 5011 and the current diffusion layer 204, and form good ohmic contact with the current diffusion layer 204, thereby ensuring the electrical performance of the light emitting diode. Meanwhile, the Al layer in the contact layer 5011 has a reflecting effect, so that the reflectivity of the contact layer 5011 can be increased, the reflection effect of the insulating reflection layer 300 lost due to the formation of the second opening 302 can be compensated, the reflection effect of the light radiated by the semiconductor laminated layer 200 can be further increased, and the light emitting effect of the light emitting diode can be improved.
Referring also to fig. 1, a connection layer 5012 is formed over the insulating reflective layer 300 and covers and connects the contact layer 5011. The connection layer 5012 may be a single metal material layer or a plurality of metal material layers, and may be a stacked structure of Al, ti, ni, cr, pt or the like, for example. The connection layer 5012 contains an Al layer, and the thickness of the Al layer is greater than that of Al in the contact layer 5011, so that the connection electrode 5012 has a high reflectivity, and can form a total reflection structure with the insulating reflection layer 300, thereby increasing the reflection efficiency of light radiated from the semiconductor stack 200 and improving the light emitting effect.
As described above, the contact layer 5011 and the connection layer 5012 can each form a multilayer structure, and can each include an Al layer. In an alternative embodiment, the thickness of the contact layer 5011 is defined as T1, the thickness of the Al layer in the contact layer 5011 is T1a, the thickness of the connection layer 5012 is T2, and the thickness of the Al layer in the connection layer 5012 is T2a, wherein 200nm is less than or equal to T1 is less than or equal to 500nm,1500nm is less than or equal to T2 is less than or equal to 5000nm, t1a= (0.1 to 0.6) ×t1, t2a= (0.2 to 0.8) ×t2, and t1a= (0.1 to 0.5) ×t2a. The contact layer 5011 and the connection layer 5012 have good adhesion and good reflection effects, and good conductive effects due to the arrangement of the Al layers and the thickness of the respective Al layers.
In another alternative embodiment, the connection layer 5012 is a multi-layered structure including a transparent conductive layer and an Ag layer, and the transparent conductive layer and the current diffusion layer 204 formed over the second semiconductor layer 203 are the same or different material layers, for example, may be ITO material layers. The projection of the transparent conductive layer in the connection layer 5012 does not overlap or intersect with the projection of the contact layer 5011 by projection onto the plane on which the surface of the semiconductor stack 200 is located. That is, the transparent conductive layer in the connection layer 5012 is not formed over the contact layer 5011, thereby avoiding the resulting excessively high voltage of the light emitting diode.
In an alternative embodiment of the present embodiment, as shown in fig. 2 and 3, the contact layer 5011 fills the second opening 302 and extends above the insulating reflective layer 300 at the periphery of the second opening 302. Specifically, referring to fig. 3, the sidewall of the second opening 302 includes a first segment 3021 and a second segment 3022, the insulating reflective layer 300 on the periphery of the second opening 302 is formed as a mesa structure 3023, and the first segment 3021 is formed as an inclined sidewall, for example, an angle α between the inclined sidewall and a plane of the current diffusion layer 204 at the bottom of the second opening 302 is between 40 ° and 70 °, and further between 40 ° and 50 °, and between 50 ° and 60 °. The second section 3022 is a connecting section of the first section 3021 and the platform structure 3023, which is formed as a smooth transition section, which may be formed as a rounded or curved transition section, for example. The contact layer 5011 covers the first and second segments 3021 and 3022 and part of the mesa structure 3023, forming a "T" -shaped structure.
In an alternative embodiment, the second opening 302 is formed as a circular hole having a circular cross-section, defining a bottom radius R1 and a top opening radius R2 of the second opening 302. As shown in fig. 4, the projection of the contact layer 5011 is a circular structure, and the radius of the contact layer 5011 is defined as R3, wherein r2= (1.5 to 3) R1, r3= (1 to 3) R1, and r3+.. Specifically, R1 is about 2 μm to 6 μm, for example about 4 μm, R2 is about 3 μm to 8 μm, for example about 6 μm, and R3 is about 3 μm to 10 μm, for example about 8 μm. The above arrangement of the contact layer 5011 can make the aperture of the second opening 302 smaller to a certain extent, and at the same time, ensure that the contact layer 5011 and the second semiconductor layer 203 form a good electrical connection, and the contact layer 5011 not only covers the bottom of the second opening 302 and the first section 3021 and the second section 3022, but also is formed on a part of the platform structure 3023, so as to increase the reliability of the contact layer 5011 and increase the reflective area thereof. The connection layer 5012 covers the contact layer 3011 and also covers a part of the insulating reflection layer 300 around the contact layer 5011, which is advantageous for improving the adhesion between the contact layer 5011 and the connection layer 5012. As shown in fig. 3, in the actual product, the contact layer 5011 can well fill the second opening 302, i.e. uniformly cover the bottom and the side wall of the second opening 302, and can uniformly extend to above the part of the insulating reflective layer 300 at the periphery of the second opening 302.
In the light emitting diode, the number of the second openings 302 may be plural, and the connection layer 5012 of the second connection electrode 501 may be formed to communicate with the contact layer 5011 at the plural second openings 302 as needed. Since the first opening 301 is formed over the mesa-exposed first semiconductor layer 201, the surface area of the mesa is generally small in order to secure a sufficient light emitting area of the light emitting diode, and thus one first opening 301 is generally formed at one mesa. As schematically shown in fig. 4, the projection from the second connection electrode 501 toward the semiconductor stack 200 direction, it can be seen that the projected area of the connection layer 5012 is larger than the projected area of the contact layer 5011, and the projection of the contact layer 5011 is located within the projected range of the connection layer 5012, whereby good contact between the connection layer 5012 and the contact layer 5011 can be ensured. Specifically, the connection layer 5012 communicates with the contact layers 5011 at the plurality of second openings 302, and the projected area of each portion of the connection layer 5012 is larger than the projected area of the contact layer 5011 with which it communicates.
Referring again to fig. 1, the light emitting diode of the present embodiment further includes a first insulating protection layer 601 and a pad electrode 700, wherein the first insulating protection layer 601 is located above the electrode structure and the insulating reflective layer 300, and specifically, the first insulating protection layer 601 covers the first connection electrode 402 and the second connection electrode 501, and the exposed surface of the insulating reflective layer 300, and further covers the sidewall of the insulating reflective layer 300. The first insulating protective layer 601 may be a material layer formed of any one or more of SiO2、SiN、Al2O3 and the like, or may have the same material layer as the insulating reflective layer 300. The first insulating protection layer 601 further insulates the light emitting diode and protects the light emitting diode from impurities and dust, further ensures mutual insulation of the first connection electrode 402 and the second connection electrode 501, and prevents the light emitting diode from being polluted or damaged by external dust, water vapor and the like.
The pad electrode 700 is positioned above the first insulating protective layer 601, the pad electrode 700 includes a first pad 701 and a second pad 702 disposed at intervals, the first pad 701 is connected to the first electrode 400 through the first insulating protective layer 601, and the second pad 702 is connected to the second electrode through the first insulating protective layer 601. Specifically, the first pad 701 is connected to the first connection electrode 402, and the second pad 702 is connected to the second connection electrode 501. The shape and number of the first pads 701 and the second pads 702 can be selected according to actual needs. The pad electrode 700 may be one or a combination of any of gold, titanium, platinum, palladium, chromium, aluminum, tin, indium, copper.
Example two
The present embodiment also provides a light emitting diode, as shown in fig. 5, which includes a semiconductor stack 200, an insulating reflective layer 300 disposed over the semiconductor stack 200, and an electrode structure disposed over the insulating reflective layer 300. The same points as those of the first embodiment are not described in detail, and the difference is that:
As shown in fig. 5, the light emitting diode of the present embodiment omits the first contact electrode 401 over the first semiconductor layer 201, and the first electrode 400 (or the first connection electrode 402) is directly filled in the first opening 301 to be in direct contact with the first semiconductor layer 201. The first contact electrode 401 is omitted, and then the first connection electrode 402 and the second connection electrode 501 can be prepared simultaneously in the same step, which reduces the complexity of the manufacturing process of the light emitting diode and is beneficial to reducing the cost.
Example III
The present embodiment also provides a light emitting diode, as shown in fig. 6, which includes a semiconductor stack 200, an insulating reflective layer 300 disposed over the semiconductor stack 200, and an electrode structure disposed over the insulating reflective layer 300. The same points as those of the first or second embodiment will not be described again, and the difference is that:
The second connection electrode 501 of the second electrode 500 in the present application is formed in a multi-layered structure, and the second connection electrode 501 is filled in the second opening 302 to be electrically connected to the second semiconductor layer 203. The second connection electrode 501 includes at least a transparent adhesive layer 5013 and a reflective layer 5014 positioned over the transparent adhesive layer 5013 in a direction gradually away from the insulating reflective layer 300. Wherein the transparent adhesion layer 5013 is a material layer capable of forming good contact with the current diffusion layer 204 above the second semiconductor layer 203, preferably a transparent material layer, for example, a transparent material layer such as ITO or GTO, further, the transparent adhesion layer 5013 may be the same material layer as the current diffusion layer 204 above the second semiconductor layer 203, so as to further increase adhesion and ohmic contact therebetween. In an alternative embodiment, the current diffusion layer 204 is ITO or GTO, and has a thickness betweenFurther, betweenThe current diffusion layer 204 with the thickness range can reduce the absorption of visible light on the basis of ensuring good current diffusion effect and forming good contact with the transparent adhesion layer 5013, thereby being beneficial to improving the light emitting efficiency of the light emitting diode. Although not shown in detail in fig. 6 in this embodiment, it is to be understood that the current blocking layer 205 described in embodiment one is also formed between the current diffusion layer 204 and the second semiconductor layer 203.
The reflective layer 5014 of the second connection electrode 501 is a metal material layer having high reflectivity, such as an Ag layer or an Al layer. Optionally, the reflective layer 5014 is an Ag layer, which has a higher reflectivity, can increase the reflection of light and improve the light emitting effect of the light emitting diode, and has a better adhesion with the transparent adhesive layer 5013, thereby improving the connection reliability and the stability of the light emitting diode. In an alternative embodiment, the thickness of the transparent adhesive layer 5013 is betweenFurther betweenIn addition to the transparent adhesive layer 5013 and the reflective layer 5014, the second connection electrode 501 may further include other metal layers, such as a single layer or a plurality of material layers Ti, pt, ni, au, formed over the reflective layer 5014.
In an alternative embodiment, the insulating reflective layer 300 is in a DBR structure, and the first opening 301 and the second opening 302 are formed by etching the insulating reflective layer 300 by ICP dry etching, in this process, in order to avoid excessive ITO loss during over etching, the dry etching is performed by combining fast etching with slow etching, and the ratio of the rate of the last section of etching DBR to the rate of ITO is 300:1 to 50:1, and the etching process can ensure that the current diffusion layer 204 is not affected by etching or is not damaged by any accident, so that the current diffusion layer 204 can be made thinner while ensuring good ohmic contact, for example, the thickness can be controlled to be in a range ofThe etching angle of the DBR is 40-70 °, and the etching angle can ensure good opening characteristics of the first opening 301 and the second opening 302 in the DBR structure, especially the first opening 301, so that the first semiconductor layer 201 exposed by the first opening 301 after etching can be repaired through the first opening 301, and good photoelectric performance of the first semiconductor layer is ensured.
In an alternative embodiment, to ensure good adhesion of the DBR structure to the current spreading layer 204 and reflective efficiency of the DBR, a layer of SiO2 is first deposited on the surface of the semiconductor stack 200, the SiO2 layer having a thickness betweenIn this embodiment, the DBR structure is formed by stacking TiO2 and SiO2 on each other, and the thickness of the DBR structure is 2 μm to 6 μm. The DBR structure with this thickness has good reflectivity, especially at the side wall of the first opening 301, and can reflect the light radiated to the side wall to the light exit surface as much as possible, so as to reduce the side wall light leakage and other light loss.
The above-described structure of the second connection electrode 501 can satisfy both of good ohmic contact with the current diffusion layer 204 over the second semiconductor layer 203 and a sufficiently high reflection effect for visible light. The second electrode 500 and the insulating reflective layer 300 in this embodiment form a total reflection structure, which can realize high reflection of visible light in a full-band and wide-angle manner, and realize higher quantum efficiency.
Example IV
The present embodiment also provides a light emitting diode, as shown in fig. 7, which includes a semiconductor stack 200, an insulating reflective layer 300 disposed over the semiconductor stack 200, and an electrode structure disposed over the insulating reflective layer 300. The same points as those of the third embodiment are not described in detail, and the difference is that:
As shown in fig. 7, in the present embodiment, the first electrode 400 includes a first contact electrode 401 formed over the mesa-exposed first semiconductor layer 201 and a first connection electrode 402 located over the insulating reflective layer 300. The first opening 301 exposes the first contact electrode 401, and the first connection electrode 402 fills the first opening 301 to be connected with the first contact electrode 401. Alternatively, the first contact electrode 401 may be a metal capable of forming a good ohmic contact with the first semiconductor layer 201, and may be Al, cr/Al, ni/Al, or the like. The first contact electrode 401 can be used as a stop layer for etching in addition to forming a good ohmic contact with the first semiconductor layer 201. When the insulating reflective layer 300 is etched to form the first opening 301, damage to the first semiconductor layer 201 (e.g., N-type GaN) caused by the etching is avoided. Further, the opening length of the first opening 301 is smaller than the bottom length of the first contact electrode 401, and the etching angle of the insulating reflective layer 300 is set to be 40 ° to 70 °, so that when the insulating reflective layer 300 is etched to form the first opening 301, the bottom of the first opening 301 is not formed outside the first contact electrode 401, and the first semiconductor layer 201 is prevented from being damaged by etching.
Example five
The present embodiment also provides a light emitting diode, as shown in fig. 8, which includes a semiconductor stack 200, an insulating reflective layer 300 disposed over the semiconductor stack 200, and an electrode structure disposed over the insulating reflective layer 300. The same points as those of the third embodiment are not described in detail, and the difference is that:
As shown in fig. 8, the light emitting diode of the present embodiment further includes a pad electrode 700, and the pad electrode 700 includes a first pad 701 electrically connected to the electrode structure first electrode 400 and a second pad 702 electrically connected to the electrode structure second electrode 500. A second insulating protective layer 602 is further formed between the pad electrode 700 and the electrode structure. Specifically, the second insulating protection layer 602 covers at least the surfaces and sidewalls of the first connection electrode 402 and the second connection electrode 501 to block Ag diffusion in the second connection electrode 501, and ensure the reflective effect of the second connection electrode 501 and the photoelectric properties of the semiconductor stack 200. Further, the second insulating protection layer 602 covers the surfaces and sidewalls of the second connection electrode 501 and the second connection electrode 402, and the exposed surfaces and sidewalls of the insulating reflective layer 300. The second insulating protection layer 602 includes at least an Al2O3 layer and an SiO2 layer formed by atomic layer deposition stacked in this order in a direction from the second connection electrode 501 to the second pad 702. The thickness of Al2O3 formed by atomic layer deposition is betweenFurther, betweenThe thickness of the SiO2 layer is 1 μm to 3 μm4, further 1 μm to 2 μm, 2 μm to 3 μm5. The thickness of the second insulating protection layer 602 is set so that it can well prevent Ag migration in the second connection electrode 501, and at the same time further protects the light emitting diode from external moisture or contaminants, and in addition, can absorb as little light as possible radiated from the semiconductor stack 200.
The second insulating protection layer 602 is formed with a via hole over the first semiconductor layer 201 and over the second semiconductor layer 203 to expose the first connection electrode 402 and the second connection electrode 501. The through hole above the first semiconductor layer 201 penetrates through the second insulating protection layer 602 to expose the first connection electrode 402, and the through hole above the second semiconductor layer 203 penetrates through the second insulating protection layer 602 to expose the second connection electrode 501. The first pad 701 and the second pad 702 fill the above-described through holes, respectively, to be connected with the first connection electrode 402 and the second connection electrode 501, respectively. The first pad 701 and the second pad 702 are spaced above the second insulating protection layer 602, and may have the same material composition, and thus may be formed through the same deposition step. Alternatively, the first pad 701 and the second pad 702 may be Al, cr/Al, or Ni/Al structural layers.
Example six
The present embodiment also provides a light emitting diode, as shown in fig. 9, which includes a semiconductor stack 200, an insulating reflective layer 300 disposed over the semiconductor stack 200, and an electrode structure disposed over the insulating reflective layer 300. The same points as those of the fifth embodiment are not described in detail, and the difference is that:
As shown in fig. 9, the first electrode 400 of the light emitting diode of the present embodiment further includes a first contact electrode 401 formed over the mesa-exposed first semiconductor layer 201. The first opening 301 exposes the first contact electrode 401, and the first connection electrode 402 fills the first opening 301 to be connected with the first contact electrode 401. Alternatively, the first contact electrode 401 may be a metal capable of forming a good ohmic contact with the first semiconductor layer 201, and may be Al, cr/Al, ni/Al, or the like. The first contact electrode 401 can be used as a stop layer for etching in addition to forming a good ohmic contact with the first semiconductor layer 201. When the insulating reflective layer 300 is etched to form the first opening 301, damage to the first semiconductor layer 201 (e.g., N-type GaN) caused by the etching is avoided. Further, the opening length of the first opening 301 is smaller than the bottom length of the first contact electrode 401, and the etching angle of the insulating reflective layer 300 is set to be 40 ° to 70 °, so that when the insulating reflective layer 300 is etched to form the first opening 301, the bottom of the first opening 301 is not formed outside the first contact electrode 401, and the first semiconductor layer 201 is prevented from being damaged by etching.
Example seven
The present embodiment also provides a light emitting diode, as shown in fig. 10, which includes a semiconductor stack 200, an insulating reflective layer 300 disposed over the semiconductor stack 200, and an electrode structure disposed over the insulating reflective layer 300. The same points as those of the sixth embodiment are not described in detail, and the difference is that:
The second electrode of the light emitting diode of this embodiment includes a second connection electrode 501 and a second contact electrode 502, where the second contact electrode 502 is located above the second semiconductor layer 203, and the second opening 302 in the insulating reflective layer 300 exposes the second contact electrode 502. The second connection electrode 501 is filled into the second opening 302 to be connected with the second contact electrode 502. In an alternative embodiment, the thickness of the second connection electrode 501 is 3 μm to 8 μm, and further, 4 μm to 7 μm or 4 μm to 6 μm.
In addition, in the present embodiment, a third insulating protective layer 603 is formed between the insulating reflective layer 300 and the semiconductor stack 200, and the third insulating protective layer 603 covers at least the surfaces and sidewalls of the first contact electrode 401 and the second contact electrode 502. Further, the surfaces and sidewalls of the first contact electrode 401 and the second contact electrode 502 and the surfaces and sidewalls of the semiconductor stack 200 are covered, and further, extend to the exposed substrate 100 surface. The insulating reflective layer 300 is formed over the third insulating protective layer 603, and in this embodiment, the thickness of the insulating reflective layer 300 is 4 μm to 10 μm. The second contact electrode 502 includes a layer of Ag material.
In an alternative embodiment, the third insulating protection layer 603 includes at least an Al2O3 layer and/or an SiO2 layer formed by atomic layer deposition that are stacked in sequence. Wherein the thickness of the Al2O3 layer is betweenThe thickness of the SiO2 layer is betweenFurther, betweenThe material selection and thickness of the third insulating protection layer 603 are set so that the third insulating protection layer can well block Ag diffusion and migration in the second contact electrode 502, and ensure good reflection effect of the second contact electrode 502 and good photoelectric effect of the semiconductor epitaxial lamination.
In order to increase the reflection effect of the insulating reflective layer 300, in this embodiment, the thickness of the insulating reflective layer 300 is 1 μm to 10 μm, and further, 2 μm to 6 μm. While making the thickness of the current diffusion layer 204 betweenWhile ensuring a good current diffusion effect, the light absorption phenomenon is reduced as much as possible, so that more light can be reflected by the second electrode 500 and the insulating reflective layer 300 as outgoing light of the light emitting diode.
As also shown in fig. 10, through holes communicating with the first opening 301 and the second opening 302, respectively, are also formed in the third insulating reflective layer 603. The first connection electrode 402 of the first electrode 400 is located above the insulating reflective layer 300, and fills the first opening 301 and the through hole in the third insulating protective layer 603 to connect with the first contact electrode 401. The second connection electrode 501 of the second electrode 500 is located above the insulating reflective layer 300, and fills the second opening 302 and the through hole in the third insulating protective layer 603 to connect with the second contact electrode 502. The second connection electrode 501 may be Al or Cr/Al stack or Ni/Al stack, and its thickness is 3 μm to 8 μm. This thickness setting can increase the reflection effect.
The second contact electrode 502 should not be too small, if it is too small, the overlay error in the process may cause the second contact electrode 502 and the second opening 302 not to correspond well, so that on one hand, the current diffusion layer 204 may be damaged due to over etching, on the other hand, the connection reliability between the second connection electrode 501 and the first contact electrode 502 may be degraded, which affects the electrical performance of the light emitting diode, and on the other hand, the area of the second contact electrode 502 should not be too large, because the DBR reflectivity is larger than the reflectivity of the second contact electrode 502, if the area of the second contact electrode 502 is too large, the light reflected by the insulating reflective layer 300 may be reduced, which affects the light emitting efficiency of the light emitting diode. Thus, in an alternative embodiment, as shown in fig. 10, the radius of the top opening of the second opening 302 is R2, which defines a circular projection of the second contact electrode 502, and the radius of the second contact electrode 502 is R4, where r4=r2 to (r2+8 μm). As described above, the area of the second contact electrode 502 is controlled to be slightly larger than or equal to the opening size of the second opening 302, so that it can be ensured that the current diffusion layer 204 under the second contact electrode 502 is protected from being etched when the DBR is dry etched to form the second opening 300, the integrity and the current diffusion effect are ensured, and at the same time, as much light as possible can be reflected by the insulating reflective layer 300, and the light emitting effect of the light emitting diode is improved.
As shown in fig. 11, compared with the prior art that the Cr/Al material is used as the metal layer directly contacting the current diffusion layer 204, the formation of the second contact electrode 502 increases the reflectivity at the second electrode 500 from less than 75% to more than 90%, especially in the wavelength band of 420 nm-500 nm, and the reflectivity reaches more than 95% in the visible light range of more than 520nm, so that the above characteristics of the second electrode 500 reduce the absorption of light and improve the optical performance of the chip. Meanwhile, the second contact electrode 502 (e.g. Ag) and the current diffusion layer 204 on the second semiconductor layer 203 can form good ohmic contact, so that the voltage of the light emitting diode is lower and the light efficiency is improved.
Example eight
The present embodiment provides a semiconductor light emitting device, as shown in fig. 12, the light emitting device 900 includes a circuit substrate 201 and a plurality of light emitting units 902 electrically connected to the circuit substrate 901, wherein the light emitting units 902 are the semiconductor light emitting elements provided in the first embodiment. As also shown in fig. 12, the circuit substrate 910 has several sets of pads 905. The pad electrode 700 of each light emitting cell 902 is electrically connected to a set of pads 905. In addition, a wiring layer 903 is provided in the circuit board 901, and the light emitting unit 902 is electrically connected to the wiring layer 903 via a pad 905. As shown in fig. 12, the light emitting device 900 may further include a housing 904 to protect the light emitting unit from external contamination or damage while not affecting the light emitting effect of the light emitting unit. The wiring layer and the bonding pad area of the light-emitting diode increase the bonding force for fixing the light-emitting diode to the bonding pad, and improve the reliability of the device.
The above embodiments are merely illustrative of the principles of the present invention and its effectiveness, and are not intended to limit the invention. Modifications and variations may be made to the above-described embodiments by those skilled in the art without departing from the spirit and scope of the invention. Accordingly, it is intended that all equivalent modifications and variations of the invention be covered by the claims, which are within the ordinary skill of the art, be within the spirit and scope of the present disclosure.