A vertical cavity surface emitting laser array structure

Abstract

The application provides a vertical cavity surface emitting laser array structure, comprising: a substrate, a first ohmic metal layer, a first electrode, a first reflection layer, an active layer, an oxidation layer, a second reflection layer, a second ohmic metal layer and a second electrode which are sequentially stacked; the first ohmic metal layer comprises a plurality of connecting parts and extending parts, the connecting parts and the extending parts are an integral structure; the extending parts are distributed along a first direction and / or a second direction; in the light emitting area, the outermost optical aperture is adjacent to at least one extending part. The application provides a vertical cavity surface emitting laser array structure, which improves the ohmic contact area near the isolation groove position, improves the carrier concentration and further improves the light emitting power of the optical aperture.

Description

A vertical cavity surface-emitting laser array structure Technical Field

[0001] The present invention relates to the field of vertical cavity surface-emitting laser technology, and in particular to a vertical cavity surface-emitting laser array structure. Background Technology

[0002] With the continuous development of science and technology, vertical-cavity surface-emitting lasers (VCSELs) have been widely used. Various VCSEL chips have been widely applied in people's daily life, work and industry, bringing great convenience to people's lives.

[0003] For vertical cavity surface emission laser arrays with multiple emission regions, since the substrate has isolation trenches to isolate the channels between the regions, under the requirement of small size, there is not enough space to place the emission structure in the position near the isolation trench in the emission region. This results in insufficient ohmic contact area near the isolation trench, which in turn leads to a reduction in the emission power in the emission region with isolation trench. Summary of the Invention

[0004] This invention provides a vertical cavity surface-emitting laser array structure that increases the ohmic contact area near the isolation trench, thereby increasing the carrier concentration and thus improving the luminous power of the optical aperture.

[0005] This invention provides a vertical cavity surface-emitting laser array structure, comprising: a substrate, a first ohmic metal layer, a first electrode, a first reflective layer, an active layer, an oxide layer, a second reflective layer, a second ohmic metal layer, and a second electrode, which are sequentially stacked.

[0006] The substrate is divided into multiple light-emitting regions by isolation trenches; the first ohmic metal layer includes multiple connecting portions and extension portions, the connecting portions and the extension portions being an integral structure; within the light-emitting region, the vertical projection of the first electrode on the first ohmic metal layer overlaps with the connecting portion; a first through hole is provided at the overlapping position, and the first electrode is electrically connected to the connecting portion through the first through hole.

[0007] The second reflective layer has a plurality of optical apertures on the side away from the substrate; the second electrode is disposed in the area outside the optical apertures; the second electrode is electrically connected to the second ohmic metal layer through a second through-hole;

[0008] The first electrode extends along a first direction, the second electrode extends along a second direction, and the extension extends along the first direction and / or the second direction; within the light-emitting region, the outermost optical aperture is adjacent to at least one of the extensions, wherein the vertical projection of the optical aperture on the substrate does not overlap with the vertical projection of the first ohmic metal layer on the substrate and the vertical projection of the first electrode on the substrate, and the first direction intersects with the second direction.

[0009] Optionally, the connecting portions adjacent to the outermost optical aperture are interconnected via the extension.

[0010] Optionally, the connecting portions between adjacent first through holes are interconnected via the extension.

[0011] Optionally, the extension is a strip-shaped metal layer.

[0012] Optionally, the arrangement of the optical apertures within the light-emitting area includes equal-spaced and non-equal-spaced arrangements.

[0013] Optionally, the enclosing shape of the isolation trench can be a regular shape or an irregular shape.

[0014] Optionally, it includes a plurality of first electrodes and a plurality of second electrodes, wherein the plurality of first electrodes are arranged along a second direction and the plurality of second electrodes are arranged along a first direction.

[0015] Optionally, the isolation trench is not provided on the substrate between adjacent second electrodes along the first direction.

[0016] Optionally, the distance between the light-emitting apertures on the periphery of the light-emitting area and the adjacent isolation trenches along the first or second direction is equal.

[0017] Optionally, the optical apertures within the light-emitting region are of the same size.

[0018] This invention provides a vertical-cavity surface-emitting laser array structure. An extension is formed by extending outward from the connection point along a first direction X and / or a second direction Y, making the outermost optical aperture adjacent to an extension. This increases the conductive area from the first electrode to the first ohmic metal layer. Current flows from the second electrode through the second ohmic metal layer and through the oxide hole. Due to the low impedance of the extension, the current flows more uniformly along the extension, then through the first via, the first electrode, and to ground. The extension increases the ohmic contact area near the isolation trench, increasing the carrier concentration and thus improving the luminous power of the outer optical aperture. Attached Figure Description

[0019] Figure 1 is a top view of a vertical cavity surface-emitting laser array structure provided in an embodiment of the present invention.

[0020] Figure 2 is a schematic diagram of the cross-sectional structure of part AA' in Figure 1;

[0021] Figure 3 is a schematic diagram of the cross-sectional structure of the BB' part in Figure 1;

[0022] Figure 4 is a schematic diagram of the direction of current from the second electrode to the first ohmic metal layer in the prior art;

[0023] Figure 5 is a schematic diagram of the direction of current from the second electrode to the first ohmic metal layer according to an embodiment of the present invention;

[0024] Figure 6 is a top view of another vertical cavity surface-emitting laser array structure provided in this embodiment of the invention;

[0025] Figure 7 shows a top view of another vertical cavity surface-emitting laser array structure provided in this embodiment of the invention;

[0026] Figure 8 is a schematic diagram of another direction of current from the second electrode to the first ohmic metal layer provided by an embodiment of the present invention;

[0027] Figure 9 shows a top view of another vertical cavity surface-emitting laser array structure provided by the embodiments of the present invention. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] For vertical cavity surface emission laser arrays with multiple emission regions, isolation trenches are required to isolate the channels between the regions. Therefore, under the requirement of small size, there is not enough space to place ohmic metal layers, electrodes and connecting vias and other light-emitting structures in the position near the isolation trench in the light-emitting region. This results in insufficient ohmic contact area near the isolation trench, which in turn leads to a reduction in the light-emitting power in the light-emitting region with the isolation trench.

[0030] In view of this, Figure 1 is a top view of a vertical cavity surface-emitting laser array structure provided by an embodiment of the present invention, Figure 2 is a cross-sectional view of part AA' in Figure 1, and Figure 3 is a cross-sectional view of part BB' in Figure 1. Referring to Figures 1 and 3, the structure includes: a substrate 1, a first ohmic metal layer 2, a first electrode 110, a first reflective layer 3, an active layer 4, an oxide layer 5, a second reflective layer 6, a second ohmic metal layer 7, and a second electrode 120, which are stacked sequentially.

[0031] The substrate 1 is divided into multiple light-emitting regions by isolation trenches 130; the first ohmic metal layer 2 includes multiple connecting portions 201 and extension portions 202, which are integral structures; in the light-emitting region, the vertical projection of the first electrode 110 on the first ohmic metal layer 2 overlaps with the connecting portion 201; a first through hole 150 is provided at the overlapping position, and the first electrode 110 is electrically connected to the connecting portion 201 through the first through hole 150;

[0032] The second reflective layer has a plurality of optical apertures 140 on the side away from the substrate 1; a second electrode 120 is provided in the area outside the optical apertures 140; the second electrode 120 is electrically connected to the second ohmic metal layer 2 through a second through hole.

[0033] The first electrode 110 extends along the first direction X, the second electrode 120 extends along the second direction Y, and the extension 202 extends along the first direction X and / or the second direction Y. In the light-emitting region, the outermost optical aperture 140 is adjacent to at least one extension 202, wherein the vertical projection of the optical aperture 140 on the substrate 1 does not overlap with the vertical projection of the first ohmic metal layer 2 on the substrate 1 and the vertical projection of the first electrode 110 on the substrate 1, and the first direction X intersects with the second direction Y.

[0034] Specifically, the vertical-cavity surface-emitting laser (VCSEL) array structure includes a substrate 1, a first ohmic metal layer 2, a first electrode 110, a first reflective layer 3, an active layer 4, an oxide layer 5, a second reflective layer 6, a second ohmic metal layer 7, and a second electrode 120, which are stacked sequentially. To improve insulation and resistance to water and oxygen, a passivation layer 11 is added between the first ohmic metal layer 2 and the first electrode 110, and between the second reflective layer 6 and the second ohmic metal layer 7. Isolation trenches 130 are formed on the substrate 1, serving as isolation boundaries to delineate the respective light-emitting regions. Within the light-emitting region, multiple independent optical apertures 140 are provided on the side of the second ohmic metal layer 7 away from the substrate 1. For example, the optical apertures 140 can be evenly spaced within the light-emitting region to ensure uniform surface emission. Oxide holes extending from the second reflective layer 6 to the active layer 4 are provided below the optical apertures 140. The relative positions of the optical apertures 140 and the oxide holes are the same, allowing for unified processing during fabrication and reducing manufacturing complexity.

[0035] Typically, the first reflective layer 3 and the second reflective layer 6 are doped with n-type and p-type materials, or p-type and n-type materials. To inject charge carriers into the active layer 4, electrical contact regions need to be applied to the n-type and p-type doped sides of the pin junction. An ohmic metal layer is formed by depositing conductive materials at different heights in the layer structure. The first ohmic metal layer 2 includes a connection portion 201. The vertical projection of the first electrode 110 onto the first ohmic metal layer 2 overlaps with the connection portion 201. A first via 150 is provided at the overlapping position, and the first via 150 is filled with conductive material. The first electrode 110 is electrically connected to the connection portion 201 through the first via 150. For example, the connection portion 201 can be circular, and its size is at least larger than the size of the first via 150. The area outside the optical aperture 140 covers the second electrode 120, and the second electrode 120 is electrically connected to the second ohmic metal layer 7 through the second via.

[0036] Referring again to Figure 1, in the vertical-cavity surface-emitting laser (VCSEL) array structure, the first electrode 110 extends along the first direction X, and the second electrode 120 extends along the second direction Y. Exemplarily, the first electrode 110 can extend along the first direction X as a strip electrode with a regular or irregular shape, and the second electrode 120 can extend along the second direction Y as a strip electrode with a regular or irregular shape. The first direction X intersects the second direction Y, and the angle between them can be selected based on the distribution of the optical aperture 140 and the design requirements of the VCSEL array structure. For ease of understanding, exemplaryly, in this embodiment of the invention, the first direction X is perpendicular to the second direction Y. Figure 4 is a schematic diagram of the direction of current from the second electrode 120 to the first ohmic metal layer in the prior art. In the prior art, the optical aperture 140 is usually arranged around the first through hole 150, so that the current flows from the second electrode 120 through the second ohmic metal layer, through the oxide hole, the first ohmic metal layer 2, the first through hole 150, and the first electrode 110 to the ground, so that the optical aperture 140 emits light. When the optical aperture 140 is arranged near the isolation trench 130, there is not enough space to place the first ohmic metal layer 2, the first electrode 110 and the first through hole 150 and other light-emitting structures, which results in insufficient ohmic contact area of ​​the oxide hole corresponding to the optical aperture 140 near the isolation trench 130, low carrier concentration and reduced light emission power. Therefore, the first ohmic metal layer 2 also includes an extension 202. The extension 202 and the connecting portion 201 are integral metal layer structures of the same layer. The extension 202 extends outward from the connecting portion 201 along the first direction X and / or the second direction Y. The outermost optical aperture 140 is adjacent to an extension 202, thereby increasing the conductive area from the second electrode 120 to the first ohmic metal layer 2. Taking the first direction X and the second direction Y as perpendicular as an example, the extension 202 extends outward from the connecting portion 201 along the first direction X and / or the second direction Y. Therefore, the first electrode 110 and the extension 202 form a cross shape. The optical aperture 140 is set in the area divided by the cross shape with the connecting portion 201 as the reference. The optical apertures 140 in the light-emitting area form a matrix arrangement. In the outermost optical aperture 140, there is an extension 202 between adjacent optical apertures 140, thereby increasing the conductive area from the second electrode 120 to the first ohmic metal layer 2 of the outermost optical aperture 140. Figure 5 is a schematic diagram of the direction of current from the second electrode to the first ohmic metal layer provided by an embodiment of the present invention. Referring to Figure 5, the current flows from the second electrode 120 through the second ohmic metal layer and through the oxide hole. Due to the low impedance of the extension 202, it flows more uniformly along the extension 202, and then flows from the first through hole 150 and the first electrode 110 to ground. The extension 202 increases the ohmic contact area near the isolation trench 130, increases the carrier concentration, and thus increases the light emission power of the optical aperture 140.

[0037] This invention provides a vertical-cavity surface-emitting laser array structure. An extension is formed by extending outward from the connection point along a first direction X and / or a second direction Y, making the outermost optical aperture adjacent to an extension. This increases the conductive area from the first electrode to the first ohmic metal layer. Current flows from the second electrode through the second ohmic metal layer and through the oxide hole. Due to the low impedance of the extension, the current flows more uniformly along the extension, then through the first via, the first electrode, and to ground. The extension increases the ohmic contact area near the isolation trench, increasing the carrier concentration and thus improving the luminous power of the outer optical aperture.

[0038] Optionally, Figure 6 provides a top view of another vertical cavity surface-emitting laser array structure according to an embodiment of the present invention. Referring to Figure 6, the connecting portions 201 adjacent to the outermost optical aperture 140 are interconnected by extension portions 202. That is, the outermost connecting portions 201 are interconnected by extension portions 202, and the connecting portions 201 are connected in a ring shape, thereby increasing the conductive area between the connecting portions 201 of the outermost optical aperture 140, further increasing the carrier concentration and thus increasing the emission power of the outermost optical aperture 140.

[0039] Optionally, Figure 7, an embodiment of the present invention, also provides a top view of another vertical cavity surface-emitting laser array structure. Referring to Figure 7, the connecting portions 201 between adjacent first through-holes 150 are interconnected by extension portions 202. That is, the connecting portions 201 within the light-emitting region are all interconnected by extension portions 202, thereby increasing the conductive area between the connecting portions 201 of the optical aperture 140 within the light-emitting region, further increasing the carrier concentration and thus increasing the luminous power of the light-emitting region.

[0040] Based on the above embodiments, Figure 8 is a schematic diagram of the direction of current from the second electrode 120 to the first ohmic metal layer provided by the embodiment of the present invention. Referring to Figure 8, the current flows from the second electrode 120 through the second ohmic metal layer and through the oxide hole. Due to the low impedance of the extension 202, it passes more evenly along the surrounding extension 202, and then flows from the first through hole 150 and the first electrode 110 to the ground. The extension 202 increases the ohmic contact area near the isolation trench 130, increases the carrier concentration, and thus increases the light emission power of the optical aperture 140.

[0041] Optionally, the extension 202 is a strip-shaped metal layer. The extension 202 extends outward from the connecting portion 201 along the first direction X and / or the second direction Y. The outermost optical aperture 140 is adjacent to the extension 202, thereby increasing the conductive area from the second electrode 120 to the first ohmic metal layer 2. The extension 202 uses a strip-shaped metal layer to reduce the process area of ​​the extension 202, so that the extension 202 can be arranged in the space near the isolation trench 130. During the light emission process, the current flows from the second electrode 120 through the second ohmic metal layer and through the oxide hole. Due to the low impedance of the extension 202, it flows more evenly along the extension 202, and then flows from the first through hole 150 and the first electrode 110 to the ground. The extension 202 increases the ohmic contact area near the isolation trench 130, increases the carrier concentration, and thus increases the light emission power of the optical aperture 140.

[0042] Optionally, the first electrode 110 is a strip electrode. Specifically, the first electrode 110 can be multiple strip electrodes, which are arranged in parallel along the first direction X. The first electrode 110 may also include an electrode pad 111, which is integrally formed with the strip electrode. The electrode pad 111 serves to lead out signals and connect to external circuits for easy array control.

[0043] For example, there are multiple first electrodes 110 and multiple second electrodes 120, with the multiple first electrodes 110 arranged along a second direction Y and the multiple second electrodes 120 arranged along a first direction X.

[0044] The first electrode 110 can extend in the first direction X as a strip electrode, and the second electrode 120 can extend in the second direction Y as a strip electrode. Multiple first electrodes 110 can be arranged sequentially in the second direction Y, and multiple second electrodes 120 can be arranged sequentially in the first direction X. Combined with the boundary of the isolation trench 130, zoned light-emitting regions are obtained, such as light-emitting region A, light-emitting region B, light-emitting region C, and light-emitting region D in Figure 1.

[0045] Optionally, Figure 9 provides a top view of another vertical cavity surface-emitting laser array structure according to an embodiment of the present invention. Referring to Figure 9, the arrangement of the optical apertures 140 in the light-emitting region includes equidistant and non-equidistant arrangements. Specifically, based on the angle setting between the first direction X and the second direction Y, and the shape design of the extension 202, the optical apertures 140 can be arranged in various ways in the light-emitting region. Among them, equidistant arrangements include square arrays, rectangular arrays, and staggered arrangements of the optical apertures 140 in the first direction X or the second direction Y. Non-equidistant arrangements can include random arrangements obtained according to the light-emitting requirements, and arrangements with periodic changes in spacing along a certain direction, thereby meeting different design requirements for light-emitting power.

[0046] Optionally, the shape of the isolation trench 130 can be a regular shape such as a rectangle, circle, triangle, parallelogram, or regular polygon. It can also be adjusted according to the light-emitting aperture and semiconductor layout structure to obtain an irregular shape, thereby reducing the size between each light-emitting area.

[0047] Optionally, isolation trenches 130 are not provided on the substrate 11 between adjacent second electrodes 120 along the first direction X. Specifically, the isolation trenches 130 between two adjacent second electrodes 120, i.e., the isolation trenches 130 marked by the dashed box, can be omitted, and the second electrodes 120 alone serve as the divider between adjacent light-emitting regions. For example, taking Figure 1 as an example, when the first first electrode 110 is energized and the first second electrode 120 is energized, the first light-emitting region can emit light, while the second light-emitting region will not emit light due to the separation by the adjacent second electrodes 120, which also serves to divide the light-emitting regions.

[0048] Optionally, the distances between the light-emitting apertures on the periphery of the light-emitting area and the adjacent isolation trenches 130 along the first direction X or the second direction Y are equal. The light-emitting apertures are uniformly arranged within the light-emitting area, such as in a matrix arrangement or with equal spacing. The distances between the centers of the light-emitting apertures on the periphery of a light-emitting area and the adjacent isolation trenches 130 along the first direction X or the second direction Y are also equal, improving the light emission uniformity at the edge of the light-emitting area. Optionally, the optical apertures 140 within the light-emitting area have the same size, which also improves light emission uniformity and ensures process uniformity, reducing the difficulty of fabrication to some extent.

[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A vertical-cavity surface-emitting laser array structure, characterized in that, include: A substrate, a first ohmic metal layer, a first electrode, a first reflective layer, an active layer, an oxide layer, a second reflective layer, a second ohmic metal layer, and a second electrode are sequentially stacked. The substrate is divided into multiple light-emitting regions by isolation trenches. The first ohmic metal layer includes multiple connecting portions and extension portions, which are integrally formed. Within each light-emitting region, the vertical projection of the first electrode onto the first ohmic metal layer overlaps with the connecting portion. A first through-hole is provided at the overlapping position, through which the first electrode is electrically connected to the connecting portion. The second reflective layer has a [missing information - likely a component or structure]. Multiple optical apertures; a second electrode is disposed in the region outside the optical apertures; the second electrode is electrically connected to the second ohmic metal layer through a second through-hole; the first electrode extends along a first direction, the second electrode extends along a second direction, and the extensions extend along the first and / or second directions; in the light-emitting region, the outermost optical aperture is adjacent to at least one of the extensions, wherein the vertical projection of the optical aperture on the substrate does not overlap with the vertical projection of the first ohmic metal layer on the substrate and the vertical projection of the first electrode on the substrate, and the first direction intersects the second direction.

2. The vertical-cavity surface-emitting laser array structure according to claim 1, characterized in that, The connecting portions adjacent to the outermost optical aperture are interconnected via the extension portions.

3. The vertical-cavity surface-emitting laser array structure according to claim 1, characterized in that, The connecting portions between adjacent first through holes are connected to each other via the extension portions.

4. The vertical-cavity surface-emitting laser array structure according to claim 1, characterized in that, The extension is a strip-shaped metal layer.

5. The vertical-cavity surface-emitting laser array structure according to claim 1, characterized in that, The arrangement of the optical apertures within the light-emitting area includes equal-spaced and non-equal-spaced arrangements.

6. The vertical-cavity surface-emitting laser array structure according to any one of claims 1-5, characterized in that, The enclosure shape of the isolation trench can be a regular shape or an irregular shape.

7. The vertical-cavity surface-emitting laser array structure according to claim 6, characterized in that, It includes a plurality of first electrodes and a plurality of second electrodes, wherein the plurality of first electrodes are arranged along a second direction; and the plurality of second electrodes are arranged along a first direction.

8. The vertical-cavity surface-emitting laser array structure according to claim 7, characterized in that, The isolation trench is not provided on the substrate between adjacent second electrodes along the first direction.

9. The vertical-cavity surface-emitting laser array structure according to claim 6, characterized in that, The distance between the light-emitting apertures in the outer periphery of the light-emitting area and the adjacent isolation trenches along the first or second direction is equal.

10. The vertical-cavity surface-emitting laser array structure according to claim 1, characterized in that, The optical apertures within the light-emitting region are of the same size.

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