Ultra-small vertical cavity surface emitting laser (VCSEL) and arrays incorporating the same
A laser diode includes a semiconductor structure having an n-type layer, an active region, and a p-type layer. One of the n-type and p-type layers includes a lasing aperture thereon having an optical axis oriented perpendicular to a surface of the active region between the n-type and p-type layers. First and second contacts are electrically connected to the n-type and p-type layers, respectively. The first and/or second contacts are smaller than the lasing aperture in at least one dimension. Related arrays and methods of fabrication are also discussed.
1. A Light Detection and Ranging (LIDAR) array, comprising:
a plurality of laser diodes arranged on a non-native substrate, wherein the plurality of laser diodes are freed of a native substrate thereof, wherein the plurality of laser diodes respectively comprise:
a semiconductor structure comprising an n-type layer, an active region, and a p-type layer, one of the n-type and p-type layers comprising a lasing aperture thereon having an optical axis oriented perpendicular to a surface of the active region between the n-type and p-type layers; and
first and second contacts electrically connected to the n-type and p-type layers, respectively, the first and/or second contacts being smaller than the lasing aperture in at least one dimension;
electrically conductive thin-film interconnects that extend along a surface of the non-native substrate and onto the first and/or second contacts to electrically connect the plurality of laser diodes; and
a plurality of driver transistors on a surface of the non-native substrate adjacent the plurality of laser diodes,
wherein the electrically conductive thin-film interconnects electrically connect respective subsets of the plurality of laser diodes in series with respective driver transistors of the plurality of driver transistors,
wherein the plurality of driver transistors are configured to control first and second subsets of the plurality of laser diodes at first and second different non-zero output power levels, respectively.
2. The LIDAR array of claim 1 ,
wherein the at least one dimension comprises length, width, or diameter in plan view.
3. The LIDAR array of claim 1 , wherein, for at least one of the plurality of laser diodes, an entire area of the first and/or second contacts in plan view is smaller than an aperture area of the lasing aperture in plan view.
4. The LIDAR array of claim 1 , wherein, for at least one of the plurality of laser diodes, a ratio of an entire area of the first and/or second contacts to an aperture area of the lasing aperture is between about 0.00167 to about 0.005, between about 0.005 to about 0.1, or between about 0.1 to about 0.33333.
5. The LIDAR array of claim 1 , wherein, for at least one of the plurality of laser diodes, the n-type and p-type layers comprise first and second Bragg reflector layers, respectively, and wherein the at least one of the plurality of laser diodes comprises a vertical cavity surface emitting laser (VCSEL).
6. The LIDAR array of claim 5 , wherein the at least one of the plurality of laser diodes further comprises:
a lateral conduction layer comprising a surface including the semiconductor structure thereon, wherein the lateral conduction layer is distinct from the first and second Bragg reflector layers, and wherein one of the first and second contacts is on the surface of the lateral conduction layer adjacent the semiconductor structure and outside of the first and second Bragg reflector layers.
7. The LIDAR array of claim 1 , wherein the semiconductor structure comprises a residual tether portion and/or a relief feature at a periphery thereof.
8. The LIDAR array of claim 1 , wherein the non-native substrate comprises electrically insulating and/or thermally conducting characteristics, and wherein the plurality of laser diodes are free of electrical connections through the non-native substrate.
9. The LIDAR array of claim 1 , wherein immediately adjacent laser diodes of the plurality of laser diodes are electrically connected in series, and wherein a spacing between the immediately adjacent laser diodes is less than about 150 micrometers, less than about 100 micrometers, or less than about 50 micrometers, and greater than about 10 micrometers.
10. The LIDAR array of claim 1 , wherein the surface of the non-native substrate is planar.
11. The LIDAR array of claim 1 , wherein the surface of the non-native substrate is curved.
12. The LIDAR array of claim 11 , wherein the non-native substrate comprises a flexible material that is bent to define a radius of curvature of the surface.
13. The LIDAR array of claim 1 , wherein the first and second contacts of each of the plurality of laser diodes comprise anode and cathode contacts, respectively, that are smaller than the lasing aperture in the at least one dimension, wherein the electrically conductive thin-film interconnects electrically connect respective ones of the anode and cathode contacts of a subset of the plurality of laser diodes anode-to-cathode, and wherein the subset includes immediately adjacent laser diodes.
14. The LIDAR array of claim 13 , wherein the subset of the plurality of laser diodes that are electrically connected defines a column of the LIDAR array.
15. The LIDAR array of claim 1 , wherein a concentration of the plurality of laser diodes at peripheral portions of the LIDAR array is less than a concentration of the plurality of laser diodes at a central portion of the LIDAR array.
16. The LIDAR array of claim 1 , wherein a distance between the respective driver transistors and the respective subsets is less than about 2 millimeters.
17. The LIDAR array of claim 1 , wherein the first and second contacts are smaller than the lasing aperture in the at least one dimension.