Systems and methods for series-connected VCSEL array
A VCSEL array comprises series-connected VCSEL sub-arrays formed on a single chip. The VCSEL sub-arrays each comprises VCSEL emitters fabricated on a semi-insulating layer. A common cathode contact of a VCSEL sub-array is electrically connected to a common anode contact of a neighboring VCSEL sub-array. To reduce leakage, the bandgap energy level of the semi-insulating layer is higher than the photon energy of the output beam. In one embodiment, the semi-insulating layer is grown on a conductive layer. A common cathode contact of the last VCSEL sub-array in a series is electrically connected to the conductive layer. In another embodiment, multiple wire-bonding areas are electrically connected to common anode contacts of multiple VCSEL sub-arrays respectively. The wire-bonding areas provide different input impedance options for a VCSEL array.
1 . A Vertical Cavity Surface Emitting Laser (VCSEL) array for generating a laser beam, comprising:
an isolation layer, the isolation layer at least electrically semi-insulating;
a plurality of VCSEL sub-arrays formed in an area on the isolation layer and including at least a first sub-array and a second sub-array, the first sub-array comprising a plurality of VCSEL structures connected in parallel with a common cathode contact and a common anode contact, each VCSEL structure comprising a first reflector region over the isolation layer, a current and/or optical confining structure, an active region over the first reflector region, a second reflector region over the active region, and a first metal layer over and electrically connected to the second reflector region, first metal layers of the plurality of VCSEL structures of the first sub-array being physically connected, the first and second sub-arrays separated by an isolation structure; and
a metal structure electrically connecting the common cathode contact of the first sub-array and a common anode contact of the second sub-array, the metal structure being made of a metallic material.
2 . The VCSEL array of claim 1 , wherein a bandgap energy level of the isolation layer is higher than photon energy of the laser beam.
3 . The VCSEL array of claim 1 , wherein each VCSEL structure further comprises a conductive layer between the isolation layer and the first reflector region.
4 . The VCSEL array of claim 3 , wherein the first sub-array further comprises a second metal layer formed on the conductive layer.
5 . The VCSEL array of claim 4 , wherein the second metal layer is electrically connected to the common cathode contact of the first sub-array.
6 . The VCSEL array of claim 4 , wherein the second metal layer is formed in a hole that exposes the conductive layer.
7 . The VCSEL array of claim 6 , wherein the metal structure is formed on a wall of the hole.
8 . A Vertical Cavity Surface Emitting Laser (VCSEL) array for generating a laser beam, comprising:
an isolation layer, the isolation layer at least electrically semi-insulating, a bandgap energy level of the isolation layer higher than photon energy of the laser beam;
a plurality of VCSEL sub-arrays formed in an area on the isolation layer and including at least a first sub-array and a second sub-array, the first sub-array comprising a plurality of VCSEL structures connected in parallel with a common cathode contact and a common anode contact, each VCSEL structure comprising a first reflector region over the isolation layer, a current and/or optical confining structure, an active region over the first reflector region, a second reflector region over the active region, and a first metal layer over and electrically connected to the second reflector region, first metal layers of the plurality of VCSEL structures of the first sub-array being physically connected, the first and second sub-arrays separated by an isolation structure; and
a metal structure electrically connecting the common cathode contact of the first sub-array and a common anode contact of the second sub-array, the metal structure being made of a metallic material.
9 . The VCSEL array of claim 8 , wherein each VCSEL structure further comprises a conductive layer between the isolation layer and the first reflector region.
10 . The VCSEL array of claim 9 , wherein the first sub-array further comprises a second metal layer formed on the conductive layer.
11 . The VCSEL array of claim 10 , wherein the second metal layer is electrically connected to the common cathode contact of the first sub-array.
12 . The VCSEL array of claim 10 , wherein the second metal layer is formed in a hole that exposes the conductive layer.
13 . The VCSEL array of claim 12 , wherein the metal structure is formed on a wall of the hole.
14 . A method for forming a Vertical Cavity Surface Emitting Laser (VCSEL) array, comprising:
forming an isolation layer, the isolation layer at least electrically semi-insulating;
forming a plurality of VCSEL sub-arrays including at least a first sub-array and a second sub-array and in an area on the isolation layer, the first sub-array comprising a plurality of VCSEL structures connected in parallel with a common cathode contact and a common anode contact, each VCSEL structure comprising a first reflector region over the isolation layer, a current and/or optical confining structure, an active region over the first reflector region, a second reflector region over the active region, and a first metal layer over and electrically connected to the second reflector region, first metal layers of the plurality of VCSEL structures of the first sub-array being physically connected, the first and second sub-arrays separated by an isolation structure; and
forming a metal structure by depositing a metallic material, the metal structure electrically connecting the common cathode contact of the first sub-array and a common anode contact of the second sub-array.
15 . The method of claim 14 , wherein a bandgap energy level of the isolation layer is higher than photon energy of the laser beam.
16 . The method of claim 14 , wherein each VCSEL structure further comprises a conductive layer between the isolation layer and the first reflector region.
17 . The method of claim 16 , wherein the first sub-array further comprises a second metal layer deposited on the conductive layer.
18 . The method of claim 17 , wherein the second metal layer is electrically connected to the common cathode contact of the first sub-array.
19 . The method of claim 17 further comprising forming a hole to expose the conductive layer, wherein the second metal layer is deposited in the hole.
20 . The method of claim 19 , wherein the metal structure is formed on a wall of the hole.