Semiconductor having enhanced carbon doping
View Patent ↗A VCSEL with undoped top mirror. The VCSEL is formed from an epitaxial structure deposited on a substrate. A doped bottom mirror is formed on the substrate. An active layer that includes quantum wells is formed on the bottom mirror. A periodically doped conduction layer is formed on the active layer. The periodically doped conduction layer is heavily doped at locations where the optical energy is at a minimum when the VCSEL is in operation. A current aperture is used between the conduction layer and the active region. An undoped top mirror is formed on the heavily doped conduction layer.
1. A VCSEL comprising:
a substrate;
a bottom DBR mirror disposed on the substrate;
a first conduction layer region of a first conductivity type, the first conduction layer region coupled to the bottom DBR mirror;
an active layer region disposed on the first conduction layer region, the active layer region containing quantum wells;
a doped second conduction layer region of a second conductivity type, the doped second conduction layer region coupled to the active layer region; and
a top mirror coupled to the second conduction layer region,
wherein the second conduction layer region includes a plurality of conduction layers each comprising a dopant including Al and repeated delta doping.
2. The VCSEL as recited in claim 1 , wherein the delta doping includes a common carbon source including at least one of CBr 4 , CCl 4 , and the mixed compounds CBr x Cl 4-x where x is an integer ranging from zero to four, inclusive.
3. The VCSEL as recited in claim 1 , wherein a resulting sheet resistance of the conduction layers in the second conduction layer region is about 250 ohms/square>Rs>100 ohms/square.
4. The VCSEL as recited in claim 1 , wherein the thickness of each of the plurality of conduction layers in the second conduction layer region is about 25 nm.
5. The VCSEL as recited in claim 1 , wherein three conduction layers are included in the second conduction layer region.
6. The VCSEL as recited in claim 1 , wherein the top and bottom mirrors are semiconductor mirrors.
7. The VCSEL as recited in claim 1 , wherein the top and bottom mirrors are dielectric mirrors.
8. The VCSEL as recited in claim 1 , wherein the VCSEL is designed to operate at wavelengths above about 1260 nm.
9. The VCSEL as recited in claim 1 , wherein the VCSEL is designed to operate at wavelengths above about 830 nm.
10. A semiconductor device comprising:
an epitaxial structure having a conduction layer region coupled to a DBR mirror on a substrate and to an active layer region containing quantum wells, the conduction layer region including a first conductor layer and a spacer layer adjacent to the first conductor layer,
wherein the first conductor layer comprises a dopant including Al and repeated delta doping formed using an amphoteric dopant source during epitaxial growth, and
wherein the first conductor layer is doped more heavily than the spacer layer, wherein the spacer layer is modulation doped to enhance conductivity of the conduction layer region.
11. The semiconductor device of claim 10 , wherein strain is applied to one or more of the layers in the conduction layer region.
12. The semiconductor device of claim 11 , wherein the strain is applied using Indium (In).
13. The semiconductor device of claim 11 , wherein the strain is applied using Antimony (Sb).
14. The semiconductor device of claim 10 , wherein the adjacent spacer layer has a higher valence band energy than the first conductor layer.
15. The semiconductor layer of claim 14 wherein the adjacent spacer layer is strained.
16. The VCSEL as recited in claim 1 , wherein at least one spacer layer is positioned among the plurality of conduction layers and wherein the at least one spacer layer is modulation doped to enhance conductivity of the second conduction layer region.
17. The semiconductor device of claim 10 , wherein the amphoteric dopant is carbon.
18. A semiconductor device comprising:
a substrate;
a bottom DBR mirror disposed on the substrate;
a first conduction layer region coupled to the bottom DBR mirror;
an active layer region disposed on the first conduction layer region, the active layer region containing quantum wells;
a second conduction layer region coupled to the active layer region; and
a top mirror coupled to the second conduction layer region,
wherein the second conduction layer region includes a plurality of conduction layers and a plurality of spacer layers, each conduction layer being spaced apart from another of the conduction layers by one of the spacer layers, and
wherein each of the plurality of conductor layers in the second conduction layer region comprises a dopant including Al and repeated delta doping formed during epitaxial growth.