Patent ID: 8076700

Claim:
A device comprising: a GaSb substrate, wherein the GaSb substrate is undoped; a AlSb layer on the GaSb substrate, wherein the AlSb layer is undoped; a In 0.69 Al 0.31 As 0.41 Sb 0.59 layer with a top side and a bottom side, wherein the bottom side is on the AlSb layer and wherein the In 0.69 Al 0.31 As 0.41 Sb 0.59 comprises varying levels of Te doping; and a In 0.27 Ga 0.73 Sb layer on the In 0.69 Al 0.31 As 0.41 Sb 0.59 layer, wherein the In 0.27 Ga 0.73 Sb layer is doped with Be; wherein the In 0.69 Al 0.31 As 0.41 Sb 0.59 layer is about 1.2 μm thick and consists of a first section of about 0.1 μm from the bottom side; a second section of about 0.1 μm from the first section; and a third section of about 1 μm from the second section; wherein the first section of about 0.1 μm of the In 0.69 Al 0.31 As 0.41 Sb 0.59 layer from the bottom side has about 1.3×10 17 Te cm −3 ; wherein the second section of about 0.1 μm of the In 0.69 Al 0.31 As 0.41 Sb 0.59 layer from the first section has a grade in Te concentration; and wherein the third section of about 1 μm of the In 0.69 Al 0.31 As 0.41 Sb 0.59 layer from the second section has about 4×10 16 Te cm −3 .