Polarity inversion of type-II InAs/GaSb superlattice photodiodes
The subject invention comprises the realization of P-on-N type II InAs/GaSb superlattice photodiodes. A high-quality InAsSb layer lattice-mismatched to GaSb is used as a buffer to prepare the surface of the substrate prior to superlattice growth. The InAsSb layer also serves as an effective n-contact layer. The contact layer has been optimized to improve device performance, most notably performance that is similar to traditional N-on-P structures.
1. An infrared detector, comprising:
a substrate;
a buffer layer on the substrate;
an InAsSb n-doped contact layer on the buffer layer substrate;
a type-II superlattice of 12 monolayers of InAs and 7 monolayers of GaSb having InSb interfaces on the InAsSb n-doped contact, said superlattice comprising a lower n-doped region, an intermediate p-doped region and an upper p-doped region, and a p-doped GaSb contact layer on the superlattice structure.
2. The infrared detector device of claim 1 wherein the substrate is GaSb.
3. The infrared detector device of claim 2 wherein the GaSb substrate is p-type.
4. The infrared detector device of claim 1 wherein the buffer layer is un-doped.
5. The infrared detector device of claim 1 wherein the type-II superlattice consists of a lower 0.45 μm thick n-doped region, an intermediate 1.9 μm thick slightly p-doped region, and an upper 0.48 μm thick p-doped region.
6. The infrared detector device of claim 1 wherein the p-doped GaSb contact layer has a thickness within the range of 100 nm to 250 nm.