Chapter 6 - GaSb/lnAs supperlattices for infrared FPAs

Abstract

Type-II heterojunctions have been found in many applications of electronic devices such as resonant tunneling diodes (RTD) and hot electron transistors. However, perhaps their most important applications are in optoelectronics, and many significant results have been achieved from type-II modulators, detectors, and laser diodes. The band alignment of any heterojunction can be categorized as type-I, type-II staggered, or type-II misaligned. The special band alignment of the type-II heterojunctions provides three important features, which are used in various devices to improve the overall performance of the device. The first feature is that a superlattice with the type-II band structure can have a lower effective bandgap than the bandgap of each layer. The second feature is the spatial separation of the electrons and holes in a type-II heterojunction. The third feature is the zener-type tunneling in a type-II misaligned heterojunction. The active layers of photovoltaic and photoconductive type-II detectors are made from superlattices with a type-II band alignment.