TYPE-II HETEROJUNCTIONS IN THE GAINASSB-GASB SYSTEM

This article reviews the pioneering investigations of the luminescence and photoelectric phenomena in type II heterojunctions based on the G aInAsSb/GaSb system. This system is remarkable because it is possible to create and study heterojunctions with both staggered and broken-gap alignment, depending on the alloy composition. Type II heterojunction s differ from type I in the existence of adjacent dual quantum wells f or electrons and holes on both sides of the interface. Simultaneous co nfinement of electrons and holes in these wells causes unique optical and electrical properties of such heterojunctions and greatly modifies the characteristics of optoelectronic devices. The review considers t he photo- and electroluminescence spectra of GaInAsSb/GaSb heterojunct ions with staggered band alignment. The importance of tunnelling-assis ted transitions through the interface in the radiative recombination o f confined carriers is shown. The influence of these transitions on th e structure and polarization characteristics of the luminescence spect ra is considered. A new mechanism of photocurrent gain in isotype n-N heterojunctions due to hole confinement at the type II interface is di scussed. Unusual asymmetric electrical properties of type II heterojun ctions with broken-gap band alignment are demonstrated and discussed i n connection with their energy band diagrams. Novel IR light sources a nd photodetectors for the 1.6-4.7 mum spectral range based on the GaIn AsSb/GaSb system are briefly reviewed.