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 GaInAsSb/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 heterojunctions differ from type I in the existence of adjacent dual quantum wells for electrons and holes on both sides of the interface. Simultaneous confinement 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 the photo- and electroluminescence spectra of GaInAsSb/GaSb heterojunctions with staggered band alignment. The importance of tunnelling-assisted transitions through the interface in the radiative recombination of confined carriers is shown. The influence of these transitions on the structure and polarization characteristics of the luminescence spectra is considered. A new mechanism of photocurrent gain in isotype n-N heterojunctions due to hole confinement at the type II interface is discussed. Unusual asymmetric electrical properties of type II heterojunctions with broken-gap band alignment are demonstrated and discussed in connection with their energy band diagrams. Novel IR light sources and photodetectors for the 1.6-4.7 mum spectral range based on the GaInAsSb/GaSb system are briefly reviewed.