Review of virtual substrate technologies for 6.3 Ångström lattice constants

Virtual substrates with lattice constants in the range mid-way between InAs and InSb have been developed using molecular beam epitaxy (MBE). The III–V alloys in this range are of particular interest for narrow bandgap device applications, such as infrared detection. In all cases, GaSb was used as the real substrate and the lattice constant was increased using linear, analog grades of GaInSb or AlGaInSb. We determined the resulting threading dislocation density with x-ray topography in InAsSb films grown on top. We describe the importance of defect reduction for determination of basic materials properties, such as fundamental bandgap, give examples of new device structures that are enabled by this technology, and discuss future directions for possible further improvements.