Ternary and quaternary alloy III-V antimonide (InAsSb and InAsSbP) virtual substrates made by liquid-phase epitaxy

Thick (>100 µm) epitaxial layers of ternary and quaternary alloy III–V antimonides (e.g. InAsSb, InGaSb, AlGaAsSb, InGaAsSb and InAsSbP) can function as ‘virtual’ substrates for mid-infrared optoelectronics applications. Such alloy substrates have adjustable lattice constants and bandgaps, and are therefore of considerable interest for epitaxial growth of lattice-matched or strain-engineered epitaxial device structures, including mid-infrared detectors and light-emitting diodes. Liquid-phase epitaxy (LPE) methods can be readily adapted for the growth of such III–V antimonide virtual substrates due to the fast growth rates (1 to 10 µm/min) that are achievable with III–V antimonide LPE. The authors report on the development of InAsSb and InAsSbP virtual substrates consisting of two or three thick compositionally step-graded epitaxial layers grown by LPE on InAs substrates. Through this approach, ternary and quaternary alloy virtual substrates are obtained, with lattice constants and bandgaps significantly different from those currently available with binary compound substrates, including virtual substrates with optical absorption edges in the 4–5 µm wavelength range.