Studies of GaSb-capped InAs/AlSb quantum wells by resonant raman scattering

Abstract

We have used resonant Raman scattering to study GaSb-capped AlSb/InAs/AlSb quantum wells grown by molecular-beam epitaxy. The shutter sequence for the growth of the InAs/AlSb heterointerfaces was such as to promote the formation of an InSb-like interface. Scattering by an InSb-like mode at ⋍ 190 cm −1 is found to resonate at approximately the InAs E 1/ E 1 + Δ 1 gap energy, supporting its assignment to an interface mode. Resonance effects in scattering by longitudinal optical (LO) phonons enabled us also to distinguish between scattering by the almost degenerate LO phonon modes in the InAs quantum well and in the GaSb cap layer. The GaSb and the AlSb one-LO phonon spectra indicate the unintentional incorporation of As at concentrations up to 18–19% in the GaSb and AlSb layers for As background pressures in the growth chamber exceeding 10 −9 torr. The incorporation of As was confirmed independently by secondary ion mass spectroscopy.