Features of molecular-beam epitaxy and structural properties of AlInSb-based heterostructures

Abstract

AlInSb layers are grown on highly lattice-mismatched GaAs (100) substrates by molecular-beam epitaxy (MBE) and studied in situ by reflection high-energy electron diffraction and ex situ by scanning and transmission electron microscopy (SEM and TEM). It is shown that one feature of AlInSb/GaAs heterostructure features is a high probability of forming microtwins; methods for decreasing their concentration are proposed. To initiate AlInSb growth on GaAs substrates under high lattice-mismatch (∼14.5%) conditions and to stimulate the transition to 2D growth, the GaAs layer surface was preliminarily exposed to an antimony flux followed by deposition of an intermediate AlSb buffer layer. The optimization of initial MBE growth stages of Sb-containing layers on the GaAs surface allows a decrease in the defect density in the GaAs/AlInSb heterostructures more than by two orders of magnitude, including a drastic decrease in the microtwin density. Optimal MBE growth conditions for Al _x Al_{1 − x} Sb are determined in a wide composition range (0 < x < 0.3). The TEM and SEM studies confirm the high structural quality of grown GaAs/AlInSb heterostructures. Hall-effect measurements showed the dependence of the carrier mobility and concentration on the aluminum content in AlInSb layers and allowed preliminary conclusions on scattering mechanisms.