Tailoring crystalline orientation in GaSb films on GaAs via Sb-controlled antimonidation of ultrathin Al layers

The integration of high-quality GaSb layers on GaAs substrates presents a promising route for developing antimonide-based optoelectronic devices on cost-effective platforms. In this work, we investigate the influence of antimony (Sb) flux during the low-temperature antimonidation process, which is proposed to promote Al–Sb reactions and the formation of an AlSb-like interlayer, on the crystallographic orientation as well as the electrical and optical properties of GaSb films subsequently grown on GaAs (001) substrates. Three samples with varying Sb supply conditions were analyzed using high-resolution x-ray diffraction, scanning transmission electron microscopy, and photoluminescence (PL) spectroscopy. Our results suggest that sufficient Sb flux during this initial stage favors the formation of a highly crystalline interlayer with dominant (002) characteristics, which, in turn, enables the subsequent epitaxial growth of GaSb with a (001) orientation. In contrast, reduced or absent Sb flux results in unfavorable (111) or mixed orientations, degraded crystalline quality, and diminished PL intensity. Electrical characterization further confirms that improved crystal orientation correlates with lower sheet resistance and higher carrier mobility. These findings highlight the critical role of Sb availability during antimonidation in determining the performance of GaSb-based heterostructures on GaAs substrates.