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Origin of the photoluminescence line at 0.8 eV in undoped and Si-doped GaSb grown by MOVPE

We study the low-temperature photoluminescence (PL) of unintentionally doped and Si-doped bulk GaSb grown by low-pressure metal–organic vapour phase epitaxy (MOVPE) from triethylgallium (TEGa), trimethylantimony (TMSb) and silane (SiH4). The background doping with Si in nominally undoped layers is shown to be caused by the TMSb precursor. Intentional Si-doping using silane results in p-doping, a reduction of the material compensation, a substantial decrease in the native acceptor concentration and a dramatic gain in the integral PL intensity compared to unintentionally doped samples. These findings suggest that the Si atoms are incorporated predominantly in the anionic sublattice. The Si-related PL line with a maximum at 0.8 eV observed in the PL spectra of both types of samples at helium temperatures is identified as a transition of a free electron to a neutral acceptor SiSb with an activation energy of ≈9 meV. The PL spectra of GaSb layers with acceptor concentrations approaching 1 × 1017 cm−3, and particularly the ‘blueshift’ of the peak at 0.800 eV with the temperature rise, can be understood by taking into account the impact of large-scale fluctuations in the charged impurity concentration. The established properties of low-pressure MOVPE-grown Si-doped GaSb are promising for the applicability of this material to GaSb-based devices.