Radiative-recombination transitions in sulphur-doped GaSb

Photoluminescence (PL) of sulphur-doped gallium antimonide prepared by a liquid-phase-electro-epitaxy growth method was investigated. Pumping-intensity-dependent and temperature-dependent PL measurements were carried out, properties of individual spectral bands were studied, and their physical origin was specified in detail. Sulphur caused compensation in GaSb, which is usually p-type if it is undoped due to the high concentration of its characteristic native acceptor (NA). As a result of compensation, recombination occurred under the condition of a fluctuating potential and spectral properties characteristic for such a material state were observed. Three bands formed the low-temperature PL spectra. Band AU, connected with the NA, exhibited extremely low peak energy for some samples (down to 765 meV). Together with the presence of a “moving” PL, with a moving rate of approximately 10 meV per decade of the pumping intensity, it is a direct consequence of perturbed energy bands. Band S, peaking at about 732 meV, is a characteristic one for sulphur-doped GaSb and is most probably connected with a sulphur-donor-to-valence-band transition. The thermal decay of the band agrees with this supposition. Intensity-dependent and temperature-dependent PL of band AI (maximum at 705–710 meV) both indicate that the band is connected with the ionised NA. PL intensity of the peak is relatively high, because compensation enhances the concentration of such centres.