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.