SPECTROSCOPIC STUDIES OF SHALLOW DEFECTS IN MBE GASB

GaSb is an important material for long wavelength optoelectronic technologies, but more information on its defect structure is required. We describe photoluminescence spectroscopy on unintentionally-doped (p-type) GaSb layers. We have resolved several excitonic and associated non-excitonic transitions. We find that the defect structure of some MBE layers exhibit similarity to that of material grown by all other major techniques. However, some defects appear to be unique to MBE growth, and in our best layers these defect transitions dominate. We report behavior of several luminescence features. A temperature dependence and excitation level study of the so-called native double acceptor has been made which confirms the DAP nature of this low temperature transition, and yields the associated donor binding energy. We have demonstrated that the 801 mev line (also unique to MBE), located in the acceptor bound exciton spectral region, is not excitonic in nature, and we comment on the possible origin of this defect.