Passivation of GaSb single crystal surfaces studied by photoluminescence

GaSb single crystals are the ideal substrates for the growth of InGaAsSb and AlGaAsSb heterostructures to fabricate optoelectronic devices in the medium infrared. GaSb surfaces are highly reactive to oxidation, the oxides grown on their surface have poor conductivity (similar to 10 Omega (-1) cm(-1)) and it produces high surface leak currents; so, the search for passivation layers to prevent such leak currents is crucial for the development of reliable and optimized devices. Different approaches to passivation films were developed; mixtures of H2O2 + citric acid and H2O2 + tartaric acid were used for anodic oxidation. Also, SiO2 films deposited by a sot-get proem were used as passivation layers. In order to test the performance of these layers, the low temperature photoluminescence (PL) spectroscopy was measured in all samples. The FL spectra show a shift of the main emission peak to lower energies and an increase in the Pl, intensity for a factor of up to 9. indicating that a passivation process is taking place in the GaSb surface. These spectra and the origin of the changes in the PL spectra are discussed.