Passivation of GaSb single crystal surfaces studied by photoluminescence

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