Ruthenium and sulphide passivation of GaAs

The effectiveness of chemical surface treatment of GaAs using (NH4)2Sx, Na2S and RuCl3 has been studied through X-ray photoelectron spectroscopy (XPS), photoluminescence (PL), spectral response and barrier height measurements. XPS studies show that the improved surface quality is due to removal of native oxides and formation of bonds with S in the case of (NH4)2Sx and Na2S and Ru in the case of RuCl3. It was found that GaS or GaRu and AsS or AsRu bonds were formed with sulphide and ruthenium treatments, respectively. The PL intensity increased by 70–90% with modification in all cases. The minority carrier diffusion length Lp increased from 0.54 to 0.70 μm due to reduction of the surface recombination velocity Sr from 5.0 × 105 to 2.1 × 105 cm s−1. The AuGaAs Schottky barrier height also increased from 0.80 to 0.92 eV for RuCl3 and (NH4)2Sx passivated samples.