RUTHENIUM AND SULFIDE PASSIVATION OF GAAS

The effectiveness of chemical surface treatment of GaAs using (NH4)(2) S-x, Na2S and RuCl3 has been studied through X-ray photoelectron spect roscopy (XPS), photoluminescence (PL), spectral response and barrier h eight measurements. XPS studies show that the improved surface quality is due to removal of native oxides and formation of bonds with S in t he case of(NH4)(2)S-x and Na2S and Ru in the case of RuCl3. It was fou nd that Ga-S or Ga-Ru and As-S or As-Ru bonds were formed with sulphid e and ruthenium treatments, respectively. The PL intensity increased b y 70-90% with modification in all cases. The minority carrier diffusio n length L(p) increased from 0.54 to 0.70 mu m due to reduction of the surface recombination velocity S-r from 5.0 X 10(5) to 2.1 X 10(5) cm s(-1). The Au/GaAs Schottky barrier height also increased from 0.80 t o 0.92 eV for RuCl3, and (NH4)(2)S-x passivated samples.