Ruthenium and sulphide passivation of GaAs

Abstract

The effectiveness of chemical surface treatment of GaAs using (NH₄)₂S_x, 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)₂S_x 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 L_p increased from 0.54 to 0.70 μ m due to reduction of the surface recombination velocity S_r from 5.0 × 10⁵ to 2.1 × 10⁵ cm s^-1. The Au/GaAs Schottky barrier height also increased from 0.80 to 0.92 eV for RuCl₃ and (NH₄)₂S_x passivated samples.