An investigation of the passivating effects of hydrogen sulphide on the GaAs(100) surface

In this paper we investigate the passivating effects of exposing a freshly etched GaAs(100) surface to hydrogen sulphide gas. The effectiveness of this passivation procedure is assessed in a comparison between the characteristics of the treated and untreated surface by a range of techniques. Spectra of the treated surface obtained by deep-level transient spectroscopy reveal a significant reduction in the intensity of a peak attributed to interface states, which is clearly detected on the untreated surface. The idealities of the diodes fabricated on the treated surface are comparable with those obtained for diodes fabricated on the freshly etched GaAs(100) surface. Both photoluminescence and Raman spectroscopy measurements also indicate a reduction in the interface state densities of the treated surface compared with the untreated surface. Variations in the effectiveness of the passivation were observed, which appear to depend on the precise procedure followed during the preparation of the surfaces prior to hydrogen sulphide exposure.