Optimisation of the ammonium sulphide (NH4)2S passivation process on In0.53Ga0.47As

The passivation of III–V semiconductor materials with sulphur is widely reported to reduce interface state defects and improve semiconductor device performance. The most common approach utilises ammonium sulphide ((NH4)2S), however there are wide variations in the reported processing parameters involved in this procedure. This study provides a comprehensive review of the various parameters used as well as determining the optimal processing conditions in terms of sample pre-treatments, temperature of the (NH4)2S solution, length of time the sample is in the solution and (NH4)2S concentration, by measuring the level of residual native oxides and surface roughness by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM), respectively.