An Auger electron spectroscopy study of annealed gold contacts to InP

Auger electron spectroscopy operated in different modes was used in this study to obtain information on the annealed Au/InP system. Noticeable lateral spreading of gold contacts was observed after 400 °C annealing, with the most dramatic edge effects visible between 430 and 500 °C annealing. It was further observed that for the annealed contacts the interface region between the InP and the gold consists mostly of an AuP compound. However, the outer surface of the annealed contact contains mostly AuIn-rich compounds, together with regions where the AuP compound extends to the top surface. For contacts annealed at 500 °C a “swallow hole” occurs where the gold contact originally was. This effect is related to the decomposition of the AuP compound, with the resultant out-diffusion of phosphorus. A model is also proposed to explain the change in shape of the predominantly circular AuP mixture (at 450 °C) to the perfect square structures after 500 °C annealing.