Effects of annealing temperature on the alloying behavior of the AuGe-GaAs〈100〉 interface

Abstract

UV(He I) and X-ray photoelectron spectroscopies (UPS and XPS) were used to examine the alloying behavior of AuGe ohmic contacts to silicon-doped 〈100〉 oriented n-type GaAs substrates. The reacted interface was then revealed by Ar ion sputter depth profiling at room temperature and after annealing in ultra high vacuum at 300°, 500°, or 700°C. The indiffusion of Au and the outdiffusion of Ga and As are evident. Instead of obtaining a maximum peak of the Ge profile on annealing in forming gas, we observed an increase of Ge indiffusion with temperature. The Au indiffusion results in a decrease in the Au 5d splitting and a shift of both levels to higher binding energy. Au-Ga alloy formation is indicated by the Au 4f levels, and is further supported by the observation of the metallic Ga peak. It has been concluded that the sample annealed at 500°C forms the Au-Ga alloy and the compound of As containing Ge more easily than the samples annealed at 300° or 700°C. This result is consistent with the observations of low contact resistance at the annealing temperature of ∼ 500°C for AuNiGe ohmic contacts to n-type GaAs.