DIFFUSION OF SILICON IN ION IMPLANTED GaAs

Silicon is the main n-type dopant used in GaAs, and it is usually incorporated into GaAs by ion implantation or by diffusion employing an external source. Ion implantation is also the only convenient way of introducing impurities exceeding the solid solubility limit. However, ion implantation studies have been done earlier only for concentrations under 10 atoms/cm [1,2]. Experimentally it has been observed that Si diffusion in GaAs is concentration-dependent. In this work we have applied Fermi-level effect model proposed by Yu et al. [3]. The purpose of this paper is to explain high concentration Si diffusion in GaAs. The implantation dose used in this study is considerably higher than in earlier studies and the annealings also extend to lower temperatures. The solid solubility of substitutional Si in GaAs as a function of temperature is given, and the observed exponential behavior is explained qualitatively.