Rapid thermal diffusion of zinc into GaAs

Abstract

Rapid thermal diffusion of zinc into semi-insulating GaAs from spin-on Zn doped silica film was performed. Spin-on films act both as Zn diffusion sources and GaAs surface encapsulant layer against decomposition during the rapid thermal diffusion. The very shallowp + layers were obtained at a diffusion temperature of 900° C for 5 sec. Non-alloyed ohmic contacts to thesep + layers were achieved with an average contact resistivity of 2.4 × 10−6 Ω cm2. The interface is very smooth. The zinc diffusion coefficient for rapid thermal diffusion with effective diffusion time of 6 sec at 900° C was numerically calculated from SIMS profiles. In contrast to the common Longini-Weisberg-Blanc model, the rapid thermal diffusion is under nonequilibrium condition. Complications due to interstitial-substitutional nonequilibrium, vacancy supply resulted from the interface stress field, and zinc precipitation are briefly discussed.