Thermal stability of WSi<i>x</i>/GaAs interface

Abstract

Secondary ion mass spectrometry (SIMS), Rutherford backscattering spectrometry (RBS), and measurements of forward current-voltage characteristics at various temperatures were used to study metallurgical reactions in WSix/GaAs formed by sputter deposition. Both SIMS and RBS showed that annealing at 800 °C results in migration of W and Si into GaAs when the atomic ratio x deviates from 0.5. On the other hand, the forward current-voltage characteristics of WSix/GaAs diodes at various temperatures showed that the excess current across the interface induced after annealing is large when x deviates substantially from 0.5, in agreement with the SIMS and RBS results. It is suggested that the migration of W and Si is directly involved in the thermal degradation of the structural and electrical properties of the WSix/GaAs interface and its x dependence.