Evidence for charged defects in intrinsic glow-discharge hydrogenated amorphous-silicon–germanium alloys

Abstract

We have applied drive-level capacitance profiling, transient photocapacitance, and junction transient photocurrent measurements to characterize the defect-state distribution for a set of device-quality glow-discharge a-Si,Ge:H films. The combination of the latter two methods can distinguish majority- from minority-carrier optical transitions. Comparing the optical spectra of intrinsic samples with those in p-type and n-type samples, we have concluded that significant densities of positively and negatively charged deep defects exist in intrinsic glow-discharge a-Si,Ge:H alloys. Our measurements also indicate how the density of these charged defects increase upon light-induced degradation and how they affect carrier recombination processes. {copyright} {ital 1998} {ital The American Physical Society}