Drive-level capacitance profiling, transient photo-capacitance and junction transient photo-current measurements were used to characterize the defect-state distribution in H-doped amorphous SiGe films. A combination of the latter 2 methods could distinguish majority-carrier from minority-carrier optical transitions. By comparing the optical spectra of intrinsic samples with those in p-type and n-type samples, it was concluded that significant densities of positively and negatively charged deep defects existed in intrinsic glow-discharge H-doped amorphous SiGe alloys. The measurements also indicated how the density of these charmed defects increased during light-induced degradation, and how they affected recombination processes.

C.C.Chen, F.Zhong, J.D.Cohen, J.C.Yang, S.Guha: Physical Review B, 1998, 57[8], R4210-3