Electronic properties of amorphous silicon and amorphous silicon-germanium alloys

Abstract

We review results obtained by employing two junction capacitance methods—drive‐level capacitance profiling and transient photocapacitance spectroscopy—to a‐Si:H and a‐Si,Ge:H alloy samples. We discuss how these measurements disclose the dominant deep defect bands and their carrier trapping dynamics in both a‐Si:H and the alloy samples. In particular these methods allow us to separate electron from hole processes and provide evidence for the existence of two distinct defect bands in the alloys. The deduced dependence of total defect density vs Ge fraction is found to agree with the predictions of a spontaneous defect formation model.