The planned research falls roughly into two categories. The first will utilize junction capacitance and ESR spectroscopy to study defect properties in various kinds of amorphous samples. First, they will extend their recent very successful studies of single heterojunction c-Si/a-Si:H structures to investigate contamination effects at the interface, and also to heterostructures of a-Si,Ge:H alloy layers on crystalline substrates. They thus hope to identify trends in the interface defect structure and in band offsets. They will continue their work with doping superlattice samples and also to initiate studies of heterostructure multilayer films. They also wish to characterize the deep defect structure of bulk a-Si,Ge:H alloy films using their techniques. The second area will be to study transport behavior using time and spatially modulated photoconductivity measurements. Through some relatively new techniques they hope to better resolve the dispersive vs. non- dispersive components of the free carrier dynamics. They also wish to apply the acphotocurrent phase shift analysis method in conjunction with their other experimental techniques to correlate, within the same samples, the deep defect distribution above and below Ef. This will provide a more critical test of the current defect models.
