GEMINATE AND NON-GEMINATE RECOMBINATION IN AMORPHOUS SEMICONDUCTORS

Abstract
One of the characteristic features of amorphous semiconductors is the low carrier mobilities which result from small carrier mean-free-paths due to disorder. When the mean-free-path becomes comparable to the Coulomb radius of an electronhole pair, both photogeneration and recombination processes can be affected. The photogeneration process can be controlled by geminate or initial pair recombination which results in a field-dependent photogeneration efficiency. The non-geminate recombination of previously created free carriers can become diffusion-controlled. This paper reviews the evidence for the occurrence of such processes in amorphous semiconductors including recent studies in a-Si : H and a-As₂Se₃.