The role of deep traps in photoconductivity transients in SI GaAs

Photoconductivity transients in semi-insulating (SI) GaAs during illumination with low intensity light are studied. By an original usage of thermally stimulated current method, the photoconductivity transient is related to the process of filling of deep traps with charge carriers. A simple model is proposed which explains the observed phenomena. It is also possible to estimate the capture cross section for dominant traps. Contrary to some previous explanations, the metastability of EL2 or other defects is not supposed. It is shown that deep levels, other than EL2, can play the dominant roles in low temperature transient phenomena. Both, the methodology and the model can be used in study of other SI semiconductors. In appendix, the possibility of large concentration of traps ( >N/sub EL2/) is discussed.