Gap states in phosphorus-doped amorphous silicon studied by isothermal capacitance transient spectroscopy

An application of the isothermal capacitance transient spectroscopy (ICTS) technique to a study of gap states in P-doped a-Si: H, as well as characteristics of a-Si: H Schottky barrier diodes used in the ICTS measurement, is described in detail. It is demonstrated that the electron-capture cross-section or the pre-exponential factor of the thermal emission rate of electron from gap states in a-Si: H can be determined, separating a temperature dependence from an energy dependence. On the basis of these advantages, the gap state profile g(E) in P-doped a-Si: H is measured precisely; the gap state bump associated with doubly-occupied dangling bonds is found to be located at 0·52 eV below E c It is also indicated that a multiphonon emission process with weak electron-phonon coupling predominates in the carrier-capture process at these states.