ENERGY-DEPENDENCE OF THE ELECTRON-CAPTURE CROSS-SECTION OF GAP STATES IN UNDOPED A-SI-H FILMS

Abstract

Isothermal capacitance transient spectroscopy (ICTS) has been employed to measure the energy dependence of the electron-capture cross section of continuously distributed defect levels in undoped a-Si:H film for the first time, via the proposed novel structure. For undoped a-Si:H films! experimental results show that the electron-capture cross section of defect levels initially decreases exponentially, reaches a minimum, and then increases exponentially with energy depth measured from the mobility edge of the conduction band. This v-shaped distribution of the electron-capture cross section of continuously distributed defect levels in undoped a-Si:H film is different from that in phosphorous-doped a-Si:H film. This means that mechanisms other than multiphonon emission can be dominant in the electron-capture process in the gap states in undoped a-Si:H film.