Transient photoconductivity in a-Si1−x C x :H thin films

Abstract

Abstract Excess electron and hole drift mobilities in a-Si1−x Cx:H thin films have been investigated using the ‘time-of-flight’ transient photoconductivity technique. A detailed analysis of the temperature and field dependence of these parameters has been carried out, permitting the computation of the energy distributions of conduction and valence band tail localized states as a function of carbon concentration in the films. It is apparent from these data that increased carbon incorporation is associated with an increase in the total number of conduction band tail states, and with a broadening of their energy distribution. The valence band tail exhibits an increased density of localized tail states, but the broadening is less pronounced in this case. The computed energy distributions of the trapping centres in both the conduction and valence band tails are supported by the experimental behaviour of the respective carrier pre-transit currents. The temperature dependences of the transient dispersion paramet...