On thermal quenching of the photoconductivity in hydrogenated amorphous silicon

Abstract

Abstract Thermal quenching (TQ) of the photoconductivity [sgrave]p is the decrease in [sgrave]p with increasing temperature. We present an explanation for TQ of [sgrave]p usually observed above 100 K in undoped and weakly doped hydrogenated amorphous silicon (a-Si:H). With computer simulations employing the theory of Simmons and Taylor, we show that TQ is caused by the natural density of gap states of a-Si: H. The onset of thermal quenching occurs at the temperature TTQ where the trapped hole density in the valence band tail has decreased to twice the density ND of dangling bonds. We elucidate the experimental observation that TTQ shifts to lower temperatures as the Fermi level shifts toward the valence band or as ND is increased and explain the reported superlinear dependence of the inverse photoconductivity [sgrave]p −1 on ND . We test and discuss the validity of the Simmons-Taylor theory by comparing the simulated and experimental temperature dependences of the Rose exponent γ, which relates the photoconductivity and the generation rate.