Optical Studies of Excess Carrier Recombination ina-Si: H: Evidence for Dispersive Diffusion

Abstract

Relaxation of photoinduced optical absorption following pulsed laser excitation was measured between 0.5 μs and 10 ms in doped and undoped $a$-Si: H as a function of temperature. The recombination was found to be bimolecular diffusion limited. The diffusion coefficient of the excess carriers is time dependent ($\sim t^{-0.3\mathrm{}}$) in agreement with the drift mobility of photocarriers and the predictions of the continuous-time random-walk theory of dispersive transport in disordered materials.