Time resolved radiative and nonradiative recombination in a-Si:H

Time resolved phonon and photoluminescence measurements are reported for a-Si:H films which are illuminated with pulsed near bandgap light. It is found that heat and light emission exhibit strikingly different time and excitation intensity dependences. The results demonstrate that the radiative and nonradiative channels are essentially uncoupled for times greater than 10/sup -7/ sec and that the radiative quantum efficiency is close to unity. The results further show that for injected electron-hole densities <10/sup 18/ cm/sup -3/ the a-Si:H is an efficient thermalizing medium in which the optically generated heat pulse travels ballistically for a distance of approx.1 ..mu..m.