Subnanosecond radiative and nonradiative processes ina-Si: H

Abstract

Radiative and nonradiative processes governing the photoluminescence at early times in $a$-Si: H have been examined with the use of a Ge detector with 250-ps resolution. The broad spectral response of the Ge detector provides a measurement of the total light decay which isolates those rates that affect the net population of short-lived states from relaxation rates of the population packet to lower energy. At 15 K, the initial lifetime is consistently about 8 ns in a variety of samples with a large range of overall quantum efficiencies, indicating an intrinsic source such as the radiative recombination of a localized exciton. The initial lifetime ${\tau }_0\mathrm{}\left(T\right)\mathrm{}$ falls by about a factor of 5 from 15 to 275 K, and the initial intensity $I_0\mathrm{}\left(T\right)\mathrm{}$ by about a factor of 10 across the same range. The temperature dependences of ${\tau }_0\mathrm{}\left(T\right)\mathrm{}$ and $I_0\mathrm{}\left(T\right)\mathrm{}$ are compared to those of a number of models in order to probe the underlying physical processes. The results are also compared to a variety of other subnanosecond measurements in $a$-Si: H.