Thermalization and radiative recombination of photo-excited carriers in a-Si: H

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Abstract
The thermalization and recombination of photo-excited carriers in a-Si: H have been studied by transient photoluminescence. The time decay of the photoluminescence after pulsed photo-excitation was measured for temperatures between 50 and 120 K and for different optical bias intensities. It is shown that the experimental results can be understood in the framework of an extended multiple-trapping model which, in contrast to the conventional multiple-trapping model, allows for transitions between the localized tail states and for electron-hole recombination. Thus, the model presented can be understood as a first step towards a common description of the transient optical and transport properties of a-Si:H. The validity of the basic assumptions made in the conventional multiple-trapping model as well as in our extended version are discussed, and possible extensions are pointed out.