Geminate recombination in a-Si: H

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Abstract
The recombination mechanism in a-Si: H is examined by studying the lifetime distribution P(τ) of the photoluminescence using frequency-resolved spectroscopy (FRS) and by light-induced electron spin resonance (LESR). The experiments are performed in a wide range of excitation densities (1016 cm−3 s−1 22 cm−3 s−1). Two ranges of distinctively different behaviour are observed: (1)AtG > 5 × 1019cm−3s−1, P(τ) shifts with G to shorter times, as one expects in a case of non-geminate recombination between nearest available neighbours. (2) At G < 5 × 1018 cm−3 s−1, P(τ) is independent of G. The transient behaviour of the photoluminescence intensity and of the LESR spin density shows convincingly that in this range geminate recombination prevails.