Recombination echoes in disordered silicon

Abstract

The influence of spin-selection rules on charge-carrier recombination in disordered semiconductors such as hydrogenated microcrystalline silicon (μc-Si : H) has been used for many years as a powerful tool for defect spectroscopy. Electrically detected magnetic resonance measures small conductivity changes that are induced by electron spin resonance, and is performed under quasi-continuous excitation of the ESR microwaves. Since the rate at which the spin population in μc-Si : H is altered is small compared to the spin-decoherence rate, no information on the dynamics of spin-dependent transitions can be obtained. In this paper, we will show that with strong microwave bursts the dynamics of spin-dependent recombination at dangling bonds is accessible. We will give experimental evidence that coherent spin phenomena, like spin-beat oscillations and recombination echoes, are observable in the photocurrent of μc-Si : H. A first qualitative model of recombination through dangling bonds in μc-Si : H is given.