Recombination mechanism of excess carriers in hydrogenated amorphous germanium

Abstract

In this work we report a study of the recombination mechanism of electrons trapped in the conduction band-tail states with holes trapped in the valence band-tail states as a function of the light intensity, G, in hydrogenated amorphous germanium (a-Ge:H). The density of trapped electrons increases with light excitation, but the saturation spin density depends only weakly on the light intensity and increases as G 0.17. On the other hand, the characteristic time constant for growth of the light-induced electron spin resonance (LESR) signal, which is related to the recombination lifetimes, follows a power law function, G −0.65. The growth and decay curves can be well fitted by a dispersive model, with a dispersive parameter of about 0.5, assuming bimolecular recombination.