Recombination mechanism of excess carriers in hydrogenated amorphous germanium

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 G0.17. 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.