Optically excited paramagnetic centers in hydrogenated amorphous germanium

Optically excited paramagnetic centers in amorphous hydrogenated germanium (a-Ge:H) are reported. The light induced electron spin resonance (LESR) spe ctra are comprised of two components, which are ascribed to electrons and h oles in the conduction- and valence-band-tail states, respectively. There i s no evidence of spin pairing, charge defect creation or LESR of Ge danglin g bonds. Over about three orders of magnitude in light intensity the decay curves are dispersive with a dispersive parameter of similar to 0.5, The sp ectra are best fit assuming bimolecular recombination. The LESR spin densit y depends only weakly on the photo-generation rate. (C) 2000 Elsevier Scien ce B.V. All rights reserved.