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.