Light-induced degradation and thermal recovery of the photoconductivity in hydrogenated amorphous silicon films

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Abstract
Kinetics of light-induced degradation and thermal recovery of the photoconductivity in hydrogenated amorphous silicon have been investigated. Rate equations for these processes were derived using the principles of reaction rate theory. Both degradation and recovery were found to be thermally activated with activation energies of 0.1 and 1.35 eV, respectively. Experimental results support the bond breaking model for the degradation. Stabilization of broken bonds is achieved by structural relaxation. Thermal recovery proceeds through hydrogen hopping from one dangling bond to another. Experimental evidence suggests the existence of an upper limit in the density of light-induced defects. A microscopic model, consistent with experimental observations, is proposed for the light-induced generation and thermal recovery of defects in a-Si:H.