Effect of ultraviolet irradiation on the white light degraded electronic properties of hydrogenated amorphous silicon films

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Abstract
The electronic properties of hydrogenated amorphous silicon (a-Si:H) thin films are known to undergo metastable light-induced changes that can be reversed by annealing at elevated temperatures. We have observed for the first time that annealing of the light-induced changes in the dark conductivity and photoconductivity of a-Si:H thin films can also be achieved by ultraviolet (UV) irradiation (wavelength ∼254 nm) of the films at room temperature. It has been shown that the bulk photoconductivity changes in spite of the fact that UV radiation is mostly absorbed near the top surface of the films. A simple explanation of the observed phenomena has been proposed involving a nonequilibrium distribution of phonons generated by absorption of high-energy photons in the material.