Light-induced effects in Schottky diodes on hydrogenated amorphous silicon

Abstract

An exposure of Schottky diodes on hydrogenated amorphous silicon (a-SiH) for several hours to light (AM1) reduces by a factor of 4 the dark forward current at V=1 V as well as the photocurrent under low illumination. Annealing above 150 °C partly reverses the process. Current-voltage measurements versus temperature show a shift of the bulk Fermi level of about 80 mV from the conduction band due to the increasing of the density of states in the midgap of a-SiH as can be seen from capacitance-voltage measurements. We explain the surprising stability of the photovoltaic functioning by the trapping of photogenerated holes which acts as an optical doping of the material.

Effect of the Nature of the Hydrogen Bonding on the Light-Induced Metastable Defects in Hydrogenated Amorphous Silicon Prepared by Radiofrequency Magnetron Sputtering

“…No significant changes are observed, on the contrary, in E 0 upon illumination for all series, indicating that the valence band tail width is not affected by light soaking, in agreement with previous results reported for a-Si : H films elaborated by PECVD at the same substrate temperature [37]. Furthermore, our results clearly show that the optimised films of series II are more stable against light exposure than optimised a-Si:H materials grown at the same substrate temperature ($250 C), either by conventional and dc magnetron sputtering [12,40] or by standard and helium dilution PECVD [41][42][43]. It was also reported previously that usually device quality a-Si : H films deposited with low defect density and disorder are very sensitive to the photodegradation phenomena [38,[41][42][43].…”