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.