Charge injection into SiO2 during field effect and photo-field-effect measurements in hydrogenated amorphous silicon

It is shown that electron and hole trapping in vitreous quartz occurs when fields larger than 105 V/cm are applied across the insulator of glow-discharge deposited amorphous silicon (a-Si:H) field effect devices. The trapping of charges of both polarities is enhanced by light having energy less than 2 eV. The charge trapping reduces the field effect and the photo-field-effect of a-Si:H at large gate voltages. It is found that strong illumination does not eliminate the effect of accumulation layers on the photoconductivity.