Abstract
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.