Photocurent spectroscopy in thin-film insulators: Voltage dependence of the external-circuit current

An analytical model for trapping-state photodepopulation measurements in conductor-thin-film-insulator-conductor structures is presented. The external-circuit-current dependence on applied voltage is determined, and it is shown that moments of the spatial distribution of trapped charge in the insulator can be extracted from collected-charge versus applied-field characteristic curves. The photodepopulation technique is compared with more widely used differential-capacitance and phtoemission-current techniques. © 1974 The American Physical Society.