Strom-Spannungsabhängigkeit bei der Photoleitung in Isolatoren mit Störstellen und nachlieferndem Kontakt

Abstract

The total current (photocurrent plus dark current) through an insulator with one ohmic contact is obtained. The insulator contains a single, discrete trap level and in addition fixed holes as recombination centers. From the total current, the photocurrent-voltage characteristic is derived. For shallow traps only, the photocurrent after an ohmic range, continuously turns into saturation. For deep traps only, however, below the threshold voltage for the onset of the space-charge-limited dark current, the photocurrent-voltage characteristic is considerably influenced by the rate of excitation by light. The superlinear rise of the photocurrent with voltage (at low rates of excitation) changes into a linear and furthermore into a sublinear rise with increasing rate of excitation. Near the threshold voltage the photocurrent passes through a maximum at very low rates of excitation because the deep traps are filled with electrons from the ohmic contact. The corresponding maximum gain may be by orders of magnitude greater than the saturation gain.