Effect of Contacts on Capacitance Transient Measurements in N-Type Hydrogenated Amorphous Silicon

ABSTRACTMeasurement of the dependence of emission capacitance transients on filling pulse duration has been extended to devices with Ohmic back contacts. Capacitance transients on devices possessing identical bulk 20-ppm P doped a-Si:H but either Ohmic contacts or blocking contacts were compared. The devices with blocking contacts completely reproduced in quantitative detail the previously observed anomalous dependence of capacitance transients on filling pulse duration. The diodes with Ohmic contacts showed no evidence of the anomalous filling pulse effect even for light-degraded, resistive samples. Current injection measurements show that blocking contacts delay the charge injection into the device by about 10–100 msec.