Photocurrent response times in undoped amorphous hydrogenated silicon

The influence of electrical contacts upon coplanar electrode photocurrent response times has been explored in undoped amorphous hydrogenated silicon (a-Si:H) by measuring contact-induced photocurrents in a virtual ground plane. The results indicate that the relatively long photocurrent response times observed in undoped a-Si:H cannot be attributed to contacts. The response times are evidence that some deep-lying defects in a-Si:H are true electron photocarrier traps and not recombination centers. The discrepancy between long-time coplanar and time-of-flight transient photocurrent measurements upon undoped a-Si:H remains unresolved.