µc-Si:H Thin-Film Devices for Optical Image Recognition

Abstract

AbstractA study of an image detector based on µc-Si:H p-i-n structures is presented. The photodetector has a TCO/µc-p-i-n Si:H configuration with two coplanar metallic contacts and a transverse one.We used a strong spatially fixed light pattern with different intensities to simulate the images and a weak moving light beam to sweep the device in the lateral direction, for its recognition. The sensor surface was scanned row by row and a signal processing procedure was applied to the data after each sweep. It was found that the induced transverse and lateral photovoltages are sensitive to the position and intensity of the image. Through a readout analysis it was possible to recognise, in a continuous way, the image position and relative intensity. The image resolution as a function of the pattern width and intensity is also analysedA small signal circuit modelling and a simulation consistent with the experimental data are presented and explained. Preliminary tests show that the detector can be used as a two-dimensional image sensor.