Wavelength response of thin-film optical position-sensitive detectors

Abstract

Three different structures of thin-film optical position-sensitive detectors based on novel hydrogenated amorphous silicon Schottky barrier (SB) structures have been studied under different light sources to measure their linear properties and wavelength response characteristics. The sputtered a-Si sensors were configured as layered structures of platinum, a-Si and indium tin oxide, forming SB-i?n devices. They exhibited output properties similar to multi-layer a-Si p?i?n devices produced by complex chemical vapour deposition procedures, which involve flammable and toxic gases. All structures were tested as possible configurations for two-dimensional sensors. The devices were tested under white light (peak wavelength 690 nm), filtered white light (peak wavelengths of 470, 550 and 650 nm) and also a red laser diode (wavelength 633 nm). Each of the three structures responded quite differently to each of the sources. Results, based on the correlation coefficient (r), which measures the linearity of output and which has a maximum value of 1, produced r values ranging between 0.992 and 0.999, in the best performances. The overall best sensitivity result obtained was 5.84 mV mm?1 shift.