Voltage tunes spectral response of multispectral amorphous-silicon-based detector

Voltage tunes spectral response of multispectral amorphous-silicon-based detector

A detector based on amorphous silicon can be made into high-resolution arrays that sense color without requiring color filters. Qi Zhu at SICAN GmbH (Braunschweig, Germany) and coworkers at University of Siegen and Silicon Vision GmbH (both Siegen, Germany) built detectors with spectral responses that shift when an applied bias voltage changes--response peaks were measured at 450, 550, and 600 nm, a range of response similar to that of the human eye.

Hydrogenated amorphous silicon (a-Si:H) is an attractive sensor material because its absorption coefficient for visible light is about ten times higher than that of crystalline silicon. Thin-film, large-area sensors can be made from a-Si:H at relatively low cost. Recent work by other researchers has shown that multiple-layer detectors can be bias-controlled to offer two spectral maxima. The Zhu grou¥experimented with more-complicated layer arrangements and added carbon to some of the insulating layers to develo¥two multispectral sensors. The detectors show good linearity in the illumination range from 1011 to 1015 photons/cm2/s and a high dynamic range of more than 56 dB when illuminated by 1000 lux.