AMORPHOUS SI/SIC 3-COLOR DETECTOR WITH ADJUSTABLE THRESHOLD

An adjustable threshold color detector (ATCD) is demonstrated, based on a hydrogenated amorphous silicon (a-Si:H) and silicon-carbide (a-SiC:H) p+-i-n+-i-n+-i-p+ multilayer. The ATCD is able to discriminate between blue (λ=450 nm), green (550 nm), and red (>650 nm) illumination by varying the externally applied voltage within a few volts. The operation of the detector can be explained regarding the ATCD as three independent devices connected in series: a p+-i-n+, a n+-i-n+, and a n+-i-p+. The novel feature is the n+-i-n+ cell. It acts as a short circuit under strong illumination, whereas in dark it is equivalent to two low quality back-to-back diodes which introduce a shift in the threshold in the photocurrent detection. Thanks to the large number of physical parameters such as layer thickness and band gap the ATCD appears extremely versatile.© 1995 American Institute of Physics.