THE OPERATIONAL PRINCIPLE OF A NEW AMORPHOUS-SILICON BASED P-I-I-N COLOR DETECTOR

The operational principle of a new type p-i-i-n color sensor is descri bed with the aid of numerical modeling. The modeling results account f or the color detection mechanism recently presented that this kind of structure exhibits [T. Neidlinger, M. B. Schubert, G. Schmid, and H. B rummack, in Amorphous Silicon Technology-1996, edited by E. A. Schiff et al. (Materials Research Society, Pittsburgh, 1996), p. 147]. By ban d gap engineering the experimental red response is maximized at larger reverse bias voltage whereas the green response has its maximum at lo w reverse bias voltage. The numerical modeling qualitatively reproduce s the characteristic shape of the steady-state current-voltage curves at different illumination wavelengths. At low and at high reverse bias voltages the influence of the internal variables and parameters is id entified and leads to the experimentally observed response. The potent ial profile of the p-i-i-n structure is of crucial importance to the c olor detection mechanism. At larger wavelengths the large potential dr op across the two highly defective front layers assists recombination in the back part of the device, which thus leads to the drop in the re d response at low reverse voltage. For the voltage-dependent shift in spectral sensitivity it is important that photogenerated carriers unde r green bias illumination are lost by recombination in the front part of the device. (C) 1997 American Institute of Physics.