Stacked ITO/(a-SiC:H)pinpi /(a-Si:H)i’n’/ITO color sensitive detectors are analyzed using a laser scanned photodiode technique. Results show that band gap engineering, together with the laser scanned technique allows a voltage controlled shift of the collection regions and color discrimination in the readout voltage that cancels the self-bias effect induced by the steady-state illumination, across the back diode. The threshold voltage, between the green and red discrimination depends on the thickness ratio between a-Si:H (-i’)/a-SiC:H (-i) layers. As this ratio increases, the self-reverse effect due to the front absorption will be balanced by the decrease of the self-forward effect due to the back absorption shifting the threshold voltage to lower reverse bias. The various design parameters, and the optical readout process trade-offs are discussed and supported by a 2D numerical simulation. A self-bias model is proposed to explain the voltage controlled spectral sensitivity.
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Vieira, M., Louro, P., Fantoni, A. et al. Band Gap Engineering and Electrical Field Tailoring for Voltage Controlled Spectral Sensitivity. MRS Online Proceedings Library 910, 1702 (2005). https://doi.org/10.1557/PROC-0910-A17-02