A hydrogenated amorphous SiC/hydrogenated amorphous Si heterojunction photodetector whose peak response could be voltage adjusted to three wavelengths, i.e., 480, 530, and 575 nm, by applying a small bias within ±2 V has been successfully fabricated. The basic principle is to use two back-to-back p-i-n junction diodes (or an n-i-p-i-n transistor) in which photons with wavelength λ<500 nm (blue) are mainly collected in the front a-SiC:H/a-Si:H heterojunction and the rest (green and red) are absorbed in the rear a-Si:H homojunction. To further distinguish the green from the red, two undoped a-Si:H layers, deposited at different conditions, were used in the rear homojunction to obtain two distinct collection regions. It is found that the required voltage to select one of the collection regions is less than 2 V. This detector shows a very high rejection ratio at various responses and thus is good for distinguishing the entire color spectrum.

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