Photocurrent multiplication in amorphous Si/crystalline Si heterojunction

A photocurrent multiplication factor over 20 has been observed on a new a-Si:Hc-Si heterojunction structure fabricated on a c-Si substrate under the deeply reverse biased voltage. In contrast, any marked increase in the dark current is not found on the photodiode, and the signal-to-noise ratio is achieved to be around 170. The spectral response indicates that the photocurrent multiplication factor gets smaller for illumination wavelengths. Photoconversion characteristics show that the photocurrent is proportional to the illumination intensity in the reverse bias voltage region in which multiplication occurs. A possible mechanism for the photocurrent multiplication involving the avalanche multiplication is discussed through various experiments regarding the photocurrent characteristics.