Effects of absorption layer parameters and hetero-interface charge on photoresponse of 12.5 μm long-wavelength HgCdTe photodiode

Abstract

The effects of absorption layer parameters and hetero-interface charge on photoresponse of long-wavelength HgCdTe photodiode have been studied. The correlations between thickness of absorption layer and absorption length and diffusion length are investigated. An empirical formula is proposed to estimate the optimal thickness of absorption layer. Our theoretical investigations indicate that, when the wavelength of incident light is longer than the cut-off wavelength, the photoresponse monotonically increases with the increase of absorption layer thickness, and saturates subsequently. The wavelength of the maximal photoresponse increases with the increase of absorption layer thickness, and tends to shift toward long wavelength region. The optimal absorption layer thickness increases with increasing minority carrier life time and wavelength of incident light. It is found that the positive interface charge can induce a p-n junction at the substrate interface and significantly reduce the photoresponse. By using the metal-oxide-semiconductor diode model, possible physics mechanisms are investigated, and an approach is proposed to reduce the effects of hetero-interface charge on the photoresponse.