The realization of nipip HIT photodetectors with an optimized thickness of intrinsic a-Si:H

Abstract

In this paper, we propose a nipip HIT structure based on the most efficient heterojunction photovoltaic structure to apply in photodetectors. At–2 V, the white-light responsivities are 1.9 mA/W and 206.2 mA/W for nipip HIT photodetectors with 5-nm-thick and 40-nm-thick top a-Si:H(i), respectively. The external quantum efficiency of nipip HIT photodetectors shows that the HIT structure with 40-nm-thick top a-Si:H(i) has a much larger quantum efficiency than the one with 5-nm-thick a-Si:H(i) at the wavelength range of 400–700 nm. Although the c-Si is not well passivated by a-Si due to the long exposure time in the air before ITO deposition, it gives us the best chance to see the contribution of a-Si on quantum efficiency. This study successfully demonstrated our previous simulation results that an appropriate increase in the thickness of a-Si:H(i) is beneficial for nipip HIT photodetectors. In contrast, the more significant UV (∼300 nm) photo-response of photodetectors with 5-nm-thick top a-Si:H(i) gives us more insight into carrier transport within the surface of the a-Si layer, and it is preferred for UV detection.