Photodetectors with an HIT structure on p-type crystalline Si wafers

► We have investigated the visible/near-infrared photodetectors based on the nipip HIT structure. ► The nipip structure has a better near-infrared response; meanwhile the pinin structure has a better blue response. ► The mechanism of difference between nipip and pinin structures has been discussed. ► If the thickness of top a-Si:H(i) can be appropriately increased, the responsivities would be further enhanced.