Interface-Controlled Performance in VLWIR Blocked Impurity Band Photodetectors

High-sensitivity very long-wavelength infrared (VLWIR) blocked impurity band (BIB) photodetectors are essential for atmospheric monitoring and astronomical observation. However, there is a gap between the traditional BIB model and the actual BIB structure, and the interface effects have not been clarified. In this work, a BIB interface model is proposed, and the potential barrier distribution of the interfacial layer and its influence on the photodetector dark current and response during operation are clarified through simulations and experiments. Phosphorus-doped silicon BIB structures with sharp and gradual interfaces were fabricated and analyzed. Experimental results demonstrate that sharp interface BIB photodetectors achieve five orders of magnitude reduction in dark current, maintaining dark current below 1 pA at forward bias up to 2.7 V, and achieving a peak blackbody detectivity exceeding $1\times 10^{{12}}$ cm Hz1/2·W−1 at $28.3~\mu $ m. In contrast, gradual interface photodetectors improved the detection of low-energy photons at longer wavelengths. These findings provide critical insights into interface engineering in BIB photodetectors and offer guidelines for optimizing VLWIR detection performance.