Heterostructured MXene/Si Photodiodes With Sub-1-nm h-BN Blocking Layers for Suppressing Dark Current

Integrating two-dimensional materials with three-dimensional photosensitive semiconductors to form Schottky junctions for high-performance photodetection has attracted much research attention due to their excellent optical and electronic properties. However, the large dark current induced by the unexpected interface defects has greatly degraded their optoelectronic performance. Here, we reported a Schottky photodiode based on MXene/h-BN/Si van der Waals heterojunction, where the sub-1-nm h-BN layer significantly suppressed the dark currents by two orders of magnitude and raised the detectivity up to 1013 Jones. Ultrathin h-BN blocking layer free of dangling bonds effectively improved the interface quality due to the decreased interface trap states, resulting in a smaller ideal factor and larger Schottky barrier height. Moreover, asymmetric carrier transport was achieved due to the hindrance of ultrathin h-BN layer on the electron tunneling from n-Si to MXene, weakening the interlayer coupling of photo-generated electron-hole pairs and enhancing the optoelectronic performance. This work demonstrated a feasible strategy to optimize MXene-based photodiodes with sub-1-nm h-BN blocking layer for high-performance photodetection.