High‐Performance N‐MoSe₂/P‐GeSn/N‐Ge van der Waals Heterojunction Phototransistor for Short‐Wave Infrared Photodetection

Abstract In this work, a high‐performance two‐terminal n‐MoSe₂/p‐GeSn/n‐Ge van der Waals (vdW) heterojunction phototransistor (HPT) is proposed and demonstrated for short‐wave infrared (SWIR) detection. With a high Sn content of 17.1% in the GeSn base region, the cutoff wavelength is extended to beyond 2400 nm. The substantial electron/hole injection ratio resulting from the large bandgap offset between the MoSe₂ emitter and the GeSn base enables the harvesting of high photocurrent gain. A record high responsivity of 12.75 A W⁻¹ and an excellent specific detectivity of 1.74 × 10¹⁰ Jones at 2250 nm are achieved under a collector‐emitter bias of 1.0 V at room temperature. A response time of 462 µs at 1550 nm outbalancing that of most vdW junction‐based devices is obtained for the non‐optimized devices. Those results show that the mixed‐dimensional GeSn HPT is one of the promising candidates for detection of infrared band above 2 µm.