Visible to Short‐Wave Infrared Broadband p‐WSe2/n‐Ge Heterojunction Phototransistor with an Annular Shallow‐Trench Schottky Barrier Collector

Van der Waals (vdW) heterostructures based on two‐dimensional materials and conventional group IV semiconductors have shown great potential for wide spectrum, highly sensitive photodetectors owing to their broadband absorption, high‐quality interface, and compatibility with complementary metal‐oxide‐semiconductor (CMOS) technology. Herein, a unique heterojunction phototransistor composed of an indium tin oxide capped p‐WSe 2 /n‐Ge vdW heterojunction serving as the emitter and an annular shallow‐trench Al/Ge Schottky junction acting as the collector is proposed. The mixed‐dimensional phototransistor exhibiting high responsivities up to 66 A W −1 at 405 nm and 124 A W −1 at 1,550 nm demonstrates a brilliant wide spectrum response performance. The high photocurrent gain can be attributed to the extra‐large carrier injection ratio of the heterojunction. The short transient response time in the order of 100 μs is achieved with the modified lateral electrical field by the annular shallow‐trench Schottky barrier collector. The combination of p‐WSe 2 /n‐Ge vdW heterojunction and the annular shallow‐trench Al/n‐Ge Schottky junction renders a low‐cost, high‐performance photodetector fabricated in a simple and CMOS compatible way for visible to short‐wave infrared broadband detection.