Self‐Aligned Heterojunction Gate Carbon Nanotube Phototransistors for Highly Sensitive Infrared Detection

Abstract Heterojunction‐gated (HG) phototransistors have shown exceptional performance in weak‐light infrared detection due to their internal gain mechanism and the opto‐electric decoupling design. However, huge room is remained on optimizing device structure to further improve the performance, integrated density and yield. In this work, a carbon nanotube (CNT) film‐based phototransistor is fabricated with a self‐aligned gate consisting of a zinc oxide (ZnO) film/PbS colloidal quantum dot heterojunction. This fabrication process involves a standard lift‐off method to form an atomic‐layer‐deposited dielectric and a self‐aligned sputtered ZnO film, which fully covers the CNT network channel to provide the maximum light absorption area. The resulting device demonstrates a high responsivity of 2.9 × 10 5 A W −1 , a specific detectivity of 9.6 × 10 13 Jones, and an ultraweak detectable intensity of 0.8 nW cm −2 at 1300 nm illumination, all at room temperature. The self‐aligned HG phototransistor presents infrared photodetection performance comparable to non‐self‐aligned one, which typically require electron‐beam lithography or high‐precision lithography. This study can be insightful in developing high‐performance, easily manufacturable CNT‐based infrared detectors and high‐resolution imaging applications.