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 × 10⁵ A W⁻¹, a specific detectivity of 9.6 × 10¹³ 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.