Opto-Electrical Decoupled Phototransistor for Starlight Detection

Highly sensitive shortwave infrared (SWIR) detectors are essential for detecting weak radiation (typically below 10⁻⁸ W·Sr⁻¹·cm⁻²·µm⁻¹) with high-end passive image sensors. However, mainstream SWIR detection based on epitaxial photodiodes cannot effectively detect ultraweak infrared radiation due to the lack of inherent gain. Here, we develop a heterojunction-gated field-effect transistor (HGFET) consisting of a colloidal quantum dot (CQD)-based p-i-n heterojunction and a carbon nanotube (CNT) field-effect transistor, which achieves a high inherent gain based on an opto-electric decoupling mechanism for suppressing noise. The stacked heterojunction absorbs infrared radiation and separates electron–hole pairs. Then, the generated photovoltage tunes the drain current of the CNT FET through an Y₂O₃ gate insulator. As a result, the HGFET significantly detects and amplifies SWIR signals with a high inherent gain while minimally amplifying noise, leading to a recorded specific detectivity above 10¹⁴ Jones at 1300 nm and a recorded maximum gain-bandwidth product of 69.2 THz. Direct comparative testing indicates that the HGFET can detect weak infrared radiation at 0.46 nW cm⁻² levels; thus, compared to commercial and reported SWIR detectors, this detector is much more sensitive and enables starlight detection or vision. As the fabrication process is very compatible with CMOS readout integrated circuits, the HGFET is a promising SWIR detector for realizing passive night vision imaging sensors with high resolutions that are high-end, highly sensitive, and inexpensive.