Peking University, December 3rd, 2024: Prof Zhang Zhiyong’s team developed a heterojunction-gated field-effect transistor (HGFET) that achieves high sensitivity in short-wave infrared detection, with a recorded specific detectivity above 1014 Jones at 1300 nm, making it capable of starlight detection. Their research was recently published in the journal Advanced Materials, titled “Opto-Electrical Decoupled Phototransistor for Starlight Detection”.

Why it matters: 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. 

Filling this gap, researchers at the Peking University School of Electronics and collaborators have presented a heterojunction-gated field-effect transistor (HGFET) that achieves ultra-high photogain and exceptionally low noise in the short-wavelength infrared (SWIR) region, benefiting from a design that incorporates a comprehensive opto-electric decoupling mechanism. 

Key Findings:

1. The team developed a HGFET consisting of a colloidal quantum dot (CQD)-based p-i-n heterojunction and a carbon nanotube (CNT) field-effect transistor, which 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.

2. Direct comparative testing indicates that the HGFET can detect weak infrared radiation at 0.46 nW cm−2 levels; thus making this detector much more sensitive than the commercial and reported SWIR detectors, and especially enables a starlight detection or vision.

Figure 1 Structure and mechanism of HFGET

Figure 2 Performance of the HGFET under 1300 nm irradiation at a constant bottom-gate voltage of −0.6 V.

Significance:

1. As the fabrication process of HGFET is highly compatible with CMOS readout integrated circuits, the HGFET offers a universal platform for achieving high-end passive night vision image sensors in thin-film semiconductors.

2. This technology paves the way for innovative optoelectronic circuits and future monolithically integrated systems with high resolution, high-sensitivity and low cost.

3. This research was supported by the Natural Science Foundation of China and the Peking Nanofab Laboratory.

Figure 3 Comparison of the performance of the HGFET detector and a commercial InGaAs photodiode (FGA015) under the same testing conditions

Figure 4 Benchmarking HGFET, InGaAs diodes and other thin-film photodetectors

Figure 5 (a) Schematic diagram of the assembled image sensor test system and (b) images of the “PKU” pattern captured under various power densities by the 64 × 64 pixel HGFET imager

Zhou Shaoyuan, a doctoral student (enrolled in 2021) at the PKU School of Electronics, is the first author of the paper, with Wang Ying and Zhang Zhiyong as the co-corresponding authors. 

The co-authors of this paper are Jiang Jianhua from PKU School of Electronics, Zhang Panpan from Beijing University of Posts and Telecommunications School of Integrated Circuits, Zhang Jianbing from Huazhong University of Science and Technology (HUST) School of Integrated Circuits, and Tang Jiang from HUST School of Optical and Electronic Information. 

Link to the paper: https://onlinelibrary.wiley.com/doi/10.1002/adma.202413247

Written by: Vissly Chan
Edited by: Niki Qiu
Source: PKU News (Chinese)