Opto-Electrical Decoupled Phototransistor for Starlight Detection.

Area of Science:

• Materials Science
• Optoelectronics
• Semiconductor Physics

Background:

• Highly sensitive shortwave infrared (SWIR) detectors are crucial for passive imaging sensors detecting weak radiation.
• Current SWIR detectors using epitaxial photodiodes lack inherent gain, limiting their ability to detect ultraweak signals.

Purpose of the Study:

• To develop a novel SWIR detector with high inherent gain for detecting ultraweak infrared radiation.
• To overcome the limitations of mainstream SWIR detection technologies.

Main Methods:

• Fabrication of a heterojunction-gated field-effect transistor (HGFET) combining a colloidal quantum dot (CQD) p-i-n heterojunction and a carbon nanotube (CNT) field-effect transistor.
• Utilizing an opto-electric decoupling mechanism for noise suppression and signal amplification.
• Employing Y2O3 as a gate insulator to tune CNT FET drain current via photovoltage.

Main Results:

• The HGFET demonstrated significant detection and amplification of SWIR signals with high inherent gain and minimal noise amplification.
• Achieved a specific detectivity exceeding 10^14 Jones at 1300 nm and a maximum gain-bandwidth product of 69.2 THz.
• Successfully detected weak infrared radiation at levels as low as 0.46 nW cm^-2, surpassing commercial and reported SWIR detectors.

Conclusions:

• The developed HGFET offers superior sensitivity for SWIR detection, enabling applications like starlight detection and passive night vision.
• The detector's fabrication process is compatible with CMOS readout integrated circuits, paving the way for high-resolution, sensitive, and cost-effective imaging sensors.