Wide-Dynamic-Range Lead-Free SWIR Image Sensors Based on InAs Thin-Film Quantum-Dot Photodiodes ^†

Area of Science:

• Materials Science
• Optoelectronics
• Semiconductor Devices

Background:

• Short-wavelength infrared (SWIR) imaging is crucial for various applications, but current technologies face integration and material limitations.
• Lead-based colloidal quantum dots (CQDs) are common but raise environmental and scalability concerns.
• Monolithic integration of SWIR sensors on silicon readout integrated circuits (ROICs) is highly desirable for advanced imaging systems.

Purpose of the Study:

• To develop a monolithically integrated SWIR image sensor using indium arsenide (InAs) quantum dot photodiodes (QDPDs).
• To demonstrate a scalable, lead-free alternative to existing CQD-based SWIR technologies.
• To achieve wide dynamic range imaging with enhanced noise suppression.

Main Methods:

• Fabrication of thin-film photodiode (TFPD) architecture using InAs QDPDs for direct integration on silicon ROICs.
• Implementation of a 3T pixel design with dual conversion gain (DCG) for wide dynamic range.
• Utilizing a frame-based digital correlated double sampling (CDS) scheme for noise reduction.

Main Results:

• Achieved external quantum efficiencies of 28% at 1200 nm and 4.8% at 1400 nm.
• Demonstrated a wide dynamic range of 83.5 dB.
• Successfully suppressed reset kTC noise and random telegraph signal (RTS) noise through the CDS scheme.
• Showcased SWIR imaging capabilities including material discrimination, imaging through smoke, and silicon wafer transmission.

Conclusions:

• InAs QDPDs represent a promising platform for next-generation SWIR imaging sensors.
• The monolithically integrated TFPD architecture offers a scalable and RoHS-compliant solution.
• The developed sensor combines high sensitivity, extended spectral coverage, and competitive performance for advanced SWIR applications.