Short-Wave Infrared Colloidal QD Photodetector with Nanosecond Response Times Enabled by Ultrathin Absorber Layers

Area of Science:

• Materials Science
• Optoelectronics
• Nanotechnology

Background:

• Ultrafast short-wavelength infrared (SWIR) photodetection is crucial for automated vision and spatial mapping.
• Colloidal quantum dots (QDs) offer tunable bandgaps and cost-effective processing for SWIR photodetection.
• Achieving nanosecond-level response times in QD-based SWIR photodiodes (QDPDs) has been a significant challenge.

Purpose of the Study:

• To report record response times in PbS-based QDPDs operating at SWIR wavelengths.
• To demonstrate QDPDs meeting the requirements for SWIR light detection and ranging.
• To investigate methods for enhancing the performance of colloidal QD photodetectors.

Main Methods:

• Fabrication of ultrathin PbS QDPDs with a thin active layer and small area.
• Implementation of a concentration gradient ligand exchange method for high-quality p-n junction formation.
• Utilizing a Fabry-Perot cavity within the QDPD to enhance light absorption.

Main Results:

• Achieved a record 4 ns response time in PbS-based QDPDs.
• Attained an external quantum efficiency of 42% at 1330 nm.
• Demonstrated 2.5-fold enhanced light absorption and 98% photogenerated charge carrier extraction.

Conclusions:

• PbS-based QDPDs can achieve ultrafast, nanosecond-level response times for SWIR applications.
• The developed QDPDs meet critical performance metrics for SWIR light detection and ranging.
• Further improvements in charge-carrier mobility could lead to sub-nanosecond response times in future PbS QDPDs.