A Bifunctional Colloidal Quantum Dot Diode for Nanosecond Short-Wave Infrared Detection and Emission

Area of Science:

• Materials Science
• Optoelectronics
• Photonics

Background:

• Short-wave infrared (SWIR) technologies are crucial for optical communication, imaging, and spectroscopy.
• Integrating light detection and emission into a single diode offers reduced footprint, lower cost, and faster communication.
• Existing dual-function devices often suffer from performance limitations due to incompatible material and design choices.

Purpose of the Study:

• To introduce a bifunctional lead sulfide quantum dot (PbS QD) diode stack for simultaneous SWIR photodetection and emission.
• To achieve unprecedented nanosecond-fast operation in both photodiode (QDPD) and light-emitting diode (QDLED) modes within a single device.
• To demonstrate a CMOS-compatible platform for integrated SWIR photonics and bidirectional optical interconnects.

Main Methods:

• Fabrication of a bifunctional PbS QD diode stack utilizing thin active layers and compact geometries.
• Characterization of device performance in photodiode mode, measuring response time, external quantum efficiency (EQE), and detectivity.
• Evaluation of device performance in light-emitting diode mode, assessing rise time, fall time, and EQE.

Main Results:

• Achieved a record 2 ns response time in QDPD mode and 11.7 ns rise/6.5 ns fall times in QDLED mode.
• Demonstrated high performance with 49% EQE and 2.6 × 10^12 cm·Hz^0.5·W^-1 detectivity for QDPD operation.
• Reported an 8.1% EQE for the QDLED operation, showcasing efficient light emission.

Conclusions:

• The developed bifunctional PbS QD diode successfully integrates high-speed photodetection and emission in a single SWIR device.
• This technology offers a pathway towards compact, CMOS-compatible SWIR systems for unified imaging, detection, and communication.
• The QD-based platform holds significant potential for advancing integrated photonics and bidirectional optical interconnects.