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Revealing Additional Size-Dependent Defect Suppression Channels Governing Detectivity in InAs Colloidal Quantum Dot
Stefan Zeiske1, Hyeong Woo Ban1, Xubiao Li1
1Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States.
Nano Letters
|November 18, 2025
Summary
Indium arsenide colloidal quantum dot photodiodes show reduced defects with larger nanocrystal size. However, device performance is mainly limited by contact and interface issues, not intrinsic defects.
Area of Science:
- Materials Science
- Nanotechnology
- Optoelectronics
Background:
- Indium arsenide (InAs) colloidal quantum dot (CQD) photodiodes offer tunable bandgaps and solution processability for infrared detection.
- Understanding defect signatures is crucial for optimizing CQD photodiode performance.
Purpose of the Study:
- To probe defect signatures in InAs CQD photodiodes using high-dynamic-range external quantum efficiency (HDR-EQE) measurements.
- To quantify the impact of defects on photodiode performance, including dark saturation current, detectivity, and noise.
Main Methods:
- High-dynamic-range external quantum efficiency (HDR-EQE) measurements.
- Analysis of Urbach tails and Gaussian sub-bandgap states to quantify trap densities.
- Estimation of defect contribution to dark saturation current, detectivity, and noise.
Main Results:
- Trap densities decrease with increasing nanocrystal size, influenced by surface chemistry.
- Defect states significantly impact dark saturation current (J0).
- InAs CQD photodiode performance is primarily limited by contact and interface properties, rather than intrinsic defects.
Conclusions:
- Nanocrystal size and surface chemistry influence defect populations and bandedge disorder.
- Intrinsic defects contribute to device performance limitations, but extrinsic factors are dominant.
- Improving contact and interface properties is key for advancing InAs CQD photodiode technology.
