Overcoming Field-Assisted Leakage and Mobility Deficits in InAs Colloidal Quantum Dot SWIR Photodetectors
Daekwon Shin, Stefan Zeiske, Jugyoung Kim, Ubaid H. Kazianga, Hyoin Kim, Hyeonjun Jeong, Jung Hoon Song, Bin Chen, Edward H. Sargent, Sohee JeongAbstract
InAs colloidal quantum dots (CQDs) synthesized using non-pyrophoric precursors are attractive for short-wave infrared (SWIR) photodetection, yet their device performance remains limited by low external quantum efficiency (EQE) and high dark current. Here, we attribute these limitations to two material-level impediments: poor carrier mobility and broadly distributed sub-bandgap states. To address the former, we adapt a butylamine-assisted InBr3 ligand-exchange process, which increases carrier mobility by ∼80-fold and enhances EQE from 11% to 25% at −1 V. Temperature-dependent electrical and defect analyses reveal that field-assisted leakage current arises from sub-bandgap states associated with agglomerated, irregularly shaped particles within the CQD ensemble. Removing these particles via size-selective precipitation reduces trap density, increases trap activation energy, and suppresses dark current by an order of magnitude. Together, these complementary strategies yield InAs CQD photodetectors with a shot-noise-estimated detectivity of 9.8 × 1010 jones at 1320 nm and a rise time of 32 ns at −0.5 V.