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

• Published in: Advanced materials (Weinheim) Vol. 36; no. 28; pp. e2402002 - n/a
• Main Authors: Deng, Yu‐Hao, Pang, Chao, Kheradmand, Ezat, Leemans, Jari, Bai, Jing, Minjauw, Matthias, Liu, Jiayi, Molkens, Korneel, Beeckman, Jeroen, Detavernier, Christophe, Geiregat, Pieter, Van Thourhout, Dries, Hens, Zeger
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01-07-2024
• Subjects: Carrier density; Carrier mobility; Carrier transport; colloidal quantum dots; Colloids; Concentration gradient; Current carriers; Electromagnetic absorption; Fabry-Perot interferometers; Lidar; Nanosecond response; P-n junctions; photodetector; Photodiodes; Quantum dots; Quantum efficiency; Response time; short‐wave infrared; ultrafast; colloidal quantum dots; photodetector; short‐wave infrared; ultrafast
• ISSN: 0935-9648; 1521-4095; 1521-4095
• DOI: 10.1002/adma.202402002

Ultrafast short‐wavelength infrared (SWIR) photodetection is of great interest for emerging automated vision and spatial mapping technologies. Colloidal quantum dots (QDs) stand out for SWIR photodetection compared to epitaxial (In,Ga)As or (Hg,Cd)Te semiconductors by their combining a size‐tunable bandgap and a suitability for cost‐effective, solution‐based processing. However, achieving ultrafast, nanosecond‐level response time has remained an outstanding challenge for QD‐based SWIR photodiodes (QDPDs). Here, record 4 ns response time in PbS‐based QDPDs that operate at SWIR wavelengths is reported, a result reaching the requirement of SWIR light detection and ranging based on colloidal QDs. These ultrafast QDPDs combine a thin active layer to reduce the carrier transport time and a small area to inhibit slow capacitive discharging. By implementing a concentration gradient ligand exchange method, high‐quality p–n junctions are fabricated in these ultrathin QDPDs. Moreover, these ultrathin QDPDs attain an external quantum efficiency of 42% at 1330 nm, due to a 2.5‐fold enhanced light absorption through the formation of a Fabry–Perot cavity within the QDPD and the highly efficient extraction (98%) of photogenerated charge carriers. Based on these results, it is estimated that a further increase of the charge‐carrier mobility can lead to PbS QDPDs with sub‐nanosecond response time.
The record 4 ns response time in colloidal quantum dot photodiodes (QDPDs) that operate at short‐wavelength infrared (SWIR) wavelengths is reported, the first result reaching the requirement of SWIR light detection and ranging based on colloidal QDs. These ultrafast QDPDs combine a thin active layer to reduce the carrier transport time and a small area to inhibit slow capacitive discharging.