Sub-ns intrinsic response time of PbS nanocrystal IR-photodetectors

• Published in: arXiv.org
• Main Authors: Maier, Andre, Strauß, Fabian, Kohlschreiber, Pia, Schedel, Christine, Braun, Kai, Scheele, Marcus
• Format: Paper Journal Article
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 22.12.2021
• Subjects: Augers; Lead sulfides; Nanocrystals; Optical communication; Photometers; Physics - Materials Science; Response time; Surface defects
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2112.11987

Colloidal nanocrystals (NCs), especially lead sulfide NCs, are promising candidates for solution-processed next-generation photodetectors with high-speed operation frequencies. However, the intrinsic response time of PbS-NC photodetectors, which is the material-specific physical limit, is still elusive, as the reported response times are typically limited by the device geometry. Here, we use the two-pulse coincidence photoresponse technique to identify the intrinsic response time of 1,2-ethanedithiol-functionalized PbS-NC photodetectors after fs-pulsed 1560 nm excitation. We obtain an intrinsic response time of ~1 ns, indicating an intrinsic bandwidth of ~0.55 GHz as the material-specific limit. Examination of the dependence on laser power, gating, bias, temperature, channel length and environmental conditions suggest that Auger recombination, assisted by NC-surface defects, is the dominant mechanism. Accordingly, the intrinsic response time might further be tuned by specifically controlling the ligand coverage and trap states. Thus, PbS-NC photodetectors are feasible for gigahertz optical communication in the third telecommunication window.