Sub-nanosecond Intrinsic Response Time of PbS Nanocrystal IR-Photodetectors

• Published in: Nano letters Vol. 22; no. 7; pp. 2809 - 2816
• Main Authors: Maier, Andre, Strauß, Fabian, Kohlschreiber, Pia, Schedel, Christine, Braun, Kai, Scheele, Marcus
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 13.04.2022
• Subjects: PbS; pump−probe; photodetectors; response time; Auger recombination; nanocrystals
• ISSN: 1530-6984; 1530-6992
• DOI: 10.1021/acs.nanolett.1c04938

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 femtosecond-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.