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

Abstract

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.

Pitfalls in Determining the Electrical Bandwidth of Nonideal Nanomaterials for Photodetection

“…For the PbS/EDT photodetector the particles were synthesized following the route of Weidman et al and the ligand exchange was performed according to Luther et al The films were prepared on a glass substrate with interdigitated electrodes (4 nm Ti/20 nm Au, 2.5 μm × 1 cm, finger width 20 μm, film height 50 nm) as reported elsewhere . In short, 7.5 mL of oleylamine and 0.04 g of sulfur were heated to 120 °C for 20 min in an oil bath under nitrogen atmosphere before being allowed to cool back to room temperature while maintaining the nitrogen flow.…”

Edge contacts accelerate the response of MoS2 photodetectors

“…13 Many methods have been used in the search for ultrafast photodetectors based on nanomaterials: chemical doping, 14 heterojunction implementation, 15,16 photonic waveguide integration, 17 and small channel lengths, 18,19 to name a few. In addition, parameters such as the choice of substrate, 18,20 interface roughness, 21 electrode material, 10,22,23 and geometry 13,24,25 or environment 26,27 must be considered each time.…”

Solution-grown ternary quasi-cube AgSbTe2 and its optoelectronic performance for broadband photodetection

“…Photodetectors, which can convert absorbed optical signals into electrical signals, have been demonstrated to be critical in the field of modern information technology, such as light imaging, optical communication, biological sensing and industrial inspection. [1][2][3][4][5][6] Traditional photodetectors are usually composed of semiconductor nanostructures owing to their high light absorption coefficients and tunable band gaps. [7][8][9][10] However, the preparation process of those photodetectors often requires a complex material growth process and a high-cost integrated procedure.…”