Abstract
The strong light emission and absorption exhibited by single atomic layer transitional metal dichalcogenides in the visible to near-infrared wavelength range make them attractive for optoelectronic applications. In this work, using two-pulse photovoltage correlation technique, we show that monolayer molybdenum disulfide photodetector can have intrinsic response times as short as 3 ps implying photodetection bandwidths as wide as 300 GHz. The fast photodetector response is a result of the short electron–hole and exciton lifetimes in this material. Recombination of photoexcited carriers in most two-dimensional metal dichalcogenides is dominated by nonradiative processes, most notable among which is Auger scattering. The fast response time, and the ease of fabrication of these devices, make them interesting for low-cost ultrafast optical communication links.
Highlights
The strong light emission and absorption exhibited by single atomic layer transitional metal dichalcogenides in the visible to near-infrared wavelength range make them attractive for optoelectronic applications
Microscope image of a monolayer metal-MoS2 photodetector is shown in Fig. 1a, and the schematic in Fig. 1b depicts the setup for a two-pulse photovoltage correlation (TPPC) experiment
Our results reveal the fast response time and the wide bandwidth of metal-MoS2 photodetectors and show that these detectors can be used for ultrafast applications
Summary
The strong light emission and absorption exhibited by single atomic layer transitional metal dichalcogenides in the visible to near-infrared wavelength range make them attractive for optoelectronic applications. In TPPC measurements, a photodetector is excited with two identical optical pulses separated by a time delay and the integrated detector photoresponse (either photovoltage or photocurrent response) is recorded as a function of the time delay. The temperature and pump fluence dependence of our TPPC results are consistent with defect-assisted recombination as being the dominant mechanism, in which the the photoexcited electrons and holes, both free and bound (excitons), are captured by defects via Auger scattering[28]. Strong Coulomb interactions in 2D TMDs, including the correlations in the positions of free and bound electrons and holes arising from the attractive interactions, result in large carrier capture rates by defects via Auger scattering[28]. Our results underscore the trade-off between speed and quantum efficiency in TMD photodetectors
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