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Nanogap quantum dot photodetectors with high sensitivity and bandwidth
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View: Figures


Image of FIG. 1.
FIG. 1.

A nanoscale nanocrystal QD photodetector. (a) Illustration of the photodetector device structure and finite element model showing the normal dc electric field concentrated in the gap. Field lines and a cross-section of the field are shown. The unit of the scale bar is . (b) SEM of a typical nanogap electrode without the nanocrystal thin-film. (c) AFM of the device after QD deposition. The zoom-in shows that the QD thin film is quite uniform and smooth, with roughness on the order of the diameter of a single QD.

Image of FIG. 2.
FIG. 2.

Experimental setup for characterizing sensitivity and bandwidth of the nanoscale QD photodetector. A single lock-in is used for modulation frequency below 50 kHz (red) and a double lock-in approach is utilized for modulation frequency above 50 kHz (blue).

Image of FIG. 3.
FIG. 3.

Experimental results for the nanocrystals QD photodetector. (a) Dark (black, square) and light (red, circle) I-V measurement under 14 nW input optical power for a 50 nm nanogap device. (b) Repeatability measurement under low light level illumination (120 pW) for a typical nanogap device. The error bars show the standard deviation associated with five separate data runs for dark and light measurements, respectively. (c) Sensitivity measurement. An input optical power as low as 500 fW can be detected by the 50 nm nanogap QD photodetector. (d) Bandwidth measurement to 200 kHz. The result is limited by the bandwidth of the double lock-in experimental setup (125 kHz).


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Scitation: Nanogap quantum dot photodetectors with high sensitivity and bandwidth