A new Schottky junction ultraviolet photodetector (UVPD) is fabricated by coating a free-standing ZnO nanorod (ZnONR) array with a layer of transparent monolayer graphene (MLG) film. The single-crystalline [0001]-oriented ZnONR array has a length of about 8-11 μm, and a diameter of 100∼600 nm. Finite element method (FEM) simulation results show that this novel nanostructure array/MLG heterojunction can trap UV photons effectively within the ZnONRs. By studying the I-V characteristics in the temperature range of 80-300 K, the barrier heights of the MLG film/ZnONR array Schottky barrier are estimated at different temperatures. Interestingly, the heterojunction diode with typical rectifying characteristics exhibits a high sensitivity to UV light illumination and a quick response of millisecond rise time/fall times with excellent reproducibility, whereas it is weakly sensitive to visible light irradiation. It is also observed that this UV photodetector (PD) is capable of monitoring a fast switching light with a frequency as high as 2250 Hz. The generality of the above results suggest that this MLG film/ZnONR array Schottky junction UVPD will have potential application in future optoelectronic devices.
Self-powered photodetectors based on CdS:Ga nanoribbons (NR)/Au Schottky barrier diodes (SBDs) were fabricated. The as-fabricated SBDs exhibit an excellent rectification characteristic with a rectification ratio up to 10 6 within AE1 V in the dark and a distinctive photovoltaic (PV) behavior under light illumination. Photoconductive analysis reveals that the SBDs were highly sensitive to light illumination with very good stability, reproducibility and fast response speeds at zero bias voltage. The corresponding rise/fall times of 95/290 ms represent the best values obtained for CdS based nanophotodetectors. It is expected that such self-powered high performance SBD photodetectors will have great potential applications in optoelectronic devices in the future.
Silicon based optoelectronic integration is restricted by its poor optoelectronic properties arising from the indirect band structure. Here, by combining silicon with another promising optoelectronic material, the CdS nanoribbon (NR), devices with heterojunction structure were constructed. The CdS NRs were also doped with gallium to improve their n-type conductivity. A host of nano-optoelectronic devices, including light emitting diodes, photovoltaic devices, and photodetectors, were successfully constructed on the basis of the CdS:Ga NR/Si heterojunctions. They all exhibited excellent device performances as regards high stability, high efficiency, and fast response speed. It is expected that the CdS NR/Si heterojunctions will have great potential for future applications of Si based optoelectronic integration.
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