Fast response CdS-CdS_xTe_1-x-CdTe core-shell nanobelt photodetector

Quasi-one-dimensional semiconductor nanostructure-based photodetectors show high sensitivity but suffer from slow response speed due to surface reaction. Here, we report a fast-response CdS-CdS_xTe_1-x-CdTe core-shell nanobelt photodetector with a rise time of 11 μs, which is the fastest among CdS based photodetectors reported previously. The improved response speed is ascribed to the suppressed possibilities of surface reaction resulting from the core-shell structure and heterojunction among the CdS, CdS_xTe_1-x and CdTe. The measured response spectrum of CdS-CdS_xTe_1-x-CdTe core-shell nanobelt photodetector covers a wide range from 355 to 785 nm. Moreover, high responsivity (1,520 A/W) and large 3 dB bandwidth (∼22.9 kHz) are obtained along with the fast response. The high performance in responsivity, sensitivity, spectral response and photoresponse speed makes this device a promising candidate for practical application in optical sensing, communication and imaging.