Enhanced diode performance in cadmium telluride-silicon nanowire heterostructures

We report on the structural and optoelectronic characteristics and photodetection properties of cadmium telluride (CdTe) thin film/silicon (Si) nanowire heterojunction diodes. A simple and cost-effective metal-assisted etching (MAE) method is applied to fabricate vertically oriented Si nanowires on n-type single crystalline Si wafer. Following the nanowire synthesis, CdTe thin films are directly deposited onto the Si nanowire arrays through RF magnetron sputtering. A comparative study of X-ray diffraction (XRD) and Raman spectroscopy shows the improved crystallinity of the CdTe thin films deposited onto the Si nanowires. The fabricated nanowire based heterojunction devices exhibit remarkable diode characteristics, enhanced optoelectronic properties and photosensitivity in comparison to the planar reference device. The electrical measurements revealed that the diodes have a well-defined rectifying behavior with a superior rectification ratio of 10(5) at +/- 5 V and a relatively small ideality factor of n = 1.9 with lower reverse leakage current and series resistance at room temperature in dark condition. Moreover, an open circuit voltage of 120 mV is also observed under illumination. Based on spectral photoresponsivity measurements, the nanowire based device exhibits a distinct responsivity (0.35-0.5 A W-1) and high detectivity (6 x 10(12)-9 x 10(12) cm Hz(1/2) W-1) in near-infrared wavelength region. The enhanced device performance and photosensitivity is believed to be due to three-dimensional nature of the interface between the CdTe thin film and the Si nanowires. The device characteristics observed here reveals that fabricated CdTe thin film/Si nanowire heterojunctions are promising for high-performance and low-cost optoelectronic device applications, near-infrared photodetectors in particular. (C) 2015 Elsevier B.V. All rights reserved.