| Summary: | 碩士 === 國立中正大學 === 光機電整合工程研究所 === 105 === In this study, we investigated the structures, the physical properties and optoelectronic properties of Ga-doped cadmium sulfide (CdS) nanowire (NW) and molybdenum ditelluride (MoTe2) flake n-p heterostructure.
First, we synthesized Ga-doped CdS NWs via chemical vapor deposition (CVD) method and X-ray photoelectron spectroscopy (XPS) analysis confirmed that Ga has been incorporated into CdS NWs with the atomic percentages of 4.92%. The red-shift and broadened full width at half maximum (FWHM) of the band-edge emission of CdS are due to the Ga dopant in CdS NWs. We then discussed the electrical transport properties of the Ga-doped CdS NWs, the electrical properties showed significant improvement with the comparison of the undoped one, and the on-off ratio is up to 105 for Ga-doped CdS field-effect transistors, gallium dopant serves as donor in CdS NWs with the average mobility 125.4 cm-2/Vs and carrier concentration 2.26×1017 cm-3. On the other hand, few-layered MoTe2 flakes were obtained by modified mechanical exfoliation from bulk, the peak difference of A1g and E12g and the intensity ratios of E12g and B12g in Raman spectra can be used to determine the numbers of layer of MoTe2. Afterward, we fabricated Ga-doped CdS/MoTe2 n-p heterostructure devices by photolithography, and the device showed typical recfication curve. Moreover, the current increased with forward and reverse biases under the increasing power of visible light irradiation, which are attributed to the different mechanisms, the increased current is owing to the diffusion of majority carriers at the interfacial region under forward bias, while is due to the minority carriers tunneled through barrier under reverse bias to form photocurrent due to the lack of majority carriers. Finally, the Ga-doped CdS/MoTe2 n-p heterostructure devices revealed photovoltaic effect with an open-circuit voltage (VOC) of 0.388 V, a short-circuit current (ISC) of 2.86 pA and conversion efficiency of 5.14 % nunder 520 nm light illumination.
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