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Improvement of optical transmittance and electrical properties for the Si quantum dot-embedded ZnO thin film

Kuang-Yang Kuo, Chuan-Cheng Liu, Pin-Ruei Huang, Shu-Wei Hsu, Wen-Ling Chuang, You-Jheng Chen and Po-Tsung Lee*

Author Affiliations

Department of Photonics and Institute of Electro-Optical Engineering, National Chiao Tung University, 1001 Ta-Hsueh Road, Hsinchu 30010, Taiwan

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Nanoscale Research Letters 2013, 8:439  doi:10.1186/1556-276X-8-439

Published: 23 October 2013

Abstract

A Si quantum dot (QD)-embedded ZnO thin film is successfully fabricated on a p-type Si substrate using a ZnO/Si multilayer structure. Its optical transmittance is largely improved when increasing the annealing temperature, owing to the phase transformation from amorphous to nanocrystalline Si QDs embedded in the ZnO matrix. The sample annealed at 700°C exhibits not only high optical transmittance in the long-wavelength range but also better electrical properties including low resistivity, small turn-on voltage, and high rectification ratio. By using ZnO as the QDs’ matrix, the carrier transport is dominated by the multistep tunneling mechanism, the same as in a n-ZnO/p-Si heterojunction diode, which clearly differs from that using the traditional matrix materials. Hence, the carriers transport mainly in the ZnO matrix, not through the Si QDs. The unusual transport mechanism using ZnO as matrix promises the great potential for optoelectronic devices integrating Si QDs.

Keywords:
Si quantum dot; ZnO thin film; Transport mechanism