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Exciton Localization of High-Quality ZnO/MgxZn1–xO Multiple Quantum Wells on Si (111) with a Y2O3 Buffer Layer

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journal contribution
posted on 27.07.2018, 00:00 by Wei-Rein Liu, Wei-Lun Huang, Yung-Chi Wu, Liang-Hsun Lai, Chia-Hung Hsu, Wen-Feng Hsieh, Tsung-Hung Chiang, H. W. Wan, M. Hong, J. Kao
We report the structural and optical properties of ten-period ZnO/MgxZn1–xO multiple quantum wells (MQWs) prepared on the most widely used semiconductor material, Si. The introduction of a nanometer thick high-k Y2O3 transition layer between Si (111) substrate and a ZnO buffer layer significantly improves the structural perfection of the MQWs grown on top of it. The high structural quality of the ZnO/MgxZn1–xO MQWs is evidenced by the appearance of pronounced high order satellite peaks in X-ray crystal truncation rods; high resolution cross-sectional transmission electron microscopy images also confirmed the regularly arranged well and barrier layers. When the well width is less than ∼2.7 nm, the quantum-confined Stark effect in MQWs can be negligible. Not only the increasing exciton-binding energy but also reducing exciton–phonon coupling determined in temperature-dependent photoluminescence spectra indicate quantum-size effect. Our results demonstrate that ZnO/MgxZn1–xO MQWs integrated on Si have great potential in UV optoelectronic device applications.