Growth of Polarity-Controlled ZnO Films on (0001) Al2O3
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The polarity control of ZnO films grown on (0001) Al2O3 substrates by plasma-assisted molecular-beam epitaxy (P-MBE) was achieved by using a novel CrN buffer layer. Zn-polar ZnO films were obtained by using a Zn-terminated CrN buffer layer, while O-polar ZnO films were achieved by using a Cr2O3 layer formed by O-plasma exposure of a CrN layer. The mechanism of polarity control was proposed. Optical and structural quality of ZnO films was characterized by high-resolution X-ray diffraction and photoluminescence (PL) spectroscopy. Low-temperature PL spectra of Zn-polar and O-polar samples show dominant bound exciton (I8) and strong free exciton emissions. Finally, one-dimensional periodic structures consisting of Zn-polar and O-polar ZnO films were simultaneously grown on the same substrate. The periodic inversion of polarity was confirmed in terms of growth rate, surface morphology, and piezo response microscopy (PRM) measurement.
KeywordsPolarity PPZnO interface ZnO nitrides buffer layers
J.S. Park appreciates the financial support for a Research Fellowship and a Grant-in-Aid from the Japan Society for the Promotion of Science (JSPS). S.K. Hong gratefully acknowledges support by a Korea Research Foundation Grant funded by the Korean Government (MOEHRD, Basic Research Promotion Fund) (KRF-2005-205-D00078).
- 24.G. Bauer, and W. Richer, Optical Characterization of Epitaxial Semiconductor Layers (Springer, Berlin, 1983), Chapter 6Google Scholar