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Surface morphology and optical properties of ZnO epilayers grown on Si(1 1 1) by metal organic chemical vapor deposition |
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| Authors: | S.C. Hung P.J. Huang W.Y. Uen S.J. Pearton C.C. Chiang G.C. Chi |
| Affiliation: | a Department of Physics, National Central University, Jhongli 32001, Taoyuan, Taiwan b Department of Material Science and Engineering, University of Florida, Gainesville, FL 32611, United States c Department of Chemical Engineering, University of Florida, Gainesville, FL 32611, United States d Institute of Nuclear Energy Research Atomic Energy Council, Longtan 32546, Taoyuan, Taiwan e Department of Electronic Engineering, College of Electrical Engineering and Computer Science, Chung-Yuan Christian University, Chung-Li 32023, Taiwan |
| Abstract: | Heteroepitaxial ZnO epilayers were grown on Si(1 1 1) substrates using a vertical geometry atmospheric pressure metal organic chemical vapor deposition (AP-MOCVD) system. The growth temperature was varied from 550 °C to 650 °C in steps of 25 °C. The ZnO growth rate and surface morphology were strong functions of the growth temperature and ranged from ∼0.16 μm/h to 1.36 μm/h. The surface morphology of the ZnO films changed from granular to sharp tips as the growth temperature increased. The effect of buffer thickness was also examined, and was found to have a strong effect on the optical properties of the ZnO. An optimized growth condition for ZnO epilayers was found at 625 °C, producing a FWHM in the room temperature photoluminescence (PL) spectrum of 4.5 nm and a preferred growth orientation along the (0 0 2) direction.Transmission electron microscopy images and selected area diffraction patterns showed excellent crystalline quality of both the buffer and ZnO overlayer. When non-optimized growth temperatures were employed, post-growth annealing was found to greatly enhance the ratio of band-edge to deep level emission. |
| Keywords: | ZnO Surface morphology |
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