Low temperature epitaxial growth of ZnO layer by plasma-assisted epitaxy |
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Affiliation: | 1. Center for Spintronics, Korea Institute of Science and Technology (KIST), Seoul 02792, South Korea;2. KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul 02841, South Korea;3. Center for Opto-Electronic Materials and Devices, Korea Institute of Science and Technology (KIST), Seoul 02792, South Korea;4. School of Electrical Engineering, Kookmin University, Seoul 02707, South Korea;5. Advanced Analysis Center, Korea Institute of Science and Technology (KIST), Seoul 02792, South Korea;6. Division of Nano & Information Technology, KIST School, Korea University of Science and Technology, Seoul 02792, South Korea;1. Department of Physics, Applied Physics and Astronomy, Rensselaer Polytechnic Institute, Troy, NY 12180, USA;2. Department of Electrical, Computer, and Systems Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180, USA;3. Oak Ridge National Laboratories, Oak Ridge, TN 37831, USA |
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Abstract: | Plasma-assisted epitaxial growth of ZnO layers were achieved on C- and R-plane sapphire substrates in oxygen plasma excited by radio frequency power at 13.56 MHz with evaporation of pure elemental Zn. The ZnO layers were grown at 300–400°C with high growth rate around 1.7 μm/h. Surface cleaning of sapphire substrates using Ar-plasma was crucial for good quality ZnO growth. Photoluminescence spectra at 10 K were dominated by band-edge emission due to bound excitons without deep level emission in green-light region. The intensity of band-edge emission was strongly dependent on applied radio frequency power to excite Ar- and O2-plasma for sapphire surface cleaning and ZnO growth, respectively, and was about 50 times larger on the layer grown in oxygen plasma than that grown in non-excited oxygen gas. The ZnO layer grown on R-plane sapphire was epitaxially grown above 300°C in oxygen plasma, however, on C-plane sapphire the ZnO layer was easily polycrystallized for thick films even at 400°C. Growth mode and surface morphology of ZnO layers were drastically changed with the substrate orientation. |
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