MOVPE growth of GaAsN: surface study by AFM and optical properties |
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Authors: | L. Auvray H. Dumont J. Dazord Y. Monteil J. Bouix C. Bru-Chevallier L. Grenouillet |
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Affiliation: | 1. Nano Functional Materials Technology Centre, Indian Institute of Technology Madras, Chennai-36, India;2. Department of Physics, Indian Institute of Technology Madras, Chennai-36, India;3. Manufacturing Engineering Section, Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai-36, India;4. Department of Metallurgical and Materials Engineering, Indian Institute of Technology Madras, Chennai-36, India;5. Corporate Technology Centre, Tube Investment of India Pvt. Ltd., Chennai, India |
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Abstract: | We report on the growth of GaAs1−xNx thin films on GaAs substrates (2° off) by metalorganic vapor-phase epitaxy, in the temperature range 500–600°C. A mixture of N2 and H2 was used as the carrier gas. Using dimethylhydrazine as nitrogen source, we incorporated up to 3.5% of nitrogen, at 530°C. The growth condition dependence of nitrogen content was studied, and it reveals a distribution coefficient 350 times lower for nitrogen than for arsine at 530°C. Nitrogen incorporation is controlled by surface kinetics. The evolution of surface morphology has been investigated by atomic force microscopy as a function of the nitrogen composition and of growth temperature. For nitrogen content up to 2%, the GaAsN vicinal surface is characterized by a step–terrace structure with bunched steps, and the step edges straighten when increasing the growth temperature. For higher nitrogen content terraces are no longer observed and, above 3%, widely-spaced cross-hatch lines, characteristic of a partial relaxation of strain in the epilayers, appear. Optical properties were studied by low (7 K) and room-temperature photoluminescence and photoreflectance. As usual for this material, a degradation of optical characteristics is observed with increasing N content along with the evolution of surface morphology. |
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Keywords: | MOVPE GaAsN AFM PL |
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