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Title
Japanese: 
English:Effect of MgZnO-layer capping on optical properties of ZnO epitaxial layers 
Author
Japanese: 牧野 哲征, 田村 謙太郎, Chia Chin Hau, 瀬川 勇三朗, 川崎 雅司, 大友 明, 鯉沼 秀臣.  
English: T. Makino, K. Tamura, C. H. Chia, Y. Segawa, M. Kawasaki, A. Ohtomo, H. Koinuma.  
Language English 
Journal/Book name
Japanese: 
English:Applied Physics Letters 
Volume, Number, Page Vol. 81    No. 12    pp. 2172-2174
Published date Sept. 2002 
Publisher
Japanese: 
English: 
Conference name
Japanese: 
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Conference site
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File
Official URL <Go to ISI>://000177911200010
 
DOI https://doi.org/10.1063/1.1506783
Abstract Photoluminescence (PL) and reflectivity spectra of ZnO epilayers capped with MgxZn1-xO layers (up to x=0.36) are reported. These capped films were epitaxially grown on lattice-matched ScAlMgO4 substrates by laser molecular-beam epitaxy. A photoluminescence spectrum from the ZnO layer taken at 5 K shows emission bands at 3.389, 3.376, and 3.362 eV. The two higher bands are due to A- and B-free exciton emissions and the lowest band is due to emission of a neutral-acceptor bound exciton (I-6). The linewidth of the I-6 emission in our uncapped sample (0.8 meV) is significantly smaller than that in the capped one (6 meV). This is probably due to strain applied across the ZnO layer because of the difference in lattice constant between the two layers. The spectral assignment of the free exciton emissions is strengthened by a comparison with a temperature-dependent PL study and a reflectivity study. With an increase in temperature, the intensity of the bound exciton emission line decreased drastically and became comparable to that of free exciton lines. Free exciton emissions are already detectable at the liquid He temperature for the capped samples, which is never achieved in the uncapped ones grown under identical conditions. This indicates the high degree of purity of the capped films.

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