Epitaxial Growth and Orientation of GaN on (1 0 0) g-LiAlO2
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Epitaxial Growth and Orientation of GaN on (1 0 0) γ-LiAlO2 E. S. Hellman, Z. Liliental-Weber and D. N. E. Buchanan MRS Internet Journal of Nitride Semiconductor Research / Volume 2 / January 1997 DOI: 10.1557/S1092578300001563, Published online: 13 June 2014
Link to this article: http://journals.cambridge.org/abstract_S1092578300001563 How to cite this article: E. S. Hellman, Z. Liliental-Weber and D. N. E. Buchanan (1997). Epitaxial Growth and Orientation of GaN on (1 0 0) γ-LiAlO2 . MRS Internet Journal of Nitride Semiconductor Research, 2, pp e30 doi:10.1557/S1092578300001563 Request Permissions : Click here
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M R S
Internet Journal o f
Nitride S emiconductor Research
Volume 2, Article 30
Epitaxial Growth and Orientation of GaN on (1 0 0) g-LiAlO2 E. S. Hellman Bell Laboratories, Lucent Technologies Z. Liliental-Weber Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley CA 94720 D. N. E. Buchanan Bell Laboratories, Lucent Technologies This article was received on June 20, 1997 and accepted on September 15, 1997.
Abstract The (1 0 0) face of γ -LiAlO2 has attracted attention as a possible substrate for GaN epitaxial growth. This is partly because this face has an excellent lattice and structural match to (1 0 0) GaN. This orientation would have a misfit of only -1.4% along the c-direction and -0.1% along the b-direction of LiAlO 2. We find that in practice this orientation relationship does not occur; instead, (0 0 0 1) oriented GaN grows with a small tilt (0.6° towards the c-direction) between the film and substrate. Although the misfit along the substrate b direction is large (-6.3%) for this orientation, the tilt perfectly accommodates the -1.4% misfit in the c direction. We present characterization of these films by RHEED, X-ray diffraction, and TEM. We propose that the tilt is driven by a reduction of interface energy which occurs in polar, incoherent interfaces.
1. Introduction The lack of a lattice-matched substrate for epitaxial growth of GaN films has stimulated an intense search for suitable materials. The most commonly used substrate, sapphire, has a very large misfit for GaN, -13.7%. Several alternatives to sapphire have been explored, including SiC [1], spinel [2], ZnO [3] [4], β-LiGaO2 [5] [6], and γ -LiAlO2 [7]. β-LiGaO2 was an obviously promising possibility for GaN epitaxy, because its crystal structure is just a wurtzite superstructure and could be grown by the Czochralski technique. [8] However, β-LiGaO2 may not be sufficiently stable, particularly at the high temperatures used for MOCVD growth, to be advantageous for GaN growth, and the results that have been obtained with it have been mixed. [9] γ -LiAlO2 [a] is chemically similar to β-LiGaO2. Although the structure [10] is not as closely related to wurtzite,
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