Electronic structure of biaxially strained wurtzite crystals GaN, AlN, and InN
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Electronic structure of biaxially strained wurtzite crystals GaN, AlN, and InN J. A. Majewski, M. Städele and P. Vogl MRS Internet Journal of Nitride Semiconductor Research / Volume 1 / January 1996 DOI: 10.1557/S1092578300002027, Published online: 13 June 2014
Link to this article: http://journals.cambridge.org/abstract_S1092578300002027 How to cite this article: J. A. Majewski, M. Städele and P. Vogl (1996). Electronic structure of biaxially strained wurtzite crystals GaN, AlN, and InN . MRS Internet Journal of Nitride Semiconductor Research, 1, pp e30 doi:10.1557/S1092578300002027 Request Permissions : Click here
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M R S
Internet Journal o f
Nitride S emiconductor Research
Volume 1, Article 30
Electronic structure of biaxially strained wurtzite crystals GaN, AlN, and InN J. A. Majewski, M. Städele, P. Vogl Walter Schottky Institut, Technische Universität München This article was received on June 11, 1996 and accepted on October 31, 1996.
Abstract We present first-principles studies of the effect of biaxial (0001)-strain on the electronic structure of wurtzite GaN, AlN, and InN. We provide accurate predictions for the valence band splittings as a function of strain which greatly facilitates the interpretation of data from samples with unintentional growth-induced strain. The present calculations are based on the total-energy pseudopotential method within the local-density formalism and include the spin-orbit interaction nonperturbatively. For a given biaxial strain, all structural parameters are determined by minimization of the total energy with respect to the electronic and ionic degrees of freedom. Our calculations predict that the valence band state Γ9 (Γ6) lies energetically above the Γ7 (Γ1) states in GaN and InN, in contrast to the situation in AlN. In all three nitrides, we find that the ordering of these two levels becomes reversed for some value of biaxial strain. In GaN, this crossing takes place already at 0.32% tensile strain. For larger tensile strains, the top of the valence band becomes well separated from the lower states. The computed crystal-field and spin-orbit splittings in unstrained materials as well as the computed deformation potentials agree well with the available experimental data.
1. Introduction The group-III nitrides AlN, GaN, and InN have recently attracted much attention as candidates for short-wavelength optical devices [1]. The stable structure of bulk materials is the wurtzite structure. For technological applications, one needs high quality epitaxial films that are presently grown mostly on c-plane sapphire or hexagonal 6H-SiC substrates and also possess the wurtzite structure. The large lattice mismatch between the mentioned substrates and the nitrides induces a substantial strain in the latter materials. Even though
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