Regensburg 2007 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 51: GaN: preparation and characterization

HL 51.5: Talk

Friday, March 30, 2007, 12:00–12:15, H13

Nonlinear elastic effects in group III-nitrides — •Michal Petrov, Liverios Lymperakis, and Jörg Neugebauer — Max-Planck-Institut für Eisenforschung, Max-Planck-Strasse 1, 402 37, Düsseldorf, Germany

The zero-dimensional nature of Quantum Dots (QD) allows the design of novel high performance optoelectronic devices. In group III-nitrides, due to the large lattice mismatch and the stiffness of the material, the quantum dots embedded in the semiconductor matrix are highly strained and the inclusion of nonlinear elastic effects is crucial. However so far experimental and/or theoretical data on the composition and pressure dependence of the elastic constants of AlGaN alloys are lacking. Therefore, we computed the composition and pressure dependence of the bandgaps and the elastic constants of the AlGaN alloys employing planewave pseudopotential calculations within the density functional theory. The calculation of the second and third order elastic constants was performed within the framework of anisotropic hyperelasticity [1]. To model ternary random alloys within a supercell formalism (which intrinsically contains periodic boundary conditions), we considered a number of different ordered configurations based on the concept of Special Quasirandom Structures (SQS). The thus calculated nonlinear coefficients are used as input for a multi-scale scheme based on Finite Elements and k.p theory calculations and allows an accurate description of the binding states and optical Coulomb matrix elements in materials QDs.

[1] P. Dluzewski, Journal of Elasticity 60, 119 (2000).