Regensburg 2016 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 62: Gallium Nitride: Optical and Electronic Properties

HL 62.4: Talk

Wednesday, March 9, 2016, 15:30–15:45, H17

Role of coherency strain for optical properties of In_xGa_1−xN active layers grown on GaN substrates — •Christoph Freysoldt¹, Siyuan Zhang^1,2, Ying Cui¹, and Jörg Neugebauer¹ — ¹Max-Planck-Institut für Eisenforschung GmbH, Düsseldorf, Germany — ²Department of Materials Science and Metallurgy, University of Cambridge, United Kingdom

In_xGa_1−xN alloys are the material of choice for the optical recombination layers in GaN-based optoelectronic devices. When going from the violet-blue spectral range (x≈15%) towards the green range x > 30%), the growth of coherent In_xGa_1−xN layers becomes increasingly difficult due to the lattice mismatch between InN and GaN. Yet, significant progress has been made experimentally to improve the quality of high-In films.

Theoretically, In_xGa_1−xN alloys have been studied by a variety of methods ranging from multi-band k·p over tight-binding to density-functional theory. In our work, we explore the role of finite coherency strain on the electronic structure of In_xGa_1−xN alloys for polar (c-plane) and non-polar (a-plane and m-plane) growth using state-of-the-art density-functional theory. Our calculations highlight that the high strains introduce non-linear effects in the elastic behavior and in the electronic structure that are missed by perturbative treatments of strain. We demonstrate that non-linear strain relaxation breaks the symmetry between a-plane and m-plane for the strain-induced valence band splitting that is relevant for inducing in-plane polarization of the emitted light.