Dresden 2014 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 37: Posters: Plasmonics, Electronic Structure and Spin-Orbit Interaction, Semiconductor and Insulator Surfaces, Nanostructures

O 37.72: Poster

Dienstag, 1. April 2014, 18:30–22:00, P2

Electronic properties and optical response of nonpolar GaN surfaces — •Marc Landmann, Eva Rauls, and Wolf Gero Schmidt — University of Paderborn, Germany

In nonpolar or semipolar GaN, the hexagonal c axis is orthogonal or inclined to the growth direction, in order to eliminate or limit the internal piezoelectric and spontaneous polarization fields that inherently limit the performance of optoelectronic devices. [1] We have calculated the electronic structure of the semipolar m-plane GaN(1-100) and a-plane GaN(11-20) surfaces within density functional theory (DFT). The band gap underestimation of (semi)local density functionals is corrected by a non-local Heyd-Scuseria-Ernzerhof (HSE) type hybrid-functional with an adjusted fraction of exact exchange. Surface characteristic states and their microscopic origin are identified in the calculated surface band structure and density of states. While the complex dielectric functions of GaN bulk and surface slabs, calculated within the independent particle approximation (IPA) on the HSE hybrid functional DFT level of theory, fail to reproduce prominent near band-edge features of the optical response, the inclusion of excitonic effects via solution of the Bethe-Salpeter equation for Coulomb correlated electron-hole pairs reproduces the experimentally observed spectral features. The optical anisotropies of the semipolar surfaces are investigated by calculation of the reflection anisotropy spectroscopy (RAS) [2] spectra and discussed alongside experimental data.

[1] J. Schörmann et al., Appl. Phys. Lett. 89 (2006) 131910.

[2] W. G. Schmidt, phys. Stat. sol. (b) 242 (2005) 2751.