Berlin 2012 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 46: Focus Session: AlGaN Materials for UV Emitters

HL 46.6: Topical Talk

Wednesday, March 28, 2012, 12:15–12:45, ER 164

Dielectric properties and band structure evolution in AlGaN alloys — •Christoph Cobet — Center of Surface and Nanoanalytics, Johannes Kepler University , Linz, Austria

During the past 10 years the optoelectronic properties of group-III-nitrides have been investigated in a wide spectral range. These efforts were driven on one hand by the demand on reference data for novel optoelectronic devices and for proving band structure calculations and on the other hand by the continuous improvement of the crystal quality of epitaxial films. Step by step it was possible to elucidate many fundamental electronic properties and to increase the general understanding of the constituting electronic background. Recently remaining uncertainties concerned for example the fundamental question whether cubic AlN has an indirect band gap and the identification of related band structure peculiarities. Moreover, the impact of the exciton formation and the exact band ordering at the Γ- and other high symmetry points in the Brillouin-zone are discussed under consideration of strain effects. It will be shown on the basis of complete AlGaN series, how these kinds of questions were addressed by measuring the entire dielectric function from the visible to the far UV.