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HL: Fachverband Halbleiterphysik

HL 29: III-V Semiconductors I (mainly Nitrides)

HL 29.6: Vortrag

Dienstag, 27. März 2012, 10:45–11:00, EW 201

Excitonic effects and optical properties of In_xGa_1−xN and In_xAl_1−xN alloys: A first-principle study — •Luiz Claudio de Carvalho, Jürgen Furthmüller, and Friedhelm Bechstedt — Institüt für Festkörpertheorie und -optiK, Max Wien Platz 1, 07743 Jena, Germany

Optical properties of group-III nitrides and of their alloys are of increasing interest. This holds especially for the emission properties in the so called green gap. A much deeper understanding of the interplay of clustering and composition fluctuations on the optical properties is needed. Random alloy and many-body theory can give an important contribution. In the present work, the optical properties and excitonic effects of wurtzite In_xX_1−xN (X = Ga, Al) alloys and those of the end components are studied using a combination of methods. The alloys are described within the cluster expansion approximation. The optical spectra and the underlying excitonic effects are studied using a state-of-the-art treatment of the quasiparticle electronic structure and the solution of the Bethe-Salpeter equation (BSE). Explicitly we use the Vienna Ab-initio Simulation Package (VASP) in order to compute the electronic structure for each local cation fraction. Based on the electronic structures, the BSE is solved and the optical absorption spectra, exciton binding energies, and electron-energy-loss spectra are computed and compared with available experimental data. At least, two different cluster statistics are investigated.