Regensburg 2007 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 51: GaN: preparation and characterization
HL 51.7: Vortrag
Freitag, 30. März 2007, 12:30–12:45, H13
Band gap and Van-Hove singularities of cubic InN — •Pascal Schley1, Rüdiger Goldhahn1, Christian Napierala1, Gerhard Gobsch1, Jörg Schörmann2, Donat J. As2, Klaus Lischka2, Frank Fuchs3, and Friedhelm Bechstedt3 — 1Institut für Physik, TU Ilmenau — 2Department Physics, Universität Paderborn — 3Institut für Festkörpertheorie und -optik, FSU Jena
InN has attracted much interest recently due to the band gap revision for the hexagonal compound from the long-time accepted value of 1.89 eV down to only 0.68 eV. Theoretical calculations predict an even lower gap for the cubic (c-) counterpart. We succeeded in growing single crystalline c-InN films on 3C-SiC substrate with a c-GaN buffer layer by MBE. Ellipsometry was applied in order to determine the dielectric function (DF) of c-InN from the near infrared into the VUV spectral region (data above 4 eV refer to the use of synchrotron radiation at BESSY II). The spectra show pronounced features in the high-energy part which arise from the Van-Hove singularities in the band structure. High-resolution transition energy determination is achieved by fitting the third derivatives of the DF. The values as well as the shape of the DF are in excellent agreement with the results of DFT-LDA calculations for which electron-hole interaction was taken into account. The position of the absorption edge depends clearly on the electron density of the films. Taking into account carrier-induced band gap renormalization and the Burstein-Moss shift we estimate the zero-density band gap of c-InN with 0.62 eV which is by 60 meV lower than for hexagonal InN.