Berlin 2005 – scientific programme
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DS: Dünne Schichten
DS 24: Postersitzung II
DS 24.14: Poster
Tuesday, March 8, 2005, 17:00–19:00, Poster TU B
Ellipsometric investigation of valence band and core level excitation in thin nitride films — •Munise Rakel1, Christoph Cobet1, Rüdiger Goldhahn2, Karsten Fleischer1, Wolfgang Richter1, and Norbert Esser3 — 1Institute of Solid State Physics, TU Berlin, Hardenbergstr. 36, D-10623 Berlin — 2Institute of Physics, TU Ilmenau, D-98648 Ilmenau — 3ISAS Institute for Analytical Sciences Berlin, Albert-Einstein-Str. 9, D-12489 Berlin
The dielectric function of GaN and InN in hexagonal and cubic crystal structure has been measured in a spectral range from 3- 30 eV using ellipsometry at BESSY II. Hexagonal a-plane InN(11-20) and m-plane GaN(1-100) were used to access both the ordinary and the extraordinary part of the dielectric tensor. Especially for GaN, the m-plane is the more preferable surface for quantum well structures because of the absence of any polarization along the growth axis [1]. In addition, we determined the optical properties of cubic crystal nitrides to provide a critical test for the various theoretical models. We observed a strong optical anisotropy in the higher interband transitions and core level excitations of a-plane InN and m-plane GaN in dependence of the sample orientation. Above 15eV the optical spectra of GaN and InN are dominated by transitions between the 3d/4d atomic orbital and the conduction bands. We compared measurements at RT and 12 K using a closed cycle helium cryostate setup. Composition and temperature related energy shifts are reported for InN, GaN and AlGaN.
[1] P.Waltereit, O.Brandt et al.; 1. Selected Brief Reports; Paul-Drude-Institut Berlin