Berlin 2015 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe
HL: Fachverband Halbleiterphysik
HL 51: Focus Session: Role of polarization fields in nitride devices II
HL 51.2: Vortrag
Mittwoch, 18. März 2015, 15:15–15:30, ER 164
Analysis of the anisotropic dielectric function of strained semipolar AlGaN — •Michael Winkler1, Juliane Klamser1, Martin Feneberg1, Rüdiger Goldhahn1, Joachim Stellmach2, Martin Frentrup2, Simon Ploch2, Frank Mehnke2, Tim Wernicke2, and Michael Kneissl2 — 1Institut für Experimentelle Physik, Otto-von-Guericke-Universität Magdeburg — 2Institut für Festkörperphysik, Technische Universität Berlin
The linear optical responses of thick semipolar (1122) AlGaN films are analyzed quantitatively. The samples were grown by metal-organic vapor phase epitaxy on m-plane sapphire substrates spanning the whole composition range between GaN and AlN.
Due to the anisotropic nature of strain and non-vanishing shear-strain elements, the crystal symmetry is no longer wurtzite but monoclinic. This case is covered by kp-theoretical calculations yielding energy distances of transitions from different valence sub-bands and corresponding relative oscillator strengths for electric field vectors in different orientations, i.e. different optical polarization directions. These data are translated to model dielectric functions which are compared and fitted to experimental results obtained by spectroscopic ellipsometry.
The quantitative analysis allows a conversion back to wurtzite material yielding direct experimental evidence of the dependence of the crystal field energy on the aluminum concentration.