Dresden 2011 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 31: III-V-Compounds: Nitrides

HL 31.6: Talk

Tuesday, March 15, 2011, 11:30–11:45, POT 51

Optical properties of quaternary AlInGaN alloys pseudomorphically grown on GaN — •Egidijus Sakalauskas¹, Benjamin Reuters², Lars R. Khoshroo², Holger Kalisch², Michael Heuken^2,3, Rolf H. Jansen², Andrei Vescan², Gerhard Gobsch¹, and Rüdiger Goldhahn^1,4 — ¹Institut für Physik, TU Ilmenau — ²Institut für Theoretische Elektrotechnik, RWTH Aachen University — ³AIXTRON AG — ⁴Institut für Experimentelle Physik, OvGU Magdeburg

The optical properties of quaternary Al_xIn_yGa_1−x−yN alloy system with 0.28<x<0.74 and 0.04<y<0.15 are presented. The (0001)-oriented AlInGaN films are pseudomorphically grown by metal-organic vapour phase epitaxy on thick GaN buffers with sapphire substrates. The ordinary dielectric function of AlInGaN samples was determined in the range 1-10 eV by synchrotron ellipsometry at room temperature (BESSY II). The sharp onset of the imaginary part of the dielectric function defines the direct absorption edge of the alloys. At higher photon energies, the pronounced peaks are observed in the dielectric function, which correspond to high-energy inter-band transitions attributed to the critical points of the band structure (Van Hove singularities), indicating a promising optical quality of the material. An analytical model, which permits to describe accurately the dielectric function (or optical constants) in the range 1-10 eV, is also presented. The band-gap and high-energy inter-band transition values are obtained by fitting the experimental dielectric function with the analytical model. The strain influence on the band gap is evaluated by using k·p formalism.