Dresden 2017 – wissenschaftliches Programm
HL 50.2: Vortrag
Mittwoch, 22. März 2017, 10:00–10:15, POT 251
Effective electron mass in cubic GaN — •Elias Baron1, Martin Feneberg1, Rüdiger Goldhahn1, Michael Deppe2, and Donat J. As2 — 1Institut für Experimentelle Physik, Otto-von-Guericke-Universität Magdeburg, Germany — 2Department Physik, Universität Paderborn, Germany
Ge-doping has been proven a very efficient way to achive free electron concentrations n above 1020cm−3 in wurtzite GaN layers while maintaining excellent structural properties of the films. Recently, we demonstrated that similar high n values can also be obtained in cubic GaN layers by germanium doping. The films were deposited by plasma-assisted molecular beam epitaxy on 3C-SiC substrates. Here, we present a comprehensive characterization of those films covering a wide range of n values by spectroscopic ellipsometry from which the complex dielectric function (DF) is deduced. The analysis of the DFs in the mid-infrared yields the transverse-optical phonon frequency and the plasma frequencies. From the latter, the dependence of the effective electron mass on n is obtained indicating a strong non-parabolicity of the conduction band. Studies around the fundamental absorption edge indicate the superposition of carrier-density dependent Burstein-Moss effect and band gap shrinkage. Excellent agreement between theory and experiment is achieved for the energetic position of the absorption edge when applying the experimentally determined dependence electron mass dependence on n.