Dresden 2020 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 72: Focus Session: Functional Metal Oxides for Novel Applications and Devices III (joint session HL/DS)
HL 72.4: Talk
Thursday, March 19, 2020, 15:45–16:00, POT 81
Phonons and free-carrier contributions of spinel ZnGa2O4 by spectroscopic ellipsometry — •Alwin Wüthrich1, Martin Feneberg1, Zbigniew Galazka2, and Rüdiger Goldhahn1 — 1Institut für Physik, Otto-von-Guericke-Universität Magdeburg, Germany — 2Leibniz Institute for Crystal Growth, Berlin, Germany
Ga based spinels with the general formula of MeGa2O4, where Me is a divalent metal, such as MgGa2O4 or ZnGa2O4 offer an ultra wide band gap and good electrical conductivity. These transparent semiconducting oxides (TSOs) have been receiving greater interest in the last years due to an outstanding importance in a wide range of scientific disciplines, such as photoelectronics, sensing systems or optical applications. Here, bulk ZnGa2O4 single crystals were grown directly from the melt by the vertical gradient freeze (VGF) method. This study presents a characterisation of these bulk crystals by spectroscopic ellipsometry, from which the complex dielectric function (DF) was deduced. Free-carrier concentrations (n) up to 1019 cm−3 were investigated in the infrared spectral range, where the phonons and plasmons were determined. The former agrees well to prior theoretical and experimental studies while from the latter the dependence of the effective electron mass on n is achieved, indicating a non-parabolicity of the conductive band.