Berlin 2018 – scientific programme
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DS: Fachverband Dünne Schichten
DS 10: Oxide Semiconductors for Novel Devices (Focussed Session): Session II
DS 10.11: Talk
Monday, March 12, 2018, 17:45–18:00, E 020
Analysis of the conductivity anisotropy of β-Ga2O3 using Van der Pauw measurenemts — •Christian Golz1, Zbigniew Galazka2, Fariba Hatami1, W. Ted Masselink1, and Oliver Bierwagen3 — 1Department of Physics, Humboldt-Universität zu Berlin, Newton-Str. 15, D-12489 — 2Leibniz Institute for Crystal Growth, Max-Born-Str. 2, D-12489 — 3Paul-Drude-Institute, Hausvogteiplatz 5-7, D-10117
Using Van der Pauw measurements, the conductivity anisotropy of β-Ga2O3 was analyzed. The structural asymmetry due to the monoclinic lattice structure of β-Ga2O3 translates into anisotropic properties like optical absorption and thermal conductivity. Due to an anisotropic effective mass and anisotropic scattering rates (e. g. due to anisotropic phonon modes), conductivity might be anisotropic as well. Square shaped β-Ga2O3 high quality bulk samples oriented in several surface orientations with lithographically processed contacts were analyzed for temperatures between 10 K and 375 K. The results were translated into the conductivity tensor (both diagonal and off-diagonal elements) by comparing them to finite element simulations of the potential in each sample and calculation of a two-dimensional conductivity tensor in the coordinate system of the sample edges. Less than 5% anisotropy were found at and above room temperature, where isotropic conductivity is within the experimental error. Larger anisotropies were found at low temperatures (about 30% at 10 K) and for a samples having a large number of low-angle grain boudaries (anisotropy above a factor of 20 at 50 K, but only 12 % at 365 K).