Dresden 2017 – scientific programme

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DS: Fachverband Dünne Schichten

DS 28: Focussed Session: Oxide Semiconductors for Novel Devices I

DS 28.7: Talk

Wednesday, March 22, 2017, 11:45–12:00, CHE 89

Dielectric function and band structure of α Ga₂O₃ — •Martin Feneberg¹, Anderson Janotti², Maciej D. Neumann³, Norbert Esser³, Luis Artus⁴, Ramon Cuscó⁴, Tomohiro Yamaguchi⁵, and Rüdiger Goldhahn¹ — ¹Otto-von-Guericke Universität Magdeburg — ²University of Delaware — ³Leibniz-Institut fur Analytische Wissenschaften - ISAS - e.V. — ⁴ICTJA-CSIC, Barcelona — ⁵Kogakuin University

Polytypes of gallium oxide are a very promising class of materials for electronic device applications. It is possible to stabilize α-Ga₂O₃ by mist chemical vapor deposition on sapphire substrates. However, the optical properties of this metastable corundum-like phase have not yet been investigated thoroughly. Spectroscopic ellipsometry at room temperature has been applied to determine the ordinary (ε_⊥) dielectric function of α-Ga₂O₃. This corresponds to an electric field direction perpendicular to the optical axis (0001), which is the growth direction of the thin (about 400nm) α-Ga₂O₃ films. A high energy spectral range up to 20eV has been investigated using synchrotron radiation. Several high-energy transitions have been resolved, which are consistent with ab-initio calculations of the dielectric function that include the solution of the Bethe-Salpeter equation, i.e. Coulomb interaction between electrons and holes. The calculations suggest that α-Ga₂O₃ is an indirect semiconductor with its valence band maximum between Γ and K points of the Brillouin zone. Strong direct absorption onsets at around 5.3 and 6.2eV are found, only slightly higher in energy than the predicted band gap.