Regensburg 2019 – scientific programme

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DS: Fachverband Dünne Schichten

DS 2: Focus Session: Oxide Semiconductors for Novel Devices (joint session HL/DS)

DS 2.1: Invited Talk

Monday, April 1, 2019, 09:30–10:00, H34

The role of suboxide kinetics and thermodynamics for the catalysis and facet formation during the molecular beam epitaxy of oxides — •Oliver Bierwagen — Paul-Drude-Institut für Festkörperelektronik, Leibniz Institut im Forschungsverbund Berlin e.V., Hausvogteiplatz 5–7, 10117 Berlin, Germany.

Based on its wide band gap of E_g=4.7 eV Ga₂O₃ is a promising oxide semiconductor for novel applications such as power electronics and UV detection. Band-gap engineering by alloying with In₂O₃ (E_g=2.7 eV) allows tuning the detection wavelength and enable heterostructure devices. Thin film growth of these oxides by molecular beam epitaxy (MBE) enables the high material quality (purity and crystallinity) required for novel applications. This contribution shows how the intermediate formation and desorption kinetics of Ga₂O and In₂O limits the MBE growth rate of Ga₂O₃ (and of In₂O₃ to a less extent).[1] Nevertheless, the stronger Ga-O than In-O bonds thermodynamically leads to a favorable incorporation of Ga into the alloy (In_xGa_1−x)₂O₃.[2] The collaborative effect of these kinetics and thermodynamics is shown to lift the growth rate limitation of Ga₂O₃ in the presence of an additional In-flux by metal-exchange catalysis.[3,4] Finally, the impact of the metal-to-oxygen flux ratio on the anisotropy of surface free energy is shown to control the formation of surface facets on both oxides.[4,5] [1] Vogt et al., Phys. Rev. Mater. 2, 120401(R) (2018). [2] Vogt et al., APL Mater. 4, 086112 (2016). [3] Vogt et al., Phys. Rev. Lett. 119, 196001 (2017). [4] Mazzolini et al., APL Mater. 7, 022511 (2019). [5] Bierwagen et al., J. Phys.: Condens. Matter 28, 224006 (2016).