Regensburg 2016 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

DS 40: Focussed Session: Oxide Semiconductors for Device and Energy Applications I
(Joint session of DS and HL, organized by DS)

DS 40.4: Topical Talk

Donnerstag, 10. März 2016, 11:30–12:00, H11

Miscibility and phase separation in (In_xGa_1−x)₂O₃ — •Martin Albrecht¹, Robert Schewski¹, Toni Markurt¹, Tobias Schulz¹, Michele Baldini¹, Günter Wagner¹, Holger von Wenckstern², Marius Grundmann², Hartwin Peelaers³, Joel Varley³, and Chris Van de Walle³ — ¹Institute for Crystal Growth, Berlin, Germany — ²Universität Leipzig — ³Materials Department, University of California, Santa Barbara, California, USA

Group III sesquioxides are distinguished from other wide band gap semiconductors by the fact, that they can be efficiently n-doped despite a wide band gap that ranges from 2.7 eV for In₂O₃ over 4.8 eV for Ga₂O₃ to 8.9 eV for Al₂O₃. Full exploitation of their properties for electronic applications requires band gap engineering formation of solid solutions. The formation of solid solutions in group III sesquioxides is challenging, since, at thermodynamic equilibrium, the binaries exhibit different thermodynamically stable structures (cubic, rhombohedral, and monoclinic) besides a significant lattice mismatch. The oxygen coordination of the metal atoms in the binary alloys is either octahedral, or mixed tetrahedral and octahedral. In this presentation we report on transmission electron microscopy studies on miscibility and phase separation in the system (In_xGa_1−x)₂O₃ grown by PLD. We identify essentially three different phases as dependent on composition, i.e. the monoclinic β-phase in the compositional range up to x=0.5, an ordered hexagonal phase in the range between x=0.5 and 0.75 and the cubic bixbyite phase at higher In contents. In atoms occupy octahedrally coordinated cation sites in the monoclinic phase.