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DS: Fachverband Dünne Schichten

DS 20: Focus Session: Emerging oxide semiconductors I (jointly with HL, DF, O)

DS 20.8: Vortrag

Mittwoch, 2. April 2014, 12:00–12:15, POT 081

MOCVD grown homo and heteroepitaxial β-Ga₂O₃ layer studied by transmission electron microscopy — •Robert Schewski, Martin Albrecht, Günter Wagner, Michele Baldini, Zbigniew Galazka, and Reinhard Uecker — Leibniz-Institut für Kristallzüchtung, Max-Born-Strasse 2, 12489 Berlin, Germany

We report on the structural properties of β-Ga₂O₃ layers, grown by MOCVD for various growth conditions. In detail, the influence of different precursors, namely pure oxygen, water, and CO₂ on the crystalline film quality has been investigated. Our studies were carried out for hetero- as well as homoepitaxially grown samples on (0001) sapphire and melt grown (100) β-Ga₂O₃ substrates, respectively. The conclusions are mainly based on transmission electron microscopy and x-ray data.

As main results, we found that pure oxygen in the growth ambient leads to the formation of nano-crystals in form of wires or agglomerates for both hetero- and homoepitaxial growth. However, by using water as oxygen precursor, smooth (rms: 6.5 nm) single crystalline layers can be achieved for homoepitaxial growth. Still, the structural quality of these thin films suffers from a substantial amount of stacking faults, which can be evidenced by TEM and x-ray data. However, annealing in oxidizing atmosphere at (900^∘C) leads to a reduction these stacking faults and thus improves the crystalline quality of the film. Another interesting observation is the formation of a pseudomorphic, 3 monolayers thick Ga₂O₃ layer in the alpha phase, directly at the interface between the sapphire substrate and the film.