Regensburg 2016 – scientific programme

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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 40.2: Topical Talk

Thursday, March 10, 2016, 10:15–10:45, H11

Mixing In and Ga sesquioxides - and their polar phases — •Vincenzo Fiorentini — Dept of Physics, Cagliari University, Italy — CNR-IOM, UOS Cagliari, Italy

This talks will report on recent first-principles theoretical work on the In and Ga sesquioxides and their ternary alloy, an up-and-coming materials system for near to deep-UV large-breakdown and transparent-conducting materials. Firstly, a qualitative phase diagram is proposed over all the full composition range. Three structures –monoclinicβ, layered-hexagonal, and cubic bixbyite– are competing for the ground state, and several regions of miscibility and phase separation interlace as function of composition, more or less independently of temperature. Electronic properties, including absorption anisotropy at low x, and a selection of interface band offsets will also be presented. Secondly, the metastable polar phase ε-Ga₂O₃ is shown to be pyroelectric (i.e. locked in a non-switchable polarized structure) with a large ferroelectric-like polarization 0.23 C/m² and a diagonal piezoelectric coefficient (0.77 C/m²) in line with those of III-V nitrides and II-VI oxides. In view of recent growth successes in that direction, the interface of ε-Ga₂O₃ to GaN is studied, both in terms of geometry, offsets, and polarization difference, suggesting interesting potential for power applications.
Work in collaboration with M. B. Maccioni, F. Ricci, R. Fornari.