Short course 2:
Single crystals and epilayers of oxide semiconductors: growth technology and properties
Lecturer: Prof. Roberto Fornari, Università di Parma, Italy
Abstract: This lecture will briefly outline the state of the art of the growth technology of semiconducting oxide single crystals and epilayers. The focus will be on metal-sesquioxides (Ga2O3, In2O3, Al2O3 and relevant alloys), as there is an increasing interest on these materials, which offer novel properties and applications with respect to traditional elementary and compound semiconductors, in particular higher bandgap and breakdown voltages.
It will be shown that the growth of bulk crystals is a challenging task because of the very high melting point, which may reach or even go beyond 2000 °C; secondly, a thermal decomposition of the growing crystal and melt may occur, which imposes the adoption of an oxidizing atmosphere and precautions to prevent damages to crucible and other parts of the growth equipment; third, the severe thermal gradients may result in twins or even cleavage or crack of the growing crystal.
Both MBE and MOVPE have successfully been applied to deposition of high-quality metal-sesquioxides films, but also HVPE and Mist-CVD proved to be effective methods for the preparation of thick layers or special polymorphs of the oxide compounds. The lecture will review merits and drawbacks of the different epitaxial approaches.
Finally, a survey of the structural, optical and electrical properties of this class of oxide semiconductors will be presented.
Biography: Roberto Fornari is a physicist and presently Full Professor of Condensed Matter Physics at the University of Parma (Italy), where he also serves as Vice-Rector for Research.
From 1981 to 2003 he worked as research scientist at the Institute of Materials for Electronics and Magnetism (IMEM) of the Italian National Research Council. From 2003 to 2013 he was director of the Leibniz Institute for Crystal Growth (IKZ) in Berlin and professor at the Physics Dept. of the Humboldt University Berlin. In September 2013 he accepted a call from the University of Parma and moved back to Italy.
His research activity has mainly been focused on semiconductors: III-V compounds, nitrides, wide bandgap semiconducting oxides. He authored/co-authored about 170 papers in international journals and about 60 papers in conference proceedings, ten patents and different chapters on crystal growth and properties of technologically important materials. He has edited books and proceedings on crystal growth and materials science, and is currently member of the editorial board of J. Crystal Growth, Cryst. Res.Technol., J. Optoelectronics and Advanced. Materials. He chaired twelve international conferences and four international schools.
He served in numerous scientific bodies and commissions: from 2010 to 2016 he was President of the International Organization for Crystal Growth (IOCG), he served in the Executive Committee of the E-MRS during 2011-17, and chaired the Crystal Growth Section of the Italian Crystallographic Association during 2000-03.