k-Ga2O3 polymorph: epitaxial growth, properties and applications

 

Ga2O3 is an ultra-wide bandgap oxide (Eg>4.5 eV) of great interest for applications in power electronics, opto-electronics, UV-detection, catalysis, etc.

Ga2O3 can crystallize in several polymorphs, the most common being a, b, e/k , with different properties and fields of applications. b-Ga2O3, the thermodynamically stable polymorph, is the most investigated for high-power electronic applications although its anisotropy, due to the monoclinic crystallographic phase, poses some problems in practical realization of devices. The a and k metastable polymorphs, on the other hand, exhibit higher symmetry lattice (corundum and orthorhombic respectively), permitting easier epitaxial growth conditions and processing.

In this talk I will present the research activity of our group, focused on the preparation and characterization of k-Ga2O3 epilayers and on the development of solar blind photodetectors for UV-C light.

I will discuss the epitaxial growth conditions that permit to tailor the Metal Organic Vapor Phase Epitaxy (MOVPE) growth of e-Ga2O3 with respect to the other polymorphs, showing the interplay of thermodynamics (different chemical potentials for the metastable k phase and the stable b phase) and kinetics (mainly related to different surface energy barriers for nuclei of different crystallographic phases/planes) effects. I also focus on the importance of lattice mismatch in the nucleation of Ga2O3 polymorph.

The development of ohmic contacts and the electrical characterization of our samples permitted to prepare test photoresistors showing good responsivity at 250 nm with solar blind characteristics.

Matteo Bosi, Institute of Electronic and Magnetic Materials (IMEM-CNR)


0929-bosi.pngDr. Matteo Bosi obtained his degree in physics in 2000 and his Ph.D. in 2003 at the Parma University (Italy). He has a permanent researcher position at IMEM-CNR institute since 2009, and in 2023 became senior researcher.

His scientific activity has been focused on epitaxial deposition by means of Metal Organic Vapor Phase Epitaxy (MOVPE) of semiconductors materials for photovoltaic, sensor and optoelectronic devices. He is author or co-author of about 130 papers published on peer-reviewed journals and of more than 50 contributions to conferences.

His current research at IMEM-CNR includes MOVPE deposition of Ga2O3 and CVD growth of 2D-MoS2. In the past he also worked on 3C-SiC, GaN, Ge, GaAs and InGaP epitaxyand on Ge and SiC nanowires synthesis for applications in sensors.