MTU-Oviedo Group Predicts New Properties of Gallium Oxide : Nanoclusters and Crystals

Recent work of MTU Physics graduate students S. Gowtham and Haiying He with Prof. Pandey, in collaboration with Prof. Miguel Blanco and Prof. Aurora Costales of Universidad de Oviedo, is focused on Gallium Oxide. As wide band gap semiconductors, thin films and single crystals of gallium oxide have drawn increasing attention in recent years for their diverse applications in semiconducting lasers, optoelectronic devices and solar cells.

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NANOCLUSTERS

A preference for planar arrangement of the constituent atoms maximizing the ionic interactions is predicted in the ground state of metal-excess and oxygen-excess gallium oxide clusters. The increase in the oxygen/metal ratio is accompanied by an increase in electron affinity and ionization potential of these clusters. ^{1, 2}

BULK

Analysis of the band structure of β-Ga₂O₃ has shown the valence band maximum to be degenerate at the Γ and M-points, with conduction band minimum occuring at Γ. Anisotropy of the electron effective mass is predicted, suggesting a higher mobility of electrons along b^* in the oxide lattice.

DEFECT CHEMISTRY

The β-Ga₂O₃ structure displays empty channels perpendicular to planar atomic sheets. It has been shown that these features lead to a different behavior for the ionic conductivity depending on the lattice doping conditions: tetravalent dopants will enhance conductivity along the channels, divalent dopants will enhance conductivity along the planar sheets. Thus, Ohm's law is anisotropic in this lattice. This can be tuned at will, allowing fabrication of novel devices.