Dr. Qixin Guo, Professor of Department of Electrical and Electronic Engineering, Director of Synchrotron Light Application Center, Saga University, Japan

Biography: Prof. Dr. Guo received B. E., M.E., and Dr. E degrees in electronic engineering from Toyohashi University of Technology in 1990, 1992, and 1996, respectively. He is currently a Professor of Department of Electrical and Electronic Engineering, Saga University as well as Director of Saga University Synchrotron Light Application Center. His research interests include epitaxial growth and characterization of semiconductor materials. Prof. Guo has published more than 300 papers in scientific journals including Nature Communications, Advanced Materials, Physical Review B, and Applied Physics Letters with more than 6000 citations (h-index: 41)

Title: Characteristics of gallium oxide based semiconductors

Abstract: Gallium oxide films have been attracted much attention as promising semiconductors for deep ultraviolet detector or light-emitting devices (LEDs), power devices, and efficient host for rare earth LEDs due to the wide bandgap and stable chemical and physical properties. A wider bandgap range is of great merit as it allows the design of devices such as high sensitive wavelength-tunable photodetectors, cutoff wavelength-tunable optical filters in more broad range. In this talk, we present on the characteristics of gallium oxide based films.

Gallium oxide based films were deposited on sapphire substrates by pulsed laser deposition. We have demonstrated that the bandgap energy of the gallium oxide based films can be tailored by adding the indium or aluminium contents in the films. We have also fabricated the gallium oxide based LEDs and observed intense green emission (548 nm) from the LEDs. The driven voltage of the LEDs was 6.2 V which is lower than that of ZnO or GaN based LEDs. Structural and optical properties of Eu doped gallium oxide films were investigated. X-ray absorption near edge structure measurements indicated that the valence of Eu ions in the Eu doped gallium oxide films varies from mixture of bivalent and trivalent to only trivalent with increasing substrate temperature. Extended X-ray absorption fine structure analysis revealed that the Eu atoms doped in gallium oxide matrix are incorporated on Ga sites in gallium oxide matrix even for the films with amorphous structure grown at low substrate temperature.

Keywords: gallium oxide, wide bandgap, epitaxial growth, x-ray absorption