Keynote Speaker

 Prof. Qixin Guo

Prof. Qixin Guo

Department of Electrical and Electronic Engineering,
Synchrotron Light Application Center, Saga University, Japan
Speech Title: Photoluminescence Characteristics of Rare Earth Doped Ultrawide Bandgap Semiconductors by Synchrotron Radiation Excitation

Abstract: Ultrawide bandgap (UWBG) semiconductors, including AlN, BN, diamond, and Ga2O3 are at the forefront of extensive research efforts, covering a wide spectrum of materials, physics, devices, and applications. Microscale light emitting diodes (μLEDs) have attracted significant attention for their applications in augmented and virtual reality displays. Achieving high pixel density, efficiency, brightness, stable emission, and full-color emission is crucial for μLEDs. However, realizing full color μLED display technology poses challenges due to conventional mass transfer processes necessitating the extraction and precise transfer of red, green, and blue μLED chips from different epitaxial wafers. Rare earth (RE) doped semiconductors, characterized by strong and sharp emission resulting from intra-4f-shell transitions in RE ion cores, hold promise for applications in color display and luminescence devices. Extensive efforts have historically been dedicated to achieving visible color emission using RE doped GaN. Reports suggest that the luminescence efficiency of dopant emissions could significantly improve with a ultrawide bandgap host.

We have shown clear observations of red, green, and blue emissions from Eu, Er, and Tm doped ultrawide bandgap Ga2O3 films, respectively. We have also observed that the normalized emission intensity of RE-doped Ga2O3 films exhibits smaller temperature variations compared to RE-doped GaN films. Investigating the optical luminescence phenomena of semiconductors provides valuable insights into both the host lattices and defects, offering essential information for enhancing growth processes. Synchrotron radiation emerges as an ideal excitation source for studying UWBG semiconductors due to its remarkable tunability of photon energy and high brightness. We have constructed the Saga University beamline BL13 at Saga Light Source (SAGA-LS), Japan, to serve as a platform for such studies. In this talk, we will present recent advancements in the luminescence experiment system and share related experimental findings on UWBG semiconductors at the conference.

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 and was the Director of Saga University Synchrotron Light Application Center in Japan from April 2012 to March 2022. His research interests include epitaxial growth and characterization of semiconductor materials. Prof. Guo has published more than 380 papers in scientific journals including Nature Communications, Advanced Materials, Physical Review B, and Applied Physics Letters with more than 10,000 citations (h-index: 53). He is ranked as world top 2% scientists by Stanford University.