Keynote Speaker

Prof. Qixin Guo

Prof. Qixin Guo

Department of Electrical and Electronic Engineering,
Synchrotron Light Application Center, Saga University, Japan
Speech Title: Full Color Light Emitting Diodes Based on Rare Earth Doped Oxide Films

Abstract: Micro scale light emitting diodes (μLEDs) have been extensively studied for augment and virtual reality display applications. It is highly required that μLEDs have high pixels per inch, high efficiency and brightness, stable emission, and full color emission. However, the realization of full color μLED display technology has been challenging because conventional mass transfer processes require the extraction of red, green, and blue μLED chips from different epitaxial wafers followed by precision transfers. Full color LEDs can be fabricated by using GaInN with different indium concentration as luminescence layers. However, the emission wavelength is unstable due to its temperature dependence of bandgap.

Rare earth (RE) doped semiconductors, which exhibit strong and sharp emission due to intra-4f-shell transitions in RE ion cores, have potential applications in color display and luminescence devices. Historically, much effort has been made to produce visible color emission using RE doped GaN. It has been reported that the luminescence efficiency of dopant emissions could be highly improved with a wide bandgap host. Moreover, the wide bandgap semiconductors exhibit highly thermal and chemical stability, which make them ideal hosts for RE ions. We have demonstrated that red, green and blue emissions are clearly observed from the Eu, Er, and Tm doped Ga2O3 films respectively. We found that the normalized emission intensity of the RE doped Ga2O3 films has a smaller temperature variation compared to that of the RE doped GaN films and showed that the bandgap of the films can be increased by adding Al into the films. In this talk, we present on the structure, surface morphology and temperature dependence of the photoluminescence of the RE doped (AlGa)2O3 films. Recent progress on the properties of the full color LEDs by using Eu, Er, and Tm co-doped Ga2O3 films will also be reported.

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 370 papers in scientific journals including Nature Communications, Advanced Materials, Physical Review B, and Applied Physics Letters with more than 9300 citations (h-index: 49).