“Our group is developing novel micro-LEDs and VCSELs based on material science and semiconductor epitaxy. These are the crucial devices for micro-LED displays or laser-drawing displays on the retina. These displays will save a lot of energy and are useful for AR and VR. Let's change the energy and digital sections of the future world together.”

Education Profile

  • PhD, University of Tokyo
  • MSc, University of Tokyo
  • BSc, Tokyo University of Science

Courses

Kazuhiro Ohkawa's courses

  • EE306 Electrical and Optical Prop. of Semiconductors
  • EE312 Semiconductor Epitaxy and Devices

Kazuhiro Ohkawa is a Professor of Electrical and Computer Engineering (ECE) and Principal Investigator of the Energy Conversion Devices and Materials (ECO Devices) Laboratory. His research projects are energy-saving devices such as LEDs and laser diodes. His keys are the original MOVPE technology and material science.

Education and early career

Ohkawa majored in Physics during bachelor and master courses. He holds a Ph.D. in Science from the University of Tokyo in the fields of MBE-grown ZnSe and their blue LEDs. He was a senior research staff at Panasonic Ltd, a professor of Physics at the University of Bremen, Germany, and a professor of Applied Physics at Tokyo University of Science.

Professor Ohkawa invented nitrogen-plasma doping for ZnSe, and their blue-green lasers and LEDs. The nitrogen-plasma source is now a standard technology for nitride MBE. After that, he started to involve in MOVPE growth of GaN. He has developed world-record deep-red InGaN-LEDs based on the original MOVPE. His nitride MOVPE simulation is contributing to worldwide industries producing InGaN LEDs, lasers, and AlGaN electronics.  He has invented nitride photocatalysts which is useful for solar hydrogen and artificial photosynthesis.
 

Areas of expertise and current scientific interests

Professor Ohkawa‘s research interests include science and device applications of energy-conversion phenomena toward a sustainable future.

Wearable, fast-response, and efficient displays are suitable to enjoy the AR and VR world. The promising candidates are micro-LED displays, and laser-drawing displays on the retina. For their realization, the key point is the development of InGaN-based red micro-LEDs and VCSELs.  A further step will be the integration of RGB micro-LEDs and VCSELs. Micro-LED displays realize not only energy-saving but also weight-light, flexible, fast-response. 

Necessary key devices are efficient red micro-LEDs. We have achieved brighter InGaN-based red micro-LEDs than AlInGaP-based ones. The higher brightness is connected to the development of novel VCSELs. Our group is strong at semiconductor epitaxy and device fabrication for such emerging devices.

Career recognitions

Professor Ohkawa has received a series of honors and recognitions for his contribution to optoelectronics, such as Honorary Professor (lifelong) at University of Bremen (Germany), Visiting Professor at Mie University (Japan), Guest Professor at Xiamen University (China), and Visiting Professor (lifelong) at Tianjin University of Technology and Education (China). He is a Fellow of the Japan Society of Applied Physics. He is doing/did consultancy for approximately 20 companies in the abovementioned research fields.

Editorial activities

His research has led to over 200 scientific publications, 28 granted US and Japanese patents, and more than 70 invited talks.

Why do micro-LEDs difficult?

The effect of the sidewalls of a semiconductor chip gets influential on efficiency by decreasing the chip size. The surface has different physics compared to solid-state materials. That is a kind of singular plane. A part of injected current loses on the surface, resulting in lower efficiency. We can realize high-quality surfaces based on epitaxy, device fabrication, and surface treatment. Recently, we invented the hydrogen passivation method to form pixels without introducing surfaces. Then, we have achieved the world-top-class red micro-LEDs. If you want to know more about that, please come to my office.

Why KAUST?

I knew KAUST from a Nobel laureate during the Nobel week in Stockholm. I joined KAUST in 2016 as the Director of the Energy Conversion Devices and Materials (ECO Devices) Lab. I recognized that KAUST creates a scientific atmosphere to realize something new. Thanks to such situations, I aim to develop new valuable devices and cutting-edge semiconductor growth methods.

Selected Publications

K. Ohkawa, F. Ichinohe, T. Watanabe, K. Nakamura, D. Iida, “Metalorganic vapor-phase epitaxial growth simulation to realize high-quality and high-In-content InGaN alloys” Journal of Crystal Growth 512, 69-73 (2019).
D. Iida, and K. Ohkawa, "Recent progress in red light-emitting diodes by III-nitride materials", Semiconductor Science and Technology 37, 013001 (2021). Invited review
Z. Zhuang, D. Iida, and K. Ohkawa, "Ultrasmall and ultradense InGaN-based RGB monochromatic micro-light-emitting diode arrays by pixilation of conductive p-GaN", Photonics Research 9, 2429-2434 (2021).
Z. Zhuang, D. Iida, and K. Ohkawa, "Effects of size on the electrical and optical properties of InGaN-based red light-emitting diodes", Appl. Phys. Lett. 116, 173501 (2020). Selected as an Editor's Pick
D. Iida, Z. Zhuang, P. Kirilenko, M. Velazquez-Rizo, and K. Ohkawa, "Demonstration of low forward voltage InGaN-based red LEDs", Applied Physics Express 13, 031001 (2020). Ranked in Most Read, Top-Cited-Paper Award from IOP Publishing