Meijo UniversityAutobiography of Isamu Akasaki Aug.,2014

Isamu Akasaki received B.Sc. in 1952 from Kyoto University and Dr. Eng. (Electronic Engineering) in 1964 from Nagoya University.
In 1952, he joined Kobe Kogyo Corporation (now, Fujitsu Ltd.) where he was a research staff member on a group studying electronic materials. Among his early contributions was the development of manufacturing process of fluorescent screen of Cathode Ray Tube for TV(Kinescope) and of scintillators for β-ray.
In 1959, he moved to Nagoya University where he held the positions of research associate and assistant professor before being appointed associate professor. His work involved pioneering experiments on the Vapor-Phase Epitaxial Growth (VPE) of Ge from the beginning. He initiated the thermodynamic analysis of impurity doping in the VPE of Ge.
In 1964, he became Head of the Basic Research Laboratory IV and then General Manager of the Semiconductor Department, both at the newly established Matsushita Research Institute Tokyo, Inc.(MRIT), where he started to research on optoelectronic materials and devices. He developed in 1968 high-quality GaAs with world’s highest electron mobility by VPE, and in 1970 the brightest GaP red LED at that time. In 1967 he began VPE of AlN and determined its angular frequencies of the longitudinal and transverse optical phonons by fitting the calculated reflectivity to the Reststrahlen band , which he and his colleague found.
He had an insight during the early stages of GaN-based nitride semiconductor research into their great potential as blue light-emitters, and yearned to pioneer a new field founded on the unique properties of nitride semiconductors: namely the wide energy gap, toughness, and non-toxicity.
In the 1970s, nitride researchers almost withdrew from the field, because they could neither grow semiconductor-grade high-quality GaN single crystals nor control their electrical conductivity(especially p-type conduction), both of which are indispensable to the development of high-performance blue light-emitters and high-speed/high-power transistors. Despite such a stalemate, Akasaki resolved in 1973 to produce high-quality GaN single crystals and to develop blue light-emitters using GaN p-n junction.
In 1974, he grew GaN single crystal by Molecular Beam Epitaxial Growth (MBE) for the first time, and in 1975 he was awarded a three-year research grant by the Japanese Government (MITI at that time) for the “Research and Development of a Blue-Light-Emitting Devices based on GaN”.
In 1978, he and his group at MRIT developed the flip-chip type GaN blue LED by Hydride Vapor-Phase Epitaxial Growth (HVPE). The external quantum efficiency was 0.12%: the highest ever reported at that time.
During this study, he recognized the great potential of GaN as a blue luminescent material, when he found tiny yet high-quality crystallites embedded in HVPE-grown crystals containing cracks and pits. He was convinced that conductivity control (even p-type conduction) should be able to be achieved if this kind of quality over an entire wafer could be made. Thus in 1978, he decided to go back one more time to basics, i.e., the fundamentals of “Crystal Growth”. On the basis of his twenty year’s experiences on crystal growth of several kinds of semiconductors including several year’s experiences on GaN, in 1979 he decided to adopt the Metalorganic Vapor-Phase Epitaxial Growth(MOVPE) (also called MOCVD) as the optimal growth method for GaN, although it was almost never employed for the growth of GaN at that time [Decision (1)]. As for the substrate he ,for a while , (until GaN substrate became available) chose sapphire as before which is stable under the harsh MOVPE growth conditions and is similar to GaN in terms of crystal symmetry [Decision (2)].
In 1981, he returned to Nagoya University as professor after making above-mentioned crucial decisions. He started afresh to improve drastically crystal quality of GaN by MOVPE with the generous cooperation of graduate students and co-researchers. He proposed a new crystal growth method for nitrides; the low-temperature (LT) buffer layer technology in order to reduce the large interfacial free energy between epitaxial GaN layer and sapphire substrate
(e.g. I. Akasaki & N. Sawaki: Jpn. Patent 1,708,203(appl:1985年11月18日),U.S. Patent 4,855,249, and later K. Manabe, H. Kato, I. Akasaki, K. Hiramatsu and H. Amano: Jpn. Patent 3,026,087 (appl:1989年3月1日), U. S. Patent 5,122,845 etc. ).
His consistent leadership and his group’s persistent efforts led to a number of breakthroughs:
In 1986, he and his group succeeded in creating extremely high-quality (semiconductor-grade) GaN by the LT-AlN buffer layer technology in MOVPE. Then using the high-quality GaN, they achieved the following as world firsts: low-resistive p-type GaN by doping with Mg and activating it by electron bombardment (LEEBI) (1989), GaN p-n junction blue/UV LED(1989), conductivity control of n-type GaN by doping with Si (1990).
Thus they had developed all the essential technologies necessary for a GaN-based p-n junction blue LED.
They achieved, for the first time, conductivity control of n-type AlGaN and p-type AlGaN by 1991, allowing the use of heterostructures and quantum wells(QW)s in the design of more efficient p-n junction light-emitting structures.
In 1990 they achieved stimulated emission in the UV region for the first time at room temperature(RT) under one order of magnitude lower optical power than before from the high-quality GaN.
This achievement, together with the development of GaN p-n junction LED, paved the way to the nitride-based short-wavelength laser diode(LD).
In 1995 they achieved the first stimulated emission at 388nm with electric current injection using a GaInN/GaN QW diode at RT,and in 1996 developed a LD with an AlGaN/GaN/GaInN QW at 376nm.
As concerns quantum effects in the nitride system, in 1991 they verified quantum size effect in AlGaN/GaN multiple layered structure grown with the LT-buffer layer in MOVPE.
In 1995 they found that the band-edge emission intensity of GaInN/GaN multiple QWs with well widths of less than 3nm(roughly corresponds to Bohr radius in GaN) is much higher than those of thicker GaInN wells.
They also found in 1997 that AlGaN and GaInN grow coherently on GaN films grown with the LT-AlN buffer layers, and AlGaN and GaInN are under tensile and compressive stresses, respectively. These stresses in strained layers generate strong piezoelectric fields which decrease the transition energy as well as the transition probability of carriers in QWs with wells thicker than about 3nm.
Thus they attributed the above-mentioned phenomenon(strong emission intensity of QWs with wells thinner than 3nm) to that quantum confined Stark effect (QCSE) caused by the piezoelectric field is suppressed in such thin QWs , due to the carrier confinement.
In 2000 they succeeded in crystal orientation control to reduce or even completely eliminate the piezoelectric fields showing the existence of non-/semi-polar nitride crystal planes.
This has triggered recent world-wide efforts to grow those crystals and develop more efficient light emitters.

They developed a high-sensitivity UV detector with very low dark current (2000) and a short-wavelength (350.9nm) UV LD on the AlGaN with low dislocation density (2004), high on/off ratio and low on-resistance normally-off mode AlGaN/GaN heterostructure field effect transistor (HFET) with a p-type gate (2006),and highly efficient GaInN solar cell (2012),and nitride-based HFET-type photosensors with extremely high photosensitivity (2013). They analysed the strain relaxation process in GaInN/GaN heterostructures by in-situ X-ray diffraction monitoring during MOVPE growth (2013). They also demonstrated GaInN-based laser pumped by an electron beam in 2014.

Isamu Akasaki has authored and coauthored more than 730 international journal/conference papers and 50 book chapters. He also edited 12 books. He has been awarded 117 Japanese and 104 foreign patents related to nitrides.
He has received numerous awards, which include the Japanese Association for Crystal Growth (JACG) Award (1989), the Chu-Nichi Culture Prize (1991), the International Symposium on Compound Semiconductors Award and Heinrich Welker Medal (1995), the Japanese government’s Medal with Purple Ribbon (1997),the International Organization for Crystal Growth (IOCG)’s Laudise Prize (1998), the C&C Prize (1998), the IEEE Jack A. Morton Award (1998), the Rank Prize (1998), Japan Science and Technology Agency (JST)’s Inoue Harushige Award jointly with Toyoda Gosei Co.Ltd.(1998), the Electrochemical Society (ECS)’s Solid State Science and Technology Award (now, Gordon E. Moore Medal for Outstanding Achievement in Solid State Science and Technology) (1999), the Toray Science and Technology Prize (2000), the Asahi Prize (2001), the Japan Society of Applied Physics (JSAP)’s Outstanding Achievement Award (2002), the Fujihara Prize (2002), the Takeda Award (2002), the Japanese government’s Order of the Ring Sun, Gold Rays with Neck Ribbon (2002),the President’s Award of Science Council of Japan (SCJ) (2003),the International Conference on Solid State Devices and Materials(SSDM)Award (2003), the John Bardeen Award (2006), the JACG’s Outstanding Achievement Award(2006), the Honorable Lifetime Achievement Award of the 162nd Research Committee on Wide Bandgap Semiconductor Photonic and Electronic Devices of Japan Society for the Promotion of Science (2007)and the Kyoto Prize in Advanced Technology (2009), the IEEE Edison Medal (2011), the JST’s Special Award for Intellectual Property Activities(2011), the Minami-Nippon Culture Prize-Honorable Prize (2011), the Society for Information Display (SID)’s Karl Ferdinand Braun Prize(2013), the Okawa Publications Prize(2014) and the Imperial Prize and the Japan Academy Prize(2014).

In 2004, he was selected as a Person of Cultural Merits by the Japanese Government, and in 2011,he was conferred the Order of Culture by the Emperor of Japan in person.
He received Medal of Honorary Citizen of Montpellier (1999)and Plaque of Honorary Citizen of Minami Kyushu(2012),Honoris Causa Doctorate from the University of Montpellier II (1999), Honoris Causa Doctorate from Linköping University (2001). He was selected as a University Professor of Nagoya University(2004), and was elected Foreign Associate of the National Academy of Engineering of the United States of America (NAE) (2008). He was granted the title of the University Professor of Meijo University (2010). He became IEEE Fellow(1999)and IEEE Life-Fellow(2013). He was granted Nagoya University Lectureship(2012).