Milestone-Proposal:High Electron Mobility Transistor, HEMT, 1979

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Docket #:2017-14

This Proposal has been approved, and is now a Milestone

To the proposer’s knowledge, is this achievement subject to litigation? No

Is the achievement you are proposing more than 25 years old? Yes

Is the achievement you are proposing within IEEE’s designated fields as defined by IEEE Bylaw I-104.11, namely: Engineering, Computer Sciences and Information Technology, Physical Sciences, Biological and Medical Sciences, Mathematics, Technical Communications, Education, Management, and Law and Policy. Yes

Did the achievement provide a meaningful benefit for humanity? Yes

Was it of at least regional importance? Yes

Has an IEEE Organizational Unit agreed to pay for the milestone plaque(s)? Yes

Has the IEEE Section(s) in which the plaque(s) will be located agreed to arrange the dedication ceremony? Yes

Has the IEEE Section in which the milestone is located agreed to take responsibility for the plaque after it is dedicated? Yes

Has the owner of the site agreed to have it designated as an IEEE Milestone? Yes

Year or range of years in which the achievement occurred:

1979: The year 1979 is when “High Electron Mobility Transistor, HEMT,” was invented.

Title of the proposed milestone:

High Electron Mobility Transistor, HEMT, 1979

Plaque citation summarizing the achievement and its significance:

The HEMT was the first transistor to incorporate an interface between two semiconductor materials with different energy gaps. HEMTs proved superior to previous transistor technologies because of their high mobility channel carriers, resulting in high speed and high frequency performance. They have been widely used in radio telescopes, satellite broadcasting receivers and cellular base stations, becoming a fundamental technology supporting the information and communication society.

200-250 word abstract describing the significance of the technical achievement being proposed, the person(s) involved, historical context, humanitarian and social impact, as well as any possible controversies the advocate might need to review.

IEEE technical societies and technical councils within whose fields of interest the Milestone proposal resides.

In what IEEE section(s) does it reside?

IEEE Tokyo Section, Japan

IEEE Organizational Unit(s) which have agreed to sponsor the Milestone:

IEEE Organizational Unit(s) paying for milestone plaque(s):

Unit: IEEE Tokyo Section Treasurer
Senior Officer Name: Yukitoshi Sanada

IEEE Organizational Unit(s) arranging the dedication ceremony:

Unit: IEEE Tokyo Section Secretary
Senior Officer Name: Toshihiko Sugie

IEEE section(s) monitoring the plaque(s):

IEEE Section: IEEE Tokyo Section Chair
IEEE Section Chair name: Iwao Sasase

Milestone proposer(s):

Proposer name: Naoki Hara
Proposer email: Proposer's email masked to public

Please note: your email address and contact information will be masked on the website for privacy reasons. Only IEEE History Center Staff will be able to view the email address.

Street address(es) and GPS coordinates in decimal form of the intended milestone plaque site(s):

10-1 Morinosato-Wakamiya, Atsugi 243-0197, Japan.GPS coordinates: 35.443405, 139.313921

Describe briefly the intended site(s) of the milestone plaque(s). The intended site(s) must have a direct connection with the achievement (e.g. where developed, invented, tested, demonstrated, installed, or operated, etc.). A museum where a device or example of the technology is displayed, or the university where the inventor studied, are not, in themselves, sufficient connection for a milestone plaque.

Please give the address(es) of the plaque site(s) (GPS coordinates if you have them). Also please give the details of the mounting, i.e. on the outside of the building, in the ground floor entrance hall, on a plinth on the grounds, etc. If visitors to the plaque site will need to go through security, or make an appointment, please give the contact information visitors will need. The intended site of the milestone plaque is Atsugi Office, Fujitsu Laboratories Ltd. where HEMT was developed toward commercialization.

Are the original buildings extant?


Details of the plaque mounting:

The plaque will be displayed in the exhibition room on the grand floor of the Atsugi Office, Fujitsu Laboratories Ltd.

How is the site protected/secured, and in what ways is it accessible to the public?

The intended plaque site is on a premise of Atsugi Office, Fujitsu Laboratories Ltd. and it is protected by guards. Fujitsu Laboratories Ltd. welcomes any visitors; the prior notification is required before a visit.

Who is the present owner of the site(s)?

Fujitsu Laboratories Ltd.

What is the historical significance of the work (its technological, scientific, or social importance)? If personal names are included in citation, include justification here. (see section 6 of Milestone Guidelines)

The major historical significance concerning High Electron Mobility Transistor (HEMT) is described in detail below.

1. Historical Background of the Birth of HEMT

The fastest transistor before HEMT’s invention was the GaAs Metal-Semiconductor Field Effect Transistor (MESFET) invented in 1966. At the time, the goals of high-speed device development were logic circuits for supercomputers, more powerful radio-wave emitters for microwave applications, and low-noise amplifiers to detect very weak radio signals. Reduction of device dimension was the main technique for improving high-speed performance. But with MESFET, impurities were added to supply electrons in the regions where electrons would travel, and scatterings by ionized impurities limit electron mobility. In 1978, a modulation-doped heterojunction superlattice was reported, which accumulated electrons in an undoped GaAs layer sandwiched between n-type AlGaAs layers. This, however, was not reported to function as a transistor capable of controlling electrons with high mobility.

2. Invention and demonstration of HEMT

Dr. Takashi Mimura of Fujitsu Laboratories conceived of HEMT and applied for a patent on it in 1979 (granted in Japan in 1987 and in the US in 1991)[1]. The key point of this design was, in a single heterojunction between n-type AlGaAs and GaAs, introducing a Schottky junction that creates a depletion layer at the surface of the n-type AlGaAs. When operated as a gate, a field effect could be exerted on the two-dimensional electron gas inside the GaAs layer, which can control electron density using the field effect. This resulted in a high-speed transistor that uses a two-dimensional electron gas, which is unaffected by dopant scattering. He published a paper in 1980 demonstrating the first operation of HEMT in which a structure with a single heterojunction of n-AlGaAs and GaAs was used to control a two-dimensional electron gas using the field effect [2]. In this paper, high-speed performances of HEMT were shown to be superior to those of MESFET; the electron mobility and the transconductance at 77K were 5.5 times and 3 times higher, respectively. Research and development on HEMT moved quickly after that, in applications such as high-speed logic circuits and microwaves. Integrated circuits with record breaking switching delay [3], first HEMT low-noise amplifiers [4], and HEMT-LSIs for supercomputers [5] all were reported.

3. Commercialization of HEMT: Low-noise amplifier

The first commercial application of HEMT was a low-noise amplifier. Because of its outstanding low-noise performance, HEMT can be used to receive very weak signals from space. In 1985, HEMT was used in the 45-meter radio telescope at Nobeyama Radio Observatory (NRO), Nagano, Japan, and in 1986, the technology contributed to discoveries relating to the interstellar molecules in Taurus Molecular Cloud about 400 light year away [6]. In the private sector, HEMT was used in satellite broadcasting receivers, and allowed parabolic antennas to be reduced to less than half the diameter, helping to popularize satellite broadcasts in Japan as well as in Europe around 1987. The market of HEMT low-noise amplifiers in 1990 was about one hundred million dollars.

4. Developments and Commercialization of HEMT to the present day

Developments and commercialization of HEMT are continuing to the present day as follows. This expandability supports the significance of HEMT.

(1) Millimeter-wave amplifier

Because HEMT can operate at high frequencies, it can be used to build amplifiers for the millimeter wave band. In the late 1990s, development moved forward on products based on millimeter-wave radar, which is used in vehicles to prevent or mitigate collisions by detecting the distance to and speed difference of the car ahead. At the time, HEMT was used in the transceivers as it is a solid-state device that can operate reliably in the millimeter wave band, allowing the radar hardware to be made smaller, no more than 700-g in weight, for practical use on passenger vehicles [7].

(2) High-efficiency amplifier

Thanks to the higher performance of HEMT, it can be used to make high-efficiency microwave high power amplifiers [8, 9]. Taking advantage of this characteristic, GaN-based HEMTs are used in high-gain amplifiers for cellular base stations, and has contributed to producing the world’s smallest base stations [10]. In that way HEMT helps support the information and communication society by contributing to the buildout of wireless networks for coping with the explosive growth in communications volume. The market of GaN-based HEMT amplifiers was about three hundred million dollars in 2016, and is expected to increase to six hundred million dollars in 2020.

More recently, demonstration of wireless transmission was reported using InP-based HEMTs in transceivers for the as-yet unused 300-GHz frequency band [11], and won Best Industry Paper Award at 2016 International Microwave Symposium, IEEE Microwave Theory and Techniques Society, that holds the promise for accommodating future needs for communications volume.

(3) High-efficiency power devices

HEMT’s high efficiency has benefited power conversion devices, as well [12], leading to the development of the world’s smallest and most efficient AC adapter [13]. Helping make hardware more efficient should contribute to reducing CO2 emissions. The market of GaN-based HEMT power conversion devices is expected to be six hundred million dollars in 2022.

What obstacles (technical, political, geographic) needed to be overcome?

Enhancing electron mobility helps make transistors faster. With GaAs MESFET (the fastest transistor before the invention of HEMT), dopants were added to produce electrons in the region where electrons would travel, but ionized impurities scattering limited electron mobility. Meanwhile, the modulation-doped superlattice structure, in which an undoped layer of GaAs was sandwiched between layers of n-type AlGaAs, was first reported in 1978, but this was not intended to allow the electron density to be controlled by an externally applied electrical field, so it was not used to produce a transistor with high electron mobility.

With HEMT, a layer of n-type AlGaAs is built up on an undoped layer of GaAs, resulting in a two-dimensional electron gas inside the GaAs layer whose density can be controlled by the field effect, and this can be operated as a gate by introducing a Schottky junction, which creates a depletion layer at the surface of the n-type AlGaAs layer. This laid the theoretical groundwork for building the first transistor that could use the high-mobility two-dimensional electron gas in inside the GaAs layer.

There were still numerous technological hurdles to be overcome before HEMT’s actual operation could be confirmed. Achieving performance in line with HEMT’s theoretical potential required creating the n-AlGaAs/GaAs heterojunction with a planar boundary to an atomic layer level of precision. This, in turn, required advanced crystal growth technology. This also required semiconductor fabrication technology that, in particular, could produce gate electrodes for controlling the electron density in the n-AlGaAs layer. In short, in addition to the ideas for the device structure, it was because Fujitsu Laboratories had exceptional technologies for crystal growth as well as semiconductor fabrication technology that it succeeded in leading the world in the development of HEMT.

What features set this work apart from similar achievements?

There are a number of distinctive features of HEMT as summarized below.

1. Unique device operation principle and excellent fabrication technologies of HEMT

As mentioned previously, this was the world’s first transistor that used the field effect to control the density of electrons having high mobility. In addition to the ideas for the device structure, it was because Fujitsu Laboratories had exceptional technologies for crystal growth as well as compound semiconductor device fabrication technology that it succeeded in the development of HEMT.

In 1990, Dr. Takashi Mimura, who conceived of HEMT, and Dr. Satoshi Hiyamizu, who was in charge of crystal growth, won the IEEE Morris N. Liebmann Memorial Award “for demonstration of the High Electron mobility Transistor (HEMT).”

In November 10, 2017, Dr. Takashi Mimura received the Kyoto Prize, which is an international award to honor those who have contributed significantly to the scientific, cultural, and spiritual betterment of mankind, in the advanced technology category for “Invention of the High Electron Mobility Transistor (HEMT) and Its Development for the Progress of Information and Communications Technology.”

2. Contribution to social life

HEMT low-noise amplifiers, which take advantage of the technology’s excellent low-noise performance, allowed for parabolic antennas used for satellite broadcasting receivers to be half the previous diameter, contributing to the popularization of satellite broadcasting in the late 1980s. Because radio signals travel without regard for national boundaries, the spread of satellite broadcasting promoted the globalization of information flows. Nowadays, it is widely believed that information transmitted from the West into Eastern Europe by satellite broadcast played an important role in bringing down the Berlin Wall, and HEMT can be said to have been a part of that indirectly.

Commercial applications of millimeter-wave radar in anti-collision systems for vehicles in the late 1990s and early 2000s would not have happened without HEMT, showing the technology’s contribution to public safety.

HEMT has also contributed to high-gain amplifiers in cellular base stations, supporting the massive growth in wireless communications that began in the late 2000s and continues to this day.

As mentioned above HEMT plays a distinguished role as a foundational technology supporting the information and communication society.

3. Contribution to environment

HEMT helps cellular base stations operate more efficiently. With the number of base stations installed around the world rising rapidly, those improvements in efficiency make a significant contribution to helping societies reduce their CO2 emissions. In addition, with HEMT being used in more power conversion devices in the future, that effect will be amplified by the spread of more efficient AC adapters and other products.

4. Contribution to science

Low-noise amplifiers based on HEMT can be used to detect very weak radio signals from space. In 1985, they were used in the radio telescope at NRO, where they contributed to the discoveries relating to the interstellar medium, and since then have been used in radio telescopes around the world to advance the field of astrophysics.

The number of technical papers concerning HEMT increased every year since the first publication of the paper of HEMT in 1980 [1], and there were 584 publications in 2016 according to the IEEE explore. HEMT has pioneered a new technical area of high frequency and high speed semiconductor devices.

Supporting texts and citations to establish the dates, location, and importance of the achievement: Minimum of five (5), but as many as needed to support the milestone, such as patents, contemporary newspaper articles, journal articles, or chapters in scholarly books. 'Scholarly' is defined as peer-reviewed, with references, and published. You must supply the texts or excerpts themselves, not just the references. At least one of the references must be from a scholarly book or journal article. All supporting materials must be in English, or accompanied by an English translation.

[1] Japanese Patent, No. 1409643, “Semiconductor Device,” Nov. 24, 1987. [Filing date Dec. 28, 1979] (Equivalent U.S. Patent, No. Re 33584, “HIGH ELECTRON MOBILITY SINGLE HETEROSTRUCTURE DEVICES,” May 7. 1991)

[2] T. Mimura, S. Hiyamizu, T. Fujii, and K. Nanbu, “A New Field-Effect Transistor with Selectivity Doped GaAs/n-AlGaAs Heterojunctions,” Japan. J. Appl. Phys., vol. 19, 1980, pp. L225-L227.

[3] T. Mimura, S. Hiyamizu, H. Hashimoto, and M. Fukuta, “High Electron Mobility Transistors with Selectively Doped GaAs/n-AlGaAs Heterojunctions,” IEEE Trans. Electron Devices, vol. ED-27, No. 11, pp. 2197-2197, 1980. Citation: 886.

[4] M. Niori, T. Saito, K. Joshin, and T. Mimura, “A 20GHz High Electron Mobility Transistor Amplifier for Satellite Communications,” IEEE ISSCC Dig. Tech., 1983, pp. 198-199.

[5] Y. Watanabe, S. Saito, N. Kobayashi, M. Suzuki, T. Yokoyama, E. Mitani, K. Odani, T. Mimura, and M. Abe, “A HEMT LSI for Multibit Data Register, “ IEEE ISSCC Dig. Tech., 1988, pp. 86-87.

[6] H. Suzuki, M. Ohishi, N. Kaifu, S. Ishikawa, and T. Kasuga, “Detection of the interstellar C6H radical,” Publ. Astron. Soc. Japan, vol. 38, pp. 911-917, 1986.

[7] Y. Ohashi, Y. Hasegawa, N. Motoni, H. Yagi, and S. Yamano,” Development of 76 GHz Single Chip MMIC High Frequency Unit,” FUJITSU TEN TECH. J, No. 19, pp. 23 - 31, 2002.

[8] T. Kikkawa, M. Nagahara, N. Okamoto, Y. Tateno, Y. Yamaguchi, N. Hara, K. Joshin, and P. M. Asbeck, “Surface-charge controlled AlGaN/GaN-power HFET without current collapse and gm dispersion,” IEEE Int. Electron Devices Meeting. Tech. Dig., pp. 25.4.1-25.4.4, 2001.

[9] K. Joshin, T. Kikkawa, H. Hayashi, T. Maniwa, S. Yokokawa, M. Yokoyama, N. Adachi, and M. Takikawa, “A 174 W high-efficiency GaN HEMT power amplifier for W-CDMA base station applications,” IEEE Int. Electron Devices Meeting. Tech. Dig., pp. 12.6.1 - 12.6.3, 2003.

[10] Fujitsu Press Release, “Fujitsu Announces Global Launch of Mobile WiMAX Base Stations; BroadOne™ WX300 is world's most compact all-in-one base station,” Feb. 6, 2008.,

[11] H. Song, T. Kosugi, H. Hamada, T. Tajima. A. El Moutaouakil, H. Matsuzaki, M. Yaita, K. Kawano, T. Takahashi, Y. Nakasha, N. Hara, K. Fujii, I. Watanabe, and A. Kasamatsu, “Demonstration of 20-Gbps Wireless Data Transmission at 300 GHz for KIOSK Instant Data Downloading Applications with InP MMIC,” IEEE International Microwave Symposium, Interactive Forum, WEIF2-29, 2016.

[12] T. Hirose, M. Imai, K. Joshin and K. Watanabe, “Dynamic Performances of GaN-HEMT on Si in Cascode Configuration,” IEEE 29th Applied Power Electronics Conference and Exposition (APEC), pp. 174-181, 2014.

[13] Fujitsu Press Release, “Fujitsu Wins Grand Prize in 26th Global Environment Award; Recognized for development of the world's smallest and most efficient AC adapter,” March. 3, 2017.

Supporting materials (supported formats: GIF, JPEG, PNG, PDF, DOC): All supporting materials must be in English, or if not in English, accompanied by an English translation. You must supply the texts or excerpts themselves, not just the references. For documents that are copyright-encumbered, or which you do not have rights to post, email the documents themselves to Please see the Milestone Program Guidelines for more information.

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