Milestones:Molecular Beam Epitaxy, 1968–1970

Title

Molecular Beam Epitaxy, 1968–1970

Citation

In 1968–1970, Molecular Beam Epitaxy (MBE) techniques using reflection high-energy electron diffraction for growing epitaxial compound semiconductor films were introduced. MBE deposits single crystal structures one atomic layer at a time, creating materials that cannot be duplicated through other known techniques. This precise crystal growth method revolutionized the fabrication of semiconductor devices, quantum structures, and electronic devices, including lasers for reading and writing optical disc media.

Street address(es) and GPS coordinates of the Milestone Plaque Sites

600 Mountain Avenue, Murray Hill, NJ 07974 40.684031, -74.401783, 600 Mountain Avenue, Murray Hill, NJ 07974 40.684031, -74.401783

Details of the physical location of the plaque

Inside entrance lobby, to left of reception desk

How the plaque site is protected/secured

There is a staffed reception desk in the lobby

Historical significance of the work

MBE should be recognized as a foundational technology in nanoscience

Molecular Beam Epitaxy and Al Cho will be forever linked, for the best of semiconductor science. It all began in the late 1960’s – beginning of 1970’s when Al Cho and J.R. Arthur through their experimental ingenuity started to characterize vapor pressures of gallium and arsenic [1] then understand the physical interaction between Arsenic and Gallium in a vacuum environment [2].

At that time, Arthur introduced the term of Molecular Beam, issued from the well-known and established Knudsen evaporation sources … but not yet epitaxy. Other early contributors are John E. Davey, and Titus Pankey n 1968, using a very specific experimental apparatus[3].

All the ingredients to cook the Molecular Beam Epitaxy technique were finally gathered. It came in 1970 that the term Molecular Beam Epitaxy was ‘’finally’’ mentioned, by Al Cho for the first time, in his paper, “Molecular Beam Epitaxy of GaAs, AlGaAs and GaP” [4], followed the next year in his review paper [5] "Film deposition by molecular-beam techniques. Between 1970 and 1974 Al Cho published numerous papers related to MBE growth of GaAs and related materials, their doping, multilayered stacks, in-situ characterization [6]. Al Cho and J.R. Arthur published together in 1975 their article simply titled ‘’Molecular Beam Epitaxy‘’ [7].

In order to understand the significance of what achieved Al Cho specifically we need to point out the fact that the only available techniques to synthetize semiconductor materials by homo- and hetero-epitaxy were Vapor Phase and Liquid Phase Epitaxy with all their limitations and their lack of scalability: to name a few, LPE is not flexible (growth at thermodynamic equilibrium – difficult to grow mismatched material), limited to high growth rate and not adapted to thin epilayers required in current and future devices – VPE is using extremely hazardous precursors and requires very high growth temperatures also meaning that facilities are more stringent to set-up and handle.

From Al Cho early works on a modified Varian-made enclosure, under a secondary vacuum, not originally built to perform epitaxial deposition to the current workhorses of epitaxy able to process multiple 200 mm, 300 mm and up to 450 mm wafers more than 50 years of innovations have been carried-out. As early as the late 1970’s, Al Cho has been advising MBE equipment manufacturers such as RIBER to adapt their vacuum chambers to fit to the needs of semiconductor science. In 1978, Al Cho, Pierre Auger and RIBER have united a community and launch the first MBE International Conference in Paris bringing together 300 scientists from all around the world.

After the development of above-mentioned concept and devices, the age of maturity has arisen for MBE in the 1990’s with the first MBE production reactors, already able to perform the growth on 200 mm substrates (or 4 x 100 mm wafers) and then 300 mm substrates (or 9 x 100 mm) and more recently with the biggest MBE reactor ever manufactured with a 4 x 200 mm capability and up to 450 mm. All these MBE reactors are fully automated and operates 24/7 in semiconductor foundries. All kind of electronic (HEMT, HBT, Hall effect sensors …) and optoelectronic (lasers, SOA, IR photodetectors and sensors …) devices are currently mass produced by MBE in US and China mostly. In addition, hundreds of R&D MBE reactors are used daily by researchers all over the world to develop next gen devices using classical III-V (As-, P-,Sb-based), II-VI, IV-IV, IV-VI, lead-chalcogenides, Transition Metals Dichalogenides, , ZnO, 2D crystals, hybrid topological insulators and ferromagnetics, graphene and hBN. MBE is a key element of the mix of deposition technologies, which include metal-organic chemical vapor deposition (MOCVD) and high-temperature chemical vapor deposition (HTCVD). Together these support fabrication of a wide variety of semiconductor devices which are indispensable in the modern world.

MBE has been considered with so much potential that researchers from NASA and Space Vacuum Center in Houston, TX have carried-out extra-terrestrials experiments in Low Earth Orbit during STS-60 in FEB. 1994, STS-69 in SEP. 1995 and STS-80 in NOV. 1995 in the frame of the Wake Shield Facility program

Footnotes

[1] Vapor pressures and phase equilibria in the GaAs system - J. R. Arthur - Journal of Physics and Chemistry of Solids, Volume 28, Issue 11, November 1967, Pages 2257-2267

[2 ] Interaction of Ga and AS2 Molecular Beams with GaAs Surfaces - J. R. Arthur J. Appl. Phys. 39, 4032–4034 (July 1 1968)

[3] John E. Davey, and Titus Pankey "Epitaxial GaAs films deposited by vacuum evaporation” Journal of Applied Physics 39.4 (1968): 1941-1948

[4]Cho, A.Y. “Molecular Beam Epitaxy of GaAs, AlGaAs and GaP”" Proc. Symp. GaAs and Related Compounds. Vol. 2. 1970

[5] Cho, Alfred Y. "Film deposition by molecular-beam techniques." Journal of Vacuum Science and Technology 8.5 (1971): S31-S38

[6]Cho, A. Y. "Morphology of epitaxial growth of GaAs by a molecular beam method: The observation of surface structures." Journal of Applied Physics 41.7 (1970): 2780-2786.

[7] Cho, Al Y., and J. R. Arthur. "Molecular beam epitaxy." Progress in solid state chemistry 10 (1975): 157-191.

Obstacles that needed to be overcome

Vacuum chambers available at the time were not designed for the epitaxy techniques. These needed to be modified, and techniques invented to grow and create single monolayers of atoms on a semiconductor surface. In addition to the reactor chamber itself, numerous obstacles needed to be overcome from surface preparation, creation of the molecular beam itself with appropriate composition, and all happening within a vacuum chamber.

Features that set this work apart from similar achievements

This is a fundamental discovery allowing for atomic layer control and growth of novel materials. This method has allowed for new devices, such as semiconductor lasers, that have had immeasurable impact on society. MBE today plays an essential role in the fabrication of III-V devices such as GaAs, InP, and GaN each providing unique capabilities in generation and detection of light and well as amplification of high frequency signals such as the radio power amplifiers powering 5G around the world.

Significant references

IEEE Medal of Honor1994 : https://corporate-awards.ieee.org/recipient/alfred-y-cho/
A. Y. Cho, "Device fabrication by molecular-beam epitaxy," 1975 International Electron Devices Meeting, Washington, DC, USA, 1975, pp. 429-432, doi: 10.1109/IEDM.1975.188914.
A. Y. Cho and F. K. Reinhart, "Molecular beam epitaxy of GaAs voltage variable capacitors," in IEEE Transactions on Electron Devices, vol. 20, no. 12, pp. 1173-1173, Dec. 1973, doi: 10.1109/T-ED.1973.17824.
A.Y. Cho and W.T. Tsang, "Masked Molecular Beam Epitaxy", Integrated and Guided Wave Optics - Technical Digest Series (Optica Publishing Group, 1978), paper WB1
A. Y. Cho and H. C. Casey, "IV-3 GaAs-AlxGa1-xAs double-heterostructure lasers prepared by molecular-beam epitaxy," in IEEE Transactions on Electron Devices, vol. 21, no. 11, pp. 741-741, Nov. 1974, doi: 10.1109/T-ED.1974.18028.

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