Journal of ELECTRONIC MATERIALS

DOI: 10.1007/s11664-017-5660-0 Ó 2017 The Minerals, Metals & Materials Society

Dr. Herbert Frank Schaake: In Memoriam PRADIP MITRA

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1.—Leonardo DRS, Electro Optical and Infrared Systems (EOIS), P.O. Box 740188, Dallas, TX 75374, USA. 2.—e-mail: [email protected]

Herbert F. Schaake (1939–2017)

Herbert F. Schaake was born in Baltimore, Maryland, USA, on April 16, 1939. He attended Baltimore Polytechnic High School and went on to the Massachusetts Institute of Technology, where he graduated with a BS (Bachelor of Science) degree in physics in 1961. Upon graduation, he entered officer training for the Air Force and served for 4 years before beginning employment at Martin Marietta in Orlando, Florida. While in Orlando, he began a graduate program in materials science and engineering at the University of Florida. After completing his masters, he went on for a Ph.D. at the University of Florida in Gainesville which he completed in 1972. His dissertation was based on the use of semi-empirical quantum mechanical calculations to deduce the properties of defects in

(Received June 13, 2017; accepted June 26, 2017)

silicon—in particular, the vacancy, donor and acceptor impurities, complexes of these, and amorphous disorder. Herb began working at Texas Instruments, Central Research Labs in Dallas, Texas, in 1973 as a member of the technical staff. His initial work investigated defects in silicon that affected charge coupled devices (CCD) and dynamic random access memory (DRAM) devices. A particular emphasis was on the precipitation of oxygen in Czochralski silicon during processing, and the role that this had on the gathering of impurities and defect formation. His subsequent work addressed defect issues in mercury cadmium telluride. His extensive work on formulating the understanding of the formation and kinetics of impurities and defects in HgCdTe had a wide-ranging impact. It is for this work Herb became nationally and internationally renowned. His initial work involved the development of appropriate etches to reveal defects, and the correlation of the etch patterns with transmission electron microscope/scanning transmission electron microscope (TEM/STEM) analysis. This led to an understanding of the role of precipitation of tellurium in HgCdTe and the development of techniques to minimize the dislocations that result from the precipitation and subsequent annealing.1 In collaboration with Roland Koestner, he demonstrated the benefits of molecular beam epitaxy (MBE) HgCdTe growth on (211)B orientation with excellent surface morphology and devoid of cellular twins that were found in HgCdTe (111)B layers.2 (211)B has since become the de facto standard orientation for MBE HgCdTe growth. Herb headed a group that improved the properties of HgCdTe for metal–insulator semiconductor (MIS) devices, and developed a more quantitative understanding of the effect of dislocations and other defects on the properties of HgCdTe devices. He also led an effort to develop high-yielding low-cost largearea CdZnTe substrates, particularly aimed at liquid phase epitaxial (LPE) growth.

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After the TI defense group was acquired by Raytheon, and the cooled IR business subsequently by DRS Technologies in 1997, he led the efforts to develop HgCdTe MW/MW two-color 256 9 256 focal plane arrays (FPAs) for the Navy, and LW/LW 256 9 256 and 512 9 512 two-color FPAs for the Missile Defense Agency. As part of these programs, Herb contributed to developing a detailed understanding of the role of the passivation, copper doping, and passivation interdiffusion. The MW/ MW FPAs are now proceeding to the mass production stage. As part of a DARPA-funded program, he then led an effort to develop midwave HgCdTe n+/p devices for operation at temperatures as high as 250 K. This effort resulted in a quantitative understanding of the activation of arsenic that had been incorporated by LPE growth under tellurium-rich conditions3 by annealing under mercury-rich conditions, and of the role of interfacial impurities such as chlorine on the shunting of detectors that resulted from an n-type surface layer formed by these impurities. Herb provided an excellent summary of his work on the kinetics of defect diffusion, acceptor activation and Te precipitation in HgCdTe at the 2016 II– VI Workshop.4 He is the author of over 70 technical publications and the inventor on 7 patents. Herb’s involvement with the, ‘‘U.S. Workshop on the Physics and Chemistry of Mercury Cadmium Telluride’’, dates back to the first Workshop held in October 1981. Thereafter, he was a mainstay at the II–VI Workshop, as it subsequently became known, and never missed the annual meeting. He served on the Workshop committee, as the Proceedings Editor and Conference Co-Chair, reviewed papers and presented his research. Herb loved mentoring students, and volunteered to judge student papers at the II–VI Workshop as well as interview nervous

high school students who wanted to attend MIT. After retiring from DRS in 2012, Herb continued to work as a consultant at EPIR Technologies and at DRS. Herb was a longtime member of the Minerals, Metals, and Materials Society and American Guild of Organists. Herb had a keen intellect and a wonderful, witty sense of humor. He had a passion for music that guided him through life. He began studying the organ while in high school, and went on to minor in music at the University of Florida. At the University of Florida, he built a harpsichord that he would later play with his son’s high school orchestra. He served as the organist at the University of Florida Lutheran Church. Herb continued his avocation of music by serving as the organist at Christ the Servant Lutheran Church in Denton, Texas, for 38 years. He helped establish the Denton Bach Society and sang in its early years. Herb’s passion for life extended to food, wine and conversation, as everyone he met will attest. ACKNOWLEDGEMENTS I am grateful to Herb’s wife, Dr. Jean Schaake, and son, Dr. Christopher Schaake, for providing the photo and sharing various aspects of Herb’s life.

REFERENCES 1. H.F. Schaake, J.H. Tregilgas, A.J. Lewis, and P.M. Everett, J. Vac. Sci. Technol. A 1, 1625 (1983). 2. R.J. Koestner and H.F. Schaake, J. Vac. Sci. Technol. A 6, 2834 (1988). 3. H.F. Schaake, J. Electron. Mater. 30, 789 (2001). 4. H.F. Schaake, Modeling the role of point defect diffusion in diode formation, impurity activation and tellurium precipitation in HgCdTe. Tutorial presented at the 2016 II–VI Workshop (Baltimore, MD, 2016).