EUGENE ERNEST HALLER (1943-2018)

BY JUNQIAO WU, OSCAR DUBÓN JR., AND CHRIS G. VAN DE WALLE

EUGENE ERNEST HALLER, emeritus professor of materials science and engineering at the University of California, Berkeley, and senior faculty scientist at Lawrence Berkeley National Laboratory, passed away June 22, 2018, at the age of 75. He was an expert in semiconductor materials and a pioneer in ultrapure semiconductors research.

Haller was born January 5, 1943, in Basel, Switzerland. He earned his diploma in nuclear physics in 1967 and his PhD in solid-state and applied physics in 1970, both from the University of Basel. In 1970 he came to the United States to work at the Lawrence Berkeley National Laboratory (LBNL), first as a postdoctoral fellow of the Swiss National Foundation for three years and then as a staff scientist.

In 1980 he was appointed associate professor in the Department of Materials Science and Mineral Engineering at UC Berkeley, where he became a full professor two years later. He remained on the UCB faculty and was also a senior faculty scientist at LBNL through 2011 when he retired. He held the Liao-Cho Innovation Endowed Chair at UC Berkeley since 2005.

His research has had extraordinary impact on the doping, alloying, purification, characterization, and understanding of semiconductors, as well as their applications. His prowess at semiconductor crystal growth produced germanium (Ge) of unprecedented purity―a prerequisite for use of the material in far-infrared detectors employed for scientific missions on satellites, airplanes, and at high altitudes. Astronomers and astrophysicists want these detectors to work at the photon noise limit of their particular experiments. Haller’s group was recognized as the world leader in photoconductors made from doped Ge and gallium arsenide and in neutron transmutation doped Ge thermistors operating at temperatures as low as a few milliKelvin.

Haller’s ultrapure Ge was key to one of the most important devices in the Spitzer telescope: the Multiband Imaging Photometer. This infrared telescope was launched into space in 2003 and is still used to study the formation of planets near distant stars.

Another example serves as an impressive illustration of the style, execution, and influence of Haller’s research. He was among the first to recognize the importance of hydrogen interactions with semiconductors. Hydrogen has major effects on materials properties, with fascinating behavior both as an isolated center and in its interactions with other impurities or defects. These interactions turn out to have many important consequences for semiconductor device technology. Haller’s studies of hydrogen in germanium laid the groundwork for a vast amount of subsequent work in this field.

From the start he focused on aspects that turned out to be crucial―for instance, the formation of complexes between hydrogen and dopant impurities, a formation that renders the donors or acceptors electrically inactive.

In this as in all the fields he worked in, he was extremely effective at communicating his results in a clear and comprehensive manner, thus invigorating the field and channeling others’ research efforts in the most productive direction. He authored or coauthored over 1,000 publications during his career.

He can also be credited with launching the field of isotopically engineered semiconductors. Many physical properties of solids depend on isotope mass; examples are vibrational frequencies, thermal conductivities, band gaps, lattice constants, and diffusion. Exploration of this dependence used to be constrained by the lack of control over isotope content.

Haller was among the first scientists to recognize a unique opportunity brought about by the end of the Cold War: the change in the political climate abruptly opened access to sizable quantities of stable isotopes of a large number of elements. He established contacts with the sources in the former Soviet Union, ensured a supply of suitable isotopes, and designed experiments to exploit the unprecedented control over isotope content. Pure or controllably mixed isotopes of a variety of elements were grown into bulk single crystals and thin epitaxial films. As appropriate for an effort of this scope, Haller initiated collaborations with groups worldwide on a broad range of studies of these isotopically engineered materials. Many fascinating results were obtained, some of them resolving previously puzzling observations, others producing entirely new science.

Haller was a central figure in establishing semiconductor materials as an important area of research for the US Department of Energy (DOE). In 1984 he founded the LBNL Electronic Materials Program, a DOE-funded program that continues to this day.

His scientific achievements were recognized with numerous prestigious awards, including the James C. McGroddy Prize for New Materials from the American Physical Society (APS) in 1999, the David Turnbull Lectureship from the Materials Research Society in 2005, and the FMD John Bardeen Award of the Minerals, Metals and Materials Society (TMS) in 2010, the year he was also elected to the NAE. He was elected a fellow of APS (1986) and the American Association for the Advancement of Science (2004).

In addition, he provided exemplary leadership for the semiconductor research community, for instance by serving on the editorial advisory boards of major journals and on numerous scientific advisory boards and panels. He was a major figure in the semiconductor defect community, providing significant leadership for its most important series of meetings, the International Conferences on Defects in Semiconductors; in 1999 he hosted and chaired the 20th ICDS meeting at Berkeley.

He was an inspiring mentor for students and young scholars. During his career he graduated over 50 PhD students and hosted numerous postdoctoral researchers and visitors. Many have gone on to prominent positions in academia, national laboratories, and industry both domestically and internationally. His generosity in supporting young scientists extended well beyond his own group; one of us (CVdW) gratefully remembers Eugene reaching out to him to discuss his PhD work, and the boost of confidence that came with being recognized by a senior figure in the field.

Haller was a dedicated mentor who could be counted on to provide not just invaluable scientific insights but also wise counsel and support throughout our careers. Similar stories from other scientists abound; we all benefited and learnt so much from interacting with him and can honestly say we would not be the scientists that we are today had it not been for his support throughout our careers. We fondly recall his sharp mind, his unrivaled talent in experimental research, his steady, inspiring leadership, his fierce loyalty, and his wry sense of humor. He loved to talk about his expanding collection of historic radios or his treasured 1939 Talbot-Lago T123 vintage car―one of only twelve remaining vehicles of this model.

Eugene Haller is missed not only for the impact of his scientific contributions but also for his deeply caring nature. He is survived by his wife, Marianne, daughters Nicole and Isabelle, and their families.