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Celebrating Semiconductor Pioneer Dr. Esther M. Conwell

March 08, 2024 by Duane Benson

It's Women's History Month—and today is also International Women's Day! To celebrate, we spotlight Dr. Esther M. Conwell, an early pioneer in silicon and germanium semiconductor physics who developed a theory pivotal to the birth of integrated circuits.

Anyone who has studied the history of twentieth-century semiconductor physics likely has heard the names Bardeen, Brattain, and Shockley. But Dr. Esther Conwell's lesser-known achievements equally enshrine her in the annals of the electronics industry.

Dr. Esther M. Conwell was a scientist who developed a critical theory describing the flow of electrons. The Conwell-Weisskopf theory is today regarded as one of the fundamental principles behind semiconductor physics and a prerequisite to modern electronics.

 

Dr. Conwell

Dr. Esther M. Conwell. Image used courtesy of the University of Rochester
 

Dr. Conwell’s work not only helped open the world of semiconductors that run the modern world but also inspired future generations of female scientists—both feats to be celebrated during Women's History Month and beyond.

 

An Unconventional Jump Into Physics

A New York City native, Dr. Conwell first took an interest in physics in high school. In college, she pursued her passion for dance and physics—two interests that, in her words, “both exact and require discipline.” While Dr. Conwell was attracted to the innate order of physics, her distaste for lab work eventually led her to theoretical physics.

The twentieth century was not a time of equality in STEM. As late as 1950, only six women in the United States were awarded doctoral degrees in physics (less than 2% of total Ph.Ds). Yet, in 1942, Conwell earned her B.S. in physics from Brooklyn University with the aim of becoming a professor. With the encouragement of one of her professors, however, she enrolled as a graduate student at Rochester University to pursue physics research. Upon arriving at Rochester in 1942, she found a veritable ghost town; most of the teaching staff had left to work on the atomic bomb under the Manhattan Project, including her advisor, physicist Victor Weisskopf.

Weisskopf was at Purdue University studying why resistance varies with temperature in semiconductor materials. Weisskopf sent this question to Conwell as her Master’s thesis project. She successfully solved the problem and later dubbed it the Conwell-Weisskopf theory. While the work was deemed important to the war effort, it wasn't classified until after the war. The war also delayed Conwell's Ph. D., which she finally earned at the University of Chicago in 1948.

 

The Theory Behind It All

Semiconductors are all about controlling the flow of electrons. Much of the chemistry and physics of semiconductor operation involves doping different materials by adding small amounts of impurities. The doping compounds become impurity ions that can donate or accept electrons, depending on the specific chemistry. Dr. Esther M. Conwell’s theory, shown below, describes how these impurity ions impede or enhance the flow of electrons.

 

The Conwell-Weisskopf Theory

The Conwell-Weisskopf Theory. Image used courtesy of Physical Review

 

The theory, which explains the movement of electrons in semiconductors due to impurity-related scattering, led to an understanding of how transistors work and was instrumental in the birth of the electronics industry.

 

Breaking Barriers for Women in Science

Dr. Conwell took pride in her life’s work on electron motion and in the trail she blazed for women in STEM.

“My life is the story of women scientists making a place in the world," she once said. 

Although Dr. Conwell had originally thought her Ph.D. would open more doors in the academic world, she was only able to secure a non-tenured position at her undergraduate alma mater, Brooklyn College, due to the discriminatory hiring practices of the day.

When she moved from academia to private industry at Western Electric, she faced gender-based discrimination once again. There, she received the formal employee classification of “female assistant engineer," and was designated a corresponding lower pay rate.

 

Esther M. Conwell

Esther M. Conwell, Ph.D. receiving the National Medal of Science from President Barack Obama. Image used courtesy of the National Science Foundation via Wikimedia Commons (Public domain)
 

Dr. Conwell left Western Electric to work at Bell Labs under William Shockley, co-inventor of the transistor, and conducted research on charge transport and high-field transport for telecommunications labs. In 1972, she was hired by Xerox in Rochester, New York, and worked on integrated optics and properties of organic semiconductors.

While in Rochester, she began teaching at the University of Rochester, where she maintained a research position throughout the rest of her life. Upon her retirement from Xerox in 1998, she became a full-time professor and turned her research toward the movement of electrons through DNA, with an eye toward electron movement in DNA for both cancer research and organic computing.

 

A Legacy of Research and Representation

Dr. Conwell has numerous awards and honors for her contributions to semiconductor science, including a rare triple membership in the National Academy of Engineering, the National Academy of Sciences, and the American Academy of Arts and Sciences. She was the first woman to win the Edison Award. In 2009, Dr. Conwell was presented the National Medal of Science by President Barack Obama in the White House for her contributions. She mentored and inspired young women in the sciences throughout her life.  Dr. Conwell passed away in 2014 at the age of 92 and was actively involved in research until her death.