"Breakthrough” is a word often found in reports about scientific or engineering achievements. Yet relatively few major inventions or innovations actually arrive out of the blue. More often, a development that appears to a casual observer as a breakthrough could be more accurately described as a “major advancement” or “a significant leap forward at the end of a series of discoveries.”
As Newton so famously put it, “If I have seen a little further it is by standing on the shoulders of giants.” But then, “breakthrough” fits so much more neatly into a headline.
Hans W. Becke and Carl F. Wheatley, a pair of RCA engineers, are credited with co-creating the insulated-gate bipolar transistor (IGBT). But as with so many other “breakthroughs” of the past few decades, the trail leading to the IGBT was blazed over many years by several different individuals and teams.
All of these researchers inserted pieces—usually sequentially, but sometimes virtually simultaneously—into the same puzzle that would eventually form the IGBT. Becke and Wheatley helped to contribute the puzzle’s last piece.
A Trail of Discoveries
By the late 1960s, with the industrialized world increasingly relying on amplifiers, motors, and other power-thirsty innovations, there was a growing need for a fast, efficient, and compact power-switching technology, preferably in semiconductor form. Whoever created such a device could expect to achieve both acclaim and financial rewards.
Not surprisingly, a number of academic and industrial researchers embarked on the quest to create a next-generation power semiconductor device. A Japanese researcher named Yamagami took the first step toward an operational IGBT by originating the concept of a metal-oxide-semiconductor (MOS) controlling a PNPN-layered (positive-negative-positive-negative) device without regenerative action. The idea was included in a Japanese patent application Yamagami filed in 1968.
By the late 1970s, B. Jayant Baliga, a General Electric engineer, conceived the idea of functionally integrating a MOS with bipolar physics (see “B. Jayant Baliga: Designing The Insulated-Gate Bipolar Transistor”). Baliga’s research, which directly led to the IGBT’s development, became public when he reported his findings in a September 1979 paper titled “Enhancement and Depletion Mode Vertical Channel MOS Gated Thyristors.” Baliga’s paper described the discovery of the IGBT mode of operation.
Virtually simultaneously a pair of RCA engineers, the late Hans W. Becke and Carl F. Wheatley, were arriving at similar conclusions about IGBT operation. In 1980, they filed a patent application describing a “power MOSFET with an anode region.” The patent claimed that “no thyristor action occurs under any device operating conditions,” meaning the device exhibited non-latch-up IGBT functionality over its entire operational range.
A Practical Need
Wheatley says the IGBT that he and Becke co-created arose out of a practical need rather than any desire to conduct leading-edge research. With RCA developing new electronic products in the late 1970s that required large amounts of voltage and power supplied quickly and efficiently, the need for a device with IGBT-like characteristics was growing daily.
“We needed to have a high-voltage and high-power device, and regular MOSFETs weren’t adequate,” Wheatley recalls. Drawing on device physics, Wheatley tried a new approach.
“I thought, what I’ll do is I’ll make the power MOSFET and I’ll have to make sure that it does have some bipolar action as well, and this will give me a lot of high current-density capability,” he says. The result was a device that exhibited plenty of lower forward drop when drawing a large amount of current, more than a conventional MOSFET.
Developing a technology to fit a particular need was nothing new for Wheatley. During his years at RCA, he invented everything from an integrated circuit designed to control a landmine self-detonator to a two-terminal all-electronic temperature sensor to the hardened power MOSFETs currently used on the International Space Station. Practical technology development, rather than pure research, was Wheatley’s specialty.
Wheatley notes that he had a much better knowledge of device physics than most of his engineering coworkers at RCA. His understanding of advanced concepts, including their current and potential applications, made him something of a de facto project leader at RCA’s semiconductor facility in Mountain Top, Pa. He also says his coworkers recognized and used his talents.
“They had responsibilities, and I would work with them and would tell them what to do and what to expect, and then they would go ahead and do it and then if it was patentable we would probably file a patent jointly,” he says. It was within this environment that Becke worked with Wheatley on the IGBT project.
As typical RCA staff engineers, Becke and Wheatley were accustomed to working on multiple projects simultaneously. On all of these initiatives, including the IGBT project, Wheatley would provide the direction while Becke would handle the time-consuming yet essential “dogwork,” as Wheatley describes it. “I told him what to do and how to do it,” Wheatley says. Becke’s reward would be co-listing on the patent.
Recognition and Honors
Wheatley retired from RCA as the manager of the Rad Hard Power and Advanced Device Design Group in 1987. In 1994, the College of Engineering of the University of Maryland honored Wheatley, an alumnus, for his work on the IGBT and various other contributions to semiconductor technology, awarding him its Centennial Medal.
Five years later, the school honored Wheatley as one of its 15 most esteemed alumni innovators, naming him to its engineering school’s Hall of Fame. Other recognitions include three awards from RCA and four awards from Harris Corp., which acquired RCA’s semiconductor operations in the late 1980s. Wheatley is the recipient of five honors from the IEEE as well, including Life Fellow.
The debate continues over whether the IGBT was invented by Becke and Wheatley, by Baglia, or whether all three individuals should share the credit. Yet the fact remains that the RCA engineers, neither of whom held advanced degrees, made a key contribution to the IGBT’s creation.
Hans W. Becke and Carl F. Wheatley: Key Patents
• U.S. Patent No. 4,364,073: Power Mosfet with an Anode Region, issued December 14, 1982, to Hans W. Becke and Carl F. Wheatley Jr.
• U.S. Patent No. 3,769,561: Current Limiting Integrated Circuit, issued October 30, 1973, to Joseph P. White, Robert Amantea, and Hans W. Becke
• U.S. Patent No. 4,677,324: Fast Switch-Off Circuit for Conductivity Modulated Field Effect Transistor, awarded June 30, 1987, to Harold R. Ronan Jr. and Carl F. Wheatley Jr.