When Leo Esaki first visited IBM’s Yorktown headquarters in 1959, he knew the company had big ambitions. “There was a strong feeling of growth,” Esaki later told THINK magazine. “There was an aura of, ‘We are going to establish the finest research organization in the world’.”

Esaki won the Nobel Prize in Physics for his work in electron tunneling in solids — research that forever changed the semiconductor industry. By age 48, he was one of the most respected research physicists in the world and a godfather of home computing. The discoveries he made during his 32-year tenure at IBM touched off a wave of miniaturization that provided the foundation for the computers and handheld electronics we rely on so heavily today. And it was all because he accepted a colleague’s invitation to visit Yorktown.

“It was a good decision,” Esaki said with the characteristic understatement that reflected the modesty of a man whose achievements spoke for themselves.

Esaki was born in Osaka, Japan, and raised in Kyoto. By the time he joined IBM at age 34, he already had a reputation as a formidable researcher. His work in tunneling phenomena while at Sony won him acclaim in the growing field of semiconductor physics and brought him to the attention of Robert Gunther-Mohr, then manager of semiconductor research at IBM. It was Gunther-Mohr who first asked Esaki to visit the company’s new laboratory in Yorktown, hoping to entice the young scientist into a long-term residency.

For a man of Esaki’s generation, moving to the United States represented a significant change, if not an outright risk. Esaki began his undergraduate study of physics at Tokyo Imperial University in 1944. Two years later, the name had been changed to the University of Tokyo, and Esaki had survived the firebombing of his city. In the aftermath of the war, the United States became the global leader in science and manufacturing, and researchers like Esaki became citizens of the world. While Esaki and his wife, Masako, maintained close ties to Japan, they reported having little difficulty in adjusting to life in the US, partly due to the international outlook at IBM. “Leo is very casual about it and very much a free spirit,” Masako said in 1973. “But he enjoys his work at IBM, and he likes living here.”

Esaki’s colleagues at IBM described him as a man of wide-ranging interests. He was equally fascinated by bridge, French food and the marketing side of the consumer electronics business. Shortly after he arrived in New York, he took up smoking cigars, a habit he would maintain for decades. Mostly, though, he focused on his work. One colleague praised his “tremendous scope of vision, intuition and imagination.” The researchers he supervised regarded him as a coworker as much as a manager, and the team he assembled worked together for years, with members often returning to his lab at Yorktown after stints in teaching and university research.

Early in his tenure at IBM, Esaki summed up his goals in one phrase: “compactness in electronics.” There are several obstacles to shrinking electronics, but the most significant is resistance — the amperage or signal strength that is lost whenever electricity passes through a conductor such as a wire or transistor. Electricity is a series of electrons moving in waves; some of these electrons don’t have enough energy to overcome obstacles in the material they are passing through, so they stop. This creates resistance.

Esaki believed that the secret to overcoming resistance and achieving compactness in electronics was a phenomenon known as electron tunneling. Researchers in quantum mechanics were just beginning to explore electron tunneling when Esaki came to IBM. Under certain circumstances, electrons can pass or “tunnel” through microscopic obstacles that would normally resist them. When this tunneling occurs, it can result in negative resistance — a phenomen physicists had previously assumed was impossible.

The research in electron tunneling that Esaki conducted at Sony during the late 1950s led to his most famous invention, the Esaki diode. Over the next two decades at IBM, he would build on his initial discoveries to refine the design and production techniques of wafer-based components in ways that revolutionized the field of semiconductors.

When Esaki arrived at IBM in 1959, transistors were the cutting edge in electronics technology, and many consumer devices still relied on vacuum tubes. The limiting factor in these components was frequency, the number of discrete signals they could transmit each second. By taking advantage of electron tunneling phenomena, Esaki diodes could operate at frequencies up to 20 times higher than existing transistors — an advantage that made them 10 times more power-efficient than components that performed similar tasks, at one-tenth the size.

The small size and high durability of the diodes and other semiconductor components that Esaki developed at IBM throughout the ’60s and ’70s, along with their relatively low cost, made them a breakthrough technology in commercial radio and telephone applications. Their most significant impact, however, was on computers. By removing constraints imposed by the size, power demands and operating temperatures of existing transistors, Esaki diodes increased the theoretical limit on computer processing speeds 500-fold. They constituted a leap forward in the miniaturization that defined the electronics industry in the second half of the 20th century, and they made IBM the industry leader in computing technology for decades to come.

Esaki retired from IBM in 1992, after 32 years as one of the company’s most famous and respected researchers. At a symposium held in his honor that May, IBM Vice President and former Director of Research John Armstrong praised “the enormous scientific importance of Esaki’s work, which has given rise to major new directions in physics all over the world.” Bidding farewell to the team of colleagues with whom he had worked for decades, Esaki reflected on his career at the company. “As a scientific refugee from Japan, IBM gave me a place I could call a home base,” he said. “Here I found the inspiration and support I needed for my work.”