By Henry Kressel
The Electron Devices Society of the IEEE (Institute of Electrical and Electronics Engineers) is celebrating during 2022-23 the 75th anniversary of the transistor, one of the most important inventions in history.
We would not be living in the world we know, and take for granted, without the transistor. Along with the heterojunction semiconductor laser, developed some years later, these two devices enable practically everything that makes the modern world function.
The Bell Telephone Laboratories, where the transistor was invented, was the largest research laboratory in the world focused on communications technologies. Its funding came from AT&T, a long-term US telephone monopoly, thanks to which the Labs were able to support high-risk, long-term research projects.
Replacing the vacuum tube
The transistor project originated when senior Bell Labs management decided to invest in the development of a semiconductor solid-state device that would replace vacuum-tube switching and amplification devices.
A major driver of this project was the poor reliability of vacuum-tube devices that were widely deployed throughout the AT&T network. Replacing these devices with reliable solid-state ones was viewed as a major cost-reduction opportunity.
This project began as an exploratory one, and three outstanding scientists were tasked with it: Walter Brattain and John Bardeen were experienced experimentalists, and William Shockley was a brilliant theoretician.
On December 16, 1947, Bardeen and Brattain demonstrated their invention: a tiny germanium chip with metal point contacts that demonstrated switching and amplification properties similar to those of a vacuum-tube device.
While this point-contact transistor demonstrated the right parameters, it was fragile and impractical. It took another invention to make the transistor practical. This was the contribution of Shockley, who invented the junction transistor first demonstrated in January 1948, which marks the practical beginning of the transistor.
All three scientists shared the Nobel Prize in Physics in 1956.
Of the pioneers, Shockley’s fundamental contributions stand out. His theoretical work regarding the physics of semiconductor devices led to their realization for many applications. including microwave and light sensing, and new transistor structures that are the basis of modern electronic systems. He later founded a company to commercialize semiconductor devices, along with scientists who later founded Intel.
The transistor invention received worldwide attention, and AT&T licensed the intellectual property globally under very favorable terms, ushering in an enormous level of product development. At the forefront of this commercial activity were the big manufacturers of vacuum tubes, which included RCA, Motorola and Philips, among others.
While various AT&T units continued to make major contributions, the contributions of other companies were greater because they were driven by commercial sales. While manufacturing products for its own use, AT&T was not legally allowed to sell equipment, just telephone and communication services.
In the 1950s, commercial transistors using germanium appeared that were used in applications such as portable radios and computing devices. Some were very costly systems using many thousands of transistors to form circuits. Important military computers were pioneers. The control computer for the US Atlas intercontinental missile was the largest, built by the Burroughs Corporation in the late 1950s.
The silicon breakthrough
While germanium transistors were indeed highly useful, they suffered from performance handicaps that limited their applications. In the 1960s two developments set the stage for the future dramatic cost reductions and performance improvements.
The first was the development of silicon semiconductor technology to replace germanium, and the second was the development of the integrated circuit.
Without silicon, integrated circuits would not have been possible. The basic work on silicon was done at Bell Labs. But the subsequent major advances in devices came from other organizations that entered the industry.
Intel pioneered the integrated circuit that set the stage for our current device and computing-system technology. The integrated circuit incorporated transistors built into the silicon and interconnected on the silicon slice. This replaced the costly interconnection of individual transistors to form circuits, thus hugely reducing costs.
The computing power of a system is a function of the number of transistors and their switching speed. The problem of increasing transistor density at declining costs was solved by the integrated circuit.
The first integrated circuits incorporated a small number of transistors. Today, because of the ability in production to shrink transistor dimensions and control switching-heat generation, billions of transistors are interconnected on a chip the same size as the 1960s chip – a thumbnail.
Moore’s Law describes the historical increase of computing power with transistor chip density doubling every two years to the point where transistor dimensions are approaching atomic ones.
Such increasing chip densities would not be possible without another development in the 1970s at the RCA Labs, CMOS (complementary metal oxide semiconductors). This invention made it possible dramatically to reduce the heat generated by switching circuits by novel transistor interconnection layouts.
CMOS became the universal chip technology enabling ever more dense integrated circuits. For example, a typical smartphone has the transistor density and computing power of a mainframe computer of the 1970s.
The remarkable history of the transistor is testimony to what can be accomplished in a technology world where human genius is harnessed to commercial ends in a free economy with funding for innovations. There never was a national czar dictating programs or controlling investments across the board.
The market was and remains very competitive. Thousands of companies were founded with venture capital to commercialize new semiconductor products. Warburg Pincus funded six successful chip companies, one of which pioneered the Ethernet connectivity technology that has become a universal standard. Another pioneered chips incorporating multiple computing processors along with memory that is used in Internet traffic management.
The sad part of the story is that the great research institutions that pioneered so much of the technology are gone. There are no organizations like Bell Labs and RCA Labs.
Henry Kressel is a technologist, inventor and long-term private equity investor at Warburg Pincus. His technological achievements while at the RCA Laboratories include pioneering semiconductor lasers that today enable fiber-optic communications, including the Internet.