History of The Transistor - Improvements in Transistor Design

Improvements in Transistor Design

Shockley was upset about the device being credited to Brattain and Bardeen, whom he felt had built it "behind his back" to take the glory. Matters became worse when Bell Labs lawyers found that some of Shockley's own writings on the transistor were close enough to those of an earlier 1925 patent by Julius Edgar Lilienfeld that they thought it best that his name be left off the patent application.

Shockley was incensed, and decided to demonstrate who was the real brains of the operation. Only a few months later he invented an entirely new type of transistor with a layer or "sandwich" structure. This new form was considerably more robust than the fragile point-contact system, and would go on to be used for the vast majority of all transistors into the 1960s. It would evolve into the bipolar junction transistor.

The spacistor was a type of transistor developed in the 1950s as an improvement over the point-contact transistor and the later alloy junction transistor. Further developments included the grown-junction transistor (1951), the surface barrier transistor, the diffusion transistor, the tetrode transistor, and the pentode transistor. The diffused silicon 'mesa transistor' was developed at Bell in 1955 and made commercially available by Fairchild Semiconductor in 1958.

With the fragility problems solved, a remaining problem was purity. Making germanium of the required purity was proving to be a serious problem, and limited the number of transistors that actually worked from a given batch of material. Germanium's sensitivity to temperature also limited its usefulness. Scientists theorized that silicon would be easier to fabricate, but few bothered to investigate this possibility. Morris Tanenbaum et al. at Bell Laboratories (Jl. of Applied Physics, 26, 686-692, 1955) were the first to develop a working silicon transistor in January 1954. A few months later, Gordon Teal, working independently at the nascent Texas Instruments (not published), developed a similar device. Both of these devices were made by controlling the doping of silicon single crystals while they were grown from molten silicon. A far superior method was developed by Morris Tanenbaum and Calvin S. Fuller at Bell Laboratories (Bell System Technical J., 35, 1-34, 1955) in early 1955 by the gaseous diffusion of donor and acceptor impurities into single crystal silicon chips. That technology was later used by Jack Kilby and Robert Noyce in their invention of integrated circuitry, thereby initiating the "Silicon Age". Germanium disappeared from most transistors by the late 1960s.

Within a few years, transistor-based products, most notably radios, were appearing on the market. A major improvement in manufacturing yield came when a chemist advised the companies fabricating semiconductors to use distilled water rather than tap water: calcium ions were the cause of the poor yields. "Zone melting", a technique using a moving band of molten material through the crystal, further increased the purity of the available crystals.

The first gallium-arsenide Schottky-gate field-effect transistor (MESFET) was made by Carver Mead and reported in 1966.