Gerald Pearson
Gerald Pearson (1905–1987) was a Bell Labs physicist who took part in two landmark semiconductor episodes: the 1948 field-effect experiments with William Shockley, which failed in an instructive way, and the 1954 silicon solar cell, which he developed with Calvin Fuller and Daryl Chapin. After a long career at Bell Labs he moved to Stanford University, where he taught and did research in electrical engineering. His record shows how a negative experimental result and a positive one can both advance a field.
The Shockley-Pearson experiments were a test of the idea that a transverse electric field could control the current in a thin semiconductor film, and they did not work as predicted. The reasoning was simple: place a plate close to a thin semiconductor layer, apply a voltage, and the induced charge should change the number of carriers and thus the conductance, which is the principle of a field-effect amplifier. Shockley calculated an effect and Pearson, as the experimentalist, tried to see it. The experiments, reported in 1948 after work in the preceding years, found a change in conductance much smaller than the calculation predicted, by orders of magnitude. The disagreement was not the end of the story: Bardeen proposed that charges trapped in states at the semiconductor's surface screened the applied field. Pursuing that surface-state explanation led Bardeen and Brattain to the point-contact transistor in December 1947, announced in June 1948, so the failed field-effect test sits at the root of the most famous invention in the field.
The solar cell showed Pearson as a measurement-minded physicist working with materials people. Chapin had been looking for a way to power telephone equipment in remote places and had tested selenium cells with disappointing results. Pearson and Fuller worked on silicon with a diffused p-n junction close to the surface, and the three announced the result on 25 April 1954 at about 6 percent efficiency. Fuller made the junction; Pearson helped characterize how it responded to light and how its parameters depended on the material. The announcement credited the group rather than a single inventor, and that is the accurate way to remember the discovery.
The two episodes are linked by the problem of the surface. The failure of the 1948 experiments came from charge states at the surface, and surface control remained the central difficulty of semiconductor devices for years. The field-effect transistor became practical only after the silicon-silicon dioxide interface was mastered, with the MOSFET of Atalla and Kahng demonstrated in late 1959 and presented in 1960. The solar cell, by contrast, benefited from a junction that sat in the bulk of a diffused layer, with a surface that mostly had to be protected from recombination. Pearson's career thus touches the two sides of the same issue, one where the surface blocks an idea and another where the junction is built to work around it.
A common mistake is to say that the 1948 experiments proved the field-effect transistor impossible, or that Pearson was the junior partner of a famous colleague. The experiments showed that the surface of the real material behaved differently from the ideal calculation, which is a quite different claim; later MOS devices proved the principle sound. And Pearson was an established Bell Labs physicist in his own right, whose later Stanford years included teaching and research on semiconductors.
Read Gerald Pearson as the experimentalist who was present at a failed field-effect test that taught the field about surfaces, and then at a successful junction device that turned sunlight into power.