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06/26/2008
Passing of a Pioneer
For me, the most exciting news of the past week is that the
Phoenix Mars Lander has indeed found convincing evidence that
it has achieved one of its objectives, confirming the presence of
ice on Mars. On June 15, Phoenix exposed some dice-size
chunks of whitish material in the trench they’ve dubbed “Dodo-
Goldilocks”. The Phoenix team couldn’t be sure that the chunks
were ice, a salt being another possibility. However, when they
looked again on June 19, some of the chunks were gone, as
anticipated if the water ice sublimed into vapor on exposure to
the Martian atmosphere. A NASA/JPL news release on June 19
quotes Phoenix Principal Investigator Peter Smith of the
University of Arizona, “It must be ice. These little clumps
completely disappearing over the course of a few days, that is
perfect evidence that it’s ice. … Salt can’t do that.”
Last month marked the passing of one of the early pioneers of
the transistor era at Bell Labs. Morgan Sparks, who died at the
age of 91, was my first boss when I came to Bell Labs in 1952.
Without the transistor and its electronic offspring, notably the
ubiquitous silicon chip, Phoenix and the many other NASA
spacecraft missions would not have been possible. Our Editor,
Brian Trumbore, called my attention to Sparks’ obituary in the
May 8 New York Times. The picture of Morgan in the Times
reminds me somewhat of famed actor Alan Alda. In the book
“Crystal Fire” by Michael Riordan and Lillian Hoddeson, Sparks
is described as a “handsome, low-key, soft-spoken man with
close-cropped hair and deep smiling eyes” who charmed William
Shockley’s secretary and married her in 1949. The marriage
lasted 57 years until her death in 2006.
Until I read Sparks’ obituary, I didn’t realize we shared a number
of things in our backgrounds. We were both born in Colorado
and both of us skipped two grades, Morgan first and fifth while I
skipped first and twelfth. We also both worked on batteries at
Bell Labs – he worked on them before his semiconductor efforts
while my battery work followed work on semiconductors. To
appreciate Sparks’ major contribution to the transistor, let’s take
a look at some of the intrigue surrounding the invention of the
transistor. I’ve probably written before about some of what
follows but hopefully there will be additional bits of interest.
Crystal Fire is a wonderfully detailed account of those early days
and of the personalities involved.
The first person I was introduced to upon arriving for work at
Bell Labs was Bill Shockley. Completely out of my league in
meetings involving Shockley and other superstars of the
semiconductor field, it was clear to me that Shockley was not
only brilliant, but also had a substantial ego. Five years before I
arrived at Bell, in 1947, Shockley headed a group working on
semiconductors. In December of that year, two members of his
group, John Bardeen and Walter Brattain, put some point
contacts down on a piece of germanium and observed
amplification of an electrical signal. They had invented the
transistor. Shockley was of the opinion that work he had done a
few years earlier proposing a so-called “field effect” paved the
way for the transistor and that he should share in the patent.
However, the Bell patent attorneys turned up an earlier 1930
patent by Polish-American immigrant Julius Lilienfeld; that
patent also involved some sort of “field effect”. The attorneys
concluded that if they filed the transistor patent application citing
Shockley’s earlier work, the patent would be denied! Bardeen
and Brattain’s transistor was clearly new and novel and Shockley
was crushed to find Bell’s patent department arguing against his
inclusion. He essentially withdrew from working with Brattain
and Bardeen and furiously began working on the theory of
another approach to making a transistor. He published a
groundbreaking paper on his work and proposed a new sandwich
structure type of transistor.
We’ve talked before about p-n junctions, where p-type material
has a deficiency of electrons (hence is positive or p-type) while
n-type material has a surplus of electrons (hence, negative or n-
type). One sandwich structure suggested was an n-p-n sandwich,
in which a very thin p-layer is like a slice of bologna between
two slices of rye bread (n-type). Instead of the point contacts,
Shockley proposed making a sandwich of germanium in which
the current would pass through the crystal. There was some
question then as to whether the current could actually pass
through a crystal of germanium. Bardeen apparently had his
doubts, feeling that all the current travels on the surface.
Here’s where Morgan Sparks entered the picture. In addition to
marrying Shockley’s secretary, Sparks took up the challenge of
actually making a sandwich p-n junction transistor. By April of
1949, he and his technical assistant, Bob Mikulyak, made a
structure that was not a sandwich but did show transistor action
of the p-n junction type that Shockley predicted. (Bob was an
interesting individual I’ve mentioned before. I heard my first
stereo sound in his home on stereo speakers he made himself.
He also for years printed our Christmas cards using the drawings
made by our cartoonist, Harry Trumbore.)
One of the strengths of Bell Labs back in those golden years was
the ability to reach out and cooperate with experts in other
areas to accomplish an objective. Morgan Sparks reached out
to Gordon Teal. Teal and John Little had bootlegged a crystal
pulling effort, receiving no encouragement from Shockley for
their efforts. Teal and Little wanted to grow single crystal
germanium by constructing a crystal puller based on a 1917 idea
of a little known Polish scientist named Czochralski. On a bus
between Bell Labs and Summit that I was to ride for many years,
Teal and Little sketched up a model for a crystal puller and I am
amazed that only two days later they had constructed a puller
using a bell jar and an induction heating coil Little happened to
have. They soon pulled their first crystal by dipping a seed
crystal into molten germanium and slowly pulling the seed out of
the melt.
Morgan Sparks got together with Teal and they collaborated on
growing and measuring p-n junctions made by adding doping
materials during the growth of the crystals. Shockley finally
realized his mistake and Teal and Little got a lab and a
wonderful, talented guy, Ernie Buehler, to handle the crystal
pulling. By March and April of 1950, Sparks and Teal had made
their sandwich n-p-n transistor and its electrical properties were
in very good agreement with the predictions of Shockley’s
theory. Their big challenge was to get that p-type “bologna” in
the middle of the sandwich very thin. They finally achieved this
as they were growing n-type germanium by dropping a little pills
of germanium doped with gallium into the melt to convert the
growing crystal to p-type and then, only ten seconds later,
dropping in a pill of germanium doped with arsenic to turn the
germanium n-type. This gave them a p-type layer of only 30
mils (thousandths of an inch) thickness.
The achievement marked the beginning of the end for the point
contact transistor, which was being produced and supplied to
various companies and researchers. The devices were
electrically noisy and the electrical characteristics were not
reproducible from one batch to another. The 30-mil thickness of
the p-layer was still not thin enough but the achievement of the
sandwich structure (and its electrical properties agreeing with
Shockley’s theory) was a feasibility experiment that helped pave
the way for the zillions of p-n junction devices that populate our
world today.
As for Sparks, he was sent to New Mexico in 1972 to be the
president of Sandia National Laboratories, then managed by
AT&T. Following his retirement in 1981, he became dean of the
Robert O. Anderson School of Management at the University of
New Mexico. I remember him as a very decent man and a boss
for whom I had the utmost respect.
Allen F. Bortrum
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