1958
`
`Morton and Pietenpol: The Technological Impact of Transistors
`
`955
`
`The frequency-production index can be expressed in
`dimensionless form and is then the number of oscilla-
`tions at the alpha cutoff frequency of the highest fre-
`quency transistor during the average time required to
`produce a transistor in the U.S.A. In dimensionless form
`IfP is 2X101" cycles per unit. This measures the sim-
`plicity of the transistor compared to man.
`Since transistor production depends on years and
`men, I have used in Table I the well established ratio' of
`70 between them in predicting frequency from volume
`and frequency-production index. The production esti-
`mates are based on conventional methods of estimating
`growth.
`
`2 This number will be recognized as 3 (10) in the customary score
`system.
`
`No business essay is complete without a reference to
`money. Assuming that the cost per unit varies as
`P,-0.3 , my estimate of average transistor prices for
`1958, 1959, and 1960, is $1.80, $1.40, and $1.20. The
`corresponding sales volumes are $125, $210, and $300
`million.
`In closing this essay, I should like to acknowledge the
`assistance that has made it possible to carry out the ex-
`tensive research involved. The significant data pub-
`lished by the Electrical Industries Association3 has been
`essential. Special thanks are due to the encouragement
`and assistance of my friends at Bell Telephone Labo-
`ratories; without it, the completion of the investigation
`would have been difficult.
`3 Wall St. J., p. 11; October 14, 1957.
`
`The Technological Impact of Transistors *
`J. A. MORTONt, FELLOW, IRE, AND W. J. PIETENPOLt, MEMBER, IRE
`
`Summary-During the past ten years the transistor has invaded
`every phase of the electronics industry. Its important features are
`its high efficiency at low power levels, its reliability, and its potential
`low cost.
`Presented here are the major milestones and problems which
`were overcome and led to devices that cover a broad field of elec-
`tronic technology, and to the growth of a new industry.
`
`E LECTRONICS is an increasingly important part
`of modern technology. It merits this distinction
`because it pervades our economy as water does a
`sponge. Since electronics has to do with the high speed
`transmission and processing of information, it becomes
`a wonderful extension of man's mind.
`Electronics has the potential of affecting every aspect
`of our modern industrial world through communication,
`entertainment, transportation, power, manufacturing,
`and business. If we can measure the transistor's effect in
`expanding the breadth and versatility of electronics, by
`imaginative implication, we can define its impact on the
`whole of modern technology.
`The bulk of present day electronics has to do mostly
`with the transmission of information. In some 45 years
`it has grown from the original deForest vacuum triode
`and modulation theory to the fifth largest American
`industry comprised largely of consumer, military, and
`industrial transmission functions.
`
`* Original manuscript received by the IRE, March 5, 1958.
`t Bell Telephone Labs., Inc., Murray Hill, N. J.
`
`For some time now, through applications of informa-
`tion and switching theory to functions such as pulse-
`code modulation, memory, and logic, electronic man has
`known how in principle to extend greatly his visual,
`tactile, and mental abilities to the digital transmission
`and processing of all kinds of information. However,
`all these functions suffer from what has been called "the
`tyranny of numbers." Such systems, because of their
`complex digital nature, require hundreds, thousands,
`and sometimes tens of thousands of electron devices.
`The large amount of power used inefficiently and the
`high cost of reliability of the electron tube have pre-
`vented these expansions of electronics in all but a few
`cases where the high cost could be tolerated, even though
`not desired.
`This is where the transistor comes in. The really
`important aspects of the transistor are its very high-
`power efficiency at low-power levels and its potential
`reliability. Because of its relatively simple mechanical
`features, it is potentially low cost-another basic re-
`quirement of "the tyranny of numbers."
`So the story of the transistor to date has really been
`the struggle to realize these potentialities of high
`performance with high reliability and low cost. Let us
`take a quick look at the major milestones and problems
`that have been passed leading to today's transistor
`technology.
`To measure the present and future stature of tran-
`sistor electronics, we will glance at a few of the many
`system functions which transistors are now performing
`
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`956
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`PROCEEDINGS OF THE IRE
`
`June
`
`or are committed to do. These examples cannot be
`inclusive-there are too many. Many of them will be
`drawn from the Bell System since the facts are more
`readily available to the authors. But some military,
`consumer, and rindustrial applications must be men
`tioned.
`
`HISTORY
`The era from the announcement of the invention of
`the point-contact transistor in mid 1948 until mid 1951
`can be likened to early childhood. In this era, key items
`in advancing the device technology and research under-
`standing came through the development of pulling
`and zone-melting methods for growing single crystals
`of germanium of unprecedented purity and uniformity.
`Work by the inventors of the transistor and their
`colleagues during this era, resulted in improved theoreti-
`cal understanding and physical realization of the junc-
`transistor with greatly improved performance.
`tion
`Fabrication of junction diodes, triodes, and photo
`transistors was accomplished by both growing and
`alloying techniques. The micropower, high gain, and
`low noise predicted for such devices was proved.
`From mid 1951 to mid 1952, a period reminiscent of
`adolescence was experienced. Gains in performance en-
`couraged further applications. However, as for an
`adolescent youngster, so too for the transistor, from
`day to day we were impressed with new performance
`possibilities-yet, at the same time, new reliability dif-
`ficulties were brought to light.
`These reliability problems were shown to be surface
`dependent, research and development programs on sur-
`face physics and reliability were initiated throughout
`the industry. This heralded the "young manhood"
`period of 1952 to mid 1955.
`During this period, larger responsibilities and defi-
`nite commitments were undertaken. For example, point
`transistors went to work in an operator tone-dialing
`trial in October of 1952. The first over-the-counter sales
`of alloy and grown-junction-transistor hearing aids took
`place around the end of 1952. A few years later no manu-
`facturer produced tube hearing aids.
`In March, 1953, point-contact phototransistors and
`transistors were employed in the card translator portion
`of direct distance-dialing equipment. In a reliability
`study over 100 million transistor hours of operation
`were attained in this application with an indicated
`failure rate of less than 0.04 per cent per 1000 hours.
`TRADIC, the first transistorized military computer,
`was demonstrated in January, 1954, and later in the
`same year, the first all-transistor personal radio became
`available in time for the Christmas market.
`Other equipment developed during this era included
`the first all-transistor industrial computer, and tran-
`sistorized telephone sets for the hard of hearing and for
`use in noisy locations. Transistorized rural carrier and
`line concentrator tests were successfully undertaken.
`On the military side, digital data transmission and
`
`processing systems, computers, and missile-conitrol sys-
`tems relied wholly or in part on transistoors for their
`successful development and trial.
`This sudden expansion in applications called foi a
`wide variety of types of transistors. Techniques for
`germanium were pushed to their limits. Gerrnarniuni
`crystals of almost perfect physical and chemical proper
`ties were developed to improve manufacturing yields.
`Diodes, triodes, tetrodes, and power units of a wide
`variety were developed and put into manufacture. Sili-
`con entered the field as an alloy-junctioni diode of greatly
`improved properties; silicon became an important bread
`and butter business.
`Gains in understanding of the surface effects in
`reliability were put to work successfully in the form of
`improved surface treatment and capsulation techniques
`Reliability surpassed that of all but the best telephonie
`tubes. In fact, one hearing aid transistor manufacturer
`complained bitterly and frequently over the disap-
`pearance of his replacement business.
`Where then did transistor electronics stand n'ear the
`end of this era of early manhood?
`The wide variety of applications called for a stagger
`ing range of characteristics. Point, grown, alloy, and
`surface-barrier techniques on germanium and silicon
`were close to their capability limits. Each structure and
`technique had serious limitations. Transistor designers
`and manufacturers were forced to develop a large num-
`ber of compromise designs-about 200. The resulting
`manufacturer's nightmare inhibited large-scale eco-
`nomical manufacturing of any one prototype. This was
`reflected in still high costs, from $2.00 to $45.00 per
`transistor.
`Meantime, research people were busy pushing ahead
`the frontiers of understanding of materials, structures,
`and techniques. Toward the end of this era they made a
`triple breakthrough of such magnitude that it started
`a new era-the "Era of Maturity." This work demon-
`strated the possibility of removing most of the limita-
`tions which forced design compromises to a multiplicity
`of types.
`By proving the feasibility of purifying silicon to
`transistor requirements, by solving the problems of
`solid-state diffusion as a technique, and by devising the
`diffused-base structure, they demonstrated the possi-
`bility of making diffused silicon transistors with cutoff
`frequencies of 50-100 mc, 5 to 10 times faster than the
`older germanium transistors while at the same time
`retaining the silicon advantages of high power, tempera
`ture, and efficiency. Application of similar structures
`and techniques to germanium pushed the frequency
`frontier into the low-microwave region.
`The magnitude of these research accomplishments
`dictated a re-evaluation of most transistor develop-
`ment-application programs starting 'in mid 1955. It was
`realized that further refinements of growing, alloying,
`and surface barrier technriques were possible but only at
`large development and manufacturing costs. IHowever,
`
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`
`1958
`
`Morton and Pietenpol: The Technological Impact of Transistors
`
`957
`
`-I
`
`'--
`
`DIFFUSED SILiCON POWER
`ALLOY GERMANIUM POWER
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`DIFFUSED BASE SILICON
`
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`
`POINT CONTACT, GROWN & ALLOY GERMANIUM
`DIFFUSED' BASE GERMANIUd
`
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`the dramatic demonstrations of potentiality of these
`new diffusion techniques, based as they were on more
`complete scientific understanding, clearly showed that
`maximum effort should be devoted to their develop-
`ment. The eventual economies of a single prototype
`diffusion technique and diffused structure, with heavy
`emphasis on silicon, were the :goals.
`
`PRESENT STATUS
`Where then has this diffusion breakthrough brought
`us today? Either in, or just entering, production are
`the following diffused devices:
`1) Silicon-power rectifiers ranging from 0.5 ampere
`up to 100 amperes which will handle reverse break-
`down voltages up to several hundreds of volts.
`2) Silicon-voltage limiters with closely controlled break-
`down voltages ranging from 4.2 volts up to 200
`volts.
`3) Diffused-base silicon transistors with frequency
`cutoffs in the 50-100-mc range. As switching tran-
`sistors they will provide 10-mc switching rates
`with attendant power dissipation up to one-quarter
`watt.
`4) Diffused-base germanium transistors with fre-
`quency cutoffs as high as 1000 mc. One code of this
`prototype designed as an oscillator has a minimum
`rating of 50 mw output power at 250 mc. Other
`codes designed for very high speed switching pro-
`vide switching rates as high as 50-100 mc.
`Today the circuit designer has at his command a
`broad range of structures and characteristics. These
`new devices in combination with improved versions of
`the older structures greatly extend the range of per-
`formance formerly possible. It is not possible here to
`compare all of their electrical characteristics, but it is
`helpful to show in Fig. 1 the frequency range as a func-
`tion of power dissipation covered by presently available
`types. The frequencies plotted are the grounded-base-
`alpha cutoff frequencies for each prototype. For video
`or broad-band amplifiers, the useable range would be
`somewhat below the cutoff frequency depending upon
`the mode of application. However, for oscillators, useful
`power outputs can be achieved to well above the fre-
`quency cutoff.
`The availability of such complete performance range
`from present semiconductor devices has profoundly
`affected the kinds and numbers of system applica-
`tions.
`In transmission systems, pulse-code modulation car-
`rier, personal radio paging, and VHF communications
`are depending upon diffused germanium devices. Al-
`though transistors have not yet found their way into
`commercial television receivers, laboratory develop-
`mnents indicate this to be highly probable with attendant
`savings in size, power, and maintenance costs.
`In power systems, the new diffused silicon rectifiers,
`voltage regulators, and lightning protectors are essential
`
`.0; ____ 1 _
`10 KC
`
`I _._A
`
`100 KC
`
`MC
`FREQUENCY
`Fig. 1-The curves indicate the power-frequency spectrum
`covered by various prototypes of transistor structures.
`
`IOMC
`
`IOOMC
`
`IOOOMC
`
`components for success. By applying diffusion to cheap
`silicon, it has been possible to design a much smaller
`and better telephone click reducer than the copper-
`oxide unit now in use for many years but dependent
`upon an uncertain supply of unique copper.
`In electronic switching, computers, and digital data
`processing, the new diffused diodes and triodes are
`greatly extending the speeds and reliability while at
`the same time greatly reducing the size and power
`required for such large and complex machines.
`In the military area too this new line of devices is
`gaining acceptance in computers, missile systems, servo-
`systems, fuses, radar, communications, and power sup-
`plies. In fact, diffused germanium transistors are now
`circling the earth in the EXPLORER and VANGUARD
`satellites.
`All in all today's variety of old and new transistors
`are finding their way into a staggering variety of tube
`and nontube replacement equipment. To round out the
`list with a few more, there should be mentioned bin-
`aural hearing aids, portable radios, phonographs and
`dictating machines, auto radios and fuel-injection sys-
`tems, portable cameras, paging receivers and instru-
`ments, machine-tool controls, clocks and watches, toys,
`and even a guidance system for a chicken feeding cart.
`As of this date, there are approximately seventy
`domestic and foreign manufacturers of transistors and
`related diodes. Production figures abroad are not avail-
`able but it is known that essentially every major West-
`ern nation, as well as Japan, is very active. It is believed,
`however, that they are somewhat behind the United
`States in application and production. We have no
`authoritative technical information on Russia's status
`but Pravda assures us that Russia is well in the fore-
`front--as usual?
`
`NEW DESIGNS
`In the laboratory stage there are a number of new
`designs which will extend the range of electrical per-
`formance of the devices presently in manufacture. One,
`which is now entering production, is the four-region
`
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`958
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`PROCEEDINGS OF THE IRE
`
`June
`
`BILLION
`
`100
`MILLION
`
`U)
`
`z
`
`LL
`In
`10
`
`z 1
`
`0
`MILLION
`
`MlILLION
`
`100
`THOUSAND
`
`YEARS
`Fig. 2-The solid portions of the curves indicate the number of units
`sold in the United States by the year. The dotted portions of the
`curves represent estimates.
`
`be designed for operation at frequencies as high as, or
`possibly higher than, those possible with advanced de-
`signed vacuum tube and traveling wave structures with
`properties competitive in many ways.
`
`GROWTH OF AN INDUSTRY
`The growth of the transistor from its birth in 1948
`to its present maturity has been rapid indeed. With the
`critical need for electronic components in today's world
`and with the many advantages offered by transistors,
`it is not surprising that such a revolution has occurred.
`The management of nearly every major electronic
`laboratory has directed teams of their most competent
`research and development people toward the design of
`these semiconductor devices.
`Through the years, meetings and symposia have
`been held for scientists to exchange information on the
`most recent technology developments. By concerted
`effort, many of the basic problems associated with
`semiconductor devices have been solved; today, tran
`sistors are being used in many industrial and military
`systems, particularly where low power, small size,
`and high reliability pay off. In the United States the
`sale of transistors alone has risen from a level of essen
`tially nothing in 1952 to 29 million units in 1957s Fore-
`casters predict that these sales will go to over 250 million
`units by 1965. If one adds to this the sale of semiconduc-
`tor diodes, it is predicted that combined sales will reach
`600 million by 1965. (See Fig. 2.) In 1957, the dollar
`volume of transistors and semiconductor diode sales
`
`p-n-p-n silicon switching diode. The electrical character-
`istics of this device are similar to those of a cold-cathode
`gas tube. However, the silicon device requires a great
`deal less power and can operate at speeds one thousand
`times faster than the gas tube Thousands of these
`diodes will be used in the switching network of all-elec-
`tronic telephone systems. Other major applications
`will doubtless be found in military and commercial
`digital computers.
`It is interesting to note that this small device requires
`precise control of almost every bulk and surface proper-
`ty known to semiconductors. It is necessary to control
`accurately the density of impurities throughout the
`bulk material, the width of the various layers, and the
`density of the imperfections in the bulk material, which
`in turn controls the lifetime of minority carriers. It is
`necessary to control not only the density of these imper-
`fections, but also the type of imperfections (the energy
`level within the forbidden gap). On the surface one
`must control and add impurities in such a rnanner that
`the density and type of surface states are within reason-
`ably narrow limits. The surface must be carefully
`cleaned and oxidized so that the device will be electrical-
`ly stable over long periods of time. In addition, the
`atmosphere around the device must be controlled so
`that there are no ions present to alter the electrical
`properties of the diode. Recent technological develop-
`ments have made possible such precise control of each
`of these properties.
`With the ever-advancing speeds of electronic com-
`puters go requirements for faster and faster computing
`diodes. By a controlled reduction of carrier lifetime,
`minority carrier storage and recovery times have beeii
`reduced to less than 2 m,isec. These designs, which are
`ready for pilot manufacture, will extend the speed of
`computer diodes by a factor of 10
`New diffused transistor structures are being made in
`the laboratory by reducing the thickness of the base
`layer and by reducing electrode spacing and cross
`sectional area. In this way the frequency range of
`germanium and silicon transistors can be extended
`another factor of 10 over that of present designs. It is
`expected that diffused germanium transistors will soon
`be made which will oscillate at frequencies as high as
`10,000 mc per second.
`For some time it has been known that a variable
`reactance can serve as an amplifier, but it
`is only
`recently that this principle has been put to practical
`microwave use. The dependence of the capacitance of a
`p-n junction upon the voltage across it makes possible
`a rapidly variable capacitance, when an appropriate
`high-frequency voltage drive is used. Furthermore,
`theory predicts that this device should have extremely
`low noise. In actuality, an amplifier of exploratory design
`has a measured gain of 15 db at a frequency of approxi-
`mately 6000 mc per second and a measured noise
`figure of 4.5 db. In this case the driver was a 12-kmc
`reflex klystron. It now seems possible that amplifiers can
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`1958
`
`Jenny: The Status of Transistor Research in Compound Semiconductors
`
`959
`
`was 69 million dollars and 103 million dollars, respec-
`tively. By 1965, it is expected that the dollar volume of
`semiconductor sales will exceed that of the older electron
`tube. A further indication of the growth can be seen by
`the fact that the Joint Electron Tube Engineering Coun-
`cil had issued 600 transistor and 1300 diode industry
`codes by the end of 1957.
`During its short ten years of life, the transistor,
`through its inherent low-power requirements, small size,
`and high reliability has permeated the entire electronics
`industry. It has already captured large sections,of the
`
`market. With materials, structures, and techniques
`presently in the laboratory and currently in manu-
`facture, the transistor will play an increasingly impor-
`tant part in modern electronic technology.
`By basic scientific contributions and imaginative in-
`ventions, scientists and engineers have laid the founda-
`tion on which is being built a truly great technological
`industry. It may well be that the extension to man's
`mind, that transistor electronics makes possible, will
`yet have a greater impact on society than the nuclear
`extension of man's muscle.
`
`The Status of Transistor Research in
`Compound Semiconductors*
`DIETRICH A. JENNYt, MEMBER, IRE
`
`Summary-New semiconductors capable of competing with ger-
`manium and silicon in transistor applications must be looked for
`among the compound semiconductors, and more specifically among
`the III-V and IV-IV compounds. Gallium arsenide and indium phos-
`phide are the most promising all-round materials for high-frequency
`as well as high-temperature performance. Indium antimonide and
`indium arsenide may be of interest for extremely high-frequency
`transistors operating at low temperatures, The aluminum com-
`pounds, gallium phosphide and silicon carbide, are potentially useful
`for very high operating temperatures at the cost of high-frequency
`performance. Some of the unusual properties of the compound semi-
`conductors have led to novel methods of junction preparation and
`new junction structures, such as the surface-diffusion and the wide-
`gap junction. Bipolar and unipolar surface-diffusion transistors have
`been demonstrated in indium phosphide, and the wide-gap emitter
`principle for high injection efficiency has been experimentally verified
`in gallium arsenide transistors. Electron lifetimes in these two com-
`pound semiconductors are estimated from the transistor results.
`
`INTRODUCTION
`Kl_HE ADVENT of the germanium transistor in
`1948, and the silicon transistor shortly thereafter,
`raised the inevitable question whether there are
`other semiconductors capable of exhibiting transistor
`action. Research in this direction was primarily stimu-
`lated by the hope of finding a semiconductor with su-
`perior properties for transistor applications. A glance at
`the periodic table and the electrical properties of the
`elements shows immediately that such a material would
`scarcely be found among the elemental semiconductors,
`except possibly diamond which has some obvious dis-
`advantages. Therefore, the search for a competitor to
`* Original manuscript received by the IRE, April 10, 1958. The
`work reported in this paper was supported in part by the U. S. Air
`Force, Wright Air Dev. Center, Dayton Ohio.
`t RCA Labs., Princeton, N. J.
`
`germanium and silicon in the transistor field was con-
`centrated on the compound semiconductors.
`Compound semicoaductors, in contrast to the elemen-
`tal semiconductors, are true chemical compounds of two
`or more elements with characteristic stoichiometric
`compositions. Representatives of this vast class of semi-
`conductors are found throughout the entire range of
`chemical compounds from the simple binaries to the
`most complex organic structures. The elemental semi-
`conductors, such as a-tin, tellurium, selenium, ger-
`manium, and silicon are, in effect, only special cases of
`the compounds. Although by far the major systematic
`research efforts, both theoretical and experimental,
`have heretofore been concentrated on germanium and
`silicon, the compounds have played an important role in
`semiconductor research from the beginning. In fact,
`the earliest evidence for a conduction mechanism differ-
`ent from that in metals was Faraday's observation of a
`negative temperature coefficient of the resistivity in the
`compound, silver sulfide, in 1833. Rectification at a con-
`tact between dissimilar materials was discovered by
`Braun with pyrites and galena, and almost simultane-
`ously by Schuster with "tarnished" copper, or copper
`oxide, in 1874. Silicon carbide and lead sulfide attained
`some importance as detectors in the early radio days,
`but they were soon displaced by the vacuum tube.
`Copper oxide has been one of the most important solid
`rectifier materials to this day, particularly in power ap-
`plications. The practical importance of these compounds
`stimulated some early fundamental research, but, due
`to the lack of a satisfactory model of semiconduction,
`little significant information was gained. In 1931, after
`quantum mechanics had come into its own, Wilson laid
`
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