BY JOHN RHEA
AND is one of the most abundant high electron mobility. That's why S materials on the planet, which silicon is so good for switches; the is one reason for the central role it faster the electrons can move has captured in modern micro- through it, the faster the computers electronics. Compounds of silicon made of silicon devices can operate. and oxygen, typically in the form of Silicon is a member of the carbon sand, account for about three- family, found in column four of the fourths of the earth's crust. In a periodic table. Carbon, the basic highly refined form, they also are building block of all life and an elec- the materials of choice for the elec- tronics material, forms more com- tronics industry because of their ex- pounds than all the other elements cellent semiconducting properties. on the table combined. The other A semiconductor is a substance members of this family are ger- about halfway between a conductor manium—used to make the first (like metal, which passes electrical transistor in 1947 and today a key current along readily) and an in- ingredient of optical fibers—tin, and Semiconductor symmetry: The starkly beautiful patterns of these gallium ar- sulator (such as rubber, which stops lead, which are basic to future appli- senide semiconductor chips resemble the electron flow). When overlaid cations of superconductivity and those of Moorish tiles. Above, a micro- with the right impurities, silicon advanced sensor systems. photograph of a monolithic microwave chips become semiconductors, car- Physical chemists have long integrated circuit; above right, a 3000- rying current along designated known that still higher rates of elec- logic-gate chip package on a high- paths and through selected gates un- tron mobility are inherent in com- speed test fixture. der certain conditions. pounds formed out of elements from This makes them good switches, columns three and five of the peri- which is essential. All data in mod- odic table. In theory, these 3-5 com- ern information processing systems pounds, as they're known, should are represented in digital form, ei- replace silicon in future high-perfor- ther as a "one" when the devices are mance information-processing sys- conducting or as a "zero" when in- tems. They haven't yet because sulating. they're hard to work with, and the In addition to its universal avail- materials-processing technologies ability, silicon has the advantage of haven't kept pace with silicon.
102 AIR FORCE Magazine / November 1989 Until now. Starting in 1986 with end bottleneck of airborne systems. erful supercomputer, the new ma- the Microwave/Millimeter Wave GaAs devices derived from MIM- chine is scheduled for initial deliv- Monolithic Integrated Circuits IC, such as the transmit/receive eries in mid-1991. (MIMIC) program at the Defense modules for the Westinghouse Meanwhile, the basic research or- Advanced Research Projects Agen- phased-array radar on the Air ganizations of Bell Laboratories cy (DARPA), 3-5 technology has ad- Force's Advanced Tactical Fighter (which demonstrated that first ger- vanced to the point where it's begin- (ATF), have begun finding their way manium transistor), Hughes, IBM, ning to close the gap with silicon. into operational systems. and others are reporting initial suc- MIMIC was aimed at analog ap- Now, building on that base, the cesses with such other 3-5 combina- plications in weapon sensor sys- solid-state physics community is tions as indium phosphide (InP), tems such as radar. Instead of pro- accelerating its efforts along two aluminum indium arsenide (Al- cessing the data as ones and zeros, paths: using these new materials in inAs), and gallium indium arsenide the MIMIC devices generated rep- the more demanding digital applica- (GaInAs). In each case, the key to resentations, or analogs, of the tar- tions and experimenting with other improved performance lies in in- gets of interest in the form of volt- 3-5 compounds that have even creasing the content of indium, be- ages that were then converted to a greater potential performance than cause it has the potential of improv- digital format and processed by on- GaAs. ing electron mobility three or four board digital computers. The idea Once again DARPA is leading the times beyond GaAs. was to quickly accumulate and pass military effort, this time with a pro- on to the computers large volumes gram to insert digital GaAs technol- Memory is the Bellwether of intelligence data for identification ogy into eleven current weapon sys- GaAs thus represents the opening and appropriate response. tems as one-to-one replacements wedge of a revolution that is trans- for existing silicon devices (see forming electronics. Today, the First of the 3-5s box). The major advances, however, technology is about where silicon MIMIC also pushed the technolo- are coming from the commercial was in the early 1970s, when Silicon gy of the first of the 3-5 compounds, world. Even before the DARPA Valley in California was turning out gallium arsenide (GaAs). With an program began, Seymour Cray, the sample quantities of the first crude electron mobility about five times legendary progenitor of supercom- microprocessors and semiconduc- that of silicon, plus reduced power puters, began designing his next ma- tor memories. Those devices have requirements and inherent resis- chine entirely out of digital GaAs since become ubiquitous, making tance to radiation, GaAs was the logic. Known as the Cray 3 and ex- possible the present era of dis- perfect material to break the front- pected to be the world's most pow- tributed computing and intelligent
AIR FORCE Magazine / November 1989 103 weapons. A bellwether is memory, hundreds of thousands of the new ellite that will increase processing which has gone from a thousand bits components, he says. speed from 75,000,000 operations a per chip to a million, at essentially In addition to assuring military second to 560,000,000—without the same price. program managers of reliable changing the system architecture or Price-performance achievements sources of supply, this increased software. Vitesse Semiconductor of like that are a function of volume volume should give the United Camarillo, Calif., is supplying production. That's what the DAR- States an edge in the inevitable 15,000-gate arrays for this project. PA program is all about, according GaAs shoot-out with Japan. Al- For the Navy, Texas Instruments to Dr. Arati Prabhakar, GaAs pro- ready, four Japanese companies— in Dallas is developing a GaAs thirty- gram manager in the agency's De- NEC, Oki, Hitachi, and Sumitomo two-bit computer operating at 200 fense Sciences Office: building the —are actively marketing GaAs inte- MHz (two hundred million cycles necessary infrastructure. That's grated circuits in the United States, per second) to improve the resolu- also why DARPA chose weapon although these are generally less tion of the AN/APS-137 surface- systems currently in production. complex devices derived from the search radar on the P-3C patrol air- "We're taking one risk at a time," companies' programs in fiber op- craft. Under a separate DARPA- she adds. tics. sponsored program, the Navy is Two of the Army demonstration There are only two, relatively projects, in particular, should drive low-volume, Air Force projects on up digital GaAs volume, according the list, but they could have the big- to Sven A. Roosild, DARPA assis- gest impact on pushing GaAs tech- tant director for electronic sci- nology. E-Systems in Greenville, ences. They are a new modem and Tex., is developing a distributed ar- frequency synthesizer being devel- ray processor for "special mission oped by E-Systems to provide anti- aircraft" under a contract from the jam capability for the AN/PRC-126 Air Force Logistics Command that radio and a digital signal processor will increase processing speed six- from Martin Marietta to replace fold while reducing subsystem bulky analog components in the RF weight by 300 pounds. Martin Mar- Hellfire antitank missile and thus ietta in Denver is developing a one- increase the lethality of its warhead. chip on-board spacecraft computer Each of these projects will require for a classified reconnaissance sat-
A Westinghouse tech- also looking at GaAs devices to im- nician finishes a prove the performance of its GaAs boule, above right, that will be Ariadne undersea antisubmarine sliced and polished warfare system. The devices would into three-inch inte- reduce power requirements by a grated wafers like the factor of five to ten at each node of one at left. The wafer is then patterned and the fiber optic cables. sawed into individual
GaAs chips (in this The Speed - Power Product case, sixteen of These DARPA-sponsored proj- them). The larger the ects illustrate another edge for wafer manufactured, the lower the finished GaAs. Compared to silicon, it has price of the chips. what is known as a speed-power product that is about six times bet- ter. That means you can send the same amount of data traffic for one- sixth the power (particularly impor- tant for spacecraft and, to a lesser extent, aircraft) or six times as much information for the same elec- trical power requirement (a better choice for terrestrial applications). Moreover, radiation resistance comes for free, which makes GaAs particularly attractive for military use. Outside the DARPA program, Giga- Bit Logic of Newbury Park, Calif., one of the GaAs chip suppliers, is under contract to the Air Force's Ballistic Systems Division at Nor- ton AFB, Calif., to develop a GaAs 104 AIR FORCE Magazine / November 1989 pares to twenty or more for com- Eleven weapon systems will be updated parable silicon devices made with with GaAs technology. the complementary metal oxide semiconductor process. Infusions of Arsenic Prices May Drop In fact, as all the new companies scramble to get on board this tech- The Defense Advanced Research Projects Agency (DARPA) this year selected nology, a worldwide drop in GaAs nine major defense contractors to participate in a program to insert digital gallium arsenide (GaAs) integrated circuits into eleven operational weapon systems. prices may be in the works, accord- The selection follows a broad agency announcement issued by DARPA on Janu- ing to Dr. David Miller, a manager at ary 22, 1988, in which the agency sought proposals from industry on ways to the Litton Airtron Division, Morris upgrade current silicon-based devices to improve performance. Plains, N. J., one of the principal Supporting the nine prime contractors are three new companies founded specifi- cally to produce GaAs digital integrated circuits for military and commercial mar- GaAs wafer suppliers. "Because of kets: GigaBit Logic of Newbury Park, Calif., TriQuint of Beaverton, Ore., and Vitesse all the hype, the hockey stick [an Semiconductor of Camarillo, Calif. allusion to steep sales curves in Program manager at DARPA is Dr. Arati Prabhakar, and the program is under the growth industries] is lying down. It's direction of Sven A. Roosild, assistant director for electronic sciences in DARPA's not straight up," he says. "There's Defense Sciences Office. The projects, by service, are as follows: Air Force: E-Systems, Greenville (Tex.) Division: distributed-array processor for overcapacity at every level." special-mission (reconnaissance) aircraft, Air Force Logistics Command. Gallium is a material for which Martin Marietta Space Systems, Denver, Colo.: spacecraft on-board processor for the United States is completely de- reconnaissance satellites (a "black" program for which the program office was not pendent on foreign sources of sup- disclosed). Army: E-Systems, ECI Division, St. Petersburg, Fla.: modem and synthesizer for ply: Canada, France, Germany, and AN/PRC-126 small unit radio, Army Communications Electronics Command Japan. "Arsenic is cheap. It's every- (C-ECOM). where," says Pawlik of GigaBit. ITT Avionics, Nutley, N. J.: digital radio frequency memory for AN/ALQ-136 jam- "Gallium is priced like silver." In mer, C-ECOM. addition to Airtron, the major wafer Martin Marietta Electronic Systems, Orlando, Fla.: signal processor for RF Hellfire seeker, Army Missile Command. suppliers include the Canadian con- McDonnell Douglas Electronic Systems, Huntington Beach, Calif.: mast- glomerate Cominco (which extracts mounted sight processor for OH-58D Scout helicopter, Army Aviation Systems gallium as a by-product of alumi- Command. num refining), MIA Com of Lowell, Navy: Grumman, Bethpage, N. Y.: radar processor for E-2C airborne early warn- ing aircraft, Naval Air Systems Command (NavAir). Mass., and the Japanese firms Mit- Honeywell Defense Avionics Systems, Albuquerque, N. M.: digital map computer subishi and Sumitomo. for the multiservice V-22 Osprey and other aircraft, NavAir. Dataquest, a market research KOR Electronics, Huntington Beach, Calif.: digital radio frequency memory for firm in San Jose, Calif., that has a AN/ULQ-21 threat jamming simulator, Navy Pacific Missile Test Center. reputation for conservative fore- Sanders Associates, Nashua, N. H.: digital radio frequency memory for the AN/ ALQ-126B used on several tactical aircraft (perhaps later on the A-12 advanced casts, projects that the merchant tactical aircraft), NavAir. market for GaAs devices will rise Texas Instruments Defense Systems and Electronics Group, Dallas: high-resolu- from $328 million this year to nearly tion upgrade for the AN/APS-137 surface search radar, NavAir. $1.3 billion by 1993. That's a thirty- ■ five percent compound annual 4 16 growth rate, but about thirty per- version of the Air Force's popular are plummeting rapidly. Dr. cent of the total today is accounted 1750 airborne computer. The one- Prabhakar estimates that a three- for by nonrecurring engineering chip, sixteen-bit microprocessor is inch-diameter wafer costs $160 to costs for technology and product intended to be capable of speeds of $175 and that the processing and development. 1 GHz (a billion cycles per second) testing of the devices adds another The growth is projected to be fast- with error correction. GigaBit Log- $2,000 per wafer. However, the in- est for digital GaAs—from $127 mil- ic is teamed with Jaycor, a company dustry is moving up to four-inch- lion this year to $656 million in in San Diego that specializes in radi- diameter wafers, which reduce 1993—which is currently domi- ation resistance, and Galaxy Micro- costs. Mike Pawlik, vice president nated by the "big three" merchant systems, a 1750 architecture design for marketing at GigaBit, estimates suppliers, GigaBit, TriQuint, and firm in San Jose, Calif, and Austin, that twenty suppliers have been Vitesse. The market for analog de- Tex., on the project. qualified on three-inch wafers and vices (not including those for DAR- Another small start-up company, eight on four-inch wafers. The sil- PA's MIMIC program) is projected Gazelle of Santa Clara, Calif., has icon industry has long been working to grow from $201 million to $621 developed a GaAs program logic ar- with five-inch wafers. million over the same period. (The ray that is compatible with conven- GaAs has an inherent cost advan- figures also do not include the out- tional transistor-transistor logic tage over silicon at the processing put of the "captive" suppliers such (TTL) but is twice as fast. This ar- end. The photolithographic process as AT&T, Hughes, McDonnell ray will replace an entire box in a used to imprint the devices onto a Douglas, Rockwell, Texas Instru- military system with a single chip. substrate requires only twelve ments, TRW, and Westinghouse, As is customary in any new tech- masking steps for even the most which produce solely for their own nology, costs are initially high but complex GaAs devices. That corn- needs.) AIR FORCE Magazine / November 1989 105 Competition for Silicon The real competition is not among the GaAs producers, ac- cording to Louis Pengue, marketing manager at TriQuint, but against the entrenched silicon devices, particu- larly top-of-the-line emitter-coupled logic (ECL), which has replaced TTL and dominated military sys- tems in recent years. He calls the The tremendous cal- problem the "FUD factor" (fear, un- culating speeds that certainty, and doubt), which he ex- gallium arsenide pects to be erased as more program chips make possible managers become familiar with the are being studied and developed by new technology. Cray Research, Inc. Reducing costs is essential to win- Cray supercom- ning acceptance, according to Mr. puters, the most Pengue. That means driving down powerful computers in the world, are used the cost per gate of a large logic In computational fluid array (10,000 gates or more) to three dynamics testing to to five cents so it can compete head- simulate various air- on with ECL. One of the best ways craft flight param- to do that is to increase the chip eters (right). Future GaAs technology size, and GaAs has been moving up could include ultra- steadily from 100 mils on a side to sensitive radars and 200 mils. (One mil is a thousandth of radios. an inch, so 100 mils is a tenth of an inch.) It needs to go beyond 300 mils, Mr. Pengue maintains, but he says there's a "fear threshold" among users at about 250 mils. If anybody should know the pluses and minuses of GaAs, it's Seymour Cray, who has been build- operations a second). It was origi- provement in sensitivity for a com- ing the world's most powerful super- nally scheduled for initial deliveries munications satellite receiver, computers for at least twenty years. right about now, but technical prob- which means the ground antenna He laid it all out at last year's Super- lems and a move of the company for use with a direct broadcast satel- computing '88 conference in Orlan- from Minneapolis to Colorado lite could be reduced to one foot in do, Fla., cosponsored by the IEEE Springs, Colo., have caused a slip of diameter. Data rates as high as Computer Society and the Associa- nearly two years. But already Cray twenty-five gigabits (twenty five bil- tion for Computing Machinery. is reported to be working on an all- lion bits) a second were achieved. "Gallium arsenide is pretty horri- GaAs Cray 4 capable of 128 giga- Reasonable extrapolations of this ble to work with. It has a lot of flops . technology could lead to ultrasen- grain," which affects the flow of sitive radars capable of spotting electrons, he said. "It's. . . tough to Out of the Sandbox stealth vehicles—or to the "Dick get everything lined up right in Looming over this GaAs free-for- Tracy" wristwatch radio. order to make the system function all is the emergence of indium phos- What may be even more exciting properly," he explained. "It's like phide. Paul Greiling, manager of is that the gallium indium arsenide working with potatoes. There are gallium arsenide research at the layer can serve as a laser diode oper- soft spots, hard spots, eyes, and Hughes Research Laboratories in ating at the wavelengths of 1,300 and skin—and it's very hard right now to Malibu, Calif., reported in July on a 1,550 nanometers (billionths of a get good quality basic material to high-electron-mobility transistor in meter). Those are the wavelengths work with. But it gets better every which individual layers of indium of state-of-the-art single-mode op- year." phosphide, aluminum indium arse- tical fibers, which would permit The Cray 3 uses GaAs for all the nide, and gallium indium arsenide data output from the computer chip logic functions (but silicon devices as thin as five individual atoms were to be in the form of photons rather for memory) to achieve breathtak- deposited using the molecular beam than electrons. That would be a big ing speeds of sixteen gigaflops epitaxial process. step toward the post-electronics (that's 16,000,000,000 floating point The result is a fifteenfold im- world of photonics (see "Beyond Electronics," p. 78, June 1989 is- sue). Nobody is predicting an end John Rhea is a free-lance writer living in Woodstock, Va., who specializes in for silicon-based electronics de- military technology issues and is a frequent contributor to AIR FORCE Magazine. vices, but the industry has begun His book Department of the Air Force is scheduled to be published this month by venturing cautiously out of its sand- Chelsea House, New York, N. Y. box. • 106 AIR FORCE Magazine / November 1989