GAaS MMIC Chips - Evolution of A(Active)ESA applications as we know today.

Gallium-Arsenide Monolithic Integrated Circuits The all-solid-state UHF ground-based radar called PAVE PAWS was built with hybrid technology, and it performed successfully. The designs of other military defense radars, such as the Reliable Advanced Solid State Radar (RASSR) and the Solid State Phased Array (SSPA) [56] sponsored by the U.S. Air Force, were based on similar solid-state hybrid technology. Eventually, however, researchers realized that a largescale, solid-state phased-array radar made with hybrid circuits would require a very large number of discrete components and associated wire bonds, which would lead to excessive cost and inferior reliability compared to the promise of monolithic technology. Consequently, the phased-array research effort shifted toward the development and deployment of fully integrated circuits composed of devices created on a common semiconductor substrate [57]. The substrate material recognized as most promising was gallium arsenide, principally for its characteristically high carrier mobility, and thus its suitability for high-frequency systems, specifically in the microwave (1 to 30 GHz) and millimeter-wave (30 to 300GHz) frequency ranges. The highest available frequencies, and accordingly the shortest wavelengths, are essential to form narrow beams for high resolution in target tracking, while lower frequencies, with better prospects to fulfill the requirement of high transmitter power, are favored for the associated functions of surveillance and search. In 1968, in an important development, E.W. Mehal and R.W. Wacker [58] and G.D. Vendelin et al. [59], all working at Texas Instruments, reported an early success in development of devices and circuits on gallium arsenide for microwave and millimeter-wave frequencies. Another significant advance in those years was a monolithic low-noise field-effect transistor (FET) microwave amplifier on gallium arsenide, reported by W. Bächtold et al. at the IBM laboratory in Zurich [60]. In Lincoln Laboratory, Blake and Roger W. Sudbury collaborated to advance support for the MMIC phased array. The Laboratory organized its effort for these projects by establishing a mutually complementary relationship between the Microelectronics group in the Solid State Research division, which contributed the development and refinement of materials along with device fabrication and testing, and the Experimental Systems group, which contributed the circuit designs for phased-array technology.

Success in these pioneering efforts depended on the solution of numerous interrelated problems. The potential advantages of higher microwave or millimeter-wave frequencies, suitable for the narrow-beam, high-resolution tracking function of radars, imposed stringent requirements on the quality of gallium-arsenide materials for monolithic wafers, as well as rigorous demands on the optics, metallurgy, and chemistry of the photolithography process. The semi-insulating gallium-arsenide substrate on
whose surface the epitaxial device layers are fabricated is advantageous for its electrically inert character, permitting low insertion loss and also low coupling loss between the closely spaced circuit components. This key dielectric property was confirmed in detailed measurements of complex permittivity of gallium arsenide in the range of 2.5 to 36.0 GHz by William E.
Courtney at Lincoln Laboratory [61]. These measurements showed that, when well processed, the material is in fact free of the frequency-dependent loss characteristics that some researchers had feared. As device and circuit quality improved, still higher performance of the substrate was required for electrical isolation of the devices, envisioned as densely positioned
on the semiconductor wafer, against interaction with each other. An early success in this effort, demonstrated at Lincoln Laboratory [62], was the process of passivation by means of proton bombardment, to create crystalline defects and thereby impart near-intrinsic-semiconductor properties.

Later, a simpler and less costly isolating technique, which was widely adopted, involved heavy doping of the intervening areas of the substrate to reduce carrier lifetime. The early efforts in device development at Texas Instruments led to both hybrid and monolithic circuits, including balanced mixers, Gunn-diode oscillators, and frequency multipliers for receiver applications at millimeter-wave frequencies. Following these basic advances, various research groups produced planar devices showing dramatically improved performance. Such advances at the Laboratory and in industry led to a surge of development, especially of gallium-arsenide metal-semiconductor field-effect transistors (MESFET), both in discrete form and as active devices on monolithic chips. The completely monolithic microwave amplifier chip with galliumarsenide MESFETs and matching circuits was first reported by R.S. Pengelly and J.A. Turner at Plessey Co. Ltd. in 1976 [63]; this achievement led to a rapid increase in the involvement of all the leading microwave research laboratories in further development of monolithic circuits. A presentation by Courtney et al. in 1980 [64] characterized the problems and potential of a monolithic receiver, which is central to the concept of a solid-state phased array.

The Laboratory took on an advisory role for government agencies that were supporting the new generation of phased-array design. At the same time the Laboratory continued to conduct its own research directed toward (1) the development of technology applicable to the transmit/receive module for array antennas in military systems, as well as (2) the enhancement of its own capability for innovation and consultation. There was interest in Lincoln Laboratory’s proposals for research in solid-state-circuit technology from the Very High-Speed Integrated Circuits (VHSIC) program under Sonny Maynard of the DoD. In the 1980s, major support for the development of monolithic microwave technology came through the efforts of Elliot Cohen, a DoD associate of Maynard’s and a major advocate, with Blake, of investigation into practical uses of gallium arsenide for microwave integrated circuits. Cohen sponsored the Microwave and Millimeter Wave Monolithic Integrated Circuits (MIMIC) program [65] within the Defense Advanced Research Projects Agency (DARPA).

The program was based on the concept of an “active element” phased array; i.e., an array with integrated-circuit phasers and transmit/receive capability as an integral part of each antenna element, locked to a central phase and amplitude standard. The MIMIC program maintained the impetus of the earlier developments and encouraged the microwave industry to construct the large gallium-arsenide processing facilities that exist today for the fabrication of phased-array and telecommunication modules. The MIMIC program’s objectives included development of volume production technology to produce large-diameter, high-quality substrates suitable for commercial production of MESFETs optimized for high power or for low noise; development of computer-computer- aided device and circuit design programs (a powerful discipline then still in its infancy); and proof of feasibility to show that monolithic circuits can findapplications in circuits that are suitable and affordable for wide use in military systems.

By 1990, active solid state devices at microwave frequencies were becoming ubiquitous; MMICs were routinely developed for commercial applications such as automobile instrumentation and civilian communications, and active transmit/receive modules were being utilized for large phased arrays. Gallium-arsenide MMIC transmit/receive-module technology is used in the X-band (8.0 to 12.0 GHz) theater-missile- defense phased-array radar system [54] built by Raytheon Corporation. The decade of the 1990s saw widespread application of gallium-arsenide monolithic integrated circuits in many fields, including radar, the Global Positioning System (GPS), direct-satellite- broadcast receivers, and commercial wireless telephony.


---------------------------------------------------------------------------------------------------------