A 100-200-400Ã‚Âµm pHEMT amplifier has been developed for Ka-Band operation. This amplifier has achieved the state-of-the-art efficiency of 40% with 235 mW output power and 20.7 dB gain at 31 GHz. Production of variations of this amplifier in quantity of 100 to 200 has been made possible by the advance of new fabrication techniques such as Reactive Ion Etching (RIE) dry recess with etch-stop layer which insures uniformity across full three-inch wafers. Amplifiers of this type are being used in a prototype phased-array antenna.
With the DARPA Wide Bandgap Semiconductor Technology RF Thrust Contract, TriQuint Semiconductor and its partners,
BAE Systems, Lockheed Martin, IQE-RF, II-VI, Nitronex, M.I.T., and R.P.I. are achieving great progress towards the
overall goal of making Gallium Nitride a revolutionary RF technology ready to be inserted in defense and commercial
applications. Performance and reliability are two critical components of success (along with cost and manufacturability). In
this paper we will discuss these two aspects. Our emphasis is now operation at 40 V bias voltage (we had been working at
28 V). 1250 µm devices have power densities in the 6 to 9 W/mm with associated efficiencies in the low- to mid 60 % and
associated gain in the 12 to 12.5 dB at 10 GHz. We are using a dual field-plate structure to optimize these performances.
Very good performances have also been achieved at 18 GHz with 400 µm devices. Excellent progress has been made in
reliability. Our preliminary DC and RF reliability tests at 40 V indicate a MTTF of 1E6hrs with1.3 eV activation energy at
150 0C channel temperature. Jesus Del Alamo at MIT has greatly refined our initial findings leading to a strain related
theory of degradation that is driven by electric fields. Degradation can occur on the drain edge of the gate due to excessive
strain given by inverse piezoelectric effect.
A 100-200-400 micrometers pHEMT monolithic amplifier has been developed for Ka-Band operation. This amplifier has achieved the state-of-the-art efficiency of 40% with 235 mW output power and 20.7 dB gain at 31 GHz. Two other circuits with 50-100-200 micrometers and 50-100-250 micrometers gate width have been fabricated in quantity of 100 to 200. This has been made possible by the advance of new fabrication techniques such as RIE dry recess with etch-stop layer which insures uniformity across full three-inch wafers. Amplifiers of this type are being used in a prototype phased-array antenna.
Advances in microwave and millimeter-wave power monolithic amplifier technology are reviewed. Device structures and circuit topologies that enhance the efficiency of monolithic power amplifiers for space communication applications are discussed. Mature GaAs MESFETs as well as emerging III-V heterostructure field-effect and bipolar transistors designed for high-efficiency operation are covered. Relative merits of various types of devices for implementation in high performance monolithic amplifiers are discussed.
A monolithic three-stage Ka-band amplifier has been designed and fabricated on a doped channel heterostructure. Devices with gate length of 0.2 micron and gate width of 50, 100, and 250 micron were cascaded. The gate and drain bias networks were also integrated. The small signal gain is 31 dB and the amplifier is capable of an output power of 190 mW with 23 dB gain and 30.2 percent power added efficiency at 31 GHz. This is a record efficiency for a multistage MMIC at this frequency.