DESIGN AND FABRICATION OF MONOLITHIC BROADBAND MICROWAVE GALLIUM-ARSENIDE LOW NOISE FET AMPLIFIERS (MMIC, CAD, CHARACTERIZATION)

The design of a broadband low noise FET amplifier is a complicated process since it requires achieving both flat gain and a low noise figure over the desired octave frequency band. Difficulties also occur in the realization of these designs due to limitations in fabrication techniques. This thesis reports the development of a practical design, characterization, and fabrication of a practically realized broadband low noise FET amplifier via MIC and MMIC techniques. The approach employed the use of commercially available design programs for circuit designs based on fabrication limitations and characterization data, and the use of newly developed fabrication techniques to realize these designs consistently.; A 7 to 14 GHz broadband low noise amplifier has been designed and fabricated on 15-mil-thick fused silica substrates via MIC techniques. The amplifier gain was 6.6 dB with a gain flatness of (+OR-) 0.3 dB, and a noise figure less than 2.5 dB over the entire octave frequency band. The hybrid balanced type low noise amplifier has also been studied.; A state of the art mid-UV (300 nm) photolithographic technology has been developed in this work at Cornell using AZ4000 series photoresist system. This process has been shown to provide a relatively simple and inexpensive technology when compared to E-beam lithography and is very suitable for GaAs MMIC fabrication.; A submicron gate length ion-implanted MESFET has been fabricated with a gate length as small as 0.65 (mu)m using this mid-UV contact printing technique. This device with a 300 (mu)m gate width was fabricated on the ion-implanted wafer with a peak concentration of 2.1 x 10('17) cm('-3), and a resulting transconductance of 120 mS/mm. A minimum noise figure of 2.9 dB with an associated gain of 7.7 dB was obtained at 12 GHz.; A 6 to 12 GHz broadband monolithic low noise amplifier with internal bias circuitry has been designed and successfully fabricated using mid-UV contact lithography. The amplifier gain was 5.6 dB with a gain flatness of (+OR-) 0.5 dB and a noise figure of less than 3.8 dB over the same frequency band. To improve the input and output VSWRs, a broadband GaAs monolithic interdigitated Lange coupler has been also investigated and successfully fabricated on LEC undoped GaAs substrates with a novel fabrication structure.