Broadband monolithic integrated power amplifiers in gallium arsenide

The development of two designs of two-stage monolithic integrated amplifiers in gallium arsenide covering the 5-10 GHz and 8-12 GHz bands is described. The amplifiers are fabricated using ion implantation of Si-29 directly and selectively into undoped, semi-insulating gallium arsenide grown by the Czochralski technique. The passive elements in the amplifiers are a combination of microstrip and lumped elements to yield low-loss impedance-transformers, power splitters and power combiners. Both interdigital and overlay metal-insulator-metal (MIM) capacitors are used in the circuits. The MIM capacitor is favored owing to its smaller size and higher Q. It is noted that together with the submicron gates of high-frequency amplifiers, the MIM capacitor is the lowest yield element in these monolithic circuits (approximately 95%). The amplifiers show excellent performance at the 1-watt level and are expected to play an important part in the realization of phased array systems in the future.