A flip-chip GaAs power FET with gate and drain via connections

A new microwave device format that combines flip-chip mounting and via-connection technologies is described. This approach avoids many of the compromises that are inherent in conventional microwave monolithic circuits and will be particularly important in power applications. This letter reviews the rationale for this device format and describes a new method of forming via connections through thick semi-insulating substrates using laser drilling. Preliminary discrete GaAs FET's have been fabricated and results have been obtained through 18 GHz. At 12 GHz, an output power of 308 mW, a 28-percent power-added efficiency, and a 4.5-dB gain have been achieved with a 0.6-mm-wide GaAs FET. Efficiencies as high as 31 percent were achieved with these preliminary devices.