High Voltage Breakdown pHEMTs for C-band HPA

High Voltage Breakdown (HVB) HPA MMIC based on GaAs pHEMTs technology represents a useful way for high power RF application. To increase the breakdown voltage respect to conventional device, a field-plate (FP) gate structure is implemented in our standard 0.5 μm process. With this solution the off-state breakdown voltage of the device has been improved from 18V to 28V, while keeping constant the drain current. As expected, FP devices showed smaller drain current collapse than standard devices under pulsed DC measurement conditions and a significant increase in power density, i.e. 1.4 W/mm. To guaranty a full advantage for real HPA applications we have carried out numerical simulations, to optimise device thermal behaviour as a function of GaAs thickness and gate pitch. On the basis of this technology development, reliable and reproducible HPA have been fabricated with an output power of circa 30 W and power added efficiency (PAE) of circa 35% in the 4.9-6.1GHz frequency range. Therefore this proposed technological solution enables the realization of very high power T/R modules with reliable GaAs technology, waiting for more disruptive and less mature GaN HEMT one.