Fabrication, Characterization and Numerical Simulation of High Breakdown Voltage pHEMTs

High Breakdown Voltage pHEMTs have been successfully developed by implementing a field-plate (FP) structure. Devices with and without FP have been fabricated on the same wafer in order to compare the improvements induced by adopting the FP. Both kind of devices showed little or no current dispersion under pulse measurement conditions. Moreover the off-state breakdown voltage improved from 23V, for the devices without FP, to 38V for the field-plated devices. At 4GHz an output power as high as 1.6W/mm was measured for a FP device, resulting in a 60% improvement with respect to the device without FP. The fabricated structures were also evaluated by carrying out 2D numerical simulations. Experimental results on MISpHEMTs have been explained by means of a donor trap at the SiN/GaAs interface located at 0.18eV from the GaAs conduction band. Finally, a good agreement between experimental and simulated device characteristics was obtained.