Abstract: In this work, an application of wide-gap updoed-Al0.22Ga0.78As bulk to perform the field-plate gate (FP-gate) on Al0.22Ga0.78As/In16Ga84As/Al0.22Ga0.78As DH-HEMTs was investigated. The simulated FPG-devices with a bulk thickness of 1200 Å, exhibit an excellent dispersing property to the electric field peak under gate electrode near to drain side, hence, the breakdown characteristics were effectively improved. Measured gate-diode performance of FPG-device presents a higher breakdown voltage (VBR) of -25.5 V than devices with single recess (SRG-device). Enhancement of device breakdown is contributive to microwave power performances. At 2.4 GHz load-pull measurement of studied devices which were biased at class AB operation, the saturated output power (POUT), power gain (GP) and power-added efficiency (PAE) were 13.06 dBm (202 mW/mm), 12.8 db and 47.3% for FPG-device. These measured results of SRG-device were 10.3 dBm(107 mW/mm), 13.2 db and 38.5%, According to the simulated results, FPG-devices structuring with a bulk layer exhibit excellent performance for high breakdown and microwave power operation.