High uniformity (Al_0.3Ga_0.7)_0.5In _0.5P/InGaAs enhancement-mode pseudomorphic HEMTs by selective succinic acid gate recess

High selectivity succinic acid: H₂O₂ solution (SA) wet etching processes were used in the gate recess process to fabricate (Al _0.3Ga_0.7)_0.5In_0.5P quaternary enhancement-mode pseudomorphic high electron mobility transistors (E-mode pHEMT). High uniformity of threshold voltage (V_th) was achieved due to a high wet etching selectivity during gate recess process. In this study, we improved the power density and uniformity of the device by using wide bandgap (Al_0.3Ga_0.7)_0.5In_0.5P Schottky layers. In addition, the best wet etching selectivity between GaAs and (Al _0.3Ga_0.7)_0.5In_0.5P was obtained for large area power transistors. The developed 0.5μm long and 1.2mm wide gate FETs exhibited a V_th of +0.1V and a maximum drain current (I _dmax) of 385mA/mm. The maximum output power at 1.9GHz was 95mW/mm with a linear power gain of 22dB and a power-added efficiency of 60%. These characteristics demonstrate this novel E-mode pHEMTs have great potential for use in microwave power device applications.