A high breakdown voltage and a low gate leakage current Al0.2Ga0.8As/In0.15Ga0.85As metal-oxide-semiconductor-pseudomorphic high-electron mobility transistor (MOSPHEMT) with low temperature and low-cost liquid-phase-deposition (LPD) process are reported for the first time. The LPD-deposited 15 nm thin Al2O3 layers are used as gate insulator. The fabricated devices achieved peak extrinsic transconductance (g(m)) value at gate bias (V-GS) of 0 V for single power supply amplifier application. The fabricated 2 x 100 mu m(2) devices exhibited a peak g(m) of 161 mS/mm, a threshold voltage of -1.2 V, and a drain-to-source current (I-ds) of 310 mA/mm. These characteristics demonstrate that the LPD-deposited Al0.2Ga0.5As/In0.15Ga0.85As MOSPHEMTs have potential for microwave power device applications. (C) 2010 Elsevier Ltd. All rights reserved.