The gate-recessed AlGaN/GaN metal-oxide-semiconductor high-electron mobility transistors (MOS-HEMTs) were fabricated using the combination technology of the photoelectrochemical (PEC) wet etching method and the PEC oxidation method. The gate-recessed structure on the AlGaN layer was first carried out using the PEC wet etching method followed by the direct growth of the gate oxide layer on the recessed surface using the PEC oxidation method. According to the measured pulsed output characteristics, the low frequency noise results and the Hooge's coefficient, the performances of the gate-recessed MOS-HEMTs are better than those of the planar gate MOS-HEMTs. The improved performances of the gate-recessed MOS-HEMTs are attributed to the removal of original damages and native defects using the PEC etching process and the passivation function using the PEC oxidation process. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3561276] All rights reserved.