The effect of the recessed gate structure on DC characteristics of n-channel depletion mode heterostructure field effect transistors (HFETs) grown by metalorganic chemical vapor deposition (MOCVD) was demonstrated. The recessed gate process was carried out by using photo-enhanced chemical (PEC) wet etching. There were improvements on the electrical characteristics after using the recessed gate AlGaN/GaN and AlGaN/GaN/InGaN/GaN HFET structures because of the better gate controllability to the drain current. It was also found that the gate voltage, V-GS, of the transconductance peak value shifted toward positive bias for the recessed gate structure. The leakage current, the transconductance (G(m)) and the saturation current of the recessed gate AlGaN/GaN/InGaN/GaN HFET with a 30-nm-thick Si-doped GaN cap layer are 1.95mA/mm, 94.82mA/mm and 230mA/mm, respectively. This performance is quite better than that of the device with no recessed gate structure. (c) 2006 Elsevier B.V. All rights reserved.