This work compares AlGaN/GaN high-electron-mobility transistors (HEMT) with different gate recess depths. Small signal analysis showed that the best device performance was achieved at an appropriate recess depth primarily that was associated with maximized intrinsic transconductance and minimized source resistance. An f(T) x L(g) product of as high as 25.6 GHz-mu m was obtained in a device with a gate recess depth of 10 nm. Further increasing the recess depth lowered the intrinsic transconductance and thereby worsened the performance. This effect was explained by the degradation of transport properties by the epitaxial damage that was itself caused by plasma-assisted dry etching processes. (C) 2010 Elsevier Ltd. All rights reserved.