High-linearity In0.52Al0.48As/InGa1-xAs HEMT's have been successfully fabricated by low-pressure metal organic chemical vapor deposition (LP-MOCVD). The studied devices exhibit high transconductance, low leakage current, high breakdown, and high-linearly operational regime due to good carrier confinement well as the low temperature growth In0.52Al0.48As barrier layer significantly suppresses buffer leakage current. Experimentally, linear operation current regime and gate voltage swing are improved in the structure utilizing a compositionally graded InxGa1-xAs channel due to the compositionally graded In(x)G(1-x)As channel enhance the device carrier mobility and confinement. An extrinsic transconductance as high as 302 mS/mm at gate length of 1.5 mum is achieved for the In0.6Ga0.4As channel structure. (C) 2003 Elsevier Ltd. All rights reserved.