A novel self-aligned T-shaped gate enhancement-mode metamorphic In0.50Al0.50As/In0.53Ga0.47As HEMTs on GaAs substrates by MOCVD is proposed and demonstrated, utilizing an optimized multi-stage composite buffer scheme. High 2-D electron gas Hall mobility values of 9100 cm(2)/V s at 300 K and 38,900 cm(2)/V s at 77 K have been achieved. The mHEMT had a threshold voltage (V-th) of +0.22 V, a maximum drain current of 786 mA/mm and transconductance up to 1.2 S/mm at V-DS = 0.5 V. The fr. and f(max) of 50-nm T-shaped gate devices were 305 and 408 GHz, respectively. To the knowledge of the authors, these results are the highest reported for MOCVD-grown enhancement mode mHEMTs on GaAs substrate. (C) 2014 Elsevier Ltd. All rights reserved.