The interesting temperature-dependent characteristics of an In0.5Al0.5As/In0.5Ga0.5As metamorphic high-electron-mobility transistor (MHEMT) using the nonannealed and ohmic-recess (NAOR) technique to reduce parasitic resistance are comprehensively studied and demonstrated. The proposed NAOR technique could reduce the parasitic resistance caused by large conduction-band discontinuity at InAlAs/InGaAs interface. Therefore, the improvement of device performance in terms of dc and parasitic resistance as well as radio frequency characteristics can be expected. In particular, as compared with the traditional MHEMT device, the higher gate/drain breakdown voltage of 22.93 (16.89) V, lower gate leakage current of 0.83 (259) mu A/mm at V-GD = -14 V, higher drain saturation current of 327 (299) mA/mm, higher maximum transconductance of 302.4 (269.6) mS/mm, and lower parasitic resistance of 1.67 (2.02 Omega mm) are obtained, respectively, for the studied NAOR device at 300 (500) K. The corresponding unity current gain cutoff frequency f(T) (maximum oscillation frequency f(max)) are 21.4 (65.5) and 19.3 (55.5) GHz at 250 and 400 K, respectively. Moreover, the relatively lower variations of device performance over a wide temperature range (300-500 K) are obtained. (c) 2008 The Electrochemical Society.