Effect of nonannealed ohmic-recess structure on temperature-dependent characteristics of metamorphic high-electron-mobility transistors

The interesting temperature-dependent characteristics of an In0.5 Al0.5 As In0.5 Ga0.5 As 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 InAlAsInGaAs 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) μAmm at VGD =-14 V, higher drain saturation current of 327 (299) mAmm, higher maximum transconductance of 302.4 (269.6) mSmm, and lower parasitic resistance of 1.67 (2.02 mm) are obtained, respectively, for the studied NAOR device at 300 (500) K. The corresponding unity current gain cutoff frequency fT (maximum oscillation frequency fmax) 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.