Performance of unpassivated MOVPE grown AlGaN/GaN/SiC HEMTs under short-term electrical bias stress is reported. Insignificant degradation in DC and RF behaviour of prepared devices after 16 It stress at V-D = 21 V and V-G = -2.5 V is observed. This can be demonstrated by a maximum drain current of 1.03 and 1.01 A/mm and a peak extrinsic transconductance of 233 and 225 mS/mm before and after bias stress, respectively. Consecutive drain voltage sweeps indicates on low current collapse in samples investigated. The RF characteristics show a decrease of the f(max)-to-f(T) ratio from 2.23 to 2.15 and the saturated output power density measured at 2 GHz from 3.60 to 3.53 W/mm after the devices were stressed. This result indicates that reliable AlGaN/GaN/SiC HEMTs without passivation can be prepared. However, additional studies are needed to understand if the material structure and/or the device processing is responsible for low current collapse and RF dispersion in these devices. (C) 2004 Elsevier Ltd. All rights reserved.