Failure signatures on 0.25 mu m GaN HEMTs for high-power RF applications

GaN HEMTs for high-frequency operation are now exhibiting outstanding results in both RF performances and long-term stability, but at the moment there is not a unique indication of which failure mechanism affects the device performances in long-time scale, nor a proved technique which allows to identify the best failure accelerating factor useful for a consistent life-time extraction. In this topic, the paper tries to point-out the efficacy of short-term tests on the investigation of failure modes on two generations of AlGaN/GaN 0.25 mu m gate-length HEMT transistors, highlighting the failure signatures corresponding to the early appearance of the failure modes typical of this technology: (i) a first mode correlated with a limited performance degradation marked by a left threshold voltage shift, and (ii) a second much more degrading failure mode, associated with a right threshold voltage shift. As a result, this simple preliminary investigation gives a consistent evaluation of the really improved reliability behaviour of the new HEMT technology, which shows excellent robustness from high-field to extremely high-power bias conditions, pushing out the more damaging failure mechanism from the typical operating conditions. (C) 2014 Elsevier Ltd. All rights reserved.