RF power degradation of GaN High Electron Mobility Transistors

We have developed a versatile methodology to systematically investigate the RF reliability of GaN High-Electron Mobility Transistors. Our technique utilizes RF and DC figures of merit to diagnose the degradation of RF stressed devices in real time. We have found that there is good correlation between selected RF and DC figures of merit. However, compared with DC stress, RF stress at the same bias point is found to be more severe and to introduce new degradation modes. At high power level, RF stress induces a prominent trapping-related increase in the source resistance most likely as a result of the creation of new traps. This is in contrast with drain degradation that often occurs under similar DC conditions. Our findings cast a doubt over the ability of DC life test in evaluating reliability under RF power conditions.