Analysis of DC and rf degradation of AlGaN/GaN High Electron Mobility Transistors based on pulsed measurements and spectroscopic techniques

In this paper we will present data concerning DC and rf testing of AlGaN/GaN High Electron Mobility Transistors having LG = 0.25 – 0.7 μm tested in on-state between VDS=15 V and 30 V. We demonstrate that both DC and rf degradation is due to the generation of defects, possibly in the AlGaN, with an activation energy of 0.5 eV. During rf testing in compression, however, a competing mechanism is activated, consisting in electron trapping and electric field reduction, thus blocking defect generation, and reducing the gate reverse current. As a consequence, rf testing in backoff may result in a more severe degradation than testing in compression. The correct identification of failure mechanisms during rf tests requires therefore a detailed consideration of testing conditions.