Study On HT Characteristics And Reliability Of GaN HEMT

As the third-generation semiconductor, GaN has demonstrated outstanding performance for high-temperature and high-power applications for its high breakdown voltage, thermal conductance and also saturation velocity. Although there has been lots of researches on GaN HEMTs' applications in high temperature and high-power areas, the study is not enough. So this paper will focus on these two points, the studies will be carried out through both simulation and experiments.Firstly, this paper studies the basic principles of GaN HEMTs, and then simulates the self-heating effects of a device when it is working normally. The heat generation and distributing are given, and also the descend of the electric characteristics. Further more, the author studies the degradation of DC characteristics when the device is applied under high-temperature (HT) circumstance.Secondly, GaN HEMTs are fabricated and their high-temperature (HT) characteristics are measured. Degradations of the DC and pulse characteristics are achieved, and possible mechanisms are given. Investigations indicate that performances of carriers (2DEG) have degraded seriously, and the location trends to move to the side of GaN. Also, the traps located at the AlGaN/GaN interface trend to be more active, and also the ones located in the barrier layer. This results in the enhancement of trap-assisted tunnel effects. All these factors lead to the degradation of the devices.Finally, the reliability of thermal storage of the devices is investigated. The results indicate that after thermal storage, the 2DEG moves to barrier layer obviously, which induces the decrease of the effectual thickness of barrier and the degradation of the interface of AlGaN/GaN, and also the decrease of mobility of 2DEG. Finally, performances of the devices degrade seriously.