面向应用的氮化镓高电子迁移率晶体管阈值电压偏移——测试平台与实验结果

Due to the low on-state resistance and fast switching transitions, GaN-HEMTs are promising for building highly efficient power converters. However, charge trapping effects within the semiconductor structure worsen various parameters of the transistor. Besides the deteriorated on-state resistance, also threshold voltage shifts occur. These impact the switching behavior as well as losses and can cause Miller induced turn-on. As data sheets do not give information regarding this effect, the power con-verter designer needs to conduct own measurements. Several parameters like temperature, drain and gate bias, as well as switching conditions impact charge trapping. Additionally, charge trapping effects show time constants ranging from μs to hours. These circumstances call for a specific test bench to assess the threshold voltage under conditions close to the intended application. By using standard laboratory equipment typically present in every power electronics lab, this paper presents a cost-effective solution to obtain the threshold voltage under application conditions. The device operates under hard- or soft-switching, and the converter operation is interrupted by short measurement intervals to acquire the threshold voltage. With a nominal value of 1.1 V, the results show a shift of ≈1 V in hard-switching and ≈0.9 V in soft-switching operation of up to 10000 s.