A Multi-Currents Method for Junction Temperature Separation of Cascode GaN

• Published in: IEEE transactions on power electronics 2024-12, Vol.39 (12), p.15567-15575
• Main Authors: Wu, Lixin, Deng, Erping, Wang, Yanhao, Xu, Shengqian, Hua, Wenbo, Yang, Shaohua, Ding, Lijian
• Format: Article
• Language: English
• Subjects: Cascode gallium nitride (GaN); diode; Gallium nitride; HEMT; HEMTs; junction temperature; Junctions; Resistance; Semiconductor device measurement; separating; Temperature measurement; Voltage measurement
• ISSN: 0885-8993; 1941-0107
• DOI: 10.1109/TPEL.2024.3424893

Gallium nitride (GaN) power electronics are becoming widely used in power conversion systems due to their high electron mobility. The cascode structure, with a Si metal-oxide-semiconductor field-effect transistor ( mosfet ) connect in series for gate control, in enhancement mode of GaN has been promoted by manufacturers due to its low price and excellent characteristic. However, the existed junction temperature method can only obtain one temperature value of two chips, rather than each of it caused by cascode structure. This structure therefore leads to different failure modes with thermal coupling between two chips. To better analyze the failure mechanism, it is important to separate the junction temperatures of the internal mosfet and the high-electron mobility transistors (HEMTs). This article proposes a new measurement method which can get the junction temperature of the two chips inside the cascode GaN can be obtained without damaging the device packaging. First, by applying different magnitudes of reverse measurement currents to the GaN power electronics in the cascode, the theoretical formulae are calculated to further derive the calibration curves for the temperature dependent changes of the electrical parameters of the internal mosfet reverse diodes and HEMT devices. By constructing a special timing circuit and combining it with actual transient thermal impedance test (just as an example of a reliability test), the junction temperature of the cascode internal GaN chips can be calculated under real operating conditions. Detailed experiments verify the feasibility of the method and the accuracy of the junction temperature calculation (the temperature deviation does not exceed 5 K).