【書報討論 2022/11/22】《第十五週》 場次二
講者：國立陽明交通大學機械工程研究所 Surya Elangovan博士生
講題：Performance and reliability characterization of GaN high electron mobility transistors (HEMTs) for power electronic applications
時間：2022/11/22 (周四) 3:30 pm - 5:30 pm
地點：工程五館 B1 國際會議廳
In power switching applications, GaN-on-Si technology (AlGaN/GaN High Electron Mobility Transistors on Si substrates) demonstrates promising characteristics and cost-competitiveness. Despite their superior performance and cost benefits, AlGaN/GaN HEMTs are still limited by their instabilities. GaN power devices are used in power-switching applications and operate at a high drain voltage during the OFF-state and a high gate voltage during the ON-state, when exceptional reliability is essential.
This seminar presentation focuses on the design, performance, and device and system level stress induced failure mechanism and structural characteristics of two types of cascode configurations: 1) a single GaN MIS-HEMT chip cascode arrangement, and 2) a multi-GaN-chips cascode architecture with four GaN MIS-HEMTS in parallel. Static characteristics and dynamic switching performance of multi-GaN and single-GaN cascode modules in resistance-capacitance and inductive load circuits are demonstrated and compared with commercialized devices. Further, two kinds of stress methods are utilized in device level OFF-state reliability tests: (1) pulsed off-state gate stress and (2) prolonged off-state gate stress (Bias Temperature Instability), all of which involve voltage, time, and temperature acceleration factors. In system level reliability test, the dynamic on-resistance (RON) behavior of each GaN cascode device is investigated under hard-switching conditions with time, duty cycle, frequency, current and temperature acceleration factors and also observes the safe operating area. During reliability testing, the extracted parameters of device conductivity (GM, max), leakage characteristics (IGS, leakage), and threshold voltage (VTH) are used to determine device instabilities and degradations. Under OFF-state reliability studies, potential failure mechanisms are identified to explain the GaN cascode configuration degradations and instabilities. These studies provide a way to comprehend the capabilities and limitations of the multi-GaN-chip cascode power module, as well as a way of accelerating the development of future GaN cascode technologies.
Keywords: MIS-HEMT, Cascode, Pulsed OFF-state bias, Bias Temperature Instability (NBTI & PBTI), Hard switching, Dynamic on state resistance.