Dynamic performances of GaN-HEMT on Si in cascode configuration

This paper describes dynamic characteristics and power loss analysis of a high-voltage GaN-HEMT in cascode. The GaN-HEMT is "normally-on" and fabricated on 6-inch Si substrate using our Si mass-production line. A figure of merit (a product of RDSon (m Ω) and Qg (nC)) of the GaN-HEMT in cascode is as low as 1400. Simple switching characteristics with resistive load and power efficiency measurements with a power factor correction (PFC) circuit driven from 100 kHz to 1MHz were performed for the evaluation. The switching times (tr/tf) are about 4 times faster than those of conventional Si-MOSFET. An analytical method of power losses including temperature dependence of component parameters is also demonstrated. Analyzed results indicate a dominant factor of power losses at high frequency and high output power operation is turn-off switching loss, and the switching loss of our GaN-HEMT in cascode configuration is lower than that of Si-MOSFET.