Cryogenic Output Capacitance Loss of GaN HD-GIT

The output capacitance (Coss) loss, which is the loss generated when the output capacitor of a device is charged and discharged, has become a problem for gallium nitride (GaN) high electron mobility transistor (HEMT) in high-frequency applications. Few research has been conducted on this type of loss, especially at low temperatures. Among them, hybrid-drain gate injection transistor (HD-GIT) has lower on-resistance due to its unique conduction mechanism and is widely used in the field of power electronics. Therefore, in this paper, a cryogenic test platform for output capacitance loss of HD-GIT was built, and the non-linear resonance method was adopted to measure the output capacitance loss of GaN devices at eight temperatures, six frequencies, and six voltage amplitudes respectively. The experimental results show that: 1) The output capacitance loss of GaN devices is positively correlated with voltage and frequency; 2) As the temperature decreases, the output capacitance loss of GaN increases. The loss at 93 K is 16.8% higher than that at 293 K. Finally, the reason for the increase in loss at low temperatures is explained through semiconductor physics theory, mainly due to the decrease in electron emission rate and the increase in capture time at low temperatures. Additionally, an HD-GIT model is established on technology computer aided design (TCAD) to simulate and verify the correctness of the theory.