| dc.description.abstract | This study utilizes a Schottky p-type GaN high electron mobility transistor (HEMT) structure, the GaN Systems GS66508B, 650 V commercial device, for in-depth investigation and analysis. The research focuses on three main aspects: (1) exploring the static characteristics of the device with an emphasis on static on-state resistance, (2) under dynamic measurements, analyzing the effect of different gate turn-on and drain turn-off voltages on dynamic on-state resistance, and (3) under dynamic measurements, analyzing the effect of different gate turn-off and drain turn-off voltages on dynamic on-state resistance.
The platform used for dynamic measurements in this study is the Double Pulse Test (DPT) method, which can be operated in either a resistive load or an inductive load mode. This research employs the resistive load mode to reduce oscillations caused by parasitic effects during switching and obtain more accurate measurement results. The switch is hard-switched to minimize the influence of thermal effects on resistance.
Regarding the static characteristics of the device, the standard gate voltage turn-on voltage is 6 V. However, it was observed that a gate voltage turn-on voltage of 7 V slightly improves the static on-state resistance compared to 6 V, while lower turn-on voltages result in deteriorated device performance. Further investigation into the gate turn-on voltage under dynamic measurements reveals a more pronounced difference. Providing a higher drain turn-off voltage shifts the device′s threshold voltage to the right, requiring a higher gate voltage to fully turn on the device.
On the other hand, for system stability and safety during switching, negative voltages are applied to the device when turning off. The impact of these negative gate voltages during device turn-off is also an important aspect of the discussion. It was found that different gate turn-off voltages have varying effects on dynamic on-state resistance. Generally, more negative gate turn-off voltages exacerbate the degradation of dynamic on-state resistance due to two main internal mechanisms. Firstly, the high bias between the drain and source during turn-off leads to high electric fields and impact ionization, generating electron-hole pairs. The holes, which could have played a role in detraping, are attracted to the negative gate voltage, leading to severe degradation of dynamic on-state resistance through a multiplication effect. Secondly, applying a negative gate bias during device turn-off causes holes in the p-GaN layer to be attracted to the gate voltage. When the device is turned on again, these holes cannot immediately return to their original positions, resulting in a rightward shift of the device′s threshold voltage and causing significant degradation of dynamic on-state resistance. | en_US |