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Testing the Switching Capability of a Normally-off 800 V - 2 A Vertical GaN Power Transistor

encapuslated vertical GaN device onto a printed circuit board
Fig. 1 Vertical GaN device after being encapsulated on PCB
The development of a normally-off vertical GaN transistor could bypass Si and SiC in both con-duction and switching performance. Therefore, the goal of the development of the device pre-sented in this paper was to create a normally-off vertical GaN transistor competitive with Si and SiC devices not only in performance but also in price. To evaluate the functionality of the 800 V - 2 A vertical GaN transistors, the bare die will be subjected to static characteristic tests. The de-vice is also switched by using a clamped inductive load test with a double pulse input.

The bare die of the device is subjected to these tests after being mounted onto a PCB and then wire bonded to it and encapsulated. The final encapsulated stage of the transistor can be seen in Fig. 1.

To initially characterize the device, a basic static characterization is performed using Agilent's B1505A Curve Tracer. These tests consist of transfer characteristics, output characteristics and on-state resistance over current. For the double pulse test used to assess the switching of the device, the gate to source voltage is driven from 0 V to 10 V and a 10 Ω external gate resistor is used. The switching waveforms of the device at a drain to source voltage of 400 V and a load current of 2 A are shown in Fig. 2 and Fig. 3. These waveforms are used to calculate the switching losses and switching on times.

These results show the potential that a vertical GaN device has in the push to find a replacement for silicon that has better performance with a lower price. Further testing objectives are to decrease the external gate resistor used for the switching test and to test the device at higher voltages.

Waveforms of device turn on under loaded current
Fig. 2. Turn-on waveforms with a load current of 2 A at a VDS of 400 V
Fig. 3. Turn-off waveforms with a load current of 2 A at a VDS of 400 V.
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