Panasonic Corp developed a GaN power transistor with a withstand voltage of 600V and will start to ship samples in March 2013.
The transistor is a so-called "GaN on Si" device, which is based on a silicon (Si) substrate. The diameter of the Si substrate is 6 inches (150mm). Sharp Corp will also start to ship samples of its GaN power transistor whose withstand voltage is 600V in April 2013. So, it can be said that the competition in the development of GaN power transistors is becoming fierce.
This time, Panasonic realized a "normally-off operation," which conducts electricity only when a voltage is applied to a gate. The threshold voltage and rated current of the transistor are 1.2V and 15A, respectively. By employing the "GIT" structure, which injects an electron hole from the p-type gate, the company increased drain current while realizing the normally-off operation.
Panasonic reduced "current collapse," which is a problem of GaN power device. A current collapse is a phenomenon in which the on-resistance of the device increases when it is operated with a high voltage, making it difficult to flow current.
When Panasonic formed a "resonance-type LLC power circuit" by using the new GaN power transistor, it was capable of 1MHz switching operation with an output of 1kW and a conversion efficiency of 96%. The product of its on-resistance and the amount of its gate charge (RonQg), which is an indicator of switching operation, was 715mΩ·nC (the on-resistance was 65mΩ, and the charge amount was 11nC).
The RonQg is about 1/13, compared with conventional Si MOSFETs. The smaller the RonQg becomes, the more it is suited for switching operation.
The GaN power transistor was exhibited at APEC 2013, which runs from March 17 to 21, 2013, in Long Beach, the US.