March 19, 2013
Panasonic Develops A 600V Gallium Nitride (GaN) Power Transistor with Its Stable Switching Operations
March 19,2013, Osaka, Japan - Industrial Devices Company, Panasonic Corporation today announced the development of a Gallium Nitride (GaN) -based power transistor with its blocking voltage of 600V which enables stable switching operations. Panasonic will start the shipment of the evaluation samples from March, 2013. Failure-free operations by 600V GaN power transistors are confirmed for the first time. The GaN transistors contribute to save energies together with smaller system size in a variety of power switching systems for industrial and consumer applications. The developed GaN transistor has the following three technical features.
1. Normally-off Gate Injection Transistor on 6-inch Si substrate
Power switching systems require normally-off operations of the transistors for the safe operations. Lowering the cost of the substrate to be employed for the growth of GaN-based films is also required for the GaN transistors to be practically used. Panasonic solves these issues by its novel normally-off Gate Injection Transistors (GITs) on cost-effective Si substrates. Panasonic' s proprietary technologies for the epitaxial growth of GaN by metal organic chemical vapor deposition (MOCVD) enable the fabrication of GaN transistors over a 6 inch Si substrate. The p-type gate of the GIT greatly helps to reduce the on-state resistance taking advantages of the conductivity modulation by the hole injection from it.
2. Stable switching operation free from “Current collapse”
So far, the increase of the on-state resistance after the application of high voltage, so-called current collapse, has been a serious problem for the commercialization of GaN transistors. The increase is the greatest obstacle to achieve the stable operations of the transistors. The origin of the collapse is believed to be trapped electrons under high electric field. Panasonic reduce the number of the traps by its novel processing technologies, in addition to new device structures relieving the electric field. The fabricated GIT on Si enables stable 600V operations free from the current collapse.
3. Highly efficient switching at high frequencies
Lateral structure of the GIT is advantageous for high speed switching owing to the lower parasitic capacitance than that in conventional Si-based power transistors with the vertical structures. Here, RonQg (Ron: on-state resistance, Qg: gate charge) is a figure-of-merit for high speed switching. The fabricated GIT exhibits the low RonQg of 715mΩnC which is one thirteenth lower than that by the state-of-the-art Si MOS transistors indicating the superior potential. Panasonic also demonstrate 1MHz operation of resonant LLC DC-DC converters at high efficiency over 96% by using the GITs on Si. This demonstration indicates that the presented GIT on Si can be used for practical systems free from the operation failure.
Tentative specifications of GaN power transistors
Threshold voltage: 1.2V
Blocking voltage: 600V
Drain current (continuous): 15A
On-state resistance: 65mΩ
Gate charge: 11nC
Applications for 130 domestic and 112 overseas patents have been filed. These research and development results have been presented at the exhibition in Applied Power Electronics Conference 2013, held in Long Beach, U.S. from March 17 to 21, 2013. This work is partially supported by the New Energy and Industrial Technology Development Organization (NEDO), Japan, under the Strategic Development of Energy Conservation Technology Project.
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