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17 December 2008


Panasonic develops 'natural super junction' GaN power device

At this week’s International Electron Devices Meeting (IEDM 2008) in San Francisco, CA, USA, Panasonic Corp (Matsushita Electric Industrial Co Ltd) of Osaka, Japan reported R&D results for a gallium nitride-based diode with a new junction structure that it terms a ‘natural super junction’. The new GaN diode, which has low operating loss, is applicable to consumer and industrial power switching systems, the firm says.

The junction structure consists of multi-layered GaN-based thin films with different compositions, with each interface producing fixed positive and negative charges due to the material's unique polarization. Due to complete balancing of the fixed charges, the layered structure acts as an insulator at reverse bias, so the breakdown voltage can be increased just by extension of the distance between the two electrodes, says the firm. Increasing the number of layers and hence current channels also effectively reduces the on-state resistance.

The proposed device structure is similar to a super junction in silicon devices, in which p-type and n-type layers are stacked alternately. However, unlike the silicon super junction, the new GaN junction structure does not require any precise control of the doping concentration in the layers. Also, high breakdown voltages can be achieved by taking advantage of naturally formed fixed charges, hence the name ‘natural super junction’.

The new GaN-based diode exhibits a breakdown voltage of 9400V with a low on-state resistance of 52mΩcm², reaching the predicted limitation of GaN-based semiconductors for the first time, it is claimed.

Also, the firm says that its proprietary technique for forming the electrodes over the recessed structure reduces the contact resistance between the electrodes and the current channels, which helps greatly in reducing the on-state resistance.

Applications have been filed for 124 domestic and 80 international patents relating to the new technology.

See related item:

Panasonic claims record gain of 22dB at 26GHz in GaN ICs

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