Panasonic Develops GaN Power Transistor on Silicon
The new GaN transistor extends the operating voltages of a variety of power switching systems including inverters for industrial use and uninterruptible power supplies.
Panasonic has developed a new technique to drastically increase the blocking voltage of Gallium Nitride (GaN) -based power switching transistors on silicon (Si) substrates.
The blocking voltage of the Si substrate can be added to that of the GaN transistor by the new structure which should enable blocking voltages over 3000V. The new GaN transistor extends the operating voltages of a variety of power switching systems including inverters for industrial use and uninterruptible power supplies.
Strong electric fields are formed along the vertical direction in the GaN transistor on a conductive Si substrate at high drain voltage. Theoretically, the blocking voltage is ideally determined by the thickness of the GaN layer and the Si substrate. However, experimentally observed values have been affected by only the GaN thickness, where the Si substrate has not contributed to the blocking voltage.
Panasonic investigated the mechanism and found that the blocking voltage increase is limited by leakage current at the interface between GaN and Si caused by electrons formed as an inversion layer.
To prevent this, Panasonic has proposed a new called Blocking-Voltage-Boosting (BVB) structure which consists of selectively formed p-type regions on the surface of the Si substrates. The p-type regions prevent the inversion electrons from flowing as leakage current.
The fabricated GaN transistor on Si with the BVB structure achieves a high breakdown voltage of 2200V with the total epitaxial thickness as small as 1.9 microns. This value is approximately five times higher than that in the conventional GaN transistor on Si with the same thickness of GaN.
Further increase of the epitaxial thickness will enable break down voltages over 3000V with existing epitaxial technologies. The GaN transistor on Si with the BVB structure will be applicable to various switching systems with higher operating voltages
Applications for 99 domestic and 64 overseas patents have been filed. These results were presented at the International Electron Devices Meeting 2010, held in San Francisco, U.S. between December 6 and 8, 2010.
Panasonic Corporation is a leader in the development and manufacture of electronic products for a wide range of consumer, business, and industrial needs. Based in Osaka, Japan, the company recorded consolidated net sales of 7.42 trillion yen (US$79.4 billion) for the year ended March 31, 2010.