Status of SiC power devices at Northrop Grumman

This paper presents an overview of SiC power devices. The progress in P–N diode development is described. It is found that in order to develop high voltage, high current diodes, it is critical to reduce dislocation density below 10³ cm⁻², and increase substrate doping of N⁺ 4H–SiC above 10¹⁹ cm⁻³. It is simply not enough to reduce the micropipe density to below 1 cm⁻². The paper introduces a new power switching device configuration, namely, JFET Controlled Thyristor (JCT). It is the most promising near term SiC switching device given its high power potential, ease of turn-off, potential for 500 °C operation and resulting reduction in cooling requirements. It is further concluded that in order to take advantage of SiC power devices, high temperature packages and components with double sided attachment need to be developed along with the SiC power devices. The progress in power MOSFET development is summarized and the phenomenon of “step-bunching” is introduced. This mechanism is responsible for causing surface roughness which results in low electron inversion layer mobility. It is found that by avoiding step-bunching, surface electron mobility of about 55 cm² V⁻¹ s⁻¹ can be obtained in 6H–SiC planar MOSFETs. The cause for low surface electron mobility in 4H–SiC is still an unknown.