Basic Studies

Silicon carbide is a relatively "new" semiconductor, in the sense that high quality single-crystal wafers have only been available since around 1990. For this reason, device processing is in its infancy and many of the fundamental material parameters have not yet been accurately measured. Our group is making basic measurements in the areas listed below...

High Field Transport: Early measurements on Lely crystals suggest that the saturation velocity of electrons in 6H-SiC is about 2x10⁷ cm/s, a factor of two higher than silicon. We have conducted new measurements of the velocity-field relationship on wafers grown by the modified sublimation technique, both to confirm earlier measurements on 6H-SiC and to extend the data to 4H-SiC.

Ion Implant Activation: Dopants are introduced into SiC wafers by ion implantation. Once introduced, the dopant atoms are "activated" by a high-temperature anneal. We have studied the activation of nitrogen, phosphorus, aluminum, and boron implants into 4H and 6H-SiC as a function of anneal time and temperature.

MOS Interface Research: The MOS interface is crucial to many semiconductor devices, including MOSFETs, CCDs, MOS integrated circuits, and MOS-based power devices. Our group is a leader in characterizing the density of interface states, mobile ions, and fixed charge at the interface between thermally oxidized SiO₂ and SiC. We are also working to optimize the oxidation and anneal conditions to enhance interface quality.

MOS Reliability: The mean time before failure (MTBF) of MOS devices under high-field and high-temperature stressing is extremely important in the design of high voltage power devices. We are engaged in a study of oxide reliability on both 4H and 6H-SiC as a function of field and temperature.

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