Post-Growth Reduction of Basal Plane Dislocations by High Temperature Annealing in 4H-SiC Epilayers

Basal Plane Dislocations (BPD) were reduced in 4H-SiC epilayers by high temperature annealing in the range of 1600 degrees C to 1950 degrees C using two annealing techniques. Samples annealed at > 1750 degrees C showed almost complete elimination of BPDs propagating from the substrate. However, surface morphology was degraded for microwave annealed samples above 1800 degrees C, with new BPDs being generated from the surface. A new capping technique was developed along with application of high N-2 overpressure to preserve the surface morphology and avoid formation of new BPDs.