Nonuniformity has been demonstrated of commercially available p-type 6H SiC bulk and epitaxial wafers by using photoluminescence (PL) mapping at room temperature. Three deep-level PL bands with peaks at 1.95, 1.35 and 1.05 eV have been detected for the first time besides the near band-edge emission associated with Al acceptors. The intensity variations of these bands on wafers differ depending on the sample. A circular pattern appeared corresponding to the dark core region of the wafer. A one-sided intensity pattern was observed in an epitaxial layer, which is speculated to reflect inhomogeneous gas flow and/or temperature gradient in the reactor. We believe that the ability of the present technique for the characterization of nonuniformity contributes greatly to the improvement of the crystalline quality of SiC.
Source:IOPscience
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