Absorption mapping of doping level distribution in n-type and p-type 4H-SiC and 6H-SiC

An optical characterization method for determination of spatial doping level concentration in n-type 4H-SiC and p-type 6H-SiC is discussed. The absorption bands of free charge carriers at 460 nm in n-type 4H-SiC are used to determine its doping concentration. In p-type 6H-SiC, the band edge related absorption at 410 nm is a measure for the doping concentration. In both cases, Hall measurements are performed for calibration. Various examples of SiC-wafer mappings are shown and the relationships to crystal growth conditions, i.e. control of doping level and distribution, are investigated.