Electrical and Optical Characterization of p-Type Boron-Doped 6H-SiC Bulk Crystals

Electrical and optical characterization was performed to obtain information about the doping and compensation levels of samples cut from boron doped, physical vapor transport (PVT) grown 6H-SiC crystals. Values for NA and ND can be derived from analysis on temperature dependent Hall effect measurement data. The charge carrier concentration p at room temperature depends approximately linearly on NA/ND. The below band-gap absorption (BBGA) maximum at about 730 nm is correlated mainly to NA, and, for constant NA, is slightly anti-correlated to ND. The same results can be obtained from an SR*a vs. E plot extrapolated to *a = 0 in the near band-gap region, as the broad absorption band induces a shift in the optically detected band-gap towards lower energies. Absorption measurements can give an estimation of NA-ND in boron doped SiC samples, and from wafers cut from the same crystal, the concentration of boron and compensating impurities can be evaluated.