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

摘要

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 N_A/N_D. The below band-gap absorption (BBGA) maximum at about 730 nm is correlated mainly to N_A, and, for constant N_A, is slightly anti-correlated to ND. The same results can be obtained from an α~(1/2) vs. E plot extrapolated to α= 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 N_A-N_D in boron doped SiC samples, and from wafers cut from the same crystal, the concentration of boron and compensating impurities can be evaluated.