Evaluation of n-type doping of 4H-SiC and n-/p-type doping of 6H-SiC using absorption measurements

A non-destructive, absorption measurement based optical method has been developed in order to determine doping type (n- or p-type), doping level and doping level distribution in 4H and 6H silicon carbide (SiC) wafers. The bandgap absorption has been calculated numerically taking into account band filling, band shrinkage and band tailing effects which are a function of donor and acceptor concentration ND and NA, respectively. The numerical results are compared with experimental data. A calibration plot of the doping dependence of the absorption of n-type 6H SiC is presented and the application for mapping of the SiC wafer doping level distribution is demonstrated.