Growth and characterization of p-type 4H-SiC epitaxial layers grown on (11-20) substrates are reported. P-type 4H-SiC epilayers with smooth surface morphology have been grown on (11-20) substrates by low-pressure, hot-wall type CVD with SiH4–C3H8–H2–TMA system. The doping concentration can be controlled in the range from about 1×1016cm−3 to 1×1019cm−3. Anisotropy of the crystalline quality is observed by x-ray diffraction measurement. P-type epilayers, in which near band-gap emissions are dominated and D-A pair peak is not observed, are obtained. Hole mobility of (11-20) epilayers is smaller than that of (0001) epilayers probably due to the lack of crystalline quality compared to (0001) epilayers. The results of both low-temperature photoluminescence and the temperature dependence of Hall effect measurements indicate that the boron concentration as undoped impurity in (11-20) epilayer is lower than that of (0001) epilayer. This may be caused by the smaller incorporation efficiency of boron into (11-20) epilayer than that of (0001) epilayer.

The influence of growth conditions and susceptor purity on the residual contamination in undoped 4H-SiC epitaxial layer grown at higher temperature such as 1600 °C is investigated. Residual N concentration is found to increase with growth temperature. Growth temperature dependence of residual N concentration is stronger than that of Al or B. The effect of degradation of SiC coating layer on the purity of the epitaxial layer is studied. SiC coating layer is degraded after very few repetition of growth-run. SIMS measurement reveals that the concentration of N, Al, B, Ti and V in epitaxial layer increases with the deterioration of SiC coating layer. Therefore, serious consideration on the effect of contamination from the susceptor graphite is required. By using various grades of graphite as susceptor, the dependence of the purity of epitaxial layer on the susceptor purity is studied. High concentration (1017 to 1018 cm−3) of N is found in graphite. Contamination of all types of impurities such as p-type impurities, transition metal impurities and N in graphite is found to affect the purity of epitaxial layers.