Incorporation of boron and the role of nitrogen as a compensation source in SiC bulk crystal growth

The incorporation behavior of the boron and nitrogen during vapor growth (PVT) of 6H-SiC bulk crystals has been studied using chemical analysis and temperature-dependent Hall effect measurements. Nominally undoped crystals show a exponential decrease in charge carrier concentration because of nitrogen depletion in the growth system. Boron incorporation is dependent on the B content in the source over a wide range of B starting concentration. The B source depletes only slowly during growth, leading to a constant B concentration N-A in the crystals. Numerical simulation shows that for low compensation (N-A/N-comp greater than or equal to 5) the charge carrier concentration at room temperature behaves like p similar to N-A/N-comp, whereas for high compensation a relation of p similar to N-A-N-comp was found. Evaluating temperature-dependent Hall effect measurements for SiC crystals doped with various amounts of B, N-A remains constant during growth, while N-comp decreases from N-comp = 2 x 10(18) to 2 x 10(17) cm(-3) as observed in nominally undoped crystals. As a result, the charge carrier concentration of B doped samples increases exponentially with growth time even though N-A-N-comp roughly remains constant. Finally, a decrease in the charge carrier concentration around faceted areas observed in p-type SiC growth is found to be related to the terrace width of macrosteps on the growth surface.