CVD growth and properties of on-axis vanadium doped semi-insulating 4H-SiC epilayers

Highly resistive homoepitaxial layers of 4H-SiC have been grown on the Si-face of nominally on-axis, n-type substrates using chemical vapor deposition. Vanadium tetrachloride has been used as the V-dopant which is responsible for the high resistivity of the epilayers. 100% 4H-polytype was reproduced in the epilayers using the optimized on-axis growth process. The upper limit of vanadium tetrachloride flow rate was also established to achieve high resistivity epilayers free of 3C polytype inclusion. A resistivity of more than 1 × 105 Ω cm has been achieved in epilayers with a very low concentration of V (1 × 1015 cm−3). Owing to the low concentration of V, superior epilayer structural quality was achieved compared to V-doped and standard high purity semi-insulating bulk grown material of similar resistivity. Epitaxial layers with varying vanadium tetrachloride flow have also been grown to study the influence of V concentration on the polytype stability, structural quality, and optical and electrical properties of epilayers. A clear correspondence has been observed in the flow-rates of vanadium tetrachloride, the atomic concentration of V, and electrical, optical, and structural properties of epilayers.