The ability to control the resistivity of the wide band gap semiconductor B12As2 by doping with silicon was verified. The electrical properties of nominally undoped and Si-doped rhombohedral B12As2 thin films on semi-insulating 6H-SiC (0001) substrates prepared by chemical vapor deposition were subjected to Hall effect measurements. Varying the Si concentration in the B12As2 thin films from 7×1018 to 7×1021 at./cm3 (as measured by secondary ion mass spectrometry) decreased the resistivities of the p-type B12As2 films from 2×105 to 10 Ω cm. The resistivities of the B12As2 films were decreased by one to two orders of magnitude after rapid thermal annealing for 30 s in argon. The spatial distribution of the hydrogen concentration was measured before and after annealing. No changes were detected, casting doubt on hydrogen as being the cause for the change in the resistivities of the B12As2 films with annealing.