We report investigations of B incorporation during the growth of B‐doped hydrogenated amorphous silicon (a‐Si:H) thin films by laser‐induced chemical vapor deposition (CVD) from mixtures of SiH4and B2H6. Because B2H6decomposition is very rapid, nearly all the B admitted into the reaction cell is incorporated in the growing film and the B concentration in the solid is B2H6flow rate limited rather than controlled by the gas phase dopant concentration. Widely varying B‐incorporation efficiencies reported for B‐dopeda‐Si:H grown by a variety of thermal CVD techniques are summarized and explained.