Low-temperature annealing after molecular-beam epitaxial growth of HI-V-based diluted magnetic semiconductors, (Ga,Mn)As and (In,Mn)As have been found to improve the crystallinity of the films. That is, the Curie temperature and the conductivity are greatly enhanced. This effect is probably due to the removal of excess As atoms which passivate doped Mn acceptors. The present method provides a way for carrying out reproducible systematic studies of these materials. (C) 2002 Published by Elsevier Science B.V.