  We study the effects of growth temperature, Ga:As ratio and post-growth
annealing procedure on the Curie temperature, Tc, of (Ga,Mn)As layers grown by
molecular beam epitaxy. We achieve the highest Tc values for growth
temperatures very close to the 2D-3D phase boundary. The increase in Tc, due to
the removal of interstitial Mn by post growth annealing, is counteracted by a
second process which reduces Tc and which is more effective at higher annealing
temperatures. Our results show that it is necessary to optimize the growth
parameters and post growth annealing procedure to obtain the highest Tc.
