Thin GaMnAs layers were grown by low temperature molecular beam epitaxy on (0 0 1), (3 1 1) A and (1 1 0) GaAs substrates. In an effort to increase the ferromagnetic transition temperature T-C, we studied growth conditions and the effectiveness of post-growth annealing under an arsenic capping layer and in air. Avoiding As antisite defects with a small As to Ga flux ratio during MBE growth and reducing Mn interstitials by annealing the GaMnAs films in air for very long time at temperatures far below growth temperature allows us to obtain (0 0 1) samples with T-C up to 150 K, (3 1 1) A samples with T-C about of 110 K and (1 1 0) samples with T-C of 89 K. (c) 2006 Elsevier B.V. All rights reserved.