Résumé
We analyse the role of structural defects in GaMnAs and demonstrate how their density can be drastically reduced by in situ post-growth annealing under As capping. Modifications of the magnetic, transport, and structural properties of annealed GaMnAs layers are presented. The main result is that Curie temperatures are strongly increased relative to those of as-grown layers, typically from 70-80 K to 150-160 K. The annealed layers exhibit well-ordered smooth surfaces, suitable for further epitaxial overgrowth.