Transport and magnetic properties of low temperature annealed Ga1-xMnxAs

We present the results of low temperature annealing studies of Ga1-xMnxAs epilayers grown by low temperature molecular beam epitaxy in a wide range of Mn concentrations (0.01 < x < 0.084). Transport measurements in low and high magnetic fields as well as SQUID measurements were performed on a wide range of samples, serving to establish optimal conditions of annealing. Optimal annealing procedure succeeded in the Curie temperatures higher than 110 K. The highest value of the Curie temperature estimated from the maximum in the temperature dependence of zero-field resistivity (T-rho) was 127 K. It is generally observed that annealing leads to large changes in the magnetic and transport properties of GaMnAs in the very narrow range of annealing temperature close to the growth temperature.