Application of pulsed laser annealing to ferromagnetic GaMnAs

In this experimental and theoretical work we focus on the technique of pulsed laser annealing applied to the metastable ferromagnetic semiconductor GaMnAs. Analytical heatflow calculations are used to illustrate the position and time dependent temperature distribution during the laser annealing process. Such heatflow calculations will also play an indispensable role for the preparation of new diluted ferromagnetic semiconductors by ion implantation and subsequent annealing. The structural, magnetic, and magnetotransport properties of ferromagnetic GaMnAs have been probed in dependence on the annealing parameters, e.g. the number of laser pulses and the pulse length. Annealing with a single KrF laser pulse of 30 ns and 0.26 J/cm² with the photon energy above the GaAs bandgap energy leads to similar magnetic properties like annealing with a single 3 ns Nd:YAG laser pulse with the photon energy below the GaAs bandgap energy. We observed that possibly due to Mn diffusion and decreasing hole concentration, several laser pulses degrade the structural and magnetic properties of GaMnAs. Our results reveal the largest saturation magnetization for a single KrF laser pulse.