Abstrakt
The knowledge of Mn interstitial concentration profile in subsequent phases of post-growth annealing is important for variety of physical problems concerning GaMnAs, which belongs to the group of diluted magnetic semiconductors (DMS). These materials are investigated for their possible application in spintronics.
The Mn ions implanted into GaAs can be situated in two different positions. Substitutional Mn ions on Ga sites act as acceptors contributing to the ferromagnetical ordering, whereas interstitial Mn ions act as double donors and destroy the ferromagnetism.
To explore the influence of the free surface to the Mn interstitial outdiffusion, a sample of GaMnAs periodically covered with nanowires of GaAs was prepared. X-ray diffraction is very suitable experimental method to differ between substitutional and interstitial Mn.
Reciprocal space maps of a GaMnAs sample were measured for two subsequent time phases of the annealing. To approve supposed model of Mn interstitial outdiffusion, time dependent drift-diffusion equations were solved by FEM.
Then a strain field, based on Mn interstitial concentration profiles in subsequent time steps of the simulation, was computed as well by FEM. Reciprocal space maps of the strain GaMnAs lattice were carried out and compared with the experimental ones.
Diffusion constant and surface recombination rate were yielded by fitting experimental and theoretical reciprocal space maps together. However, we obtained different values of the constant for each phase of the annealing.
In spite of this fact, we got some estimate of these values, which can be useful. Additionally, we suggested a way to improve the model of the surface recombination.