Studies of Mn/GaAs digital alloys using x-ray absorption fine structure and x-ray diffraction methods

Local structure and effective chemical valency of Mn atoms in Mn/GaAs digital alloys have been investigated using the x-ray absorption fine structure techniques. The samples were prepared by molecular-beam epitaxy with different thickness of GaAs layers separating the nominal Mn monolayers. Lattice constants of the digital alloys are found by x-ray diffraction to increase linearly in a very narrow range (about 0.3%) with the Mn/GaAs ratio in the samples. Our data show that Mn atoms in the nominal Mn monolayers actually combine with GaAs to form (Ga,Mn)As alloys with Mn atoms substituting for the Ga sites in GaAs. This result clearly rules out the possibility of dominant MnAs formation.