Interstitial manganese in (Ga,Mn)As detected by electron paramagnetic resonance

Various types of Mn in epitaxially grown (Ga,Mn)As have been investigated. Ionized interstitial manganese donors MnI2+ have been found to occur in (Ga,Mn)As at dopant concentrations as low as 0.5%. A comparison with spectra from interstitial MnI2+ inside bulk-doped GaAs:Mn yields a slight decrease of 1.5% in the hyperfine splitting with increasing dopant concentration. This is attributed to an increase in the lattice constant of (Ga,Mn)As with increasing manganese concentration. Contrary to Mn interstitials, Mn dopants on Ga lattice sites acts as acceptors. It is shown that Mn on Ga lattice sites MnGa2+ is non-uniformly distributed. A low percentage of isolated Mn acceptors can be distinguished from the exchange broadened MnGa2+ signal. Thus, electron paramagnetic resonance is a promising tool for the investigation of (Ga,Mn)As and the classification of various types of Mn dopants responsible for the magnetic properties of (Ga,Mn)As.