The optical absorption edge of nanocrystallineGa1−xMnxN films deposited by reactive sputtering

Abstract

We have focused on the optical absorption edge of nanocrystallineGa1−xMnxN (0.00≤x≤0.18) films deposited by reactive RF magnetron sputtering. The films obtained are nanocrystallinewith grain sizes of about 25 nm, having wurtzite structure and strong orientation texture in thec-axis direction. The optical characterizations of the absorption edges were obtained in the190–2600 nm spectral range. The increase of the Mn content causes an increase ofthe absorption coefficient which can be clearly noticed at low energies, and aquasi-linear decrease of the optical gap. Broad absorption bands observed around∼1.3 and ∼2.2 eV were associated with transitions between the Mn acceptor level and the valence andconduction bands, respectively. The observed changes in the optical properties due to theMn incorporation observed in these nanocrystalline films are similar to those reported forferromagnetic GaMnN single-crystal films.