Alloy splitting of the Fe_Ga acceptor level in dilute Al_xGa_1−xN

The results of conventional deep-level transient spectroscopy (DLTS) and high-resolution Laplace DLTS measurements of the Fe_Ga(0/−) acceptor level in dilute Al_xGa_1−xN layers (x ≤ 0.05) grown by MOVPE technique (metal-organic vapor phase epitaxy) on native ammono-GaN substrates are analyzed and discussed. It is shown that the electron emission signal related to the Fe_Ga acceptor level in Al_xGa_1−xN splits into individual components due to aluminum fluctuations in the second-nearest neighbor (2NN) shell around the Fe_Ga impurity atoms. The calculations of the probability of finding a given number of aluminum atoms in the 2NN shell of the Fe_Ga defect agree well with the experimental concentrations determined from Laplace DLTS peak intensities. This finding shows that in dilute Al_xGa_1−xN layers grown by MOVPE, aluminum and iron atoms are randomly distributed in the material. Finally, we demonstrate that the energy level of the Fe_Ga acceptor with no Al atoms in the 2NN shell in the Al_xGa_1−xN samples shifts linearly with the aluminum content and the shifts are 28 and 55 meV relative to that in GaN for the samples with x = 0.025 and 0.05, respectively.