FeGa (0/−) acceptor level as a reference energy level in dilute AlxGa1−xN

Laplace deep-level transient spectroscopy and photoluminescence have been used to demonstrate that the Fe _Ga (0/−) acceptor level in dilute Al _xGa _1−xN (x ≤ 0.063) can be considered as a common reference level as expected for energy levels of transition metals in isovalent semiconductor compounds. Furthermore, the conduction and valence band offsets (ΔE _C and ΔE _V, respectively) in GaN/Al _xGa _1−xN heterojunctions, as a function of Al content for samples grown by the metalorganic vapor-phase epitaxy technique on native Ammono-GaN substrates, have been found. The band-offsets determined in this study are ΔE _C = 1.17x eV and ΔE _V = −0.95x eV over the range of x studied and are in good agreement with other experimental results reported for actual GaN/Al _xGa _1−xN heterojunctions as well as with the recent theoretical calculations based on hybrid density functional theory. Moreover, we confirmed that the band bowing effect related to compositional dependence in Al _xGa _1−xN is accommodated practically only in the conduction band as suggested by theoretical calculations.