Compositional dependence of electron traps in Ga(As,N) grown by molecular-beam epitaxy

Two predominant electron traps at about 0.80 and 1.1 eV above the valence band edge E-V are observed in Ga(As,N), which do not depend on composition. The gap level at E-V+1.1 eV is due to defects associated with nitrogen atoms on As sites (N-As). For more than 2.5% N, it is resonant with the conduction band. The level at E-V+0.80 eV is connected with nitrogen dimers, i.e., two N atoms on a single As site [(NN)(As)]. The dimer defect occurs at the growing Ga(As,N) surface and can be removed by rapid thermal annealing, in contrast to the stable N-As-related gap state in the bulk.