Origin and annealing of deep-level defects in p-type GaAs/Ga(As,N)/GaAs heterostructures grown by molecular beam epitaxy

Deep-level defects in p-type GaAs/Ga(As,N)/GaAs heterostructures grown by m olecular beam epitaxy are investigated by deep-level transient Fourier spec troscopy. Depth-resolved distributions of hole traps are measured in as-gro wn and annealed heterojunctions in order to identify the defects, which lea d to the degradation of the Ga(As,N) properties. Four defects are recognize d in the heterostructures studied. Two dominant hole traps are found in Ga( As,N) at energies of about 0.35 and 0.45 eV above the valence band edge. Th ese midgap levels originate from copper- and iron-related defects, the form ation of which is connected with operation of the nitrogen plasma cell duri ng Ga(As,N) growth. Both traps, which are removed by annealing, are discuss ed as the possible nonradiative centers that deteriorate the optical proper ties. Two other hole traps of intrinsic origin are related to the GaAs grow th conditions close to the Ga(As,N)-on-GaAs interface, where the GaAs growt h is affected by the nitrogen plasma despite a closed shutter. As far as el ectronic levels in the lower half of the band gap are concerned, the Ga(As, N) layers and GaAs-on-Ga(As,N) interfaces become practically defect free af ter rapid thermal annealing. (C) 2001 American Institute of Physics.