Abstract
Deep-level defects in p-type GaAs/Ga(As,N)/GaAs heterostructures grown by molecular beam epitaxy are investigated by deep-level transient Fourier spectroscopy. Depth-resolved distributions of hole traps are measured in as-grown and annealed heterojunctions in order to identify the defects, which lead to the degradation of the Ga(As,N) properties. Four defects are recognized 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. These midgap levels originate from copper- and iron-related defects, the formation of which is connected with operation of the nitrogen plasma cell during Ga(As,N) growth. Both traps, which are removed by annealing, are discussed as the possible nonradiative centers that deteriorate the optical properties. Two other hole traps of intrinsic origin are related to the GaAs growth conditions close to the Ga(As,N)-on-GaAs interface, where the GaAs growth is affected by the nitrogen plasma despite a closed shutter. As far as electronic 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 after rapid thermal annealing.
Published Version
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