Cathodoluminescence studies of anomalous ion implantation defect introduction in CdTe

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Abstract
Shallow 100‐keV Xe+ ion implantations in CdTe are shown to introduce at least two species of 300 K‐stable defect complexes to depths of at least several thousand angstroms beyond the calculated projected ion range. The predominant defect species, which is nonradiative in the range 1–1.6 eV, produces severe quenching of the native 1.4‐eV cathodoluminescence excited from micron depths. Measurements of the injection level dependence of the quenched 1.4‐eV luminescence show that the quenching occurs primarily through the introduction of additional recombination centers rather than through the annihilation of native luminescence centers. Another defect species gives rise to an implantation‐induced band near 1.2 eV. The 1.2‐eV defects are more localized than the quenching defects and appear to be concentrated primarily at depths of several thousand angstroms beyond the projected ion range. Our experiments, which were performed on Te‐rich donor‐compensated CdTe, show that the anomalous defect introduction is sensitive to whether the donor doping is present on the Cd sublattice or on the Te sublattice. In comparison to Cl‐doped material, In‐doped material shows less quenching and a stronger 1.2‐eV band. We also find that the production of 300 K‐stable quenching centers is enhanced by implanting at 80 rather than 300 K. We conclude that all our results implicate primarily Te vacancies in the anomalous deep introduction of both the quenching centers and the 1.2‐eV centers.