Depth-Resolved Cathodoluminescence of Carbon Implanted Gallium Arsenide.
AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OHIO SCHOOL OF ENGINEERING
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Three samples of VPE GaAs grown on SI Cr compensated substrate were examined by depth resolved cathodoluminescence using electrom beam energies from 2.5 KeV to 15 KeV at 10 K and 39 K. The samples had been carbon-implanted, at a 120 KeV implant energy, with fluences of 10 to the 13th power, 10 to the 14th power and 10 to the 15th power carbon ionssq cm, respectively. The resulting cathodoluminescent spectra contained eight energy peaks an unresolved exciton peak at 1.514 eV, a conduction band-to-carbon acceptor peak at 1.494 eV, a carbon donor-to-carbon acceptor peak at 1.490 eV, a possible carbon-donor-to-zinc acceptor peak at 1.487 eV, two optical phonon peaks at 1.457 eV and 1.454 eV, an unresolved As vacancy complex at 1.408 eV, and, finally, an unresolved Ga vacancy complex or As Cu A complex at 1.361 eV. An attempt was made to observe impurity concentration dependent energy peak shifts, of the conduction band-to-carbon acceptor and the carbon donor-to-carbon acceptor energy peaks, which had been reported for carbon implanted bulk-grown GaAs and attributed to carbon impurity banding. The failure to observe energy peak shifts in the higher-purity VPE GaAs indicates that a more probable explanation for the peak shifts observed in the bulk-grown GaAs involves the use of a tunneling-assisted transition model.
- Solid State Physics