Enhanced Diffusion in Ion-Bombarded GaAs
Anomalously high penetrations of Zn in GaAs were obtained by room temperature and 80 °K ion bombardment of the sample surfaces prior to diffusion from a surface source. Boat-grown n-type GaAs of relatively high purity was irradiated with 1012 400 keV Xe-ions/cm2 either before or after evaporative deposit of a SiO2:Zn film from a low viscosity alcoholic solution. Photoluminescence measurements at He temperatures showed that the characteristic emission (1.490 eV) was degraded but not shifted in energy by the ion-bombardment. The samples were vacuum annealed at 500°C for two hours and the luminescence remeasured. Masked unimplanted portions of the samples luminesced at the same energy as before heat treatment, indicating negligible Zn diffusion in this region. The irradiated portions, however, luminesced at about 1.480 eV, which is typical for transitions at the Zn acceptor level for Zn substituting for Ga in the GaAs lattice. Furthermore, the half-width and the temperature dependence of this emission is the same as for Zn-melt-doped GaAs. Measurements of the Zn-luminescence, as material was removed by vibratory polishing, revealed little change in intensity with depth for the room-temperature implant but showed a well-defined peak in the intensity at about the Xe-ion projected range (~1000 A) for the 80°K implant. In both cases, the Zn-luminescence was replaced by host-lattice luminescence at a depth of 1.22–1.94µ The implied difference in defect distributions for the two implant temperatures is in agreement with the backscattering measurements of Vook and Picraux.
KeywordsFractional Change Depth Position Defect Species GaAs Lattice Disorder Distribution
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