Anneal Behavior of Aluminum-Implanted Germanium

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Abstract
P-Type single crystal germanium is implanted with 1.5×1015 aluminum ions/cm2 at room temperature at 10 keV. Carrier distributions are determined by means of anodic stripping of thin layer combined with Hall effect and sheet resistivity measurements. Anneal behavior of crystalline states is investigated by the observation of implanted surface using reflection electron-diffraction technique after succesive stripping of surface layer. It is found that some of the incident ions penetrate to about 1400 Å during room temperature implantation beyond the range predicted by LSS theory. The minority of deeply penetrated aluminum occupies the substitutional sites and becomes acceptors, while the majority remains electrically inactive. The lattice reordering takes place at 300–400°C but does not remarkably contribute to the increase in carrier concentration. Carrier concentrations increase remarkably after the anneals at 500–600°C by the transition of aluminum atoms to the substitutional sites from the as-implanted inactive sites. Radiation enhanced diffusion of aluminum as observed in silicon is not observed in germanium.