Abstract
A detailed electrical measurement study has been carried out for Mg-implanted GaAs using plasma deposited Si 3N 4 capping, pyrolytic Si 3N 4 capping, and close-contact capless annealing techniques. Mg ions were implanted in Cr-doped semi-insulating GaAs at 120 keV with doses of 1 × 10 13 to 3 × 10 15/cm 2 at room temperature. The implanted samples were then annealed at temperatures from 600 to 900°C in flowing hydrogen gas. P-type layers werre produced at all dose levels. Maximum electrical activations occured at 750°C anneal for ion doses ⩾3 × 10 13/cm 2, and an activation efficiency of 100% was obtained for a dose of 3 × 10 13/cm 2 after capless annealing at 750°C for 30 min. The annealing characteristics of surface-carrier concentrations and mobilities obtained by the three capping/annealing methods generally agree for high doses, but there are considerable differences in dopant profiles. Electrical activation was also investigated as a function of annealing time at 750°C. Dopant profiles were very sensitive to ion dose, annealing temperature, and annealing times, and generally showed significant redistribution of Mg ions. Moreover, double-peak structures in the dopant profiles were observed for high doses, and a maximum carrier concentration of 2 × 10 19/cm 3 was obtained. The capless annealing method used in this study was successful and reproducible.
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