The role of crystal-growth properties on silicon implant activation processes for GaAs

Crystal properties such as bulk resistivity, mobility, and dislocation density which influence ion-implantation activation are reported for liquid-encapsulated Czochralski, horizontal gradient freeze, and vertical gradient freeze semi-insulating GaAs crystals. The liquid-encapsulated Czochralski crystals used in this study include as-grown, boule-annealed, and indium-alloyed GaAs. Wafer maps displaying the concentration and spatial distribution of neutral EL2 are presented for each crystal. Wafers from the various crystals were implanted with 29Si at a dose of 3×1012 ions/cm2 and an energy of 60 keV. Macroscopic variations in the donor distribution and peak carrier density demonstrate that point defects impact significantly the donor implant activation processes.