Damage gettering of Cr during the annealing of Cr and S implants in semi-insulating GaAs

Chromium depth distributions have been measured in Cr-doped GaAs as a function of annealing temperature from 650 to 850 °C under an SiO2 encapsulation for samples implanted with either S or Cr. Following a 650 °C/20-min anneal, the Cr is ’’gettered’’ into two regions of residual damage, one peaked at ∼0.85 Rp and one peaked at about Rp +1.5ΔRp and with integrated densities proportional to the implant fluences. As the anneal temperature is increased, the integrated densities of Cr under these two damage peaks and a third deeper one observed under S implants decrease exponentially following an Arrhenius-type mechanism with activation energies of approximately −1.8, −0.87, and −0.4 eV, respectively. These results are shown to be consistent with a simple thermodynamic model for the formation (association) of Cr defect complexes under the damage peaks. Theoretically estimated binding energies of the complexes are consistent with the experimental activation energies.