Anomalous Diffusion of Defects in Ion-Implanted GaAs

Abstract

Lattice disorder was studied in ion implanted GaAs as a function of implant and anneal temperature by proton channeling effect measurements. Nonchanneled 85 keV ¹⁶O⁺ implants were made near to the <111> axis into the A(Ga) or B(As) faces. No dependence of the lattice disorder production on the implant face was observed for implant temperatures between 87 and 296 °K. For implantations at 250 °K the lattice disorder production is ≈ 50% lower than that at 87 °K and agrees with the disorder remaining following anneal of an 87 °K implant to 250 °K. For implantations at 87 and 250 °K a disorder peak is formed at a depth which corresponds to the approximate ion range; the disorder grows linearly with ion fluence without a significant change in depth of lattice disorder. However, for low fluence implants at 275 and 296 °K the disorder peak moves to depths greater than the ion range with increasing fluence and broadens until no distinct peak can be resolved by 450 keV proton channeling. The disorder production also changes drastically from the linear dependence on ion fluence observed at ⩽ 250 °K to a nearly cube root dependence at 275 and 296 °K. The deep anomalous diffusion observed for implants at ⩾ 275°K is not observed when low temperature implants are annealed to 300 °K. This indicates that the defect or mechanism responsible for the anomalous diffusion during implantation at temperatures ⩾ 275°K is not present upon the anneal of low temperature implants to corresponding temperatures.

This work was supported by U.S. Atomic Energy Commission.