Rapid ion-implantation-induced amorphization of Inx Ga1-x As relative to InAs and GaAs

We report on the rapid implantation-induced amorphization of the ternary Inx Ga1-x As alloys. Unlike Alx Ga1-x As, Inx Ga1-x As did not exhibit amorphization kinetics intermediate between the two binary-alloy extremes. Instead, our investigation of the crystalline-to-amorphous phase transformation over the entire stoichiometry (x) range demonstrated that Inx Ga1-x As alloys with x=∼0.06-0.53 were rendered amorphous at fluences less than that required for both InAs and GaAs. Implantation-induced disorder was quantified with Rutherford backscattering spectroscopy in the channeling configuration and fit to the Hecking model to yield the probabilities of direct-impact and stimulated amorphizations. The phase transformation was dominated by stimulated amorphization, which was a maximum at the stoichiometry (x=∼0.34) most easily amorphized, while the probability of direct-impact amorphization was effectively stoichiometry independent. From extended x-ray-absorption fine-structure spectroscopy measurements of unimplanted Inx Ga1-x As alloys, separate stoichiometry-dependent In-As and Ga-As bond lengths were measured. Distortion in both the bond-length and bond-angle distributions was apparent though structural perturbation was primarily accommodated in the latter as consistent with measured deviations from the tetrahedral bond angle. We attribute the relative ease with which the Inx Ga1-x As alloys were amorphized to the presence of localized regions of strain due to structural distortion. Equivalently, atomistic configurations comprised of strained bond lengths and bond angles represent pre-existing and preferential sites for stimulated amorphization. To demonstrate the general applicability of our model, we report on preliminary measurements with the Inx Ga1-x P alloys which also exhibit a bimodal bond-length distribution and distortion in the bond-angle distribution. Comparable amorphization behavior to that of the Inx Ga1-x As alloys has been observed.