Rutherford backscattering spectrometry in combination with channeling has been used to compare the ionirradiation-induced amorphisation of In 0.53 Ga 0.47 As with that of InAs and GaAs. In contrast to the well-known behaviour of Al x Ga 1Γx As, the ternary alloy In 0.53 Ga 0.47 As did not exhibit amorphisation kinetics intermediate between those of the two binary extremes. Specifically, the critical nuclear energy deposition required to render In 0.53 Ga 0.47 As amorphous was less than that of both InAs and GaAs for irradiation temperatures of Γ196 C and 23 C. This rapid amorphisation resulted from a greater probability for direct-impact amorphisation in the ternary alloy. We suggest irradiation-induced defect clusters or amorphous nuclei in In 0.53 Ga 0.47 As serve as a means of relieving strain and accordingly exhibit enhanced stability. Such strain is present in the ternary alloy, at the atomic scale, due to the significant differences in In-As and Ga-As bond lengths and the random ordering of In and Ga on the Group III sublattice and is manifested by a broadening of the bond length and bond angle distributions.