Interfacial damage in ion-irradiated GaAs/AlAs superlattices

Damage creation at GaAs/AlAs/GaAs interfaces during irradiation with MeV Kr and Ar ions was investigated by ion channeling experiments. The GaAs layers became amorphous while the AlAs layers showed unusual damage behavior. At one interface, AlAs on GaAs, an amorphous phase grows into the AlAs while at the opposite interface, GaAs on AlAs, the AlAs remains crystalline. The asymmetry is also observed in samples with five alternating layers; amorphization occurs at the two AlAs on GaAs interfaces but not at the GaAs on AlAs interfaces. The rate at which the amorphous layer grows does not depend on the deposited damage energy alone, but rather depends on the ratio of the ionization to damage energies, demonstrating the importance of ionization in the damage process. At large ratios of ionization to damage energies, the growth rate can be zero or even negative.