Temperature dependence of ion-beam mixing in crystalline and amorphous germanium isotope multilayer structures

The renewed interest in Germanium as base material for electronic applications has stimulated extensive experimental and theoretical studies. Successful integration of Ge in nanoelectronic devices requires fundamental understanding of ion-implantation-induced target modification and damage. In this contribution the temperature dependence of ion-beam mixing induced by 310 keV gallium (Ga) ion implantation in crystalline and preamorphized germanium (Ge) is reported. Isotopically enriched multilayer structures of alternating 70Ge and natGe layers are used to visualize the self-atom mixing. The distribution of the implanted Ga atoms and the ion-beam induced self-atom mixing was determined by means of secondary ion mass spectrometry. Different temperature regimes of self-atom mixing are observed. At temperatures up to 423 K the mixing is independent of the initial structure whereas at 523 K the intermixing of the preamorphized Ge structure is about twice as high as that of the crystalline material. At 623 K the intermixing of the initially amorphous Ge structure is strongly reduced and approaches the mixing of the crystalline material. The temperature dependence of ion-beam mixing is consistently described by competitive amorphization and recrystallization processes.