The role of strain in the crystallisation of Ge implanted (100) Si

Abstract

The effect of strain on the epitaxial crystallisation of Ge implanted (100) Si has been investigated. Crystallisation kinetics were monitored using in situ time-resolved reflectivity (TRR), whilst post-anneal defect distributions were measured by Rutherford backscattering and channelling spectrometry (RBS-C) and transmission electron microscopy (TEM). It is shown that for fluences above a critical value strain-relaxation occurs during crystallisation at a depth determined by the Ge fluence. Strain relaxation is accompanied or preceded by a roughening of the crystalline/amorphous interface and a reduction in the crystallisation velocity. Continued crystallisation in the strain-relaxed material then leads to a reduction in interface roughness and an increase in velocity, suggesting a correlation between strain and interface roughness. Preliminary results are also reported for ion-beam-annealed alloy layers. For thin alloy layers, ≤ 100 nm, ion-beam induced epitaxial crystallisation (IBIEC) is shown to produce epitaxial alloy layers of high crystalline quality, however, for thick GeSi alloy layers, ≥ 800 nm, IBIEC competes with ion-beam induced random crystallisation.