Laser-induced integrated processing for heteroepitaxial SixGe(1−x) alloys

An integrated laser assisted process has been applied to prepare heteroepitaxial SixGe(1−x) alloys on Si(100) using the combination of laser induced chemical vapour deposition (LCVD) and pulsed laser induced epitaxy (PLIE). Both processes have been carried out with 193 nm radiation of an ArF excimer laser leading first to high quality amorphous hydrogenated germanium (a-Ge:H) thin films by LCVD and then to unstrained epitaxial SixGe(1−x) alloys by PLIE. The optimization for depositing homogeneous, low impurity a-Ge:H films has been followed by profilometry, Raman spectroscopy and X-ray diffraction (XRD). Subsequent melting and recrystallization by PLIE was studied by X-ray photoelectron spectroscopy (XPS) for analysing the distribution tail of the graded SixGe(1−x) alloys and conventional XRD analysis to determine the epitaxy of the relaxed, Ge-rich, SixGe(1−x) phase. The analyses evidenced the formation of thin unstrained epitaxial SixGe(1−x) layers, which can be used as buffer layers for the growth of symmetrically strained superlattices.