Metal organic vapor phase epitaxy of hexagonal Ge-Sb-Te (GST)

Epitaxial, hexagonal Ge-Sb-Te was grown on Si(111) substrates by Metal Organic Vapor Phase Epitaxy (MOVPE) using the precursor digermane. The effect of reactor pressure, growth temperature and in situ pre-treatment on morphology and Ge-Sb-Te composition was studied. The composition is sensitive to reactor pressure and growth temperature. Compositional control is achieved at a reactor pressure of 50hPa. Substrate pre-treatment affects film coalescence. The use of hydrogen and a suitable precursor pre-treatment leads to enhanced surface coverage. X-ray diffraction reveals a trigonal structure with lattice parameters close to that reported for Ge1Sb2Te4 crystallizing in the R3¯m phase. The composition was confirmed by energy-dispersive X-ray spectroscopy.