Metal organic chemical vapor deposition of GexSbyTez layers grown by using degermane

GexSbyTez (GST) films grown on Si(111) substrates by epitaxy tend to be polycrystalline and therefore rough. Especially the incorporation of Germanium in the films is problematic. Thin and smooth film surfaces are however a prerequisite for memory applications. In the past we demonstrated that the metal organic chemical vapor deposition (MOCVD) growth of highly mismatched III/V materials such as InAs/GaAs can be accomplished conformally, if a low temperature growth process is used. This knowledge is transferred to MOCVD growth of GST. To this end as a Ge precursor digermane was employed which is expected to decompose at low temperatures. Commercial sources for Sb (triethylantimony) and Te (diethyltellur) were chosen, which are suitable for low temperature deposition. At first the growth of Sb2Te3 layers was optimized. Than digermane was added to the growth process. Growth was evaluated by SEM, XRD and Raman measurements. It was found that GST can be deposited at the same conditions as Sb2Te3. SEM pictures show well coalesced, trigonal crystalline structures and XRD measurements verify the integration of Ge. The influence of growth parameters on layer growth is presented.