Heteroepitaxial Growth of Si[sub x]Ge[sub 1]−[sub x] Alloys by Thermal Decomposition of SiH[sub 4] and GeH[sub 4]

Abstract

Epitaxial layers of alloys have been grown on germanium substrates by the simultaneous thermal decomposition of and GeH4 in hydrogen. Growth was in the 800°°850°C temperature range at growth rates on the order of 0.1 µm/min for alloy epitaxy. Using the back‐reflection Laue method, the alloys were determined to be single crystal with the substrate orientation, while x‐ray diffractometer measurements indicated alloy compositions with x in the range . The defect density of lower Si concentration alloys ranged from 104 to 107 cm⁻². Hall measurements of alloy layers without intentional doping indicated p‐type alloy material with Hall (hole) mobility in the 250–400 cm2/V‐sec range at carrier concentrations of 2–5 × 1017 cm^–3 for 4–5 atomic per cent Si in the alloy. Current‐voltage characteristics of p‐n heterojunctions formed between alloy and substrate were found to be rectifying while p‐p heterojunctions were weakly rectifying. A frequency dependence of the junction capacitance was observed which presumably is a result of defect states at the interface between the substrate and alloy.