Influence of Precursor Gas on SiGe Epitaxial Material Quality in Terms of Structural and Electrical Defects

We have investigated the structural and electrical properties of n-type doped Si1− x Ge x epitaxial layers (x = 24–26%) grown by chemical vapor deposition with conventional [SiH2Cl2 (DCS)/GeH4] and high-order (Si2H6/Ge2H6) precursor combinations. X-ray diffraction, atomic force microscopy, and deep-level transient spectroscopy (DLTS) measurements were performed for characterization. The crystalline properties and surface morphology of the Si1− x Ge x layer with Si2H6/Ge2H6 grown at temperatures as low as 550 °C show good structural quality similar to that with DCS/GeH4 grown at 615 °C. On the other hand, in terms of electrical properties, the DLTS measurement reveals the existence of vacancy-related complexes in the as-grown layer with Si2H6/Ge2H6. We found that post-deposition annealing at 200 °C for the Si1− x Ge x epitaxial layer is effective for annihilating vacancy-related defects with densities down to as low as that of conventional precursors.