Ultrathin low temperature SiGe buffer for the growth of high quality Ge epilayer on Si(100) by ultrahigh vacuum chemical vapor deposition

The authors report a method to grow high quality strain-relaxed Ge on a combination of low-temperature Ge seed layer on low temperature ultrathin ${\mathrm{Si}}_{0.8}{\mathrm{Ge}}_{0.2}$ buffer with thickness of $27.3\mathrm{nm}$ by ultrahigh vacuum/chemical-vapor-deposition method without the need to use chemical mechanical polish or high temperature annealing. On $8\mathrm{in.}$ Si wafer, the etch-pit density was $6\times {10}^6{\mathrm{cm}}^{-2}$ . The root-mean-square surface roughnesses of Ge epitaxy by atomic force microscopy were 1.4 and $1.2\mathrm{nm}$ for bulk Si and silicon-on-insulator substrates, respectively. Micro-Raman spectroscopy shows extremely uniform distribution of residual strain in the overgrown Ge epitaxy on $8\mathrm{in.}$ wafers.