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 Si0.8Ge0.2 buffer with thickness of 27.3nm by ultrahigh vacuum/chemical-vapor-deposition method without the need to use chemical mechanical polish or high temperature annealing. On 8in. Si wafer, the etch-pit density was 6×106cm−2. The root-mean-square surface roughnesses of Ge epitaxy by atomic force microscopy were 1.4 and 1.2nm 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 8in. wafers.