Atomic H-mediated (Si 14/Ge 1) 20 superlattice buffers for the growth of Si 0.75Ge 0.25 alloy layers with low residual strain

Abstract

We report on the growth of high-quality 2000-Å-thick Si 0.75Ge 0.25 alloy layers using short-period (Si 14/Ge 1) 20 superlattice (SSL) buffer with atomic H exposure. H exposure has been used to decrease the segregation of Ge in the SSL layers. The buffer layers were grown at different temperatures from 300 to 400 °C, and the Si 0.75Ge 0.25 alloy layers were then grown at 500 °C on the top of the buffer layers. From the XRD data, it can be seen that the residual strain of the alloy layers decreases as the growth temperature of the buffers increases. The root-mean-squared (rms) surface roughness estimated from the AFM images showed a decreasing trend as the growth temperature of the SSL buffer layers decreased. The SSL layer grown at 350 °C with H exposure is found to be effective for the growth of strain relaxed and smooth Si 0.75Ge 0.25 alloy layers.