Low temperature growth of Ge 1 − xSn x buffer layers for tensile–strained Ge layers

Abstract

We have investigated the dependence of Sn precipitation and crystallinity of Ge 1 − x Sn x layers on the growth temperature. We also demonstrated a growth of a tensile–strained Ge layer on strain-relaxed Ge 1 − x Sn x buffer layers. In order to suppress Sn precipitation in Ge 1 − x Sn x layers and improve the crystalline quality, we strongly suggest that point defects have to be introduced by using low temperature growth MBE. The point defects effectively contribute to the lateral propagation of misfit dislocations at the Ge 1 − x Sn x /virtual Ge substrate. The point defects would be also effective to stabilize substitutional Sn atoms in Ge 1 − x Sn x layers due to the formation of Sn-vacancy pairs. As a result, Sn precipitation was suppressed in the Ge 1 − x Sn x layer by low temperature growth, and we realized the Ge 1 − x Sn x layer with a Sn content of 7.1%. We also achieved the formation of the Ge layer with a tensile–strain value of 0.71%.