Fabrication of strained Ge film using a thin SiGe virtual substrate

Abstract

This paper describes a method using both reduced pressure chemical vapor deposition (RPCVD) and ultrahigh vacuum chemical vapor deposition (UHVCVD) to grow a thin compressively strained Ge film. As the first step, low temperature RPCVD was used to grow a fully relaxed SiGe virtual substrate layer at 500 °C with a thickness of 135 nm, surface roughness of 0.3 nm, and Ge content of 77%. Then, low temperature UHVCVD was used to grow a high quality strained pure Ge film on the SiGe virtual substrate at 300 °C with a thickness of 9 nm, surface roughness of 0.4 nm, and threading dislocation density of ∼ 105 cm−2. Finally, a very thin strained Si layer of 1.5–2 nm thickness was grown on the Ge layer at 550 °C for the purpose of passivation and protection. The whole epitaxial layer thickness is less than 150 nm. Due to the low growth temperature, the two-dimensional layer-by-layer growth mode dominates during the epitaxial process, which is a key factor for the growth of high quality strained Ge films.