Critical Ge concentration for 2× n reconstruction appearing on GeSi covered Si(100)

• Published in: Surface science 1998-05, Vol.406 (1), p.L592-L596
• Main Authors: Guo, L.W, Huang, Q, Li, Y.K, Ma, S.L, Peng, C.S, Zhou, J.M
• Format: Article
• Language: English
• Subjects: Composition; defects and impurities; Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Physics; RHEED; Solid surfaces and solid-solid interfaces; Surface relaxation and reconstruction; Surface segregation; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties)
• ISSN: 0039-6028; 1879-2758
• DOI: 10.1016/S0039-6028(98)00234-9

Using reflection high-energy electron diffraction (RHEED), we monitored in situ the appearing of 2× n reconstruction with different Ge compositions of GeSi alloys deposition, at growth temperature 600°C. A relation between the thickness and Ge composition has been determined. To understand the relation, we perform a Ge segregation simulation using the two-state exchange kinetic model. As the Ge concentration in the top layer reaches about 0.8 for all Ge compositions, due to Ge segregation, the 2× n reconstruction begins to appear to release the accumulated misfit strain. For a GeSi alloy with very low Ge composition, such as Ge 0.05Si 0.95 alloy, there is no 2× n reconstruction shown even when the deposited GeSi alloy film thickness exceeds its critical thickness, because the saturated Ge concentration of the top layer in such alloys is lower than 0.8.