Temperature-dependent raman spectroscopy analysis of epitaxially grown Ge0.91Sn0.09 on GaAs (001) substrate

Abstract

We report on the epitaxial growth of Ge0.91Sn0.09 alloy epilayers on a GaAs (001) substrate by low-temperature molecular beam epitaxy. Temperature-dependent Raman measurements were used to investigate the behavior and stability of Sn in Ge1–xSnx grown on GaAs by examining the behavior of the longitudinal optical phonon modes originating from both the Ge1–xSnx epilayers and the GaAs substrate. The Raman data reveals improved crystalline quality and increased Sn content in the Ge1–xSnx epilayer as the temperature is increased from 100 to 580 K. However, at a temperature of about T = 620 K, the mobility and segregation of Sn in the Ge1–xSnx epilayers dramatically increases. This behavior is similar to reports of Sn mobility and potential segregation from Ge1–xSnx grown on both Ge and Si substrates, despite differences in atom chemistry between Ge1–xSnx and the different substrates. Likely, the transition temperature for which Sn becomes mobile in Ge1–xSnx is dominated by its dependence on the bonding between Ge and Sn and level of strain in the Ge matrix.