Optical properties of tensile-strained and relaxed Ge films grown on InGaAs buffer

Abstract

GeO2/Ge/InxGa1−xAs heterostructures grown on (100) GaAs substrates were studied using Raman spectroscopy and photoluminescence (PL) spectroscopy. Both nearly pseudomorphic tensile-strained and nearly completely relaxed Ge films were grown and studied. The maximum tensile strain for Ge films with a thickness of ≈7 nm reaches 2.25%. PL data confirm the conclusions that the band gap offset of Ge/InxGa1−xAs is sensitive to the polarity of the bonds at the interface, and also to a parameter of x and the relaxation of strain. Depending on these parameters, the Ge/InxGa1−xAs may be type-I or type-II heterostructures.