Rutherford backscattering studies of strain-relaxed SiGe films grown on Si substrate with compositionally graded buffer layers

We investigated the structural properties of 2-μm thick Si 0.58 Ge 0.42 thin films grown on a combined set of Si 1− x Ge x stepwise buffer layers and a Si 0.51 Ge 0.49 strain-inverted layer on Si substrates. Raman spectroscopy and Rutherford backscattering measurements showed smaller residual strain and superior crystalline lattice ordering compared to a sample without any buffer layer. Furthermore, a Si 0.58 Ge 0.42 thin film with a low dislocation density of less than 10 5 cm −2 and a smooth surface roughness of 0.903 nm can be achieved by using a combined set of Si 1− x Ge x stepwise buffer layers and a Si 0.51 Ge 0.49 strain-inverted layer, because most dislocations can be confined within each Si 1− x Ge x buffer layer.