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 Si0.58Ge0.42 thin films grown on a combined set of Si1−xGex stepwise buffer layers and a Si0.51Ge0.49 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 Si0.58Ge0.42 thin film with a low dislocation density of less than 105cm−2 and a smooth surface roughness of 0.903nm can be achieved by using a combined set of Si1−xGex stepwise buffer layers and a Si0.51Ge0.49 strain-inverted layer, because most dislocations can be confined within each Si1−xGex buffer layer. ► fabricated strain-relaxed Si0.58Ge0.42 thin films grown with graded buffer layer by MBE. ► evaluated the material quality of Si0.58Ge0.42 films by Raman and RBS spectroscopies. ► SiGe films with graded buffer layer showed superior crystalline lattice ordering.