Raman spectroscopy investigation of strain evolution in relaxed and pseudomorphic layers of Si_0.4Ge_0.6 films grown on (001) Si substrates

Abstract In this study, the laminated strain of relaxed and the pseudomorphic layer in the Si 0.4 Ge 0.6 films grown on (001) Si substrates are studied by Raman spectroscopy. With the SiGe films ranging from 20 nm to 1200 nm in thickness, biaxial strains are revealed through room-temperature Raman peak analysis. Notably, a highly strained layer named the pseudomorphic layer is observed in the 30 nm sample. The peak broadening induced by the scattering of phonons at the thickness of 30 nm suggests dense dislocations at the substrate-pseudomorphic layer interface. The study also finds that the relaxed layer has a much more dramatic relaxation compared to that of the pseudomorphic layer, while the pseudomorphic layer maintains a high degree of strain. These findings contribute to the understanding of the SiGe alloy growth, enhancing the fabrication of intricate SiGe-based devices with improved strain control and relaxation dynamics.