Multiple quantum wells with ultrathin high-Sn fraction GeSn layers: Structural and optical properties

The conditions of the formation of GeSn/Si multiple quantum wells (MQWs), including ultrathin GeSn layers with the Sn content of up to 47 %, were determined using the molecular beam epitaxy technique. The photoluminescence (PL) properties of GeSn/Si MQWs were studied in the near-infrared range. The analysis of the band diagrams of the GeSn/Si heterostructure, as well as the results of measuring the PL spectra of the Ge 0.53 Sn 0.47 /Si MQWs at different excitation densities, confirmed the formation of a type-II heterostructure. It was found that the decrease of the GeSn deposition temperature and the GeSn layer thickness leads to the increase of the PL signal associated with interband optical transitions. In addition, the significant decrease of the PL associated with vacancy complexes is observed compared to the signal from interband transitions. It was demonstrated that the most intense PL signal is observed from structures with the smallest thickness of GeSn layers of about 1 monolayer. Temperature-dependent PL studies for GeSn/Si MQWs were carried out and the activation energies of the processes leading to the temperature quenching of PL intensities were determined.