Quantum-confined photoluminescence from Ge_(1-x)Sn_x/Ge superlattices on Ge-buffered Si(001) substrates

摘要

We report the first observation of room-temperature quantum-confined photoluminescence (PL) from low-dimensional Ge_(1-x)Sn_x/Ge superlattices (SLs) up to a high Sn content of 6.96%. Both direct and indirect emissions associated with the interband transitions between minibands in the conduction bands and valence band were observed at room temperature. As the Sn content is increased, the energy difference between the lowest direct and indirect transitions is reduced, indicating an effective modification of the band structure desired for optoelectronics. The integrated PL intensity ratio of direct to indirect recombinations is significantly enhanced with increasing Sn content due to the reduced Γ-L energy separation and quantum confinement effect. Those results suggest that Sn-based low-dimensional structures are promising material for efficient Si-based lasers.