Origin and suppression of V-shaped defects in the capping of self-assembled In As quantum dots on graded Si_(1-x)Ge_x/Si substrate

摘要

Self-assembled InAs quantum dots (QDs) on graded Si_(1-x)Ge_x/Si substrate were observed to adopt a truncated pyramidal shape when capped with GaAs. Our results suggest that atomic migration from the QD apex to the GaAs cap layer contributes to the formation of the symmetrical V-shaped defects near the top edges of the truncated pyramidal QDs. By employing an In_(0.1)Ga_(0.9)As cap, material migration and strain around the QDs were reduced, hence suppressing the occurrence of the V-shaped defects. Furthermore, photoluminescence thermal quenching rate of the QDs is significantly slower compared to the QDs with GaAs cap. Finally, 1.3 μm room-temperature photoluminescence was observed.