Growth of multi-stacked InAs/GaNAs quantum dots grown with As2 source in atomic hydrogen-assisted molecular beam epitaxy

We have investigated the effect of using As2 source on the self-assembly process of 5 layer stacked InAs quantum dots (QDs) on GaAs(0 0 1) grown by atomic hydrogen-assisted molecular beam epitaxy. The deposition thickness of each QD layer was varied from 1.32 to 2.32 monolayers (MLs), and InAs QDs were embedded by a GaNAs strain-compensating layer (SCL). By using As2, high-density QDs with higher aspect ratio were formed during the stage of QD formation. A mono-modal size distribution with size fluctuation in diameter of 9.2% was obtained for As2 sample, which was better than that of 13.6% obtained for As4 sample. On the other, As4 sample showed a bimodal size distribution in the initial stage of QD formation. The size distribution gradually improved with increasing InAs deposition and eventually saturated to become larger QDs with a mono-modal size distribution for As4 sample. The saturated QDs exhibited almost the same PL properties emitting at around 1100 nm with a narrow linewidth of 40 meV at 77 K for both As2 and As4 samples.