Extremely Low Density InAs Quantum Dots with No Wetting Layer

Abstract

Extremely low density InAs quantum dots (QDs) are grown by molecularbeam droplet epitaxy. The gallium deposition amount is optimized tosaturate exactly the excess arsenic atoms present on the GaAs substratesurface during growth, and low density InAs/GaAs QDs(4×106 cm−2) are formed by depositing 0.65 monolayers(MLs) of indium. This is much less than the critical depositionthickness (1.7 ML), which is necessary to form InAs/GaAs QDs with theconventional Stranski–Krastanov growth mode. The narrowphotoluminescence linewidth of about 24 meV is insensitive to cryostattemperatures from 10 K to 250 K. All measurements indicate that there isno wetting layer connecting the QDs.