Extremely Low Density InAs Quantum Dots with No Wetting Layer

Extremely low density InAs quantum dots (QDs) are grown by molecular
beam droplet epitaxy. The gallium deposition amount is optimized to
saturate exactly the excess arsenic atoms present on the GaAs substrate
surface during growth, and low density InAs/GaAs QDs (4×10⁶cm ^-2) are formed by depositing 0.65 monolayers (MLs) of indium. This is much less than the critical deposition thickness (1.7ML), which is necessary to form InAs/GaAs QDs with the conventional Stranski--Krastanov growth mode. The narrow
photoluminescence linewidth of about 24meV is insensitive to cryostat
temperatures from 10K to 250K. All measurements indicate that there is
no wetting layer connecting the QDs.