Ellipsometric study of InAs wetting layer in InAs/GaAs quantum dots at the threshold of quantum dot formation

摘要

Using room temperature spectroscopic ellipsometry, we measured the pseudo-dielectric function of self-assembled InAs/GaAs quantum dots at the onset of quantum-dot nucleation in the spectral range from 0.8 to 6 eV. The nominal In coverage varied from 1 to 2.6 ML. In addition to the quantum-dot-related feature at 1.1 eV, we observed two high energy transitions near 1.34 and 1.38 eV which arose from the InAs wetting layer. These two high energy features merged in 1-ML-thick wetting layer. We fitted the dielectric function of InAs wetting layer in the visible range performing multilayer analysis, and found strong excitonic enhancement and blue shift of the E_(1) peak.