Optical study of InAs/GaAs quantum dots using spectroscopic ellipsometry

Abstract

Using spectroscopic ellipsometry, we measured the pseudo-dielectric function of self-assembled InAs/GaAs quantum dots at room temperature. We observed strong excitonic peak at 0.9 eV which was attributed to quantum dot transitions. We also observed a plateau from 1.2 eV to 1.4 eV which arose from step-like joint density of states originating from InAs wetting layer. Our room temperature data is very similar to the 1.8 K photoluminescence excitation spectra of InAs/GaAs quantum dots reported in literature. Higher-energy dielectric response of the quantum dots enabled us to estimate the morphology of the quantum dots using effective medium analysis. The result was compared to atomic force microscopy measurement results. Effective medium analysis showed that GaAs cap layer was preferentially grown on InAs wetting layer rather than on InAs islands.