Electrical study of InAs/GaAs quantum dots with two different environments

Abstract

Unusually complex spectra have been obtained for InAs/GaAs quantum dot (QD) structures when studied as a function of applied bias by deep level transient spectroscopy (DLTS). In spite of their complexity, basic processes for electron escape from the QDs have been recognized. We show that due to the variety of transitions involving direct tunneling and more complex thermal transitions, due to QD size fluctuations, and environmental dependent QD carrier population, measurement conditions have to be carefully suited for characterizing transport properties of the QDs. Additionally, on the basis of results of a comparative study under chosen measurement conditions, we conclude that the states of the InAs QDs shift towards the middle of the energy gap if the QDs are capped with a Ga‐rich InGaAs insertion. It explains a red‐shift of the emission wavelength that was found by photoluminescence measurements (PL). (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)