Cross-sectional STM study of InAs quantum dots for laser devices

Abstract

We present cross-sectional scanning tunnelling microscopy results of stacked InAs quantum dots embedded in GaAs grown by metal-organic chemical vapour deposition, for which room temperature lasing has been demonstrated recently. The fivefold stack shows a perfect vertical alignment and a layer-dependent dot shape, which is related to local strain during the growth process. For low tunnelling voltages, a corrugation mainly due to the different electronic structure of InAs dots and GaAs host is observed, while in the case of higher voltages the observed topographic elevations at the dot positions are more related to an outward relaxation of the strained dots at the cleavage surface. A numerical simulation of strain relaxation upon cleavage by theory of elasticity agrees well with the observed heights of protrusions. Copyright © 1999 John Wiley & Sons, Ltd.