Scanning transmission-electron microscopy study of InAs/GaAs quantum dots

We present results obtained from a scanning transmission-electron microscopy study of InAs/GaAs quantum dot (QD) layers. It is shown that the QD’s are embedded within an ${\mathrm{In}}_x{\mathrm{Ga}}_{1-x}\mathrm{As}$ confining layer following overgrowth with GaAs. Using energy dispersive x-ray analysis (EDX) the QD dimensions can be measured with reasonable accuracy and are not affected by strain contrast. In QD bilayers where the dots are uncorrelated along the growth direction, a comparison of the indium EDX signals from the confining layer and a dot allow us to estimate the compositions of these regions as ${\mathrm{In}}_{0.07}{\mathrm{Ga}}_{0.93}\mathrm{As}$ and ${\mathrm{In}}_{0.31}{\mathrm{Ga}}_{0.69}\mathrm{As},$ respectively.