Scanning transmission electron microscopy (STEM) study of InAs/GaAs quantum dots

Scanning transmission electron microscopy (STEM) and energy dispersive X-ra y analysis (EDX) have been used to investigate the size and composition of InAs/GaAs quantum dot (QDs). It is shown that the QD exist within the wetti ng layer and not on it. In QD bilayers where the dots are uncorrelated alon g the growth direction a comparison of the indium EDX signals from the wett ing layer (WL) and a dot allow us to estimate the compositions of these reg ions as In0.07Ga0.93As and In0.31Ga0.69As respectively. We have used the ST EM technique to investigate the effects of annealing QDs in order to modify the emission energy. EDX measurements show that the dots increase in size by a factor of 2 for the longest anneals and there is a concomitant decreas e in the indium concentration resulting in blue shifts up to 300 meV and a narrowing of the linewidth to similar to 12 meV.