Indium segregation in (111)B GaAs-InxGa1-xAs quantum wells determined by transmission electron microscopy

We have used energy-filtered transmission electron microscopy combined with low-temperature photoluminescence to study the effects of indium segregation within (111)B oriented GaAs-InGaAs single quantum wells. The microscopy provides an accurate measure of the relative indium profile whilst the photoluminescence allows the determination of the absolute concentrations of indium. A thermodynamic model of the segregation process reproduced the main features of the distribution of indium in the quantum wells. We have also studied a single quantum well grown immediately following the deposition of an InAs monolayer, intended to compensate for the loss of indium by segregation. Both modelling and measurement show that the effect is merely to broaden significantly the resulting quantum well.