摘要
The precipitation of arsenic in InGaAs/GaAs and GaAs/AlGaAs multiple-quantum-well (MQW) structures grown by molecular-beam epitaxy at 230 °C has been studied by transmission electron microscopy. For InGaAs/GaAs MQWs with strained InGaAs wells, upon annealing at 500 and 600 °C, arsenic precipitates tend to be completely confined in InGaAs wells near the InGaAs/GaAs interfaces, resulting in dual two-dimensional planes of precipitates in each InGaAs well. In contrast, this strong confinement of precipitates does not exist in InGaAs/GaAs MQWs with partially or totally strain-relieved InGaAs wells and in unstrained AlGaAs/GaAs MQWs. The present results suggest that the As precipitation process in strained GaAs-based MQWs is not only driven by the bond strength in different materials, but also by the lattice-mismatch-induced strain. © 2006 IOP Publishing Ltd.