MOCVD Growth And Characterization Of InAs/GaAs Quantum Dots Under High Ⅴ/Ⅲ

Self-assembled InAs/GaAs quantum dots(QDs) have received much attention due totheir three dimensional carrier confinement thus having potential and application prospectsfor novel optoelectronic device like quantum dot solar cells, quantum dot detector andquantum dot lasers. Strained-layer epitaxy has evolved to the most effective way forfabricating QDs. While the self-assembled growth of QDs has by molecular beamepitaxy(MBE) has made great progress, it is still challenging by metal organic chemicalvapor deposition(MOCVD) due to more complicated and less controllable growthmechanism in MOCVD system. However, QDs grown by MOCVD is particularly importantfor QDs devices application. This thesis focuses on the research of InAs/GaAs quantum dotsgrown under a high Ⅴ/Ⅲ ratio via MOCVD. Specific research contents are listed asfollows:The effects of Ⅴ/Ⅲ on the morphology of InAs/GaAs QDs were investigated. Resultsshow that the morphology of InAs QDs can be manipulated by the variation of Ⅴ/Ⅲ.Keeping Ⅴ/Ⅲ=1000, the effects of other growth parameters on the morphology ofInAs QDs were studied. The results show that:①InAs clusters tend to appear as thetemperature is too high or too low. At a proper growth temperature, the migration length ofIn atom is proper for the formation of uniform QDs.②With a longer growth time, InAsclusters appear due to the Ostwald ripen effect.③The growth interruption time affect theQDs morphology by affecting the atoms migration length. When the time is too short, bigdots have not yet decomposed into small point thus making the final quantum dots too large,poor uniformity. While with a long interruption time, the quantum dots prefer gathering dueto the Ostwald ripen effect, leading to a poor morphology.④An arsenic hydride conditionduring the cooling period effects the morphology of quantum dots by promoting dots gatherthemselves together. Without AsH3protection condition, uniform QDs are acquired. Theresearch on these process parameters under the condition of high Ⅴ/Ⅲ has a vitalsignificance.