STRAIN-INDUCED QUANTUM DOTS - FABRICATION AND OPTICAL-PROPERTIES

High quality quantum dots have been fabricated by using self-organized InP islands as stressors. The tensile strain due the islands creates local potential minima in an InGaAs/GaAs quantum well under the island s, and confines both electrons and holes into these minima. The ground state emission from the dots is redshifted by up to 105 meV from the quantum well emission due to this lateral confinement potential, and c learly resolved emission peaks are observed from the excited states. F rom the time-resolved photoluminescence measurements an interlevel rel axation time of 0.6 ns between the first excited state and the ground state and a radiative lifetime of 0.9 ns for the quantum dot ground st ate are obtained. Photoluminescence up-conversion measurements show su bpicosecond onset of the dot luminescence at high excitation densities , suggesting that Coulomb scattering is responsible for the fast captu re process. A large Zeeman splitting of the higher angular momentum st ates is observed in a magnetic field perpendicular to the sample surfa ce.