In recent years, high-quality quantum dots (QD) have been fabricated using
self-organized island growth of strained layers, e.g., InAs on GaAs. In our
approach, self-organized InP islands are used as stressors on top of a nea
r-surface quantum well (QW), typically an InGaAs/GaAs QW. The strain held o
f the InP island causes a nearly parabolic lateral potential below the isla
nd. Vertical confinement is obtained by the QW potential. The QD structure
can be easily tailored by changing the QW composition and thickness, the di
stance of the QW from the InP stressor, or the size of the stressors by var
ying the growth temperature. Furthermore, coupled QDs and QD superlattices
have been fabricated by introducing two or more QWs into the structure. Nar
row linewidth QD ground and excited state transitions are obtained by low-t
emperature photoluminescence (PL). The experimental transition energies agr
ee well with the theoretical modeling based on the finite element method. T
ime-resolved luminescence experiments yield a radiative recombination time
of 0.9 ns and an interlevel relaxation time of 0.6 ns for the electrons, PL
up-conversion experiments show a fast rise time of similar to 1 ps for all
QD transitions, which suggests that Coulomb scattering is the dominant sca
ttering mechanism in the initial stage in agreement with the modeling. The
effect of magnetic held on the optical properties of the QDs has been studi
ed using a held up to 8 T; where a large Zeeman splitting of the excited QD
states has been observed in agreement with a single-particle model.