We report continuous wave and time resolved photoluminescence studies of
self-assembled InP quantum dots grown by metalorganic chemical vapor
deposition. The quantum dots are embedded into indirect band-gap
In0.5Al0.5P layers or In0.5Al0.3Ga0.2P layers with
a conduction band line-up close to the direct-to-indirect crossover. As
revealed by photoluminescence spectra, efficient interdiffusion of species
from the barrier layers produces (Al,In)P or (Al,Ga,In)P-dots. This
interdiffusion creates potential barriers that are repulsive for electrons
of X valleys around the QDs. Both samples show a fast exponential decay
component with a time constant between 0.5 and 0.7 ns. In addition, the
sample with indirect band gap matrix shows a slow non-exponential
time-decay, which is still visible after more than 100 µs. The fast
component is attributed to direct recombination of electron-hole pairs in
the dots whilst the slow component, which follows a power law t−0.75
results from recombination of holes in the dots and electrons in metastable
states around the dots.