We investigate the thermal quenching of the multimodal photoluminescence from InAs/InP (001) self-assembled quantum dots. The temperature evolution of the photoluminescence spectra of two samples is followed from 10 K to 300 K. We develop a coupled rate-equation model that includes the effect of carrier thermal escape from a quantum dot to the wetting layer and to the InP matrix, followed by transport, recapture or non-radiative recombination. Our model reproduces the temperature dependence of the emission of each family of quantum dots with a single set of parameters. We find that the main escape mechanism of the carriers confined in the quantum dots is through thermal emission to the wetting layer. The activation energy for this process is found to be close to one-half the energy difference between that of a given family of quantum dots and that of the wetting layer as measured by photoluminescence excitation experiments. This indicates that electron and holes exit the InAs quantum dots as correlated pairs.

We have studied the optical properties of ultrathin InAs/InP quantum wells and Stranski-Krastanov nanostructures using photoluminescence and photoluminescence excitation experiments. For InAs epilayers thinner than 2.4 monolayers, the emission spectrum consists of a single peak and the ground-state exciton energy is in good agreement with predictions based on the tight-binding method for ultrathin quantum wells. Beyond this thickness, the photoluminescence spectra evolve to a multimodal emission indicative of the presence of families of quantum dots with small heights. The emission of these quantum dots is blue-shifted significantly (∼100 meV) from the predicted values. The discrepancy is explained by As/P intermixing that occurs during quantum dot formation.

No abstract