Spins of resident electrons in charged quantum dots ͑QD's͒ act as local magnets inducing the Zeeman splitting of excitons trapped into dots. This is evidenced by the observation of quantum beats in the linearly polarized time-resolved photoluminescence of a biased array of self-assembled InP QD's. An external magnetic field is found to shorten the spin beats' decay time keeping constant the frequency of the beats. A model using the pseudospin formalism allows one to attribute the observed quantum beats to the radiative decay of hot trions having two electrons that occupy different energy levels in a QD.

The paper reports on quantum beats observed in the photoluminescence kinetics of a single layer of the InP self-assembled quantum dots in a magnetic field. It is found that the beats arise only after removal of excess charges from the quantum dots by an external electrical bias. The quantum beats are shown to be related to the interference of the excitonic fine-structure states split by the magnetic-field. The dependences of the beat characteristics on the magnetic-field strength and orientation are studied. Theoretical analysis based on a model spin Hamiltonian has allowed us to describe adequately the shape of the oscillating component of the signal. We have determined the values of the electron g-factor components and estimated the spread and the mean value of the hole g factor, as well as of the electron-hole exchange splitting parameters.

Phonon resonances observed in the photoluminescence ͑PL͒ spectra of InP and In 0.35 Ga 0.65 As selfassembled quantum dots ͑QD's͒ in an external electric field are studied in detail. The resonances are shown to arise from fast phonon-assisted relaxation of hot carriers, and to become observable when the PL is quenched by nonradiative losses from excited states. A simple model is developed that considers tunneling of the carriers from the QD's into the barrier layer as the main process responsible for PL quenching in the presence of an electric field. From this model, the depth of the potential well for holes is estimated to be 10-20 meV for the InP QD's. The PL kinetics measurement is performed with a time resolution of 6 ps. Clear evidence of surprisingly fast carrier relaxation with emission of high-energy acoustic phonons is found. Further acceleration of the carrier relaxation is observed under strong optical pumping. We consider this effect to be caused by Auger-like carrier-carrier scattering processes. Acceleration of the relaxation observed at elevated temperatures is ascribed to stimulated phonon emission.