Magnetoluminescence Study of Annealing Effects on the Electronic Structure of Self-organized InGaAs/GaAs Quantum Dots

We have studied the effects of annealing a self-organized InGaAs/GaAs quantum dot sample between 580 and 700°C by magnetoluminescence measurements at 2 K and fields up to 15 T. High-excitation power density luminescence spectra reveal up to three features in addition to the ground-state emission arising from radiative recombination processes between excited states of the quantum dots. With increasing annealing temperature all emission lines shift to higher energies while varying their splittings indicating a systematic increase in volume and Ga content of the dots. From the diamagnetic shift and the Zeeman splitting of the ground-state emission we obtain an increase of the spatial extent of the exciton wave function but a decrease of the effective g-factor upon annealing. The magnetic field splittings of excited-state transitions exhibit a strong dependence on annealing and are well accounted for within a simple oscillator model with total angular momentum mainly determined by the dot envelope functions.