Magnetoluminescence of Annealed Self-Organized InGaAs/GaAs Quantum Dots

We have investigated the effects of annealing a self-assembled InGaAs/GaAs quantum dot sample between 580 and 700 C by magnetoluminescence measurements at 2 K and fields up to 15 T. By using a high power density of about 5 kW/cm2 for the excitation of the luminescence we were able to observe 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. The diamag-netic shift of the ground-state emission as well as the Zeeman splittings of excited-state transitions exhibit a strong dependence on annealing and clearly speak for an increase in volume and Ga content of the dots. In the past few years self-organized InGaAs/GaAs quantum dots (QDs) have been increasingly used as the active medium in semiconductor lasers because of their pecu-liar optical and electronic properties [1]. In particular, the zero-dimensional (0D) den-sity of states with its sharp peaks at the discrete energy levels, and the enhanced exci-tonic binding due to carrier confinement, largely contribute to improving the lasing performance of quantum dot structures [2]. Although the energy spectrum of a quan