Dynamics of spontaneous and stimulated emissions in GaN-based semiconductors

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Abstract
Recombination dynamics of spontaneous and stimulated emissions have been assessed in InGaN-based light emitting diodes (LEDs) and laser diodes (LDs), by employing time- resolved photoluminescence and pump and probe spectroscopy. As for an In0.02Ga0.98N-ultraviolet-LED, excitons are weakly localized by 15 meV at low temperature, but they become almost free at room temperature. It was found that addition of small amount of In results in the reduction of nonradiative recombination centers originating from point defects. The internal electric field does exist in InGaN active layers, and induces a large modification of excitonic transitions. However, it alone does not explain the feature of spontaneous emission observed in an In0.3Ga0.7N- blue-LED such as an anomalous temperature dependent of peak energy, almost temperature independence of radiative lifetimes and mobility-edge type behavior, indicating an important role of exciton localization.

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