Influence of the quantum-well thickness on the radiative recombination of InGaN/GaN quantum well structures

Temperature-dependent photoluminescence (PL) measurements are performed on In0.23Ga0.77N/GaN single-quantum-well structures with different well thickness. Based on a band-tail model, the exciton localization effect is studied. The exciton localization effect is enhanced by increasing quantum-well thickness up to 2.5 nm. If the quantum-well thickness is further increased to above 2.5 nm, the exciton localization effect becomes weak. Finally, when the quantum-well thickness is increased to 5 nm, the exciton localization effect cannot be observed. In addition, the PL intensity decreases monotonically with increasing the quantum-well thickness. In connection with an excitation-power dependent PL measurement, the result of the quantum-well thickness dependent PL intensity can be attributed to quantum confined Stark effect, which becomes particularly strong in the wide quantum-well structure. Based on our optical investigation, the presented article indicates that the emission mechanism is dominated by the exciton localization effect in the thin quantum-well structures, while the quantum confined Stark effect dominates the radiative recombination in the wide quantum-well structures. Since understanding the emission mechanism is very important for further improving the performance of an InGaN/GaN-based optical device, the presented results in this article should be highly emphasized.