Effects of Rapid Thermal Annealing on the Optical Properties of GaAs Quantum Dots Grown by Using the Droplet Epitaxy Method

GaAs/Al(0.3)Ga(0.7)As quantum dots (QDs) were fabricated by using the droplet epitaxy (DE) method. A one-step rapid thermal annealing (RTA) treatment on all of the QD samples was performed at 740 degrees C. Temperature and excitation power density dependences of photoluminescence (PL) were determined to investigate optical properties. When the temperature is increased from 15 to 200 K, the PL peak energy is red-shifted from 1.648 to 1.590 eV while the full width at. half maximum (FWHM) is increased. Non-radiative recombination is found to be clue to the PL quenching mechanisms at high temperatures. The activation energy (E(a)) is approximately 32 meV. When the integrated PL intensity (I(PL)) is plotted against the excitation power density on log-log scale at different temperatures, we find that the superlinearity becomes stronger as the temperature increases. To investigate the effect of annealing temperature on the optical properties of the QDs. we carried out the two-step RTA treatment at various temperatures from 800 to 1000 degrees C. As the temperature increases, the PL peak position is blue-shifted clue to the change in the composition and the size distribution, and the highest PL intensity is observed for the sample annealed at 900 degrees C. The I(PL) versus the excitation power density shows a slope that changes with changing temperature in the two-step RTA.