Room temperature luminescence from self-organized quantum dots with high size uniformity

Abstract

Self-organized growth of In x Ga 1-x As/GaAs quantum dots (QD) for 0.5 2% is needed, from thermodynamic considerations, for the onset of 3D growth. The presence of fine excitonic features superimposed on the emission peaks confirms that the second peak observed in the PL spectra of quantum dots is from an excited state transition. We believe that the saturation of the ground-state emission observed under moderately high excitation photon densities is due to the long decay time constant (∼2.2 ns) as measured by time-resolved photoluminescence. Temperature variation of luminescence intensity shows a sharper decay for the ground-state emission than for the excited-state emission. Room-temperature luminescence is thus dominated by the excited state emission. Broad area lasers made from separate confinement heterostructure (SCH) laser structures with In 0.4 Ga 0.6 As quantum dots as the active region showed lasing from excited state, with J th = 650 A/cm 2 , and the single-mode ridge lasers gave a modulation bandwidth of 5 GHz at 2.51 th .