1.28μm lasing from stacked InAs∕GaAs quantum dots with low-temperature-grown AlGaAs cladding layer by metalorganic chemical vapor deposition

We report the device characteristics of stacked $\mathrm{In}\mathrm{As}∕\mathrm{Ga}\mathrm{As}$ quantum-dot lasers cladded by ${\mathrm{Al}}_{0.4}{\mathrm{Ga}}_{0.6}\mathrm{As}$ layer grown at a low temperature by metalorganic chemical vapor deposition. A blueshift in emission energy by the effect of postgrowth annealing can be suppressed when the annealing temperature is below $570°\mathrm{C}$ . We achieved the $1.28\mu \mathrm{m}$ continuous-wave lasing at room temperature of five layer stacked $\mathrm{In}\mathrm{As}∕\mathrm{Ga}\mathrm{As}$ quantum dots embedded in ${\mathrm{In}}_{0.13}{\mathrm{Ga}}_{0.87}\mathrm{As}$ strain-reducing layer whose $p$ -cladding layer is grown at $560°\mathrm{C}$ . From the experiments and calculations of the gain spectra of fabricated quantum-dot lasers, the observed lasing originates from the first excited state of stacked InAs quantum dots.