Lasing at 1.28 μm of InAs-GaAs quantum dots with AlGaAs cladding layer grown by metal-organic chemical vapor deposition

We report the device characteristics of stacked InAs-GaAs quantum dot (QD) lasers cladded by an Al_0.4Ga_0.6As layer grown at low temperature by metal-organic chemical vapor deposition. In the growth of quantum dot lasers, an emission wavelength shifts toward a shorter value due to the effect of postgrowth annealing on quantum dots. This blueshift can be suppressed when the annealing temperature is below 570°C. We achieved 1.28-μm continuous-wave lasing at room temperature of five layers stacked InAs-GaAs quantum dots embedded in an In_0.13Ga_0.87As strain-reducing layer whose p-cladding layer was grown at 560°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. We also discuss the device characteristics of fabricated quantum dot lasers at various growth temperatures of the p-cladding layer.