Low Threshold Current Operation of Stacked InAs/GaAs Quantum Dot Lasers with GaP Strain-Compensation Layers

We report the device characteristics of stacked InAs/GaAs quantum dots (QDs) with GaP strain compensation (SC) layers grown by metalorganic chemical vapor deposition. By inserting GaP SC layers within the stacked structures, decrease in the density of QDs by stacking QDs can be suppressed and the heterostructure interface between a p-clad and an active layer can be improved due to reduction of overall compressive strain within the stacked QDs. Ground-state lasing at a wavelength of 1.265 mum of six layers of InAs/GaAs QDs with GaP SC layers is demonstrated at a threshold current density of 108 A/cm² . We also assess the internal loss and maximum modal gain of the fabricated QD lasers by using a segmented contact method. The internal loss is as low as 5 cm^-1, and the maximum modal gain of the ground state of the stacked QDs is approximately 10 cm^-1