Quantum dot lasers based on a stacked and strain-compensated active region grown by metal-organic chemical vapor deposition

We demonstrate an $\mathrm{InAs}∕\mathrm{GaAs}$ quantum dot (QD) laser based on a strain-compensated, three-stack active region. Each layer of the stacked QD active region contains a thin GaP $(\Delta a_{\mathrm{o}}=-3.8\%)$ tensile layer embedded in a GaAs matrix to partially compensate the compressive strain of the InAs $(\Delta a_{\mathrm{o}}=7\%)$ QD layer. The optimized GaP thickness is $\sim 4\mathrm{MLs}$ and results in a 36% reduction of compressive strain in our device structure. Atomic force microscope images, room-temperature photoluminescence, and x-ray diffraction confirm that strain compensation improves both structural and optical device properties. Room-temperature ground state lasing at $\lambda =1.249\mu \mathrm{m}$ , $J_{\mathrm{th}}=550\mathrm{A}∕{\mathrm{cm}}^2$ has been demonstrated.