Stacking, polarization control, and lasing of wavelength tunable (1.55 μm region) InAs/InGaAsP/InP (1 0 0) quantum dots

We report the growth, device fabrication, and performance of stacked InAs/InGaAsP/InP (1 0 0) quantum dots (QDs) in telecom lasers. Wavelength tuning of the QDs grown by metalorganic vapor-phase epitaxy (MOVPE) over the 1.55-μm region at room temperature (RT) is achieved using ultrathin GaAs interlayers underneath the QDs, which suppress As/P exchange to reduce the QD height in a controlled way. Unpolarized photoluminescence from the cleaved side, important for realization of polarization-insensitive semiconductor optical amplifiers, is obtained for closely stacked QDs due to vertical electronic coupling. The wavelength shift due to group-V-atom intermixing in the QDs during growth at higher temperatures of device structures is compensated by adjusting the GaAs interlayer thickness and V/III flow ratio during QD growth. Device quality of the QDs is highlighted by continuous-wave ground-state lasing at RT of narrow ridge-waveguide QD lasers.