Small-signal modulation response of InP/GaInP quantum-dot lasers

We report on investigations concerning the modulation dynamics of InP/GaInP quantum-dot (QD) lasers grown by metalorganic vapor-phase epitaxy. Room-temperature operation of our lasers occurs at threshold current densities ${\mathrm{(j}}_{\mathrm{thr}})$ around $\text{1.8\hspace{0.5em}}{\mathrm{kA/cm}}^2$ and emission wavelengths (λ) between 696 and 710 nm with characteristic temperatures of about 50 K. At $\text{−33\hspace{0.05em}°}\mathrm{C}$ a differential gain ${\text{dg/dn≈1.5×10}}^{\text{−16}}\hspace{0.17em}{\mathrm{cm}}^2$ is determined. Measurements on GaInP/AlGaInP quantum-well lasers with similar λ yield comparable values for $\mathrm{dg/dn.}$ The decrease of $\mathrm{dg/dn}$ in our QD lasers at elevated temperatures is attributed to a lack of carrier confinement, which foils the benefits expected from the zero-dimensionality of the active medium. A maximum intrinsic modulation bandwidth of 12.7 GHz at $\text{−33\hspace{0.05em}°}\mathrm{C}$ is determined.