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 (jthr) around 1.8 kA/cm2 and emission wavelengths (λ) between 696 and 710 nm with characteristic temperatures of about 50 K. At −33 °C a differential gain dg/dn≈1.5×10−16 cm2 is determined. Measurements on GaInP/AlGaInP quantum-well lasers with similar λ yield comparable values for dg/dn. The decrease of 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 −33 °C is determined.