Derived a “quantum capture” time of ∼30ps from high-frequency impedance measurements on In(Ga)As/GaAs single-mode quantum dot lasers, which qualitatively agrees with the measured modulation bandwidths of 5-6GHz. Additional, femtosecond differential transmission measurements on quantum dot laser heterostructures strongly suggest that there is a significant “hot carrier” problem in the separate confinement heterostructure (SCH) quantum dot lasers. It has been demonstrated that tunneling injection of electrons improves high-speed and other performance characteristics of quantum well lasers by reducing the hot carrier population in the active region. We report here the performance characteristics of quantum dot tunnel injection lasers and demonstrate large modulation bandwidth (15GHz) at room temperature in these devices for the first time.