The ultrafast gain dynamics in an electrically pumped InAs/InGaAs/GaAs quantum-dot amplifier are measured at room temperature with femtosecond resolution, and compared with results on an InGaAsP bulk amplifier. The role of spectral hole burning and carrier heating in the recovery of the gain compression is investigated. Reduced carrier heating for both gain and refractive index dynamics of the quantum-dot device is found, which is a promising prerequisite for high-speed applications.Gain and refractive index dynamics in semiconductor optical amplifiers (SOAs) have been widely investigated in the past, both experimentally and theoretically. Besides a fundamental interest, these studies give a direct insight about the ultimate limit in highspeed performances of semiconductor devices due to the intrinsic carrier dynamics. It is well known that the subpicosecond dynamics in bulk and quantum-well (QW) SOAs are dominated by spectral hole burning (SHB), with a recovery time below 100 fs, and carrier-heating (CH) effects, recovering over several hundreds of femtoseconds [1]. The recent achievement of fabricating InAs-based electrically pumped quantum-dot (QD) lasers [2] allows to extend these previous investigations to the quasi zero-dimensional case. Quantum-dot lasers fabricated until now do not show modulation bandwidths better than QW lasers, and are conjectured to be limited by the carrier capture into and relaxation in the QDs [2, 3]. However, most of the work dedicated until now to characterize directly carrier dynamics in self-organized QDs used mainly time-resolved photoluminescence experiments on unprocessed samples at low temperatures in the picosecond and nanosecond regime.In this work, the ultrafast gain dynamics of an electrically pumped InAs/InGaAs/ GaAs QD amplifier are measured at room temperature (RT), as schematically shown in Fig. 1, and compared with a bulk InGaAsP amplifier. A pump-probe experiment is performed with an heterodyne detection scheme, similar to earlier measurements on bulk and quantum well active waveguides [1]. Fourier-limited 150 fs laser pulses are 1 ) Corresponding