Carrier relaxation of modulation-doped InAs/GaAs quantum dots

We present the carrier relaxation of modulation-doped InAs/GaAs quantum dots depending on the excitation wavelength and modulation-doping concentration by using the time-resolved spectroscopy. At the excitation below GaAs band gap, the relaxation processes become very slow, implying the observation of phonon bottleneck effects. On the other hand, at excitation far above GaAs band gap, phonon bottleneck effects are broken down due to Auger processes. Increasing modulation-doping concentration, Coulomb scattering between electrons in GaAs-doped layer and carriers in InAs quantum dots makes the relaxation times become fast.