Direct measurement of electron capture in InAs-InAlAs quantum dots

Summary form only given. Promising quantum-dot devices such as lasers and infrared photodetectors have lead to an intensive study of the optical properties of quantum dots. The physics of carrier dynamics in quantum dots is of particular importance for devices especially because a drastic slow down of the relaxation is expected due to the discrete nature of the electronic energy states (phonon bottleneck effect). Nevertheless, short capture and relaxation times have been measured and explained in terms of Coulomb collisions between electrons or electrons and holes We here present femtosecond pump-probe experiments in the mid-infrared range where, in contrast to previous experiments, the electron dynamics is clearly separated from that of holes. Electron-hole pairs are injected into the barrier by a 800-nm pump and the probe is tuned to an intraband transition in the conduction band.