Ultrafast processes in InAs/GaAs quantum dot based electro-absorbers

Quantum dot (QD) based semiconductor electro-absorbers have attracted a lot of attention recently due to their unique dynamical properties, which make them perfect components for various types of mode-locked lasers. It has been shown that time resolved pump-probe spectroscopy can provide a direct insight into dynamics of carrier tunnelling processes at high reverse bias voltage and demonstrates the electro-absorption properties of a bi-layer QD waveguide. This study performs a detailed investigation of the ultrafast processes which govern the intradot recovery dynamics of a QD InAs/GaAs structure under reverse bias condition by means of the single colour pump-probe technique. By studying the GS and ES recoveries as a function of reverse bias voltage, the dominance of Auger mediated recovery when the ES is initially populated while phonon mediated recovery dominates for the GS case is illustrated.