The role of vertical transport and capture of electrons and holes for the transient optical response in quantum-well heterostructures

摘要

The transient optical response of quantum wells (QWs) after optical and electrical carrier injection into the barrier layers is studied experimentally and theoretically. We have varied the transport geometry in GaAs/AlGaAs and InGaAs/InAlGaAs heterostructures and emphasize the basic principles for a theoretical treatment of electron and hole capture into QWs for a proper description of vertical carrier transport in the barriers of QW heterostructures. Comparing our experimental data with the results of theoretical model calculations, we determine the capture, reflection and transmission probabilities, the ambipolar diffusivities and the ambipolar mobilities in the barriers of GaAs/AlGaAs, as a model system. The temporal evolution of the electron and the hole capture current densities at the QWs are studied in detail for a wide variation of the injected carrier densities. Amplitude modulation experiments are performed for InGaAs/InAlGaAs QW laser devices providing increasing 3 dB frequencies for decreasing confinement layer thickness, indicating the influence of carrier transport in the barriers.