Simultaneous Measurements Of Electron And Hole Sweep-Out From Quantum-Wells And Modeling Of Photoinduced Field Screening Dynamics
Optic Effect Device; Absorption; Electroabsorption; Dependence; Saturation; Engineering, Electrical & Electronic; Optics; Physics, Applied
We measure both electron and hole escape times from a GaAs-AlGaAs quantum well in an electric field at room temperature. This gives important information for the design of high speed quantum-well modulator and optical switching devices. The measurements are made by picosecond optical pump-probe techniques on samples containing a single quantum well in a waveguide. The use of a single well avoids multiple well transport and resonant tunneling effects. Carriers excited in the quantum well by the pump beam result in a transient bleaching signal from excitonic saturation and, as they leave the well, a transient electroabsorption signal because the movement of charge partially screens the electric field. We model both processes, including important electrical equilibration processes (such as diffusive conduction) of the sample as a whole. This modeling and the use of two samples with asymmetric barrier heights allows the measurement of the electron and hole emission as a function of applied electric field. Both electrons and holes are emitted in a few picoseconds at high fields (e.g., 100 kV/cm) in low barrier (e.g., 20% Al) structures, and in hundreds of picoseconds at low fields (e.g., 20 kV/cm) in higher barrier (e.g., 40% Al) structures. Preliminary analysis suggests that the emission mechanism is thermionic rather than by tunneling, but the results are not well explained by conventional thermionic emission models.
Ieee Journal of Quantum Electronics
"Simultaneous Measurements Of Electron And Hole Sweep-Out From Quantum-Wells And Modeling Of Photoinduced Field Screening Dynamics" (1992). Faculty Bibliography 1990s. 414.