TIME RESPONSE OF A TUNABLE-ELECTRON-DENSITY QUANTUM-WELL AND RESERVOIR STRUCTURE

We present a theoretical model for the electron escape time from the quantum well back to the reservoir of a novel InxGa1-xAs/In1-yAlyAs multiple quantum well optical modulator. Three different mechanisms are considered: direct tunneling, phonon assisted sequential tunneling, and thermionic emission. At high forward biases, phonon assisted sequential tunneling and thermionic emission dominate, while at high reverse biases, direct tunneling from the quantum well ground state to the reservoir determines the turn-off time constant. The calculated escape time is in good agreement with the experimental data.