Speed response analysis of an electron-transfer multiple-quantum-well waveguide modulator

A numerical model is presented for the electronic properties of a novel In_xGa_1-xAs/In_1-yAl_yAs multiple-quantum-well waveguide modulator and a theoretical analysis of electron and hole escape mechanisms from the quantum well is developed. The influence of carriers and dopant ion charges on the band structure is simulated with a self-consistent Poisson-Schrödinger solver. The different escape mechanisms for both electrons and holes are: direct tunneling, phonon-assisted sequential tunneling, and thermionic emission. At high forward biases, the electron escape time limits the device speed, while at high reverse biases, heavy holes take a longer time than electrons for escaping the quantum well. For both particles, phonon-assisted sequential tunneling is a key mechanism in determining the device speed operation. The calculated escape times are in good agreement with the experimental data.