Carrier thermalization by phonon absorption in quantum-well modulators and detectors

In quantum-confined Stark effect based modulators and quantum-well detectors, carriers are produced at the band-edge by optical absorption. In most applications these earners generate photocurrent and to do so these initially “cold” electrons must thermalize since the photocurrent is dominated by over the barrier escapes of the carriers. The intrinsic speed of the device is thus limited by this thermalization time. We carry out a Monte Carlo simulation to study the carrier heating by phonon absorption in quantum-well structures as a function of well size and barrier height. Carrier thermalization times are dominated by intrasubband polar optical phonon processes and typical times are 1-4 ps depending upon the well and barrier design