<title>Monte Carlo simulation of intersubband relaxation in single and multiple quantum wells</title>

Abstract

We studied intersubband relaxation of carries during ultrafast photoexcitation in single and coupled quantum wells using ensemble Monte Carlo simulation, Intra- and intersubband scattering due to polar and nonpolar optical phonons, acoustic phonons, and intercarrier scattering are included in the simulation. The polar optical mode description is given in terms of a two-pole dielectric continuum model for the alloy barriers. In the present work we focus on relaxation when the 2-1 subband spacing is smaller than the optical phonon energy so that suppression of the intersubband polar optical phonon scattering rate occurs. Our results for a single well show that intercarrier intersubband scattering dominates over acoustic phonon scattering during the initial relaxation of carriers from 2-1, with a strong contribution due to polar optical phonon emission from the tails of the heated distributions as well. We have studied optical pumping for a 3 level coupled quantum well system in which (Delta) E<SUB>12</SUB> is less than h(omega) <SUB>0</SUB>, and calculate the change in occupancy of the excited subbands through pumping of the 1-3 transition.