Intersubband Relaxation of Electrons in AlxGa1−xAs/GaAs Quantum Wells During Photoexcitation

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Abstract
Using an ensemble Monte Carlo simulation of coupled electrons and nonequilibrium slab mode polar optical phonons in single and multiple quantum well systems, we have studied the relaxation of photoexcited carriers in ultra-fast optical intersubband relaxation experiments. Here we study intersubband relaxation in three different types of systems: i) wide wells in which the intersubband separation is less than the optical phonon energy, ii) narrow wells in modulation doped multi-quantum well structures, and iii) coupled asymmetric quantum wells. Simulated results using self-consistent envelope functions in the quantum well system show the importance of nonequilibrium hot phonons and self-consistency in explaining the experimental results from time resolved Raman, intersubband absorption, and photoluminescence spectroscopy.