Many-body theory of carrier capture and relaxation in semiconductor quantum-dot lasers

In quantum-dot laser devices containing a quasi-two-dimensional wetting layer, a pump process initially populates the wetting-layer states. The scattering of carriers from these spatially-extended quasi-two-dimensional states into the quantum-dot states as well as the relaxation of carriers between the quantum-dot levels are studied theoretically. Based on the wave functions for the coupled quantum-dot/wetting-layer system interaction matrix elements are calculated for carrier-carrier Coulomb interaction and carrier-phonon interaction. Scattering rates for various capture and relaxation processes are evaluated under quasiequilibrium conditions. For elevated carrier densities in the wetting layer, Coulomb scattering provides processes with capture (relaxation) times typically faster than $10\phantom{\rule{0.3em}{0ex}}\mathrm{ps}\phantom{\rule{0.3em}{0ex}}(1\phantom{\rule{0.3em}{0ex}}\mathrm{ps})$. When energy conservation allows for interaction with LO phonons, comparable rates are obtained.