Relaxation of a kinetic hole due to carrier-carrier scattering in multisubband single-quantum-well semiconductors

Abstract

We describe a theoretical model for carrier-carrier scattering in an inverted semiconductor quantum well structure using a multisubband diagram. The model includes all possible nonvanishing interaction terms within the static screening approximation, and it enables one to calculate accurately the temporal evolution of the carrier densities and the gain following a perturbation by a short optical pulse. We present a theoretical formalism and detailed numerical calculations. The addition of more than one subband in each band as well as the use of all exchange terms yields several results. First, the degree of gain saturation is reduced while, at the same time, the recovery is faster as scattering events among different subbands take place. Also, carrier transfer between subbands is observed which modifies the overall carrier dynamics.

Spin and energy relaxation in germanium studied by spin-polarized direct-gap photoluminescence

“…In the doped samples, on the other hand, the energy relaxation of 'high-energy' electrons is governed by collisions with the background carriers. These Coulomb collisions come from a binary process in which a photoexcited electron collides with a background carrier, 62,63 and also a collective process in which the photoexcited electron interacts with the thermal plasma of background carriers. 64,65 The energy relaxation of photoexcited electrons due to Coulomb collisions is effective in the X and L valleys but not in the Γ valley.…”

Influence of wetting-layer wave functions on phonon-mediated carrier capture into self-assembled quantum dots

“…We do not consider contributions to the capture rate from Auger processes and many-body effects, as the focus of the paper is on how the chosen wave functions affect the calculated capture times. However, a comprehensive many-body approach would also rely on the use of appropriate single particle eigenstates; 17 so the results may have wider implications than just for the carrier capture problem considered. Exploiting the rotational symmetry, the problem of solving the Schrödinger equation is reduced to two dimensions, making a finite element method ͑FEM͒ efficient.…”

Temperature dependence of the coupling between n-type δ-doping region and quantum dot assemblies

“…6 This improvement stems from the strong coupling between the two active layer elements, viz., the strained In x Ga 1−x As single QW and the Te n-type ␦-DR, which results in a higher initial carrier population in the QW and in an additional cold-carrier injection path into the diode laser active region ͑deep states at the ␦-DR͒. Electrons are readily equilibrated in the highly populated ␦-DR due to electron-electron ͑e-e͒ scattering, 7 and injection schemes into the QW active region can be enhanced, either by e-e scattering or by tunneling. 8 As was recently demonstrated by Bhattachary et al 9 for laser direct modulation experiments, the physical mechanisms controlling the modulation bandwidth are different at room temperature and low temperature.…”