CARRIER-CARRIER SCATTERING IN PHOTOEXCITED QUANTUM-WELLS - INADEQUACY OF THE 2-PARTICLE COLLISION MODEL AT LOW-DENSITIES

Carrier-carrier scattering of a near-bandgap excited electron-hole plasma in an intrinsic GaAs quantum well is studied using two different Monte Carlo (MC) techniques. In the first one, the two-particle collisions are modelled using a screened Coulomb interaction. In the second one, the many-particle interaction is incorporated through classical molecular dynamics (MD). At low excitation densities (2 x 10(10) cm-2) molecular dynamics gives a much slower thermalization of the plasma than the 'two-particle collision' technique. This difference is ascribed to the breakdown of the two-particle collision model, because the screening of Coulomb interaction at low densities is too weak to limit the range of the two-particle interaction to the mean interparticle distance. The agreement of 'two-particle collision' simulations with experiment seems to be fortuitous. The disagreement Of MD with experiment implies that the theory is still incomplete.