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

Carrier-carrier scattering of a near-bandgap excited electron-hole pla sma in an intrinsic GaAs quantum well is studied using two different M onte Carlo (MC) techniques. In the first one, the two-particle collisi ons are modelled using a screened Coulomb interaction. In the second o ne, the many-particle interaction is incorporated through classical mo lecular dynamics (MD). At low excitation densities (2 x 10(10) cm-2) m olecular dynamics gives a much slower thermalization of the plasma tha n the 'two-particle collision' technique. This difference is ascribed to the breakdown of the two-particle collision model, because the scre ening of Coulomb interaction at low densities is too weak to limit the range of the two-particle interaction to the mean interparticle dista nce. The agreement of 'two-particle collision' simulations with experi ment seems to be fortuitous. The disagreement Of MD with experiment im plies that the theory is still incomplete.