Carrier relaxation and collective phenomena in nonequilibrium semiconductor electron-hole plasmas.

A quantitative analysis of carrier-carrier scattering for electron-hole semiconductor plasmas is presented. Material parameters appropriate for GaAs are used for all calculations. Calculations are performed using the Boltzmann equation for carrier-carrier scattering. Screening of the Coulomb potential is treated in the fully-dynamical random phase approximation. Results are shown for roomtemperature near-equilibrium and far-from-equilibrium plasmas. Also, the equilibrium zero momentum scattering rates are calculated as a function of temperature (T = 10K to T = 1000K) and density (n = 10¹⁵ cm⁻³ to n = 10¹⁹ cm⁻³). Ultrafast scattering rates (on the order of 10 fs) are found to result for a carrier distribution with vacant low-momentum states. These rates are shown to be associated with the undamping of the acoustic plasmon which influences the scattering through screening of the Coulomb potential. Further analysis of plasmon undamping is presented, showing the conditions necessary for undamping of the acoustic mode. Results from a separate set of calculations, showing the time-evolution of the Wigner distribution for a semiconductor quantum wire, are shown. These numerical calculations were performed using the collisionless quantum Boltzmann equation for the case of a lightly-damped plasmon and an unstable growing plasma mode. Comparison is made with results predicted by the linear theory (Lindhard). Results showing the effects of increasing the field strength beyond the linear regime are also presented