ANOMALOUS REDUCTION IN THE ENERGY-LOSS OF ELECTRONS IN P-TYPE SEMICONDUCTORS

We report the observation of an anomalous decrease in the energy-loss rate of minority electrons in p-type GaAs at doping levels above p>2x1 0(19) cm(-3). This unusual behavior of the electron-hole energy transf er is a general property of plasmas at high carrier densities and is d ue to the transition from dominant plasmon-mediated scattering to free -carrier-screened single-particle scattering. This effect is observabl e when the excess energy of hot carriers interacting with a cold plasm a is comparable to the plasmon energy (h) over bar omega(pl).