Antonio C. S. Algarte

Relaxation dynamics of hot carriers and phonons in semiconductors: Influence of the excitation conditions

The so-called hot-phonon effect that accompanies the rapid relaxation processes in the photoinjected plasma in semiconductors is analyzed, resorting to a nonlinear quantum kinetic theory based on a nonequilibrium ensemble formalism. We concentrate the study on the process of generation and decay of the nonequilibrium longitudinal optical phonon population per mode. Particular attention is paid to the question of the influence of the conditions of excitation imposed on the system, which determine the occurrence of different regimes of relaxation by means of carrier–phonon interactions. Comparison of the relaxation dynamics in the case of several semiconductors with different polar strengths is done.

Diffusion of photoinjected carriers in nonequilibrium polar semiconductors

Abstract Ambipolar diffusion of photoinjected carriers in nonequilibrium polar semiconductor plays, in conjunction with other effects, an important role in the relaxation processes in such hot carrier systems, providing a mechanism for a slowing down of the relaxation processes. Diffusion processes are governed by an ambipolar diffusion coefficient. In these far-from-equilibrium semiconductors such transport coefficient depends on the nonequilibrium macroscopic state of the sample, as it evolves in time. Resorting to an informational statistical thermodynamics, we derive an expression for this ambipolar diffusion coefficient accounting for its dependence on the time evolution of the dissipative processes that develop in the medium. The theoretical results are compared with experimental data obtaining a good agreement.

Einstein relation for nonlinear charge transport in photoexcited polar semiconductors

Abstract We consider nonlinear charge transport of carriers in a photoexcited plasma in polar semiconductors. The diffusion and mobility kinetic coefficients in such conditions are obtained resorting to a nonequilibrium statistical thermodynamic approach. A generalized Einstein relation is derived for the nonequilibrium carriers (electrons and holes) for weak and intermediate electric field strengths. We discuss the effect of the irreversible evolution of the system and of the non-Ohmic behavior on such generalized Einstein relation.