Diffusion of photoinjected carriers in plasma in nonequilibrium semiconductors

Abstract

We consider effects of diffusion in the photogenerated carrier system in highly photoexcited polar semiconductors. We develop a quantum quasihydrodynamic description of the system based on the nonequilibrium statistical operator formalism. We derive a generalized Fick's diffusion equation for the charge density of the carriers, with the ambipolar diffusion coefficient obtained at the microscopic level and depending on the evolving macroscopic (nonequilibriium thermodynamic) state of the sample. A detailed numerical calculation for the case of GaAs is done, obtaining good agreement with experimental data.

A NONEQUILIBRIUM STATISTICAL ENSEMBLE FORMALISM MaxEnt–NESOM: Basic Concepts, Construction, Application, Open Questions and Criticisms

“…The diffusion coefficient in a nonlinear transport theory has been considered by Hope et al as already noticed. 137 Vasconcellos et al 153 have presented a quasithermohydrodynamic theory built in the framework of MaxEnt-NESOM for the study of effects of diffusion in the photogenerated carrier system in highly photoexcited polar semiconductors. It was developed a quantum quasi-hydrodynamic description of the system based on the nonequilibrium statistical operator formalism.…”

Topics in Present-day Science Technology and Innovation: Ultrafast Relaxation Processes in Semiconductors

“…The dashed curve is a calculation when ambipolar diffusion of electrons and holes out of the active volume of the sample (the region of focusing of the laser beam) is neglected, resulting in a more rapid relaxation, contrary to what is observed; the arrow indicates the end of the exciting laser pulses, which was taken with a rectangular profile. This then evidences the influence in the change of the density in the photoinjected plasma, a change illustrated in Figure 12, (showing the calculation and the experimental data), resulting from radiative recombination and, mainly, the aforementioned ambipolar diffusion 80 . It can be noticed that the latter is also responsible for the emergence of the shoulder that can be seen in the plot in Figure 10.…”

Ensemble formalism for nonequilibrium systems and an associated irreversible statical thermodynamics

“…In the particular case of NESEF, which provides statistical foundations to IST, as noticed in Section 2, it yields a nonlinear quantum transport theory of large scope [56], which consist of a far-reaching generalization of Mori's theory [19], together with an accompanying response function theory for far-from-equilibrium systems [13,32,84], and a generalized Boltzmann transport theory [33]. As already noticed, NESEF has been applied to the study of ultrafast relaxation processes in the so-called photoinjected plasma in semiconductors with particular success, in the sense of obtaining very good agreement between theory and experiment [66][67][68][69][70][71][72][73][74][75][76][77][78][79][80] and see Chapter 6 in the book of the Ref. [13].…”