A influência dos fonons acústicos e óticos não-polares nas propriedades de transporte de portadores fotoexcitados submetidos a campos elétricos intensos

Abstract

A set of 21 coupled non-linear integro-differential equations was obtained for the study of photoexcited carriers transport ln III-V semiconductors submit ted to high electric field intensi ties. A quantum transport theory, obtained from Nonequilibrium Statistical Operator Method the Zubarev's and from the Bogoliubov's assumption of the existence of relaxation times for micro-information has been used. All of the possible interactions between carriers and phonons (intra and intervalley) were taken into account, as well as the carriers coulomb interaction. In the scheme of central parabolic bands for electrons and heavy holes, and in the limit of high temperatures, the set of integro-differential equations was reduced to seven coupled differential equations. An analysis of all of the momentum relaxation times of the carriers, naturally revealed from the quantull\ transport theory that was used, has shown the role of acoustical and non-polar phonons in the transport phenomena of photoexcited carriers submitted to high electric fields, determining the existence of structures (maximum and minimum) in the electron transient veloci ty, and i ts absence in the case of the heavy hole veloci ty. The numerical solution of the differential equations has revealed the existence of non-lineari ties in the behavior of the heavy hole and phonon temperatures, that was related to the abrupt growth of the stationary temperature of electrons for electric fields ~6 kV/ctn. An overshoot in the electron velocity for fields higher than 6 kV/cm was verified, as well as the presence of structures for lower values, while heavy holes showed a monotonic temporal evolution for any electric field intensity. Finally, even without the intervalley scattering, it was observed the effect of negative differential resistivity between 6 kV/cm and 7.3 kV/cm.