Nonequilibrium phonon effects on the transient high-field transport regime in InP

Abstract

We present a detailed investigation of the transient transport regime in InP at room temperature based on an original method to solve numerically the coupled hot-phonon-hot-carrier time-dependent Boltzmann equations for the case of a steplike high dc electric field pulse. The method enables a study of the perturbation of the phonon distribution function induced by hot carriers and the corresponding modifications of the carrier distribution function. The numerical accuracy of the method is far beyond other existing methods, and, as a consequence, the time behavior of the main transport parameters can be resolved in great detail. The presence of nonequilibrium phonons is found to be responsible for an overall increase in the time duration of the transient regime. Modifications in the time evolution of the main transport parameters are also observed; in particular, the carrier drift velocity exhibits a second overshoot for electric fields near the threshold value for negative differential mobility. The sensitivity of the results to the value of the phonon relaxation time is also discussed.

Effect of nonequilibrium phonons on hot-electron spin relaxation in n-type GaAs quantum wells

“…2(b), one notices that when the nonequilibrium phonon effect is taken into account, v x can be either increased or decreased. These results are in consistence with the previous studies [9,11,13]. In fact, the influence of nonequilibrium phonons on hot-electron transport consists of two competing effects: the reabsorption of momentum from the nonequilibrium phonons tends to increase the electron mobility, while the enhanced electron heating strengthens the electron-phonon scattering (including both the electron-AC phonon and electron-LO phonon scatterings) and tends to decrease the electron mobility [9,11,13].…”

“…The nonequilibrium phonons in turn are able to affect the electron dynamics, including the spin relaxation. In fact, the hot-electron transport with nonequilibrium phonons has been investigated [8][9][10][11][12][13][14][15][16], showing that the calculated electron energy loss rate and mobility fit better with experimental data than those obtained with the equilibrium phonons [10,13,14]. These studies also indicate that it is necessary to treat phonons as nonequilibrium ones in the hot-carrier system because these phonons will (a) E-mail: mwwu@ustc.edu.cn affect spin relaxation by modifying the carrier heating and drifting processes.…”

“…If the phonon relaxation is fast enough or the phonons (particularly, the acoustic (AC) phonons) can easily penetrate through the well interfaces, these phonons can be deemed as in equilibrium with the bulk modes. In our study we assume that the AC phonons keep in equilibrium and the longitudinal-optical (LO) phonons are in nonequilibrium [9][10][11][12][13]15]. In order to investigate the spin relaxation of electrons which are inhomogeneously coupled with the nonequilibrium LO phonons, we combine the rate equation of the LO phonons (eq.…”

“…This formula in fact depicts the dominant decay route of an LO phonon near the center of the Brillouin zone into a transverse AC phonon and a different LO phonon at the L critical point of the Brillouin zone. The relaxation time approximation with a constant τ pp related only to the lattice temperature has been widely utilized in the study of hot-electron transport with the presence of nonequilibrium LO phonons [10][11][12][13][14].…”

“…In fact, the influence of nonequilibrium phonons on hot-electron transport consists of two competing effects: the reabsorption of momentum from the nonequilibrium phonons tends to increase the electron mobility, while the enhanced electron heating strengthens the electron-phonon scattering (including both the electron-AC phonon and electron-LO phonon scatterings) and tends to decrease the electron mobility [9,11,13]. Generally the former (latter) effect dominates in the regime with low (high) electric filed and/or high (low) temperature [9,11,13], as indicated in fig. 2(b).…”