Energy Broadening Associated With Finite Collision Duration In Hot Carrier Transport In Semiconductors

Abstract

Recent fascinating progress in fabrication techniques has made it possible to construct very small device structures. Investigations of hot carrier transport in such small devices are usually based on the semi-classical Boltzmann transport equation (BTE). As the electron energy increases, however, the mean free time between two successive scatterings with phonons becomes comparable to the collision duration time, defined here as the characteristic time required to build up the energy conserving delta-function in the collision term (M hundreds fs), so that the energy broadening associated with such small time scale is no longer negligible [collisional broadening (CB)]. In addition, since the wavevector (momentum) of an electron is not a good eigenstate of the total Hamiltonian, the electron state continuously changes during collision duration [intra-collisional field effects (ICFE)].[l] Therefore, these quantum effects could be important in deep submicron devices in which the mean free time of hot electrons could be less than 100 fs and a quantum kinetic transport equation (QTE) should be used to analyze hot carrier problems. In the present work, a QTE which takes the aforementioned quantum effects into account is derived from the quantum Liouville equation. A new-simple strategy for incorporating the energy broadening associated with finite collision duration (CB) is suggested to generalize the conventional Monte Carlo simulations.