Electron-phonon interaction in nanowires: a Monte Carlo study of the effect of the field
This paper shows the investigations about electron-phonon interaction in nanowires basing on the Monte Carlo study of the effect of the field. It is based on the observation that the core elements in modern electronic devices (optical switchers, highly sensitive photo-FET's, etc.) are semiconductor quantum wires. The electronic characteristics of these devices are basically determined by the carrier transport in the wire. The carrier distribution is highly non-equlibrium so that besides the usual spatial evolution a fast process of thermal relaxation occurs, caused by energy dissipation from phonons. Some difficulties of this process description are connected with very small (c.a. nanometer) scales and the characteristic for the evolution process under consideration are the sub-picosecond thus, it requires a quantum mechanical description. The authors introduce a quantum-kinetic equation (Eq. (1)), whose derivation can be found in earlier work of some of the authors et al. [Wigner transport models of the electron-phonon kinetics in quantum wires, Phys. Rev. B 74, 035311 ) (2006)]. Basing on this proposal it is possible to introduce the following effects: {\parindent=7mm \begin{itemize}\item[(i)] the non-Markovian character of the equation introduced by the time integral that leads to retardation of the quantum evolution; \item[(ii)] the lack of energy conservation that causes the collisional broadening and appearance of carriers in the classically forbidden energy regions; \item[(iii)] the collisions with phonons have finite duration, which affects the carrier trajectories; \item[(iv)] the action of the electric field during the collision process -- the intra-collisional field effect (ICFE). \end{itemize}} In the case of preparation of generation simulators of transport processes occurring on femtosecond and nanometer scales the mentioned above problems should be taken into account. The study of the effects (i) -- (iii) was done in earlier work -- in this paper we have the study of ICFE. The proposed Eq. (1) is very inconvenient for numerical simulations thus in Section 2 we have the necessary mathematical transformations that solve this problem. They are used in Section 3 to solve the transport equation for the following physical conditions: a GaAs wire with 10 nm square cross section and the initial carrier distribution corresponds to a Gaussian distribution both in energy and space that is generated by a laser pulse with 150 meV excess energy. In this Section the reader can find the results of simulations.
scientific article; zbMATH DE number 5843123