ENSEMBLE MONTE-CARLO SIMULATION FOR ELECTRON-TRANSPORT IN QUANTUM-WIRE STRUCTURES

Ensemble Monte Carlo simulations are performed for the GaAs (100) oriented square well wire. The model considers the infinite potential approximation as well as the extreme confinement limit, i.e., one-dimensional subbands are formed in the L and X valleys as well as in the GAMMA valley. We discuss the electron dynamics in quantum wire structures from steady-state, transient, and diffusion aspects. Even at very low electric fields (10-100 V/cm), the non-Maxwellian distribution, originating from the one-dimensional density of states, leads to electron heating and a deviation from the Einstein relation, as well as mobility enhancement. At high fields, the anisotropic mass effects of the satellite valleys gives rise to a saturation velocity enhancement as well as a diffusivity increase. The low-temperature simulations show temporal oscillations of velocity due to the periodical phonon emissions. This effect possibly suppresses the diffusion noise, since no additional carrier diffusion is introduced with a periodic velocity oscillation. The velocity overshoot phenomena are studied based on the relaxation time approximation and are compared to the transient Monte Carlo results. The satisfactory agreement obtained between these two results indicates the validity of the phenomenological approach to quantum wire structures.