Modeling of ultra-small-scale electron transport in GaAs

A multivalley transport model based on conservation equations for ultra-small-scale compound semiconductor devices, is developed. The model is applied to analysis of electron transport in n-type GaAs subjected to rapidly time-varying fields. A semiconductor test model is also included to illustrate the effects of intervalley and anisotropic scattering. The developed description is compared to the Monte Carlo method and the single-valley conservation equations where transport parameters are averaged over all valleys. It is shown that the single-valley approach cannot properly take into account intervalley transfer effects. Results also show that the macroscopic effective mass, which has been assumed only energy dependent in device analysis, strongly depends on average velocity when forward scattering, such as polar-optical phonon and ionized impurity scattering, is involved