A temperature dependent model for the saturation velocity in semiconductor materials

Abstract

Precise modeling of the saturation velocity is a key element for device simulation, especially for advanced devices such as e.g. High Electron Mobility Transistors (HEMTs) where the saturation velocity vsat is directly related to the available gain of the device. We present a model implementing the temperature dependence of the saturation velocity vsat into the two-dimensional device simulator MINIMOS-NT. The new model covers all relevant materials such as the elementary semiconductors Si and Ge, and the binary III-V group semiconductors GaAs, AlAs, InAs, GaP and InP. Furthermore, a composition dependent modeling for alloyed semiconductors such as e.g. Si1−xGex, AlxGa1−xAs or InxGa1−xAs is included. The implementation reflects a comprehensive literature survey on available experimental data and Monte Carlo (MC) simulation data. The work is completed by new MC simulations, especially for material compositions, where no experimental data are available. The extraction of the saturation velocity reveals a significant difference between the saturation velocity in the bulk and the effective (saturation) velocity extracted from rf-measurements e.g. for High Electron Mobility Transistors. Since this effective value is often used for device characterization, the difference gives insight into modeling the determining quantities of HEMTs.