The use of Kubo formula to examine low temperature transport limited by interface roughness and phonons in metal–oxide–semiconductor field effect transistors

Abstract

An approach to study transport in semiconductors using the Kubo formula is developed and applied to Si metal–oxide–semiconductor field effect transistors (MOSFETs). It is known that interface roughness is an important source of scattering in a MOSFET device operating at high sheet charge concentration (∼1012 cm−2). However, in spite of its importance, due to the complexity of the problem very simple models based on the Born approximation are used to study transport. The Born approximation breaks down when the interface quality is poor and transport occurs in lower energy localized states (for example, at low temperature). In this article we present results of a numerical method based on a three-dimensional approach to examine the interface roughness effects on electronic spectrum as well as on transport. Using the approach suggested by the Kubo formula we solve for the electronic states in the presence of interface roughness. Kubo formula is then used to study the transport properties as a function of sheet charge density, interface roughness level, and temperature. The model can easily be applied to other problems where scattering effects are very strong, e.g., in amorphous semiconductor devices.