Investigation of conductivity and piezoresistance of n-type silicon on basis of quantum kinetic equation and model distribution function

Conductivity and first-order piezoresistance coefficient pi(11) are investigated in detail for strained n-type silicon crystal. As scattering system were adopted impurities and longitudinal acoustic phonons. The consideration is based on quantum kinetic equation and corresponding precise balance equation. The main point of the used method is special model of non-equilibrium distribution function. Final results for mobility of unstrained crystal and piezoresistance coefficient pi(11) are compared with experimental data and consequent theoretical results obtained by another method, grounded on the widespread isotropic tau-approximation. The latter consists in modelling of the collision integral by the simple form which contains scalar relaxation time depending on energy. Comparison shows the Substantial numerical difference between values, calculated with the help of the two mentioned methods. (C) 2008 Elsevier B.V. All rights reserved.