Nonlinear Thermoelectroelastic Analysis of III-N Semiconductor Devices

The diffusion-drift electron transport description is combined with finite deformation theory to model thermoelectroelastic behaviors in piezoelectric semiconductors under conditions when the mechanical strains/displacements are not small so that the usual assumption of linearity cannot be justified. The nonlinear treatment includes both kinematic and constitutive corrections as well as a proper treatment of the electrostatic conditions at free surfaces. The theory is illustrated using numerical simulations of various III-N devices of technological interest, including of conventional AlGaN/GaN HEMTs and of semiconducting microelectromechanical structures that can require the nonlinear theory's rotational invariance even when the strains are small. Despite uncertainties in the values of the various material coefficients, it seems likely that the nonlinear corrections are often substantial.