Cross-Sectional Shape Effects of Gate-All-Around Nanowire Field-Effect Transistors

The cross-sectional shape of gate-all-around nanowire transistor is common to deviate from its design due to the fabrication variations. The cross-sectional shape effects on device performances are studied. Nanowire FETs, which approach the quantum limit of square, rectangular, circular, elliptical, trapezoidal, and triangular cross sections, are investigated by using three-dimensional self-consistent Poisson-Schrodinger simulations under the nonequilibrium Green’s function formalism. The cross-sectional shape has evident effects on the device performances. Corner effects are observed and shown to be a key factor on the device characteristics. Specifically, the quantum confinement in the cross section can remarkably change the carrier distribution and potential profile near corners by comparison to the classical case. Furthermore, it is shown that the elliptical shaped nanowire may be able to carry larger on current than the circular shaped nanowire. This effect can be explained through the quantum confinement effect, which changes the relative importance of different valleys and subbands.