Ab initio validation of continuum models parametrizations for ultrascaled SOI interfaces

作者：Biel Blanca^*; Donetti Luca; Godoy Andres; Gamiz Francisco

来源：Microelectronic Engineering, 2013, 109: 286-289.

DOI：10.1016/j.mee.2013.03.012

• SOI
• Ab initio
• k.p
• Effective mass
• SiO2

We provide a systematic Density Functional Theory (DFT) analysis of the bandstructures and bandgap values for hydrogenated and oxidized SOI structures with thicknesses ranging between 0.6 and 6.3 nm. The abrupt termination of the Si wavefunction at the surfaces in H-terminated slabs gives rise to gap values that can be more than 1 eV higher than the ones obtained for Si/SiO2 nanostructures of the same thickness, a fact that points out the necessity for a correct description of the interface in ultrascaled SOI devices. Additionally, we found that oxidized structures with thicknesses below 3 nm present an oscillating behavior in the bandgap value with the number of monoatomic Si layers in the structure. In order to estimate the validity range of standard simulation tools parametrized to the bulk Si experimental values, the results obtained from the ab initio calculations are contrasted to the ones provided by continuum models, namely k.p and effective mass. It can be inferred that the description of the bandstructure provided by these parametrizations is not adequate for thicknesses around 3 nm and below. To further explore this issue, transport effective masses for three selected thicknesses have been computed in the two dimensional transport plane, from both the ab initio and the bandstructures. The results emphasize the necessity to check the parametrizations traditionally employed in the simulation of nanodevices against descriptions providing atomic-scale detail, and suggest the possibility of improving such parametrizations through individual fittings to the atomistic bandstructure of the structure of interest.

• 出版日期2013-9