Self-consistent quantum-mechanical calculations in ultrathin silicon-on-insulator structures

Schrödinger’s and Poisson’s equations have been self-consistently solved in ultrathin silicon-on-insulator (SOI) structures. The interaction between the front and back inversion layers has been studied as a function of the silicon film thickness, electron concentration, and temperature. The splitting of the subband energy levels, due to the possibility of quantum-mechanical interaction between the two inversion layers, strongly depends on the silicon film thickness tSi. The total subband structure can qualitatively vary with the applied gate voltages. For the thinnest devices (tSi<15 nm), volume inversion may occur even for rather large electron concentration and low temperature. For intermediate SOI thicknesses (tSi≂15–50 nm), many more subbands are populated in SOI structures than in their bulk silicon counterparts.