Effect of a thin transition layer at a Si-SiO₂ interface on electron mobility and energy levels

If the Si-SiO2 interface has a graded composition in a transition layer of order 0.5 nm, as suggested by work of Raider and Flitsch and of Pantelides and Long, then electrons in the lowest subband for a (001) interface are found to have up to 1% of their charge within the transition layer at large interface electric fields. Scatterers in the transition layer can account for interface scattering which has generally been attributed to surface roughness. Penetration of the wave functions into the transition layer also lowers the energy levels associated with the four-fold degenerate subband ladder significantly relative to those of the lowest, two-fold degenerate, ladder. © 1977.