Strain distribution and carrier confinement in Si/SiO2 quantum point contacts and wires

The strain distribution and strain-induced confinement of carriers in Si/Si O2 quantum wires (QWRs) and quantum point contacts (QPCs) have been analyze d by elastic continuum and envelope wave function models. Recently, a compr essive strain up to 1% has been predicted to exist in the thermally oxidize d SiO2 surrounding the Si waveguide. We show that 1% radial strain in the t hermal oxide leads to lowering of the band edge inside the Si wire and to c onfinement of electrons in a quantum-dot-like potential having a depth of s imilar to 40 meV. The binding energy of the lowest electron level is -34 me V in a 240 nm long and 60 nm high QWR. The lowest energy level rises above the band edge in the contact pads when the QWR is made narrower than 12 nm. For the QPC, no bound states exist according to our calculations. (C) 2000 American Institute of Physics. [S0021-8979(00)00209-7].