A 1ST-PRINCIPLES STUDY OF THE ELECTRONIC-PROPERTIES OF SILICON QUANTUM WIRES

We describe the results of first-principles pseudopotential calculatio ns for H-terminated Si wires, with thicknesses up to 16 angstrom, whic h yield the band gaps, effective masses and optical matrix elements. T he zero-phonon radiative lifetime for recombination of localised excit ons in a 16 angstrom-wide wire is calculated to be 560 mus. This is in reasonable agreement with the value of 130 mus deduced from experimen ts on samples of porous Si. Comparison with effective-mass theory indi cates that the latter is likely to be valid for wires wider than about 33 angstrom. Our results are consistent with a model in which the lum inescent properties of porous Si are due to quantum-confined carriers in wire-like crystalline Si structures.