Dielectric constant and light emission in Si/SiO2 superlattices

The real part of the frequency-dependent dielectric function epsilon(1)(omega) and the light-absorption coefficient alpha(omega), of Si slabs confined within SiO2 barriers have been calculated as a function of Si-slab thickness d(si). The calculation uses the imaginary part epsilon(2)(omega) of the dielectric function obtained from tight-binding calculations. The resulting static dielectric constants are found to increase with the decreasing Si-slab width, contrary to some reported theoretical results for H-terminated Si or pure-Si clusters. The calculated integrated light absorption in the range 1.0-2.6 eV is a maximum for for slabs with d(si) similar to 20 Angstrom, in agreement with experimental work on light emission from Si/SiO2 superlattices and other oxidized Si nanostructures. (C) 1999 American Institute of Physics. [S0003-6951(99)02252-4].