Supercell approach to the optical properties of porous silicon
Por:
Cruz M., Wang C.
Publicada:
1 ene 1999
Resumen:
We calculate the optical constants of porous silicon (por-Si) from the electronic band structure obtained by means of an (Formula presented) tight-binding Hamiltonian and a supercell model, in which the pores are columns dug in crystalline Si. The position of the absorption edge of the material is defined by two competing effects: (i) transitions assisted by the scattering of carriers on the lattice of pores, which effectively decrease the “indirectness” of por-Si and result in a redshift of the absorption edge, and (ii) quantum confinement, which increases the band gap. The interplay between these effects is illustrated by calculating the imaginary part of the dielectric function for 8-, 32-, and 128-atom supercells with different porosities. We also show how the supercell model can be extended to take into account weak disorder, which produces nonvertical optical transitions in (Formula presented) space and smoothens the absorption spectra. Our results, obtained without any adjustable parameters, are compared with experimental data. © 1999 The American Physical Society.
Filiaciones:
Cruz M.:
Escuela Superior de Ingeniería Mecánica y Eléctrica, UC IPN, Mexico
Instituto de Investigaciones en Materiales, UNAM, Mexico Distrito Federal, 04510, Mexico
Centro de Investigacíon en Energía, UNAM, Temixco, Morelos 62580, Mexico
Wang C.:
Instituto de Investigaciones en Materiales, UNAM, Mexico Distrito Federal, 04510, Mexico
Centro de Investigacíon en Energía, UNAM, Temixco, Morelos 62580, Mexico
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