From undulating Si quantum wires to Si quantum dots: a model for
porous silicon
Marcello Luppi, Elena Degoli, Stefano Ossicini
Istituto Nazionale per la Fisica della Materia (INFM) and Dipartimento di Fisica,
Universita` di Modena e Reggio Emilia, Campi 213/A, I-41100 Italy
Quantum confinement in crystalline Si was the first model proposed to explain the
efficient photoluminescence of porous Si1. Quantum confinement effects result in an
enlargement of the band gap, in a relaxation of the momentum-conserving role, and in
a size dependence of the absorption and luminescence energy. Fresh structures can be
theoretically modeled as quantum wires, while aged structures are usually more dot
like23. Here we discuss, for the first time, ab-initio results for the electronic and
optical properties of undulating Si quantum wires, i.e. with variable width. We are
able to follow the evolution of the optoelectronic properties as a function of the Si
nanostructure dimensionality in going from Si quantum wires to Si quantum dots. A
careful comparison with several experimental results (bandgap, dielectric function,
absorption, radiative lifetimes) is presented and discussed.
1
L. T. Canham, Appl. Phys. Lett. 57, (1990) 1046;
S. Ossicini, in "Properties of Porous Silicon", edited by L. T. Canham, EMIS DataReview series,
INSPEC IEE London, p. 207 (1997);
3
S. Ossicini, phys. stat. solidi (a) 170 (1998) 377.
2