INTEC   05402
INSTITUTO DE DESARROLLO TECNOLOGICO PARA LA INDUSTRIA QUIMICA
Unidad Ejecutora - UE
artículos
Título:
Microcrystalline silicon thin films: A review of physical properties
Autor/es:
A DUSSAN; R H BUITRAGO; R.R. KOROPECKI
Revista:
MICROELECTRONICS JOURNAL
Editorial:
Elsevier
Referencias:
Año: 2007
ISSN:
0026-2692
Resumen:
In this work we present a study of the optical, electrical, electronic and structural properties of Boron doped hydrogenated
microcrystalline silicon thin films (mc-Si:H). The films were deposited in an RF plasma reactor using as reactive gas a mixture of silane
and diborane, both highly diluted in hydrogen. The Boron concentration in the reactive gas was modified from 0 to 100 ppm. The
addition of Boron to the silicon films not only moves the Fermi energy level to the center of the gap, but also induces changes in all the
physical properties. The Boron effect on structural and morphological properties was studied by X-ray diffraction and atomic force
microscopy (AFM); the rugosity and grain size increased with the Boron concentration. The absorption coefficient measured by the
constant photocurrent method (CPM) at low photon energies also showed an increase, which can be explained and correlated with an
increase in the density of state (DOS) in the gap, due to Borons bonding. At high temperatures ðT4300KÞ the controlling transport
mechanism is thermally activated; the curves conductivity log versus the inverse of temperature gives straight lines. The activation
energy, measured from the valence band, decreases with Boron concentration, as expected, passing through a maximum, corresponding
this point to the position of Fermi energy of an intrinsic film. At low temperatures ðTo300KÞ the predominant transport mechanism
was variable range hopping (VRH). The behavior of the charge hopping under different electrical fields was followed. Results showed
that conductivity remained constant in a VRH regime only for a narrow range of electrical field.mc-Si:H). The films were deposited in an RF plasma reactor using as reactive gas a mixture of silane
and diborane, both highly diluted in hydrogen. The Boron concentration in the reactive gas was modified from 0 to 100 ppm. The
addition of Boron to the silicon films not only moves the Fermi energy level to the center of the gap, but also induces changes in all the
physical properties. The Boron effect on structural and morphological properties was studied by X-ray diffraction and atomic force
microscopy (AFM); the rugosity and grain size increased with the Boron concentration. The absorption coefficient measured by the
constant photocurrent method (CPM) at low photon energies also showed an increase, which can be explained and correlated with an
increase in the density of state (DOS) in the gap, due to Borons bonding. At high temperatures ðT4300KÞ the controlling transport
mechanism is thermally activated; the curves conductivity log versus the inverse of temperature gives straight lines. The activation
energy, measured from the valence band, decreases with Boron concentration, as expected, passing through a maximum, corresponding
this point to the position of Fermi energy of an intrinsic film. At low temperatures ðTo300KÞ the predominant transport mechanism
was variable range hopping (VRH). The behavior of the charge hopping under different electrical fields was followed. Results showed
that conductivity remained constant in a VRH regime only for a narrow range of electrical field.ðT4300KÞ the controlling transport
mechanism is thermally activated; the curves conductivity log versus the inverse of temperature gives straight lines. The activation
energy, measured from the valence band, decreases with Boron concentration, as expected, passing through a maximum, corresponding
this point to the position of Fermi energy of an intrinsic film. At low temperatures ðTo300KÞ the predominant transport mechanism
was variable range hopping (VRH). The behavior of the charge hopping under different electrical fields was followed. Results showed
that conductivity remained constant in a VRH regime only for a narrow range of electrical field.ðTo300KÞ the predominant transport mechanism
was variable range hopping (VRH). The behavior of the charge hopping under different electrical fields was followed. Results showed
that conductivity remained constant in a VRH regime only for a narrow range of electrical field.