Optical-absorption bands in the 1-3 eV range in n-type SiC polytypes

Sukit Limpijumnong, Walter R L Lambrecht, Sergey Rashkeev, Benjamin Segall

Research output: Contribution to journalArticle

47 Citations (Scopus)

Abstract

Measured optical-absorption bands in the 1-3 eV range in fairly heavily doped n-type SiC polytypes 3C, 6H, 4H, 8H, and 15R are shown to arise from optical transitions between the lowest conduction band, which is to some extent perturbed by impurity effects, to higher conduction bands. The energies of the transitions are in good agreement with the differences between unperturbed low-lying energy bands calculated using the full-potential linear muffin-tin orbital method in the local-density approximation. The polarization dependence is explained by selection rules deriving from the symmetry of the bands involved. This indicates that the states involved in the transitions must to a good extent retain the symmetry characters of the unperturbed bands. On the other hand, the calculated absorption peaks from a pure band-to-band model are much narrower, and slightly lower in energy than the experimental ones. Calculations of the density of states over a restricted range of k space for the final states indicate that a partial breakdown of periodicity and hence the Δk = 0 selection rule can account for a major part of the broadening. This explanation is consistent with the degenerate carrier concentration, associated with the overlap of the impurity band tail with the bottom of the conduction band. In 6H-SiC, one feature in the absorption spectrum appears nevertheless to be associated with a more purely band-to-band-like transition. It is a sharp one-dimensional van Hove singularity in the joint density of states at the M point associated with the camel's-back structure of the lowest conduction band. At a lower carrier concentration, this feature is not present, and the transitions appear to have a more localized impurity-to-band character.

Original languageEnglish
Pages (from-to)12890-12899
Number of pages10
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume59
Issue number20
Publication statusPublished - 1 Dec 1999
Externally publishedYes

Fingerprint

Conduction bands
Light absorption
Absorption spectra
optical absorption
absorption spectra
Impurities
Carrier concentration
conduction bands
Local density approximation
Optical transitions
Tin
Electron transitions
impurities
Band structure
Polarization
symmetry
trucks
optical transition
energy bands
periodic variations

ASJC Scopus subject areas

  • Condensed Matter Physics

Cite this

Optical-absorption bands in the 1-3 eV range in n-type SiC polytypes. / Limpijumnong, Sukit; Lambrecht, Walter R L; Rashkeev, Sergey; Segall, Benjamin.

In: Physical Review B - Condensed Matter and Materials Physics, Vol. 59, No. 20, 01.12.1999, p. 12890-12899.

Research output: Contribution to journalArticle

Limpijumnong, Sukit ; Lambrecht, Walter R L ; Rashkeev, Sergey ; Segall, Benjamin. / Optical-absorption bands in the 1-3 eV range in n-type SiC polytypes. In: Physical Review B - Condensed Matter and Materials Physics. 1999 ; Vol. 59, No. 20. pp. 12890-12899.
@article{9b94ee4a1eb84744b8e2060eca57618b,
title = "Optical-absorption bands in the 1-3 eV range in n-type SiC polytypes",
abstract = "Measured optical-absorption bands in the 1-3 eV range in fairly heavily doped n-type SiC polytypes 3C, 6H, 4H, 8H, and 15R are shown to arise from optical transitions between the lowest conduction band, which is to some extent perturbed by impurity effects, to higher conduction bands. The energies of the transitions are in good agreement with the differences between unperturbed low-lying energy bands calculated using the full-potential linear muffin-tin orbital method in the local-density approximation. The polarization dependence is explained by selection rules deriving from the symmetry of the bands involved. This indicates that the states involved in the transitions must to a good extent retain the symmetry characters of the unperturbed bands. On the other hand, the calculated absorption peaks from a pure band-to-band model are much narrower, and slightly lower in energy than the experimental ones. Calculations of the density of states over a restricted range of k space for the final states indicate that a partial breakdown of periodicity and hence the Δk = 0 selection rule can account for a major part of the broadening. This explanation is consistent with the degenerate carrier concentration, associated with the overlap of the impurity band tail with the bottom of the conduction band. In 6H-SiC, one feature in the absorption spectrum appears nevertheless to be associated with a more purely band-to-band-like transition. It is a sharp one-dimensional van Hove singularity in the joint density of states at the M point associated with the camel's-back structure of the lowest conduction band. At a lower carrier concentration, this feature is not present, and the transitions appear to have a more localized impurity-to-band character.",
author = "Sukit Limpijumnong and Lambrecht, {Walter R L} and Sergey Rashkeev and Benjamin Segall",
year = "1999",
month = "12",
day = "1",
language = "English",
volume = "59",
pages = "12890--12899",
journal = "Physical Review B-Condensed Matter",
issn = "0163-1829",
publisher = "American Institute of Physics Publising LLC",
number = "20",

}

TY - JOUR

T1 - Optical-absorption bands in the 1-3 eV range in n-type SiC polytypes

AU - Limpijumnong, Sukit

AU - Lambrecht, Walter R L

AU - Rashkeev, Sergey

AU - Segall, Benjamin

PY - 1999/12/1

Y1 - 1999/12/1

N2 - Measured optical-absorption bands in the 1-3 eV range in fairly heavily doped n-type SiC polytypes 3C, 6H, 4H, 8H, and 15R are shown to arise from optical transitions between the lowest conduction band, which is to some extent perturbed by impurity effects, to higher conduction bands. The energies of the transitions are in good agreement with the differences between unperturbed low-lying energy bands calculated using the full-potential linear muffin-tin orbital method in the local-density approximation. The polarization dependence is explained by selection rules deriving from the symmetry of the bands involved. This indicates that the states involved in the transitions must to a good extent retain the symmetry characters of the unperturbed bands. On the other hand, the calculated absorption peaks from a pure band-to-band model are much narrower, and slightly lower in energy than the experimental ones. Calculations of the density of states over a restricted range of k space for the final states indicate that a partial breakdown of periodicity and hence the Δk = 0 selection rule can account for a major part of the broadening. This explanation is consistent with the degenerate carrier concentration, associated with the overlap of the impurity band tail with the bottom of the conduction band. In 6H-SiC, one feature in the absorption spectrum appears nevertheless to be associated with a more purely band-to-band-like transition. It is a sharp one-dimensional van Hove singularity in the joint density of states at the M point associated with the camel's-back structure of the lowest conduction band. At a lower carrier concentration, this feature is not present, and the transitions appear to have a more localized impurity-to-band character.

AB - Measured optical-absorption bands in the 1-3 eV range in fairly heavily doped n-type SiC polytypes 3C, 6H, 4H, 8H, and 15R are shown to arise from optical transitions between the lowest conduction band, which is to some extent perturbed by impurity effects, to higher conduction bands. The energies of the transitions are in good agreement with the differences between unperturbed low-lying energy bands calculated using the full-potential linear muffin-tin orbital method in the local-density approximation. The polarization dependence is explained by selection rules deriving from the symmetry of the bands involved. This indicates that the states involved in the transitions must to a good extent retain the symmetry characters of the unperturbed bands. On the other hand, the calculated absorption peaks from a pure band-to-band model are much narrower, and slightly lower in energy than the experimental ones. Calculations of the density of states over a restricted range of k space for the final states indicate that a partial breakdown of periodicity and hence the Δk = 0 selection rule can account for a major part of the broadening. This explanation is consistent with the degenerate carrier concentration, associated with the overlap of the impurity band tail with the bottom of the conduction band. In 6H-SiC, one feature in the absorption spectrum appears nevertheless to be associated with a more purely band-to-band-like transition. It is a sharp one-dimensional van Hove singularity in the joint density of states at the M point associated with the camel's-back structure of the lowest conduction band. At a lower carrier concentration, this feature is not present, and the transitions appear to have a more localized impurity-to-band character.

UR - http://www.scopus.com/inward/record.url?scp=0000607601&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0000607601&partnerID=8YFLogxK

M3 - Article

VL - 59

SP - 12890

EP - 12899

JO - Physical Review B-Condensed Matter

JF - Physical Review B-Condensed Matter

SN - 0163-1829

IS - 20

ER -