Nature of exciton transitions in hexagonal boron nitride

J. Li; X. K. Cao; T. B. Hoffman; J. H. Edgar; J. Y. Lin; H. X. Jiang

doi:10.1063/1.4944696

Nature of exciton transitions in hexagonal boron nitride

J. Li, X. K. Cao, T. B. Hoffman, J. H. Edgar, J. Y. Lin, H. X. Jiang

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Abstract

In contrast to other III-nitride semiconductors GaN and AlN, the intrinsic (or free) exciton transition in hexagonal boron nitride (h-BN) consists of rather complex fine spectral features (resolved into six sharp emission peaks) and the origin of which is still unclear. Here, the free exciton transition (FX) in h-BN bulk crystals synthesized by a solution method at atmospheric pressure has been probed by deep UV time-resolved photoluminescence (PL) spectroscopy. Based on the separations between the energy peak positions of the FX emission lines, the identical PL decay kinetics among different FX emission lines, and the known phonon modes in h-BN, we suggest that there is only one principal emission line corresponding to the direct intrinsic FX transition in h-BN, whereas all other fine features are a result of phonon-assisted transitions. The identified phonon modes are all associated with the center of the Brillouin zone. Our results offer a simple picture for the understanding of the fundamental exciton transitions in h-BN.

Original language	English
Article number	122101
Journal	Applied Physics Letters
Volume	108
Issue number	12
DOIs	https://doi.org/10.1063/1.4944696
State	Published - Mar 21 2016

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title = "Nature of exciton transitions in hexagonal boron nitride",

abstract = "In contrast to other III-nitride semiconductors GaN and AlN, the intrinsic (or free) exciton transition in hexagonal boron nitride (h-BN) consists of rather complex fine spectral features (resolved into six sharp emission peaks) and the origin of which is still unclear. Here, the free exciton transition (FX) in h-BN bulk crystals synthesized by a solution method at atmospheric pressure has been probed by deep UV time-resolved photoluminescence (PL) spectroscopy. Based on the separations between the energy peak positions of the FX emission lines, the identical PL decay kinetics among different FX emission lines, and the known phonon modes in h-BN, we suggest that there is only one principal emission line corresponding to the direct intrinsic FX transition in h-BN, whereas all other fine features are a result of phonon-assisted transitions. The identified phonon modes are all associated with the center of the Brillouin zone. Our results offer a simple picture for the understanding of the fundamental exciton transitions in h-BN.",

author = "J. Li and Cao, {X. K.} and Hoffman, {T. B.} and Edgar, {J. H.} and Lin, {J. Y.} and Jiang, {H. X.}",

note = "Funding Information: The efforts on h-BN material growth are supported by DHS ARI Program (No. 2011-DN-077-ARI048), the studies of the fundamental optical properties of h-BN are supported by DOE (DE-FG02-09ER46552), and the studies of the basic structural properties of h-BN are supported by NSF (ECCS-1402886). Jiang and Lin are grateful to the AT&T Foundation for the support of Ed Whitacre and Linda Whitacre endowed chairs. Publisher Copyright: {\textcopyright} 2016 AIP Publishing LLC.",

year = "2016",

month = mar,

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doi = "10.1063/1.4944696",

language = "English",

volume = "108",

journal = "Applied Physics Letters",

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T1 - Nature of exciton transitions in hexagonal boron nitride

AU - Li, J.

AU - Cao, X. K.

AU - Hoffman, T. B.

AU - Edgar, J. H.

AU - Lin, J. Y.

AU - Jiang, H. X.

N1 - Funding Information: The efforts on h-BN material growth are supported by DHS ARI Program (No. 2011-DN-077-ARI048), the studies of the fundamental optical properties of h-BN are supported by DOE (DE-FG02-09ER46552), and the studies of the basic structural properties of h-BN are supported by NSF (ECCS-1402886). Jiang and Lin are grateful to the AT&T Foundation for the support of Ed Whitacre and Linda Whitacre endowed chairs. Publisher Copyright: © 2016 AIP Publishing LLC.

PY - 2016/3/21

Y1 - 2016/3/21

N2 - In contrast to other III-nitride semiconductors GaN and AlN, the intrinsic (or free) exciton transition in hexagonal boron nitride (h-BN) consists of rather complex fine spectral features (resolved into six sharp emission peaks) and the origin of which is still unclear. Here, the free exciton transition (FX) in h-BN bulk crystals synthesized by a solution method at atmospheric pressure has been probed by deep UV time-resolved photoluminescence (PL) spectroscopy. Based on the separations between the energy peak positions of the FX emission lines, the identical PL decay kinetics among different FX emission lines, and the known phonon modes in h-BN, we suggest that there is only one principal emission line corresponding to the direct intrinsic FX transition in h-BN, whereas all other fine features are a result of phonon-assisted transitions. The identified phonon modes are all associated with the center of the Brillouin zone. Our results offer a simple picture for the understanding of the fundamental exciton transitions in h-BN.

AB - In contrast to other III-nitride semiconductors GaN and AlN, the intrinsic (or free) exciton transition in hexagonal boron nitride (h-BN) consists of rather complex fine spectral features (resolved into six sharp emission peaks) and the origin of which is still unclear. Here, the free exciton transition (FX) in h-BN bulk crystals synthesized by a solution method at atmospheric pressure has been probed by deep UV time-resolved photoluminescence (PL) spectroscopy. Based on the separations between the energy peak positions of the FX emission lines, the identical PL decay kinetics among different FX emission lines, and the known phonon modes in h-BN, we suggest that there is only one principal emission line corresponding to the direct intrinsic FX transition in h-BN, whereas all other fine features are a result of phonon-assisted transitions. The identified phonon modes are all associated with the center of the Brillouin zone. Our results offer a simple picture for the understanding of the fundamental exciton transitions in h-BN.

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SN - 0003-6951

VL - 108

JO - Applied Physics Letters

JF - Applied Physics Letters

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Nature of exciton transitions in hexagonal boron nitride

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