Band-edge transitions in hexagonal boron nitride epilayers

Majety, S.; Cao, X. K.; Li, J.; Dahal, R.; Lin, J. Y.; Jiang, H. X.

doi:10.1063/1.4742194

Cited by 50 publications

(67 citation statements)

References 28 publications

(58 reference statements)

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“…Based on the intense photoluminescence at low temperature from epitaxial hBN layers deposited on sapphire substrates, Majety et al [16] also supported the finding that hBN is a direct bandgap semiconductor. Using state-of-the art all-electron GW approximation, Arnaud et al [22] asserted hBN is in fact an indirect band gap semiconductor.…”

Section: Discussionsupporting

confidence: 48%

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Characterization of bulk hexagonal boron nitride single crystals grown by the metal flux technique

Edgar

Hoffman

Clubine

et al. 2014

Journal of Crystal Growth

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Section: Discussionsupporting

confidence: 48%

“…The laser beam was focused onto the sample surface with a lens. The PL signal was collected and dispersed by a monochromator (1.3 meters), and then detected by a microchannel-plate photomultiplier tube together with a single photon-counting system [16].…”

Section: Methodsmentioning

confidence: 99%

Characterization of bulk hexagonal boron nitride single crystals grown by the metal flux technique

Edgar

Hoffman

Clubine

et al. 2014

Journal of Crystal Growth

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“…[7][8][9][10] Epitaxial h-BN layers with high optical qualities can be achieved, 7,20 but these materials generally lack the intrinsic FX transitions above 5.7 eV due to the presence of native and point defects. 7,20 Most recent studies have suggested that the D-series emission lines are due to the recombination of excitons bound to deep acceptors formed by carbon impurities occupying the nitrogen sites, and h-BN epilayers exhibiting pure intrinsic FX emission can be obtained by growing the materials under high ammonia flow rates. 21 However, the detailed features of the FX transitions in h-BN epilayers are distinctly different from those in h-BN bulk crystals, 21 which is what remains to be investigated and understood.…”

mentioning

confidence: 99%

“…A deep UV time-resolved PL system was utilized to probe the emission properties. 13,20 The system consists of a frequency quadrupled 100 fs Ti:sapphire laser providing an excitation photon energy of 6.28 eV and a monochromator (1.3 m) in conjunction with a single photon counting detection system providing a timeresolution of 20 ps and a streak camera system providing a time-resolution of 2 ps.…”

mentioning

confidence: 99%

Nature of exciton transitions in hexagonal boron nitride

Cao

Hoffman

et al. 2016

Applied Physics Letters

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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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“…Thus, it is likely that the material has direct band gap of around 6 eV. In addition, it was shown that h-BN has higher luminescence efficiency than AlN [23]. Thus h-BN could be employed as a deep UV emitter and detector competing with AlN.…”

Section: Properties and Applications Of Sp 2 -Bnmentioning

confidence: 99%

Chemical Vapour Deposition of sp2 Hybridised Boron Nitride

Chubarov¹

2014

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The aim of this work was to develop a chemical vapour deposition process and understand the growth of sp 2 hybridised Boron Nitride (sp 2 -BN). Thus, the growth on different substrates together with the variation of growth parameters was investigated in details and is presented in the papers included in this thesis. Deposited films of sp 2 -BN were characterised with the purpose to determine optimal deposition process parameters for the growth of high crystal quality thin films with further investigations of chemical composition, morphology and other properties important for the implementation of this material towards electronic, optoelectronic devices and devices based on graphene/BN heterostructures.For the growth of sp 2 -BN triethyl boron and ammonia were employed as B and N precursors, respectively. Pure H 2 as carrier gas is found to be necessary for the growth of crystalline sp 2 -BN. Addition of small amount of silane to the gas mixture improves the crystalline quality of the growing sp 2 -BN film.It was observed that for the growth of crystalline sp 2 -BN on c-axis oriented -Al 2 O 3 a thin and strained AlN buffer layer is needed to support epitaxial growth of sp 2 -BN, while it was possible to deposit rhombohedral BN (r-BN) on various polytypes of SiC without the need for a buffer layer. The growth temperature suitable for the growth of crystalline sp 2 -BN is 1500 °C. Nevertheless, the growth of crystalline sp 2 -BN was also observed on -Al 2 O 3 with an AlN buffer layer at a lower temperature of 1200 °C. Growth at this low temperature was found to be hardly controllable due to the low amount of Si that is necessary at this temperature and its accumulation in the reaction cell. When SiC was used as a substrate at the growth temperature of 1200 °C, no crystalline sp 2 -BN was formed, according to X-ray diffraction.Crystalline structure investigations of the deposited films showed formation of twinned r-BN on both substrates used. Additionally, it was found that the growth on Om man skulle kunna göra ljusdioder av BN skulle dessa sända ut ljus med en våglängd på cirka 220 nm alltså den typen av ultraviolettljus (UV) som ozonlagret filtrerar bort från solen. Av sådana ljusdioder skulle man sedan kunna göra vita ljusdioder genom att använda en luminofor, vilket är ett material som absorberar UV-ljus och sedan sänder ut vitt ljus, men ännu mera spännande skulle det vara att använda ljusdioderna för vattenrening då denna typ av UV-ljus dödar bakterier.Eftersom BN bildar samma kristallstrukturer som kol, så är den grafitlika, sp 2 -hybridiserade formen av BN mycket intressant att använda tillsammans med grafen.Beräkningar har visat att om man använder sp 2 -BN som substrat till grafen så kommer man åt större del av de förutspådda materialegenskaperna för grafen än om man använder andra substrat.Syftet med detta arbete har varit att utveckla en syntesprocess för tunna filmer av sp 2 -BN med tillräckligt hög kvalité för att kunna börja utforska alla möjligheter med BN, för detta har en teknik som kal...

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Band-edge transitions in hexagonal boron nitride epilayers

Cited by 50 publications

References 28 publications

Characterization of bulk hexagonal boron nitride single crystals grown by the metal flux technique

Characterization of bulk hexagonal boron nitride single crystals grown by the metal flux technique

Nature of exciton transitions in hexagonal boron nitride

Chemical Vapour Deposition of sp2 Hybridised Boron Nitride

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