High-output-power 255/280/310 nm deep ultraviolet light-emitting diodes and their lifetime characteristics

Fujioka, Akira; Asada, Katsuhiko; Yamada, Hirohito; Ohtsuka, Takumi; Ogawa, Takuma; Kosugi, Takao; Kishikawa, D.; Mukai, Takashi

doi:10.1088/0268-1242/29/8/084005

Cited by 91 publications

(55 citation statements)

References 16 publications

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“…For optoelectronic devices like light emitting diodes (LEDs) or laser diodes operating in the ultraviolet (UV) range, semiconductors with a wide bandgap are important. Therefore, numerous groups work on aluminum nitride (AlN), aluminum gallium nitride (AlGaN), aluminum indium gallium nitride (AlInGaN), and on LEDs and lasers based on these semiconductors . The efficiency of these LEDs could recently be further increased because of the improvements in crystal quality of AlGaN layers with high Al content, and the use of AlN single crystals as substrates, which significantly reduce the dislocation density .…”

Section: Introductionmentioning

confidence: 99%

Model for the deep defect‐related emission bands between 1.4 and 2.4 eV in AlN

Lamprecht

Jmerik

Collazo

et al. 2017

Physica Status Solidi (b)

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We report on defect‐related photoluminescence bands in the range from 1.4 to 2.4 eV in aluminum nitride bulk crystals and layers. Using continuous photoluminescence, photoluminescence excitation, and time‐resolved photoluminescence spectroscopy, we assign these bands to donor–acceptor pair transitions between shallow donor states or related slightly deeper DX− states of silicon or oxygen donors, and three different types of deep acceptors. These three different acceptors are most likely a (VAl−2false(ON)) complex, a (VAl−ON) complex, and an aluminum vacancy VAl, or different charge states of these.

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Section: Introductionmentioning

confidence: 99%

Model for the deep defect‐related emission bands between 1.4 and 2.4 eV in AlN

Lamprecht

Jmerik

Collazo

et al. 2017

Physica Status Solidi (b)

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“…Semiconductors with wide bandgap are important for ultraviolet (UV) devices like light emitting diodes (LEDs) or laser diodes. Several groups published results on such UV LEDs based on aluminum nitride (AlN), aluminum gallium nitride (AlGaN), and aluminum indium gallium nitride (AlInGaN), . Recently, the performance of UV LEDs based on AlGaN could be increased due to the improved quality of AlGaN layers with high Al content, , .…”

Section: Introductionmentioning

confidence: 99%

Slow decay of a defect‐related emission band at 2.05 eV in AlN: Signatures of oxygen‐related DX states

Lamprecht

Grund

Bauer

et al. 2016

Physica Status Solidi (b)

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We report on a defect‐related broad emission band at around 2.05 eV in bulk aluminum nitride crystals nominally undoped, but containing high concentrations of carbon, oxygen, and silicon. Time‐resolved photoluminescence spectroscopy yields two different exponential decays of this band: A slower process with 1.5 ms lifetime, and a faster process with a characteristic lifetime below 100 ns, which is activated with around 180 meV energy. The slow decay is ascribed to a spin‐forbidden transition between an oxygen‐related DX− S=1 state and a deep acceptor, which for higher temperatures turns into a donor‐acceptor pair transition between the effective‐mass‐like shallow oxygen donor state to the same deep acceptor. The acceptor is tentatively assigned to carbon or a carbon‐related complex.

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“…By using the pulsed atomic layer epitaxy (PALE) approach discussed in Section 6, and an AlN/Al0.85Ga0.15N superlattice strain-relief buffer, output power levels of 10.2 mW at 1 A pulsed current and 1 mW at 100 mA CW current were achieved in LEDs emitting at 325 nm and grown on sapphire substrates. In recently developed high-power DUV LEDs, the AlN/AlGaN superlattice buffer approach was employed by several groups [4,16]. For example, the LEDs emitting at 278 nm with an EQE of 10.4% and an output power of 9.3 mW at 20 mA CW current utilized strainrelief AlN/AlGaN superlattices on 10 μm thick AlN layers by migration-enhanced metalorganic chemical vapor deposition (MEMOCVD) [4].…”

Section: Aln/algan Superlattice Buffermentioning

confidence: 99%

“…For example, the LEDs emitting at 278 nm with an EQE of 10.4% and an output power of 9.3 mW at 20 mA CW current utilized strain-relief AlN/AlGaN superlattices on 10 µm thick AlN layers by migration-enhanced metalorganic chemical vapor deposition (MEMOCVD) [4]. In 255, 280, and 310 nm DUV LEDs with output powers of 45.2, 93.3, and 65.8 mW and EQEs of 1.3%, 3.0%, and 2.4%, respectively, at 350 mA pulsed current, AlN/AlGaN superlattices were also implemented as a basic design strategy for strain-relief [16].…”

Section: Aln/algan Superlattice Buffermentioning

confidence: 99%

Status of Growth of Group III-Nitride Heterostructures for Deep Ultraviolet Light-Emitting Diodes

et al. 2017

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Abstract:We overview recent progress in growth aspects of group III-nitride heterostructures for deep ultraviolet (DUV) light-emitting diodes (LEDs), with particular emphasis on the growth approaches for attaining high-quality AlN and high Al-molar fraction AlGaN. The discussion commences with the introduction of the current status of group III-nitride DUV LEDs and the remaining challenges. This segues into discussion of LED designs enabling high device performance followed by the review of advances in the methods for the growth of bulk single crystal AlN intended as a native substrate together with a discussion of its UV transparency. It should be stated, however, that due to the high-cost of bulk AlN substrates at the time of writing, the growth of DUV LEDs on foreign substrates such as sapphire still dominates the field. On the deposition front, the heteroepitaxial growth approaches incorporate high-temperature metal organic chemical vapor deposition (MOCVD) and pulsed-flow growth, a variant of MOCVD, with the overarching goal of enhancing adatom surface mobility, and thus epitaxial lateral overgrowth which culminates in minimization the effect of lattice-and thermal-mismatches. This is followed by addressing the benefits of pseudomorphic growth of strained high Al-molar fraction AlGaN on AlN. Finally, methods utilized to enhance both p-and n-type conductivity of high Al-molar fraction AlGaN are reviewed.

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High-output-power 255/280/310 nm deep ultraviolet light-emitting diodes and their lifetime characteristics

Cited by 91 publications

References 16 publications

Model for the deep defect‐related emission bands between 1.4 and 2.4 eV in AlN

Model for the deep defect‐related emission bands between 1.4 and 2.4 eV in AlN

Slow decay of a defect‐related emission band at 2.05 eV in AlN: Signatures of oxygen‐related DX states

Status of Growth of Group III-Nitride Heterostructures for Deep Ultraviolet Light-Emitting Diodes

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