The 2020 UV emitter roadmap

Amano, Hiroshi; Collazo, Ramón; Santi, Carlo De; Einfeldt, S.; Funato, Mitsuru; Glaab, Johannes; Hagedorn, Sylvia; Hirano, Akira; Hasegawa, Hideki; Ishii, Ryota; Kashima, Yukio; Kawakami, Yoichi; Kirste, Ronny; Kneissl, Michael; Martin, Robert; Mehnke, Frank; Meneghini, Matteo; Ougazzaden, A.; Parbrook, P. J.; Rajan, Siddharth; Reddy, Pramod; Römer, Friedhard; Ruschel, Jan; Sarkar, Biplab; Scholz, F.; Schowalter, L. J.; Shields, P. A.; Sitar, Zlatko; Sulmoni, Luca; Wang, Tao; Wernicke, Tim; Weyers, M.; Witzigmann, Bernd; Wu, Yuh Renn; Wunderer, Thomas; Zhang, Yuewei

doi:10.1088/1361-6463/aba64c

Cited by 317 publications

(229 citation statements)

References 214 publications

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“…It should be noted that the definition of IQE in this article is the ratio of the number of photons generated per unit time to the injection current. [ 26 ] At a current of 250 mA, the LOP of samples B and C is enhanced by 38.7% and 67.1% as compared with that of sample A, respectively. The efficiency droop, can be defined by the expression (IQE max ‐IQE min )/IQE max , is 32.2%, 9.3%, and 6.2% for samples A, B, and C, respectively.…”

Section: Resultsmentioning

confidence: 99%

Improved Wave Function Overlap and Carrier Confinement of AlGaN‐Based Deep‐Ultraviolet Light‐Emitting Diodes with Graded Composition Multiple Quantum Wells

Xiao

Liu

et al. 2021

Physica Status Solidi (a)

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AlGaN-based deep-ultraviolet light-emitting diodes (DUV-LEDs), which emit at around 280 nm, have attracted a great deal of interest due to their wide range of potential applications such as water purification, sterilization, biological disinfections, and medical therapy. [1][2][3] Nevertheless, the efficiency of DUV-LEDs is much lower than that of the InGaN-based visible LEDs, which has become a bottleneck limiting their widespread commercial applications. The strong built-in polarization electric field and insufficient carrier confinement in the multiple-quantum-well (MQW) active region are two important issues limiting the output performance of the DUV-LEDs. To improve the carrier confinement, a simple method is to increase Al composition of the barrier layer. However, it brings some drawbacks including a more serious lattice mismatch between wells and barriers, which will produce the dislocations and severe quantum-confined Stark effects (QCSEs). The strengthened polarization electric field will further reduce the electronhole wave function overlap, and deteriorate the radiative recombination rate of the MQWs. In addition, the strong confining potential of quantum wells (QWs) will increase the ratio of Auger recombination. [4,5] The DUV-LEDs generally possess shallower wells to lower the lattice mismatch between the QWs and the quantum barriers (QBs), however, which will result in poor carrier confinement. Therefore, there is a trade-off between the carrier confinement and the overlap of the wave functions. [6] In particular, the insufficient carrier confinement in the MQWs will result in large amount of electrons concentrated in the last QW (LQW) close to the p-type electron blocking layer (p-EBL), and the electrons would be easily leaked into the p-type region to decrease the emission efficiency, especially at high current density injection. [7][8][9][10] To suppress electron leakage, many studies have focused on the p-EBL, [11][12][13][14] however, the p-EBL might also introduce a higher barrier in the valence band, hindering the injection efficiency of the holes. Recently, great efforts have been made to deal with the issues mentioned earlier. [15][16][17][18][19][20][21] The tailored Si-doping in the QBs is used by Zhu et al. to enhance the confinement of electrons in the QWs. [8] Li et al. designed triangular QBs to suppress the electron overflow and decrease the electrostatic field in the active region. [15] Lin et al. show a quaternary AlInGaN MQW design to reduce the polarization effect and suppress the electron leakage. [16] The compositional modulation schemes for the Al x Ga 1-x N MQWs have proposed by Kojima et al. to reduce the separation of the electron-hole wave functions. [17] Graded Al-composition in the QW layers shown by Yu et al. showed an improvement of the electron-hole wave function overlap due to the screening of the QCSE. [18]

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Section: Resultsmentioning

confidence: 99%

Improved Wave Function Overlap and Carrier Confinement of AlGaN‐Based Deep‐Ultraviolet Light‐Emitting Diodes with Graded Composition Multiple Quantum Wells

Xiao

Liu

et al. 2021

Physica Status Solidi (a)

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“…Among various candidates, aluminum gallium nitride (AlGaN) alloys hold a great promise to develop semiconductor DUV lasers due to their ultrawide, direct, and tunable bandgap energies from 3.4 to 6.2 eV that correspond to %364-200 nm in the emission wavelength, respectively. [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] In addition, due to the strong chemical bonding, AlGaNbased devices possess high melting points, excellent mechanical strength, and are highly degradation-resistant, which make them highly suitable for applications in extreme and harsh environments.…”

Section: Introductionmentioning

confidence: 99%

“…[62][63][64][65] Additional challenges that hinder the development of the electrically injected AlGaN DUV lasers include the quantum confined Stark effect (QCSE) in QWs due to the large electric polarization fields and the transition from the transverse electric (TE) polarization to the unfavorable transverse magnetic (TM) polarization. [6,9,10,12,15,66] On a separate track to develop AlGaN DUV lasers, the molecular beam epitaxy (MBE)-grown AlGaN has drawn a lot of attention in recent years. [21,[67][68][69][70][71][72][73][74][75][76][77][78] Compared with MOCVD, MBE offers features such as residual atmosphere corresponding to ultrahigh vacuum, growth under high-vacuum conditions, a separate control on the substrate temperature and the temperature of each source, and in situ growth monitoring with the reflection high-energy electron diffraction (RHEED).…”

Section: Introductionmentioning

confidence: 99%

Recent Progress on Aluminum Gallium Nitride Deep Ultraviolet Lasers by Molecular Beam Epitaxy

Zhang

Yin

Zhao

2021

Physica Rapid Research Ltrs

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Over the past decades, the aluminum gallium nitride (AlGaN) alloy system has received wide interest for the development of semiconductor deep ultraviolet (DUV) lasers due to its direct, tunable, and ultrawide bandgap energies (3.4-6.2 eV). The progress, nonetheless, has been remained slow, which is ascribed to a few major challenges, including large dislocation and defect densities, difficulty in obtaining p-type high-Al-content AlGaN layers with a sufficient p-type conduction, the large electric polarization fields, and the unfavorable optical polarization. In recent years, with AlGaN alloys grown by molecular beam epitaxy (MBE), including both thin films and nanowire structures, remarkable advancements have been made, such as highly conductive p-type high-Al-content AlGaN epilayers with resistivities as low as 0.7 Ω cm and DUV lasing down to 239 nm with nanowire structures under a direct current injection. Herein, the recent progress on the DUV lasers by the MBE-grown AlGaN is reviewed. The challenges and prospects of the MBE-grown AlGaN for DUV lasers are also discussed.

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“…A LED is a solid-state semiconductor device that emits light when is connected to direct current. Such light source shows important advantages, such as a low driven voltage, a very fast response time, a straightforward intensity control and it does not contain dangerous heavy metals (in particular mercury) [39]. UVC LEDs do contain small amounts of elements such as the metals gallium and magnesium and the metalloids silicon and boron (although boron is not predominantly used), which are bound within a stable crystal structure and cannot leach into the environment.…”

Section: Introductionmentioning

confidence: 99%

Design of optical cavity for air sanification through ultraviolet germicidal irradiation

Lombini

Diolaiti

Rosa

et al. 2021

Preprint

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The transmission of airborne pathogens represents a major issue to worldwide public health. Ultraviolet light irradiation can contribute to the sanification of air to reduce the pathogen transmission. This study concerns the design of a compact filter for airborne pathogen inactivation by means of UV-C LED sources, whose effective irradiance is enhanced thanks to high reflective surfaces. Ray-tracing and computational fluid dynamic simulations are both used to model the device and to maximize the performance inside the filter volume. Simulations foresee the inhibition of SARS-Cov 2 also in the case of high air fluxes. This study demonstrates that current available LED technology is effective for air sanification purposes.

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The 2020 UV emitter roadmap

Cited by 317 publications

References 214 publications

Improved Wave Function Overlap and Carrier Confinement of AlGaN‐Based Deep‐Ultraviolet Light‐Emitting Diodes with Graded Composition Multiple Quantum Wells

Improved Wave Function Overlap and Carrier Confinement of AlGaN‐Based Deep‐Ultraviolet Light‐Emitting Diodes with Graded Composition Multiple Quantum Wells

Recent Progress on Aluminum Gallium Nitride Deep Ultraviolet Lasers by Molecular Beam Epitaxy

Design of optical cavity for air sanification through ultraviolet germicidal irradiation

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