Review—On The Search for Efficient Solid State Light Emitters: Past, Present, Future

Weisbuch, C.

doi:10.1149/2.0392001jss

Cited by 73 publications

(40 citation statements)

References 159 publications

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“…Their demonstration of GaN-based light-emitting diodes (LEDs) triggered intense worldwide research and development efforts, not only for general lighting applications, but also in many other areas, such as displays, sensing, biotechnology, and medical instrumentation. The promise of superior energy efficiency is the main driving force of many research activities on GaN-LEDs [2,3]. However, high efficiency is only observed at low injection current density and low power ( Fig.…”

Section: Introductionmentioning

confidence: 99%

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Efficiency Models for GaN-Based Light-Emitting Diodes: Status and Challenges

Piprek¹

2020

Materials

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Light-emitting diodes (LEDs) based on Gallium Nitride (GaN) have been revolutionizing various applications in lighting, displays, biotechnology, and other fields. However, their energy efficiency is still below expectations in many cases. An unprecedented diversity of theoretical models has been developed for efficiency analysis and GaN-LED design optimization, including carrier transport models, quantum well recombination models, and light extraction models. This invited review paper provides an overview of the modeling landscape and pays special attention to the influence of III-nitride material properties. It thereby identifies some key challenges and directions for future improvements.

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Section: Introductionmentioning

confidence: 99%

“…The promise of superior energy efficiency is the main driving force of many research activities on GaN-LEDs [ 2 , 3 ]. However, high efficiency is only observed at low injection current density and low power ( Figure 1 ).…”

Section: Introductionmentioning

confidence: 99%

Efficiency Models for GaN-Based Light-Emitting Diodes: Status and Challenges

Piprek¹

2020

Materials

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“…

The most exciting property of III-N compounds is the widest achievable range of fundamental bandgaps, from the near-IR to deep ultraviolet (UV), which is far from being fully used in optoelectronics, since the fabrication of only lighting and UVA light-emitting diodes (LEDs) (both composed of In-containing compounds) has been successfully commercialized, leading to revolutionary changes in this area. [1][2][3] The best-reported LEDs possess a quantum efficiency as high as 90% at room temperature (RT), whereas the typical value of this parameter for the mass-produced LEDs is about 60% with an output power of up to several tens of Watts, which, nevertheless, exceeds the parameters of incandescent lamps.Development of the semiconductor UV emitters based on (Al,Ga)N compounds for UVB and UVC spectral ranges, having operating wavelengths λ ¼ 280-315 nm and λ ¼ 210-280 nm, respectively, is also of great demand, as portable, energysaving, and environmental-friendly UVC emitters with a tuned operating wavelength are strongly desired for optical disinfection of various pathogens (with λ: 220-265 nm), [4][5][6] optical spectroscopy for detecting biological and chemical agents (in the entire UVC range), [7,8] non-line-ofsight UV-optical communication systems (in the solar-blind range λ < 290 nm), etc. [9] Progress in this field has been achieved over the past 20 years due to the activity of numerous research groups from the University of South Carolina and SETi, [10,11] Riken, [12] Technical University of Berlin and the Ferdinand-Braun-Institut, [13] Sandia National Laboratories and Ohio State University, [14] Nagoya University, [15] Ioffe Institute, [16] etc.

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confidence: 99%

Monolayer‐Thick GaN/AlN Multilayer Heterostructures for Deep‐Ultraviolet Optoelectronics

Jmerik

Торопов

Davydov

et al. 2021

Physica Rapid Research Ltrs

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Recent progress in the development of monolayer (ML)‐thick GaN/AlN multilayer heterostructures for deep‐ultraviolet (UV) optoelectronics is reviewed. Analysis of both plasma‐assisted molecular beam epitaxy and metal–organic vapor phase epitaxy shows that extreme interface sharpness and sub‐ML accuracy in setting the layer thickness are attractive features of the former, whereas the lowest density of threading dislocations and wide possibilities for the implementation of various 2D growth mechanisms are the advantages of the latter. The structural properties of ML GaN/AlN heterostructures are evaluated not only by standard X‐ray diffraction and scanning transmission electron microscopy, but also by Raman spectroscopy. Theoretical and experimental studies of the optical properties of ML‐thick GaN/AlN quantum wells (QWs) reveal that quenching of the quantum‐confined Stark effect, suppression of transverse electric transverse magnetic polarization switching, as well as the excitonic nature of UV‐radiative recombination in ultrathin (1–2 ML) QWs ensure in such structures a high internal quantum yield of 75% for UV radiation at 235 nm at room temperature. The possibilities of using ML‐GaN/AlN heterostructures to fabricate UVC emitters of spontaneous and stimulated emissions in a wide range of output powers with various pumping techniques are considered, and the most important problems are formulated.

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“…The quantities entering equations (1) and 2, namely the A, B and C coefficients and the IE, although their determination require great care as discussed previously, are needed to obtain the IQE. IE is a particularly difficult quantity to measure, and we refer to the detailed discussion in the study by Weisbuch [77]. In addition, great care must be exerted when extracting coefficients from purely optical excitation measurements for use in LED simulations as the internal fields are different from those under electrical excitation.…”

Section: Experimental Evidence Of Directly Observable Disorder-inducementioning

confidence: 99%

Disorder effects in nitride semiconductors: impact on fundamental and device properties

Weisbuch

Nakamura

et al. 2020

Nanophotonics

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Semiconductor structures used for fundamental or device applications most often incorporate alloy materials. In “usual” or “common” III–V alloys, based on the InGaAsP or InGaAlAs material systems, the effects of compositional disorder on the electronic properties can be treated in a perturbative approach. This is not the case in the more recent nitride-based GaInAlN alloys, where the potential changes associated with the various atoms induce strong localization effects, which cannot be described perturbatively. Since the early studies of these materials and devices, disorder effects have indeed been identified to play a major role in their properties. Although many studies have been performed on the structural characterization of materials, on intrinsic electronic localization properties, and on the impact of disorder on device operation, there are still many open questions on all these topics. Taking disorder into account also leads to unmanageable problems in simulations. As a prerequisite to address material and device simulations, a critical examination of experiments must be considered to ensure that one measures intrinsic parameters as these materials are difficult to grow with low defect densities. A specific property of nitride semiconductors that can obscure intrinsic properties is the strong spontaneous and piezoelectric fields. We outline in this review the remaining challenges faced when attempting to fully describe nitride-based material systems, taking the examples of LEDs. The objectives of a better understanding of disorder phenomena are to explain the hidden phenomena often forcing one to use ad hoc parameters, or additional poorly defined concepts, to make simulations agree with experiments. Finally, we describe a novel simulation tool based on a mathematical breakthrough to solve the Schrödinger equation in disordered potentials that facilitates 3D simulations that include alloy disorder.

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Review—On The Search for Efficient Solid State Light Emitters: Past, Present, Future

Cited by 73 publications

References 159 publications

Efficiency Models for GaN-Based Light-Emitting Diodes: Status and Challenges

Efficiency Models for GaN-Based Light-Emitting Diodes: Status and Challenges

Monolayer‐Thick GaN/AlN Multilayer Heterostructures for Deep‐Ultraviolet Optoelectronics

Disorder effects in nitride semiconductors: impact on fundamental and device properties

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