GaN–InGaN LED efficiency reduction from parasitic electron currents in p-GaN

Togtema, Gregorey L.; Georgiev, Vasil; Georgieva, Dimka; Gergova, Rositsa; Butcher, Kenneth; Alexandrov, Dimiter

doi:10.1016/j.sse.2014.08.009

Cited by 7 publications

(6 citation statements)

References 12 publications

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“…[28] SiO 2 (PE-ALD) [7,24,25] β-Ga 2 O 3 (PE-ALD) [38] Silicon nitride (PE-ALD) [22,23,27,31,37,40] Plasma treatment (PE-ALD) [26] Electron treatment (CVD based) [36,39] GaN (CVD based) [42,44,45,55] InN (CVD based) [41][42][43]45,47,48,53,57,58] InGaN (CVD based) [49,51,54,56] InN nanopillars (CVD based) [46,50,52,55] The oxygen contamination overview provided in this introduction is followed by an experimental examination of some effects related to the surface modification of cathode materials by the generated plasma. In particular, we examine changes that have been observed for aluminum and stainless-steel cathodes.…”

Section: Materials (And Process) Referencementioning

confidence: 99%

“…This is a pulsed method for deposition of GaN at temperatures below 670 • C, much lower than typical MOCVD growth temperatures of over 950 • C. However, ALD-like smoothness could be obtained with root mean square atomic force microscopy roughness measurements of below 1 nm [42,44,55] and, more importantly, when grown on GaN templates, oxygen contamination levels of ~10 16 cm −3 were measured by SIMS [42], similar to the levels of commercial MOCVDgrown material. Migration-enhanced epitaxy with a hollow cathode plasma source has also shown some excellent results for InN [41,42,47,48] and InGaN [49]. For instance, some of the sharpest InN film photoluminescence ever reported was independently measured by McGill University [47], while some excellent quality epitaxial material has also been achieved [48].…”

Section: Materials (And Process) Referencementioning

confidence: 99%

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Recent Advances in Hollow Cathode Technology for Plasma-Enhanced ALD—Plasma Surface Modifications for Aluminum and Stainless-Steel Cathodes

Butcher

Georgiev²,

Georgieva³

2021

Coatings

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Recent designs have allowed hollow cathode gas plasma sources to be adopted for use in plasma-enhanced atomic layer deposition with the benefit of lower oxygen contamination for non-oxide films (a brief review of this is provided). From a design perspective, the cathode metal is of particular interest since—for a given set of conditions—the metal work function should determine the density of electron emission that drives the hollow cathode effect. However, we found that relatively rapid surface modification of the metal cathodes in the first hour or more of operation has a stronger influence. Langmuir probe measurements and hollow cathode electrical characteristics were used to study nitrogen and oxygen plasma surface modification of aluminum and stainless-steel hollow cathodes. It was found that the nitridation and oxidation of these metal cathodes resulted in higher plasma densities, in some cases by more than an order of magnitude, and a wider range of pressure operation. Moreover, it was initially thought that the use of aluminum cathodes would not be practical for gas plasma applications, as aluminum is extremely soft and susceptible to sputtering; however, it was found that oxide and nitride modification of the surface could protect the cathodes from such problems, possibly making them viable.

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Section: Materials (And Process) Referencementioning

confidence: 99%

Section: Materials (And Process) Referencementioning

confidence: 99%

Recent Advances in Hollow Cathode Technology for Plasma-Enhanced ALD—Plasma Surface Modifications for Aluminum and Stainless-Steel Cathodes

Butcher

Georgiev²,

Georgieva³

2021

Coatings

View full text Add to dashboard Cite

show abstract

“…It causes intensive investigation of their design, technology, and features, carried out by both by industry and university research teams. The studies focus on different design concepts such as vertical [1][2][3], lateral [4,5] or 3D core-shell [6][7][8][9] devices, discussing their fabrication technologies [10][11][12], or aiming at their features employing experimental [13,14] or numerical [15][16][17] approaches.…”

Section: Introductionmentioning

confidence: 99%

Numerical Model of Current Flow and Thermal Phenomena in Lateral GaN/InGaN LEDs

2021

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GaN-based light-emitting diodes (LEDs) became one of the most widely used light sources. One of their key factors is power conversion efficiency; hence, a lot of effort is placed on research to improve this parameter, either experimentally or numerically. Standard approaches involve device-oriented or system-oriented methods. Combining them is possible only with the aid of compact, lumped parameter models. In the paper, we present a new electro-thermal model that covers all the complex opto-electro-thermal phenomena occurring within the operating LED. It is a simple and low computational cost solution that can be integrated with package- or system-oriented numerical analysis. It allows a parametric analysis of the diode structure and properties under steady-state operating conditions. Its usefulness has been proved by conducting simulations of a sample lateral GaN/InGaN LED with the aid of ANSYS software. The results presented illustrate the current density and temperature fields. They allow the identification of ‘hot spots’ resulting from the current crowding effect and can be used to optimise the structure.

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“…Hence, a series resistance across the transparent conductor and other parasitic components has a more pronounced effect on the overall power efficiency. Such a series component also increases the device temperature and lowers the internal quantum efficiency [20][21][22][23][24][25].…”

Section: Introductionmentioning

confidence: 99%

Coupled thermo–electrical analysis of highly scaled GaN micro-LEDs with meshed hybrid conductors

Shin¹,

Bae²,

Lim³

et al. 2020

Semicond. Sci. Technol.

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Display technology with ultrafine pixels for near-eye application is a rapidly growing field due to the recent emergence of augmented/mixed reality. With the constant demand for high energy efficiency, long lifetime, and high luminosity, micro-LED displays based on compound semiconductors are promising candidates for such applications. However, miniaturizing LEDs results in significant drawbacks in terms of their quantum efficiency, current injection efficiency, and heat extraction. With relatively low device resistance compared to that of liquid crystals or organic LEDs, micro-LEDs are also more susceptible to the effects of parasitic resistance. In this study, gallium nitride based micro-LED displays with very small pixels (5 µm pixel, 10 µm pitch) are fabricated to study the thermal-electrical effect of meshed hybrid conductors on the optical emission efficiency. In situ thermographic imaging with I-V measurement confirms a significant trade-off among heat transfer, electrical conductivity, and light extraction efficiency. An increase of 37.9% in the emission efficiency (2540 pixels per inch, 5 µm pixels, 1 mm 2 display, at 49.2 • C) is achieved by optimizing the thermal and electrical conduction paths. This study experimentally confirms the importance of thermal management and multi-physics analysis in designing ultra-small-pixel micro-LEDs with high energy efficiency.

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GaN–InGaN LED efficiency reduction from parasitic electron currents in p-GaN

Cited by 7 publications

References 12 publications

Recent Advances in Hollow Cathode Technology for Plasma-Enhanced ALD—Plasma Surface Modifications for Aluminum and Stainless-Steel Cathodes

Recent Advances in Hollow Cathode Technology for Plasma-Enhanced ALD—Plasma Surface Modifications for Aluminum and Stainless-Steel Cathodes

Numerical Model of Current Flow and Thermal Phenomena in Lateral GaN/InGaN LEDs

Coupled thermo–electrical analysis of highly scaled GaN micro-LEDs with meshed hybrid conductors

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