Modeling the electrical degradation of AlGaN-based UV-C LEDs by combined deep-level optical spectroscopy and TCAD simulations

Roccato, Nicola; Piva, Francesco; Santi, Carlo De; Buffolo, Matteo; Fregolent, Manuel; Pilati, Marco; Susilo, Norman; Vidal, Daniel Hauer; Muhin, Anton; Sulmoni, Luca; Wernicke, Tim; Kneissl, Michael; Meneghesso, G.; Zanoni, Enrico; Meneghini, Matteo

doi:10.1063/5.0144721

Cited by 17 publications

(10 citation statements)

References 47 publications

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“…They attributed the improved lifetime to the low dislocation density with AlN substrates. 148 Roccato et al 149 reported a combined deep level spectroscopy and TCAD simulation study where they identified the traps appearing during aging and then simulated what effect their spatial location would have on the device lifetime kinetics. Three deep trap states at E C −0.94 eV, E C −3.06 eV, and E C −3.52 eV were identified and suggested to be located near the electron blocking layer.…”

Section: Literature Resultsmentioning

confidence: 99%

“…What is clear from the literature is i. Multiple degradation mechanisms may be present 41,108,109,[142][143][144][145][146][147][148][149][150] ii. Migration of defects already present in the as-grown structure, or created during subsequent operation, can migrate into the active regions.…”

Section: Literature Resultsmentioning

confidence: 99%

“…Migration of defects already present in the as-grown structure, or created during subsequent operation, can migrate into the active regions. 41,97,[142][143][144][145][146][147][148][149][150] iii. Careful attention must be paid to removing residual hydrogen incorporated in the epi structure from the growth precursors.…”

Section: Literature Resultsmentioning

confidence: 99%

“…107-109 v. The dislocation density should be minimized, favoring use of AlN substrates and careful optimization of buffer layers. [1][2][3][4]149,150 vi. The purity of the growth precursors and avoidance of oxygen in the growth ambient is critical.…”

Section: Literature Resultsmentioning

confidence: 99%

“…The purity of the growth precursors and avoidance of oxygen in the growth ambient is critical. 62,149 vii. The degradation rate is a strong function of current density during operation, showing typically a cube power dependence and also on LED temperature.…”

Section: Literature Resultsmentioning

confidence: 99%

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Review—Reliability and Degradation Mechanisms of Deep UV AlGaN LEDs

Letson

Conklin

Wass

et al. 2023

ECS J. Solid State Sci. Technol.

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There are numerous applications for deep UV AlGaN light-emitting diodes (LEDs) in virus inactivation, air and water purification, sterilization, bioagent detection, and UV polymer curing. The long-term stability of these LEDs is also of interest for long-duration space missions such as the Laser Interferometer Space Antenna, the first gravitational wave detector in space. We review the literature on long-term aging of these devices as a function of drive current, temperature, and dc versus pulsed operation. LEDs typically show a gradual decline in output power (up to 50%) over extended operating times (>100 h) and the rate of decline is mainly driven by current and temperature. Experimentally, the degradation rate is dependent on the cube of drive current density and exponentially on temperature. The main mechanism for this decline appears to be creation/ migration of point defects. Pre-screening by considering the ratio of band edge-to-midgap emission and LED ideality factor is effective in identifying populations of devices that show long lifetimes (>10,000 hours), defined as output power falling to 70% of the initial value.

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Section: Literature Resultsmentioning

confidence: 99%

Section: Literature Resultsmentioning

confidence: 99%

Section: Literature Resultsmentioning

confidence: 99%

Section: Literature Resultsmentioning

confidence: 99%

Section: Literature Resultsmentioning

confidence: 99%

See 3 more Smart Citations

Review—Reliability and Degradation Mechanisms of Deep UV AlGaN LEDs

Letson

Conklin

Wass

et al. 2023

ECS J. Solid State Sci. Technol.

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Study on Degradation of Deep‐Ultraviolet Laser Diode

Zhang,

Yoshikawa,

Kushimoto

et al. 2024

Physica Status Solidi (a)

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The degradation of an AlGaN‐based deep‐ultraviolet laser diode during operation is studied. A rapid increase in threshold current without any facet mirror damage under direct current stress below the threshold current is observed, which is considered to limit the lifetime of continuous wave lasing to the level of seconds. The evolution of current–light and current–voltage characteristics suggests that the dominant mechanism of degradation is the increased loss of carriers before they can reach the active layer, i.e., the decrease in carrier injection efficiency. The decrease in emission intensity, which is more pronounced at lower current densities, and subsequent increase in sub‐threshold current indicate the increase in defect density under current stress, which is similar to the well‐analyzed degradation mechanism found in AlGaN‐based light‐emitting diodes.

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Enhanced Wall‐Plug Efficiency over 2.4% and Wavelength Dependence of Electrical Properties at Far UV‐C Light‐Emitting Diodes on Single‐Crystal AlN Substrate

Kobayashi,

Sato,

Okuaki

et al. 2024

Physica Rapid Research Ltrs

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In this work, the wavelength dependence of the efficiency and the lifetime of far UV‐C light‐emitting diodes (LEDs) on a single‐crystal AlN substrate is systematically analyzed from experiments and simulations. A positive relation between efficiency and emission wavelength is observed. The wall‐plug efficiency reaches 0.47, 1.0, 2.1, and 2.4% at 227, 230, 233, and 235 nm wavelengths, respectively. The simulation results show that carrier injection plays a critical role in the efficiency change in the far UV‐C region rather than in the internal quantum or light extraction efficiency. The lifetime test clearly demonstrates a trade‐off between the L70 lifetime and the emission wavelength, although the initial optical power increases with the longer wavelength. The measurement results under various wavelengths and stress currents indicate that the carriers injected in quantum wells motivate power reduction during current stress. Moreover, the internal quantum efficiency affects the degradation rate because the influence of defects becomes stronger during stress. Finally, the reliability of a 231 nm LED is investigated at a reduced current of 35 mA. The projected L70 and L50 lifetimes are 11,000 and 28,000 h, respectively, from the fitting model based on the defect generation during aging.This article is protected by copyright. All rights reserved.

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Modeling the electrical degradation of AlGaN-based UV-C LEDs by combined deep-level optical spectroscopy and TCAD simulations

Cited by 17 publications

References 47 publications

Review—Reliability and Degradation Mechanisms of Deep UV AlGaN LEDs

Review—Reliability and Degradation Mechanisms of Deep UV AlGaN LEDs

Study on Degradation of Deep‐Ultraviolet Laser Diode

Enhanced Wall‐Plug Efficiency over 2.4% and Wavelength Dependence of Electrical Properties at Far UV‐C Light‐Emitting Diodes on Single‐Crystal AlN Substrate

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