Current-induced degradation process in (In)AlGaN-based deep-UV light-emitting diode fabricated on AlN/sapphire template

Dalapati, Pradip; Yamamoto, Kosuke; Egawa, Takashi; Miyoshi, Makoto

doi:10.1016/j.optmat.2020.110352

Cited by 22 publications

(12 citation statements)

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“…UV-7 was operated at an If value that was the lowest percentage of the maximum rated current for any of the products in the test matrix, but was operated at the same overall current as other comparable high-powered UV-C LEDs (e.g., UV-5, UV-6). Current densities used during RTOL-2 were generally lower than those found in most literature studies [14,15,17,20].…”

Section: Rtol-2mentioning

confidence: 55%

“…Although previous studies of the reliability of UV LEDs are more limited in scope than this report, there have been notable studies spanning the UV-A [12][13][14], UV-B [15,16], and UV-C [10, [16][17][18][19][20][21][22] bands. The forward current (If) densities in these studies ranged from 27 amps per square centimeter (A/cm 2 ) to 140 A/cm 2 .…”

Section: Previous Studies About Uv Led Reliabilitymentioning

confidence: 95%

“…Several general trends have emerged from these studies, and perhaps the most significant finding involved increased leakage currents at voltages well below the threshold voltage (Vth). The parasitic shunt circuits that give rise to such low voltage leakage currents appeared to reduce active carrier concentration through modifications of Shockley-Read-Hall (SRH) mechanisms and are thought to be directly tied to aging-induced reductions of emissions from UV-A, UV-B, and UV-C devices [10, [12][13][14][15][16][17][18][19][20]22]. Evidence for parallel shunt circuits is provided in the current-voltage (I-V) measurements of an LED by a growing feature at voltages below Vth.…”

Section: Previous Studies About Uv Led Reliabilitymentioning

confidence: 99%

“…Evidence for parallel shunt circuits is provided in the current-voltage (I-V) measurements of an LED by a growing feature at voltages below Vth. Other major findings from these studies were that low current radiometric studies were likely to be most sensitive to increased SRH behavior [10, 15,20], device efficiency and reliability could be improved by reducing threading defect densities [21], and higher temperatures and/or higher If values tend to reduce device lifetimes [23].…”

Section: Previous Studies About Uv Led Reliabilitymentioning

confidence: 99%

“…A variety of analytical methods have been applied to investigating the causes of RFM loss in UV LED products. Some of the methods include electrical methods such as I-V [10, 12-15, 17, 20, 34-37] and capacitance-voltage measurements [20; 37]; spectroscopic methods such as deep-level transient spectroscopy (DLTS) [10,13]; and chemical analysis methods such as secondary ion mass spectrometry (SIMS) [10, 17] and X-ray diffraction (XRD) [20]; imaging methods such as transmission electron microscopy (TEM) [10, 17,37], atomic force microscopy (AFM) [20], and photoluminescence mapping [10]; and numerical simulations [35]. The conclusion from this prior research is that defects in the UV LED epitaxial structure create parallel circuits that provide tunneling pathways for non-radiative carrier recombination.…”

Section: Failure Mechanisms Involving Electrical Degradation Of Uv Le...mentioning

confidence: 99%

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Operating Lifetime Study of Ultraviolet (UV) Light-Emitting Diode (LED) Products

Davis

Rountree

Pope

et al. 2022

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Light-emitting diodes (LEDs) can emit radiation that spans the range from near infrared (IR) to all three bands of ultraviolet (UV) radiation: UV-A, UV-B, and UV-C. This report focuses on LEDs that emit in one of the three UV bands because they have the potential to displace lowpressure mercury vapor (LPMV) lamps in a variety of industrial processes, including ink and adhesive curing, medical procedures, and germicidal disinfection. However, before emerging UV LED technologies can displace LPMV lamps, the efficiency and reliability of these sources must meet the user's expectations in each application. An earlier report focused on the construction and initial performance of commercial UV LED products in radiometric and current-voltage (I-V) tests [1]. This report focuses on the long-term performance and reliability of the same set of commercial products. The intent of this report is to provide to the lighting industry a benchmark of the state of UV LEDs as of mid-2021 when these products were purchased. Understanding the failure modes and failure rates of UV LEDs is important in improving UV product reliability at the LED, lamp, and luminaire level and is critical to developing products with higher efficiency, lower carbon footprint, and significantly reduced environmental impact than LPMV lamps.Operating Lifetime Study of Ultraviolet (UV) Light-Emitting Diode (LED) Products viii maintenance [RFM] was 0.50 or lower). Four products (i.e., UV-3, UV-5, UV-9, and UV-11) did not experience any failures during RTOL-1, but the other nine products had failure rates ranging from 10% to 100%. The most common failure mode was a parametric failure, which accounted for 50 failures during the test. Only seven DUTs failed abruptly, and four out of these seven devices were UV-2 DUTs. These findings demonstrate that there is a wide range of reliability in commercially available UV LED products.Different DUTs of the 13 UV LED products were divided into two groups for RTOL-2 based on their power rating. Group-A, which had If values less than 55 milliampere (mA), was operated for 2,500 hrs during RTOL-2, whereas Group-B, which had If values greater than 100 mA, was operated for 3,000 hrs during RTOL-2. Even though product operation times were longer in RTOL-2 compared with RTOL-1, the cumulative failure rate was lower, as might be expected for the milder stress conditions (i.e., lower If values). A total of 32 failures occurred during RTOL-2 (which is 25% of the total product population): 11 abrupt failures and 21 parametric failures. This finding corresponds to a cumulative failure rate of 25%. Most of the failures during RTOL-2 were concentrated in fewer products; this observation was in contrast to findings from RTOL-1, during which failures were more widespread. For example, during RTOL-2, 7 abrupt failures occurred in the UV-2 DUTs and a greater than 50% parametric failure rate was measured for the UV-8 and UV-14 DUTs. These three products accounted for 22 out of the 32 failures recorded in RTOL-2.Based on this work and combine...

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Section: Rtol-2mentioning

confidence: 55%

Section: Previous Studies About Uv Led Reliabilitymentioning

confidence: 95%

Section: Previous Studies About Uv Led Reliabilitymentioning

confidence: 99%

Section: Previous Studies About Uv Led Reliabilitymentioning

confidence: 99%

Section: Failure Mechanisms Involving Electrical Degradation Of Uv Le...mentioning

confidence: 99%

See 3 more Smart Citations

Operating Lifetime Study of Ultraviolet (UV) Light-Emitting Diode (LED) Products

Davis

Rountree

Pope

et al. 2022

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Progress of Reliability and Failure Mechanisms for GaN‐Based Light‐Emitting Diodes

Zhao

Liu

2022

Physica Status Solidi (a)

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To achieve high reliable GaN-based LEDs with a controllable lifetime is one of the key issues for applications. In this review, an overview of reliability studies for different GaN-based LEDs, especially the research progress in our group based on our specially designed in situ multifunctional highly accelerated aging test system over the past few years, is presented. The contents not only cover highpower GaN-based LEDs, mid-power GaN-based LEDs, deep UV GaN-based LEDs, micro-LEDs, and phosphors under different operating conditions but also include the influence of point defects on the degradation, the correlation between luminous flux and color quality, and so on. Finally, prospects for reliability are discussed with the further development of the GaN-based devices.

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Degradation analysis with characteristics and simulations of 265 nm UV-C LED

Zhu

Chen

et al. 2021

J Mater Sci: Mater Electron

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We report the degradation study on AlGaN-based 265 nm ultraviolet light emitting diodes (UV-LEDs) under a series of constant current stress. The failure mechanisms were investigated systematically by measuring the optical and electrical characteristics of the LEDs before and after aging. The variation of carrier concentration in the active region was analyzed by capacitance-voltage. Combining the extracted apparent charge distribution pro les with the simulation results of the devices before and after the stress, we found that the change of carrier concentration in the multiple quantum wells was related to the donor diffusion on the n-side. On the p-side, both the acceptor concentration of electron blocking layer (EBL) and the defects in p-GaN contact layer were also found to be under constant change. The reduction of the EBL doping concentration has contributed to an increase of the diode depletion width during the stress. The changes in the LEDs before and after stressing indicate a compensating effect occurred in the p-type EBL close to the quantum wells, which leads to the degradation of the optical power of the 265 nm UV-LEDs.

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Current-induced degradation process in (In)AlGaN-based deep-UV light-emitting diode fabricated on AlN/sapphire template

Cited by 22 publications

References 50 publications

Operating Lifetime Study of Ultraviolet (UV) Light-Emitting Diode (LED) Products

Operating Lifetime Study of Ultraviolet (UV) Light-Emitting Diode (LED) Products

Progress of Reliability and Failure Mechanisms for GaN‐Based Light‐Emitting Diodes

Degradation analysis with characteristics and simulations of 265 nm UV-C LED

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