Thermal droop in III-nitride based light-emitting diodes: Physical origin and perspectives

Meneghini, Matteo; Santi, Carlo De; Tibaldi, Alberto; Vallone, Marco; Bertazzi, Francesco; Meneghesso, G.; Zanoni, Enrico; Goano, Michele

doi:10.1063/5.0005874

Cited by 59 publications

(37 citation statements)

References 167 publications

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“…The LED efficiency is known to decline with increasing chip temperature [ 109 , 110 , 111 ]. However, self-heating is a three-dimensional problem and only considered by a few self-consistent GaN-LED simulations [ 10 , 112 , 113 ].…”

Section: Self-heating Modelsmentioning

confidence: 99%

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: Self-heating Modelsmentioning

confidence: 99%

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

Piprek¹

2020

Materials

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“…However, high self-heating and low heat dissipation are the critical issues needed to be addressed during the operation of LEDs. Therefore, extensive research and development efforts have been devoted to reducing the thermal heat generated in the InGaN/GaN-based LEDs to reduce the thermal droop, which rapidly drops the device efficiency under a high input electrical power especially in the high voltage regime(qV > Zω) [11][12][13][14][15][16][17][18]. Over the past couple of decades, plenty of architectures and solutions have been proposed to address the scientific and technological challenges introduced by the thermal heat, including adding the heat sink, increasing the heat dissipation area, changing n-electrode length, and exploiting the thermoelectric generator [19][20][21][22][23].…”

Section: Introductionmentioning

confidence: 99%

Efficiency Boosting by Thermal Harvesting in InGaN/GaN Light-Emitting Diodes

Zhang

Qiu³

et al. 2021

Front. Phys.

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On the same micro-LED display panel, LED pixels are always operated with high and low biased voltages simultaneously to show different brightness and colors. Thus, it is vitally important to understand the effect of the heat transmission between LEDs under high and low biased voltages. In this work, we design two different LED groups: Group A is two LEDs bonded together for heat transmission and Group B is two LEDs separated from each other. Then, the two LEDs are operated at one fixed and one tuned biased voltage respectively in each group in a vacuum chamber and the efficiency of the two groups is studied both experimentally and numerically. Here, our experimental results demonstrate that Group A exhibits a maximum improvement of 15.36% in optical output power compared with Group B. The underlying reason is that the wall-plug efficiency of the LED with a voltage lower than photon voltage (V < ℏω/q) is surprisingly enhanced by elevated temperature owing to the heat transmission by the LED under a high biased voltage in Group A. Our further study shows that in such a low voltage region the improvement in the efficiency is attributed to the enhanced carrier concentrations with elevated temperature. On the other hand, the LED in Group A under a high biased voltage further raises the overall efficiency by alleviating the thermal droop due to reduced temperature. Device temperature measurement and numerical calculation of radiative recombination under different temperatures further support the superior performance of Group A LEDs. Our research results can act as the research prototype to design the high-efficient LED arrays for better energy recycling and thermal control.

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“…The increase in defect-assisted leakage paths as a consequence of stress was also testified by the correlation between the variation in the log-log OP slope and the device current at low bias level, reported in Figure 11 . At low voltages, current is strongly determined by defect-assisted conduction processes [ 22 , 33 , 34 , 35 , 36 ]; therefore, we can state that these defects are the main responsibility for the variation in optical emission observed in low bias regimes.…”

Section: Experiments Results and Discussionmentioning

confidence: 97%

Gradual Degradation of InGaAs LEDs: Impact on Non-Radiative Lifetime and Extraction of Defect Characteristics

et al. 2021

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We present a detailed analysis of the gradual degradation mechanisms of InGaAs Light-Emitting Diodes (LEDs) tuned for optical emission in the 1.45–1.65 μm range. Specifically, we propose a simple and effective methodology for estimating the relative changes in non-radiative lifetime, and a procedure for extracting the properties of defects responsible for Shockley-Read-Hall recombination. By means of a series of accelerated aging experiments, during which we evaluated the variations of the optical and electrical characteristics of three different families of LEDs, we were able to identify the root causes of device degradation. Specifically, the experimental results show that, both for longer stress time at moderate currents or for short-term stress under high injection levels, all the devices are affected: (i) by a partial recovery of the optical emission at the nominal bias current; and (ii) by a decrease in the emission in low-bias regime. This second process was deeply investigated, and was found to be related to the decrease in the non-radiative Shockley-Read-Hall (SRH) lifetime due to the generation/propagation of defects within the active region of the LEDs. Devices tuned for longer-wavelength emission exhibited a second degradation process, which was found to modify the carrier injection dynamics and further speed-up optical degradation in the low bias regime. These processes were ascribed to the effects of a second non-radiative recombination center, whose formation within the active region of the device was induced by the aging procedure. Through mathematical analysis of the degradation data, we could quantify the percentage variation in SRH lifetime, and identify the activation energy of the related defects.

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Thermal droop in III-nitride based light-emitting diodes: Physical origin and perspectives

Cited by 59 publications

References 167 publications

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

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

Efficiency Boosting by Thermal Harvesting in InGaN/GaN Light-Emitting Diodes

Gradual Degradation of InGaAs LEDs: Impact on Non-Radiative Lifetime and Extraction of Defect Characteristics

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