Research Note
Degradation of InGaN blue light-emitting diodes under continuous and low-speed pulse operations

https://doi.org/10.1016/S0026-2714(03)00093-3Get rights and content

Abstract

Long-term accelerated degradation tests on InGaN blue light-emitting diodes were performed under continuous and low-speed pulse operations, and the half-life of the optical output was estimated. It was estimated that the lifetime under pulse operation is 2–4 times longer than that in continuous operation. A higher pulse repetition rate confers a longer life.

Introduction

Advances in light-emitting diode (LED) technology––both in its applications for display devices and the illumination source itself––have resulted in higher brightness capacity. Blue LED based on GaN has been realized; the three colors have been gathered, and white luminescence attained [1], [2]. Compared to light bulbs, LED has advantages of long life, energy efficiency, and compactness. It is expected that LED technology will replace bulbs in the near future. Field applications are various, ranging from high-speed pulsation to intermittent and continuous operations. For the design of such systems, however it will be necessary to predict the expected lifetime and responses to environmental and usage conditions. While blue LED of high brightness has been realized using a wide band-gap semiconductor, the data on its reliability are scarce [3], [4].

Herein, we report on differences in commercial InGaN blue LED degradation among several types of operations. The current accelerated test was performed for both pulsing and continuous operations, and the dependence of degradation in light output on the operating conditions were investigated, along with the estimated lifetimes.

Section snippets

Experimental detail

The sample used was a commercial blue LED of the Nichia InGaN type. The device chip was mounted on a lead frame (silver plating) and molded using epoxy resin. At the recommended DC current of 20 mA, the LED had the following characteristics: brightness, 1.4–1.7 candela; peak emission wavelength, 466–469 nm; and 30 nm spectral half-width. Continuous current tests were performed for 3100 h in a dried test chamber at 40 °C, at the following three DC current stress IF (estimated current density JF)

Results and discussion

Fig. 1 shows the degradation of the optical output P/P0 (normalized to the initial value P0) in continuous current operation and pulse operation tests. It was found that the degradation during pulse operation was small in comparison with that during continuous operation. In fact, the shorter the pulse width WP, the smaller the degradation in pulse operation. Various approximate LED degradation pattern formulas have been reported for use with particular materials and structures [4], [5], [6]. In

Conclusion

Accelerated current tests on InGaN blue LEDs were performed under continuous and low-speed pulse operations. A half-life of approximately 2–4 × 104 h was estimated under the pulse condition of 40 mA at 40 °C Lifetime depended on pulse width: the shorter the pulse width, the longer the lifetime. Lifetime during the pulse operation was estimated to be 2–4 times longer than that during the continuous operation.

References (8)

There are more references available in the full text version of this article.

Cited by (34)

  • Optogenetic brain neuromodulation by stray magnetic field via flash-enhanced magneto-mechano-triboelectric nanogenerator

    2020, Nano Energy
    Citation Excerpt :

    In general, the μLEDs with a pulse operation have 2–4 times longer lifetime than a constant operation due to its small heat accumulation in the device. Based on our experimental results of a constant (Fig. S17 in the Supporting Information) and pulse operation (Fig. S22 in the Supporting Information), it is estimated that our f-μLED can be used to optogenetic brain stimulation for minimum several days by using MMTENG as the pulsed-power source [77,78]. This estimated usage time is enough to realize brain stimulation, considering that researchers irradiated light to brain for several minutes to hours in the recent papers [79–81].

  • LEDs for large displays

    2018, Nitride Semiconductor Light-Emitting Diodes (LEDs): Materials, Technologies, and Applications: Second Edition
  • Chip and package-related degradation of high power white LEDs

    2012, Microelectronics Reliability
    Citation Excerpt :

    Another important feature of white LEDs is their high expected reliability: expected lifetimes of these devices can be in excess of 50,000 h [5], and this can be a strong argument to convince customers to adopt LEDs instead of incandescent or fluorescent lamps for lighting applications. However, over the last few years, several authors [6–27] have demonstrated that the lifetime of white LEDs can be shorter than expected: this is due to the existence of a number of physical mechanisms that can determine the degradation of LEDs, when they are submitted to high current or high temperature stress. State-of-the-art high-power LEDs are based on semiconductor chips with an area of 1 mm2, that can be operated at current levels in the range between 350 mA and 1 A, depending on the specific model and manufacturer.

View all citing articles on Scopus
View full text