Investigation of Step-Stress Accelerated Degradation Test Strategy for Ultraviolet Light Emitting Diodes

Abstract

III-nitride-based ultraviolet light emitting diode (UV LED) has numerous attractive applications in air and water purification, UV photolithography, and in situ activation of drugs through optical stimulus, solid state lighting, polymer curing, and laser surgery. However, the unclear failure mechanisms and uncertainty reliability have limited its application. Therefore, a design of an appropriate reliability test plan for UV LEDs has become extremely urgent. Compared to traditional reliability tests recommended in LED lighting industry, the step-stress accelerated degradation test (SSADT) is more cost-effective and time-effective. This paper compares three SSADT testing plans with temperature and driving currents as stepwise increasing loads to determine an appropriate test strategy for UV LEDs. The study shows that: (1) the failure mechanisms among different SSADT tests seem to be very different, since the driving current determines the failure mechanisms of UV LEDs more sensitively, and (2) the stepped temperature accelerated degradation test with an appropriate current is recommended for UV LEDs.

Optimizing Light Illumination: Fabrication and Analysis of Lighting Materials for LED Reflectors

“…Lighting indicators are determined on three samples with a size of at least 60-60 umm and a thickness corresponding to the thickness of the glass. The test result is taken as the arithmetic mean of the results of three parallel determinations, rounded to the second decimal place [20]. The polymer was applied using a hand lay-up molding process technique for the composite material.…”

Lifetime Prediction of Current-and Temperature-Induced Degradation in Silicone-Encapsulated 365 nm High-Power Light-Emitting Diodes

“…Unlike the numerous publications analyzing the degradation behavior of blue and phosphor-converted LEDs, only a few papers were published regarding the degradation mechanisms and behavior of In 1−x Ga x N-based UV-A LEDs [13], [15], [16], [17], [18], [19], [20], [21]. Compared directly with emitters of the blue spectral range, a significantly shorter lifetime of ultraviolet or near-ultraviolet structures can be observed [3].…”

“…Additionally, energetic ultraviolet photons could provoke degradation mechanisms in the packaging of the semiconductor devices. Especially silicone encapsulated emitters are exposed to package-related degradation, occurring by yellowing or cracking of the silicone lens [15], [17]. As a result, the ultraviolet emitters can be expected to undergo a variety of possible aging mechanisms, which can be observed in both the LED's package and the semiconductor's structure significantly affecting the lifetime of the device [21].…”

Using a Multi-Layer Stacked AlGaN/GaN Structure to Improve the Current Spreading Performance of Ultraviolet Light-Emitting Diodes

“…Ultraviolet light-emitting diodes (UV-LEDs) have received positive attention from scholars and companies around the world to due to their properties, such as: high switching speeds; lack of heat radiation; their non-toxic, uniform illumination; high energy; and long service life [1][2][3][4]. However, there are still many obstacles to overcome to further improve their photoelectric performance, one of which is the current crowding effect [5].…”