Degradation Mechanisms in GaN LEDs

FIGURE 2 L-I characteristic of the InGaN/AlGaN LED on sapphire under DC operation at 30°C. The inset shows the ageing result under a constant current density of 60 A/cm2 (30 mA) at 30°C. 

FIGURE 3 Variation of output power from an InGaN/AlGaN LED as a function of ageing time under various injected current densities. Each ageing test was performed for 24 hr at 30°C. 

To investigate the degradation, accelerated ageing tests were carried out under the injected current densities of 100 and 200 A/cm2 at ambient temperatures of 30, 50 mid 80°C. The half-intensity lifetimes, defined as the time at which the optical power decreases to 50% of its initial value, were 656.7, 365.7 mid 170 hr for 100 A/cm2 and 43.3, 19.3 and 8.6 hr for 200 A/cm2 at the ambient temperatures of30, 50 and 80°C, respectively. The output power P can be expressed by [12] 

InGaN/AlGaN LED were determined to be 0.23 eV and 7 hr1 at 100 A/cm2, and 0.25 eV and 270 hr 1 at 200 A/cm2, respectively. Thus, the output power from the InGaN/AlGaN LED decreases during the ageing test under higher injected current densities and ambient temperatures. 

TABLE 2 Summary of Ea and p0 for InGaAsP [12], AlGaAs [13] and InGaN LEDs. 

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C3.2 Toyoda Gosei GaN LEDs C3.3 GaN LEDs grown on 6H-SiC C3.4 Colour conversion of GaN LEDs C3.5 Degradation mechanisms in GaN LEDs... 

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