As the etching time increased, the R-plane was destroyed. Figure 5b MK-2206 presents the reflectivity of A-1210477 PSS-ANP templates that had been annealed for various annealing times. The reflectivity of the PSS-ANP template that was annealed for 5 min was approximately 99.5%, which exceeded that of the PSS. This fact may have contributed to the scattering and reflection from the surface topography of the PSS-ANP. Figure 5 Reflectivity of (a) etched
sapphire substrate and (b) PSS-ANP that had been annealed for various times. Figure 6 plots the light output power as a function of the injection current for the GaN-based LEDs with and without the PSS-ANP template. The light output power of all of the samples initially increased linearly with the injection current. At an injection current of 20 mA, the light output power for the GaN LEDs without the PSS-ANP template was 8.24 mW. All LEDs with the PSS-ANP template had doubled the light intensity of the LED without the PSS-ANP template at a low injection current between 10 and Captisol ic50 40 mA. However, the output intensity of LEDs with the PSS-ANP template that had been etched for 5 and 10 min was reduced as the injection current increased above 50 mA. At a high injection current, such as 100 mA, the PSS-ANP template
that had been etched for 20 min doubled the light extraction. This improvement in the light output power of the LED with the PSS-ANP template that had been etched for 20 min is caused by the thermal conductive effect of the void in the template structure. Figure 7 plots the typical logarithmic I-V characteristics of the GaN LEDs with and without the PSS-ANP template. The inset Oxalosuccinic acid plots the I-V characteristics in a linear scale. An injection current of 20 mA in the LEDs with and without the PSS-ANP template yielded forward biases of 3.7 and 3.75 V, respectively. The saturation
current of both LEDs was approximately 10−10 A. Both LEDs had the same electrical characteristics. Accordingly, the PSS-ANP template did not influence the electrical characteristics of the GaN-based LED because the active area of the GaN-based LED with the PSS-ANP template was separate from the optical reflective area. Therefore, combining the conventional GaN-based LED with the PSS-ANP template is an excellent means of improving the light output power of a GaN-based LED on a sapphire substrate. Figure 6 Light output power as a function of injection current of GaN LEDs with and without PSS-ANP template. Figure 7 Typical logarithmic I – V characteristics of GaN LEDs with and without the PSS-ANP template. Inset plots I-V characteristics on linear scale. Conclusion In summary, this study reports on the construction of a template by dispersing ANPs on a PSS to improve the light output power of GaN-based LEDs. The sapphire substrate was etched in hot H2SO4 solution to produce a mixture of polycrystalline aluminum sulfates.