6, 13.5, 15.1, and 16.5 HSP inhibitor mW, respectively. Hence, the enhancement percentages of LED with PQC on p-GaN surface,

LED with PQC on n-side roughing, and LED with PQC structure on p-GaN surface and n-side roughing were 16%, 30%, and 42%, respectively, compared to that of the conventional LED. The higher enhancement of LED with both PQC structures was scattering and guiding light from LED top surface and n-side roughing onto the LED top direction [14, 21, 24] to increase more light output power. In addition, the corresponding wall-plug efficiencies (WPE) of conventional LED, LED with PQC on p-GaN surface, LED with PQC on n-side roughing, and LED with PQC structure on p-GaN surface and

n-side roughing were 19%, 22%, 24%, and 26%, respectively, which addresses a substantial improvement by the PQC structures on top surface and n-side roughing as well at a driving current of 20 mA. Comparing with the conventional LED, the WPEs of LED with PQC on p-GaN surface, LED with PQC on n-side roughing, and LED with PQC structure on p-GaN surface and n-side roughing were MG 132 increased by 15.8%, 26.3%, and 36.8%, respectively, at an injection current of 20 mA, The enhancement of WPE of LED with PQC structure on p-GaN surface and n-side roughing is relatively high comparing with other researches [10, 13, 14, 24, 25], which is because the light emitted from LED scattered by top PQC pattern and guided onto the LED top direction by n-side roughing [22, 23, 26], therefore resulting in the enhancement of WPE. During life test, 20 chips of conventional LEDs and LED with PQC structure on p-GaN surface and n-side roughing Bcl-w were encapsulated and driven by 50 mA injection current at 55°C of ambient temperature. As shown in Figure 5, after 500 h, it was found that the normalized

output power of conventional LEDs and LED with PQC structure on p-GaN surface and n-side roughing only decreased by 6% and 7%, which indicates that the PQC structure is a reliable and promising method for device production. In general, the light output power of conventional type was decayed about 10% in aging test (55°C/50 mA), therefore indicating that the LED with PQC on p-GaN surface and n-side roughing did not damage the LED structure. Figure 5 The life test results of the conventional LEDs and LED with PQC structure. The testing condition is under driving current of 50 mA and 55°C of ambient temperature. Conclusions The GaN-based LEDs with PQC structure on p-GaN surface and n-side roughing by nano-imprint lithography are fabricated and investigated.