Research On Fabrication Of Photonic Crystal Light Emitting Diodes(LED) By Nanoimprint Lithography

The light emitting diodes(LED) has flourished for the past few decades as ultimate light source. High efficiency, reliability, low power consumption and durability are the key factors for the rapid development of the LED. There is only 4% of the internal light would be extracted from surface, because the high refractive index of GaN results in a critical angle foe the light escape cone to be about 24°.This thesis focus on the research of design of photonic crystal and fabrication of Photonic crystal LED. We design four lattice arrays of photonic crystal by Rsoft, and analyze the design with fabrication technology and conductive effect of ITO electrode. Triangular lattice 2D photonic crystal with air hole is choosed for fabrication. The duty cycle, period and radius of photonic crystal are 0.8, 418nm, 167nm, respectively. The photonic crystal is made on P-GaN layer of blue LED by nanoimprint lithography and ICP etching. For reducing the damage of LED, we employ twice nanoimprint, soft imprint and ICP etching with low RF power for fabrication of photonic crystal.The result of experiment shows that the photonic crystal was successful transferred to P-GaN layer. After laser pump, the intensity of the PL(photoluminescence) of photonic crystal LED wafer with the hole of 70nm depth exhibited 2 times higher than that of the LED without photonic crystal. The light radiation power of photonic crystal LED with hole of 70nm and 100nm depth improve 10% and 7%, respectively, than that of the LED without photonic crystal at 350mA. The forward voltage increment of photonic crystal LED is little compared to no patterned LEDs ..