Research for Patterned Sapphire Substrates of GaN-based LEDs

Patterned Sapphire Substrate(PSS) which can reduce the density of threading dislocation and enhance the effect of scattering is widely used to fabricate high-power Light-Emitting-Diode(LED) chip.In this paper,the finitedifference time-domain(FDTD) method was used to simulate and analyze the light extraction efficiency(LEE) of GaN-based micro-scale and nano-scale patterned sapphire substrates LED.The results show that the nano-patterned sapphire substrate(NPSS) has a significantly better LEE than that of micro-patterned sapphire substrate(MPSS).And in NPSS,the LEE of the pillar structure improveed 96.6% comparing to other nano-patterned structures.Large areas of table-like nano-sapphire patterned substrates are successfully prepared through soft embossing technology.The photoluminescence(PL) of the LED grown on table-like nano-sapphire patterned substrates is 8 times stronger than that of the LED grown on the unpatterned sapphire wafers.