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 finite-difference 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.