Research Of Nitride-based Nano-patterned Sapphire Substrates LEDs

GaN-LED is attracted extensive attention and research as it is widely used in traffic, display and other industries. However, in conventional GaN-LED, only less than5%of the light energy generated in the active layer escapes into the air ultimately. Patterned Sapphire Substrate which can reduce the density of threading dislocation and enhance the effect of scattering has been widely used to fabricate high-power Light-Emitting-Diode (LED) chip.The paper contains the optimization of the patterned sapphire substrate parameters and the preparation of nano-patterned sapphire substrate LED by using nano-imprint technology. In theoretical aspects, the finite-difference time-domain (FDTD) method is used to simulate and analysis the 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 pillar structure can obtain a best improvement of96.6%which is better than other nano-patterned structures.For the experiments, a large area of cone-like nano-sapphire patterned substrates (cone-NPSS) and hole-like nano-sapphire patterned substrates (hole-NPSS) are successfully prepared by Lift-off process combined with the soft embossing technology. The finite-difference time-domain (FDTD) method is used to simulate and compare the GaN-based cone and hole-like nano-scale patterned sapphire substrates LED (NPSS-LED). Comparing these two results, it shows that above two NPSS-LEDs have improvements of light extraction efficiency (LEE) by46.5%,52.2%respectively.Furthermore, photoluminescence intensity of LED on cone-PSS and on hole-PSS is higher than LED on conventional sapphire substrates. The results show that above two NPSS-LEDs have improvements of photoluminescence intensity of peak by12.5times,6.5times respectively.