Fabrication of patterned sapphire substrate and effect of light emission pattern on package efficiency

Abstract

Pyramidal nature PSS (n-PSS) substrates were produced by a simple wet etching process without standard lithography and dry-etching processes. We found that the output power of the LED on the pyramidal n-PSS substrates is larger than the output power of the LED chip on the flat c-plane sapphire substrate by 46.4% to 51.5%. LED chip on the n-PSS(III) substrate with 73% pattern coverage has the highest output power among LED chips on all n-PSS substrates. The light emission patterns of LED bare chips on different n-PSS and r-PSS substrates were studied. The shape of the light emission pattern was qualitatively defined by the broadness angle, which is the angle at the maximum intensity of the light emission pattern away from the normal direction. The broadness angle is inversely proportional to the facet angle of pyramids created on the n-PSS substrates. In addition, we found that the light extraction efficiency at the GaN/silicone interface has a dependence on the light emission pattern of the bare chips on different n-PSS substrates. The broader light emission pattern (larger broadness angle) would result in higher light extraction efficiency at the GaN/silicone interface.