Nitride Semiconductor LED With Uneven Substrate Interface

The patent applies the curvature principle by forming an uneven interface between the light transmissive substrate and the dielectric layer. Instead of a flat interface, the substrate surface is made curved or uneven through etching or molding processes, which causes incident light to scatter in multiple directions. This curvature transformation increases the probability of light extraction by reducing total internal reflection, thereby resolving the contradiction between manufacturing simplicity and light extraction efficiency.

The patent applies the local quality principle by creating regions with different refractive indices at the substrate-dielectric interface. The uneven interface structure creates local variations in optical properties, where some regions have higher refractive index for light guidance while other regions provide lower effective refractive index for improved light extraction. This spatial variation in optical quality allows simultaneous optimization of both light guidance and extraction efficiency.

The patent applies the partial action principle by forming an uneven interface structure that provides sufficient light scattering without requiring excessive complexity. The unevenness is introduced to the extent needed to achieve optimal light extraction efficiency, rather than creating maximally complex structures. This balanced approach achieves the necessary light scattering effect while controlling manufacturing complexity and cost.