A substrate for semiconductor light emitting devices is provided. The
substrate is characterized in that the substrate is a single crystal
material and has a nanocrystal structure capable of diffracting an
electromagnetic wave. The nanocrystal structure is disposed on a surface
portion of the substrate and includes an etched region and an unetched
region, wherein the etched region has a depth of 10-200 nm. Due to the
periodicity of the nanocrystal structure, the semiconductor material
grown on the substrate has fewer defects, and the material stress is
reduced.