A light emitting device (LED) is a semiconductor device to convert a current into light. Since a red LED has been commercialized, the LED, together with a green LED, is used as a light source of electronic devices including information communication equipment.
In order to improve light emitting efficiency of the LED, the following two schemes have been suggested. One scheme is to increase the probability of combination of injected electrons and holes at a light emitting layer to improve internal quantum efficiency. The other scheme is to increase light extraction efficiency such that light generated in the light emitting layer can be effectively emitted to an exterior.
However, if a concave-convex pattern is formed on the interfacial surface of a hole injection layer for the purpose of increasing light extraction efficiency, the internal quantum efficiency can not be increased. Accordingly, it is necessary to provide a new scheme to improve the light extraction efficiency while improving the internal quantum efficiency.