The embodiment relates to a light emitting device, and more particularly, to a light emitting device and a light emitting device package capable of improving luminous efficiency.
Generally, a light emitting device (LED) includes a p-n junction diode having a characteristic of converting electric energy into light energy. The p-n junction diode can be formed by combining group III-V elements of the periodic table. The light emitting device can represent various colors by adjusting the compositional ratio of compound semiconductors.
When a forward voltage is applied to an LED, electrons of an n layer are combined with holes of a p layer, so that energy corresponding to an energy gap between a conduction band and a valance band may be released. This energy is mainly realized as heat or light, and the LED emits the energy as the light. For instance, a nitride semiconductor represents superior thermal stability and wide band gap energy so that the nitride semiconductor has been spotlighted in the field of optical devices and high-power electronic devices. In particular, blue, green, and UV light emitting devices employing the nitride semiconductor have already been developed and extensively used.
According to the related art, the nitride semiconductor is formed by sequentially laminating an N-type first semiconductor layer, an active layer and a P-type second semiconductor layer on a silicon (Si) substrate.
However, when a GaN semiconductor layer is grown on a silicon substrate, since the substrate and the semiconductor layer have mutually different crystal structures, a lattice mismatch is generated while being spaced apart from an interface or due to a thermal expansion coefficient difference, a stress is generated.
The crystal mismatch and the thermal expansion coefficient difference cause a dislocation and a crack, so that electric and optical characteristics of a light emitting device are deteriorated.