Red light emitting device and lighting system

A red light emitting device comprising:

• a first semiconductor layer having first conductivity type dopants;
• an active layer including a quantum well and a quantum barrier on the first semiconductor layer;
• a second semiconductor layer having second conductivity type dopants on the active layer;
• a third semiconductor layer having the second conductivity type dopants on the second semiconductor layer;
• and
• a fourth semiconductor layer having the second conductivity type dopants on the third semiconductor layer,
• wherein the third semiconductor layer includes an AlxGa1-xInP layer (0≤x≤1), and an Al concentration that is graded,
• wherein the quantum barrier includes a last quantum barrier closest to the second semiconductor layer, the last quantum barrier including:
• a first quantum barrier having a first Al concentration;
• and
• a second quantum barrier having a second Al concentration higher than the first Al concentration, the second quantum barrier being provided closer to the second semiconductor layer than the first quantum barrier,
• wherein the second Al concentration of the second quantum barrier is higher than the first Al concentration of the first quantum barrier throughout an entirety of the second quantum barrier layer,
• wherein the first quantum barrier and the second quantum barrier have equal thickness,
• wherein the fourth semiconductor layer includes a superlattice structure having at least one GaP layer/InxGa1-xP layer (0≤x≤1) pair,
• wherein the superlattice structure of the fourth semiconductor layer includes a plurality of outer GaP layers, wherein a first outer GaP layer is provided on the third semiconductor layer, the at least one GaP layer/InxGa1-xP layer (0≤x≤1) pair are provided on the first outer GaP layer, and a second outer GaP layer is provided on the at least one GaP layer/InxGa1-xP layer (0≤x≤1) pair,
• wherein the fourth semiconductor layer is doped with a second conductive type dopant having a first dopant concentration, and the GaP layer is doped with the second conductive type dopant having a second dopant concentration lower than the first dopant concentration,
• wherein the InxGa1-xP layer (0≤x≤1) is not doped with the second conductive type dopant,
• wherein the first and second outer GaP layers are doped with the second conductive type dopant having the first dopant concentration higher than the second dopant concentration,
• wherein the GaP layer represents an energy level higher than that of the InxGa1-xP layer (0≤x≤1), and
• wherein the first and second outer GaP layers represent an energy level higher than that of the GaP layer.