Red light emitting device and lighting system
A red light emitting device, a method of fabricating a light emitting device, a light emitting device package, and a lighting system are provided. The red light emitting device may include a first semiconductor layer having a first conductivity, an active layer provided on the first semiconductor layer and including a quantum well and a quantum barrier, a second semiconductor layer having a second conductivity and provided on the active layer, a third semiconductor layer having the second conductivity on the second semiconductor layer, a fourth semiconductor layer having the second conductivity on the third semiconductor layer, and a fifth semiconductor layer having the second conductivity on the fourth semiconductor layer. The third semiconductor layer and the fourth semiconductor layer may include an AlGaInP-based semiconductor layer, and an Al composition of the fourth semiconductor layer may be lower than an Al composition of the third semiconductor layer.
1. A red light emitting device comprising:
a first semiconductor layer having a first conductivity;
an active layer provided on the first semiconductor layer including a quantum well and a quantum barrier;
a second semiconductor layer having a second conductivity provided on the active layer;
a third semiconductor layer having the second conductivity and provided on the second semiconductor layer; and
a fifth semiconductor layer having the second conductivity and provided on the third semiconductor layer,
wherein the third semiconductor layer includes an AlGaInP-based semiconductor layer, and
an Al composition of the fifth semiconductor layer is lower than an Al composition of the third semiconductor layer,
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 fifth semiconductor layer includes a superlattice structure of a GaP layer/In x Ga 1-x P layer (0≤x≤1),
wherein the superlattice structure of the fifth semiconductor layer includes outer GaP layers including a first outer GaP layer provided on the third semiconductor layer and a second outer GaP layer provided opposite the first outer GaP layer,
wherein the fifth 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 In x Ga 1-x P 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 In x Ga 1-x P layer (0≤x≤1), and
wherein the first and second outer GaP layers represent an energy level higher than that of the GaP layer.
2. The red light emitting device of claim 1 , wherein
the Al composition of the third semiconductor layer includes an (Al x3 Ga 1-x3 ) y In 1-y P layer (0.80≤x3≤90, 0.4≤y≤0.6).
3. The red light emitting device of claim 1 , wherein the quantum well includes an (Al p Ga 1-p ) q In 1-q P layer (0.05≤p≤0.20, 0.4≤q≤0.6).
4. The red light emitting device of claim 3 , wherein the quantum well has a thickness in a range of 150 Å to 170 Å.
5. The red light emitting device of claim 1 , wherein the first Al concentration or the second Al concentration is graded toward the second semiconductor layer in the last quantum barrier.
6. A lighting system comprising a light emitting module including the red light emitting device of claim 1 .
7. The red light emitting device of claim 1 , a total Al concentration of the fifth semiconductor layer is lower than a total Al concentration of the third semiconductor layer.
8. 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 Al x Ga 1-x InP 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/In x Ga 1-x P 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/In x Ga 1-x P 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/In x Ga 1-x P 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 In x Ga 1-x P 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 In x Ga 1-x P layer (0≤x≤1), and
wherein the first and second outer GaP layers represent an energy level higher than that of the GaP layer.
9. The red light emitting device of claim 8 , wherein the fourth semiconductor layer is thicker than the second semiconductor layer.