KR102354251B1 - Light emitting device and lighting device - Google Patents

Abstract

The embodiment relates to a light emitting device, a light emitting device package, and a lighting device.
A light emitting device according to an embodiment includes a first conductivity type semiconductor layer, an active layer disposed on the first conductivity type semiconductor layer, and a second conductivity type semiconductor layer disposed on the active layer, wherein the active layer includes a plurality of barrier layers and a plurality of and a well layer of , wherein each of the plurality of barrier layers may include a P-type barrier layer doped with a P-type dopant and an undoped barrier layer disposed on the p-type barrier layer.

Description

Light emitting device and lighting device {LIGHT EMITTING DEVICE AND LIGHTING DEVICE}

The embodiment relates to a light emitting device, a light emitting device package, and a lighting device.

A light emitting device (Light Emitting Device) is a pn junction diode having the characteristic of converting electrical energy into light energy, and can be produced with compound semiconductors such as Group 3III and Group V on the periodic table, and various colors can be realized by adjusting the composition ratio of the compound semiconductor. It is possible.

When a forward voltage is applied, the electrons of the n-layer and the holes of the p-layer combine to emit energy corresponding to the bandgap energy of the conduction band and the valence band. Here, when the energy is emitted in the form of light, it may become a light emitting device. For example, nitride semiconductors are receiving great attention in the field of developing optical devices and high-power electronic devices due to their high thermal stability and wide bandgap energy. In particular, a blue light emitting device, a green light emitting device, and an ultraviolet (UV) light emitting device using a nitride semiconductor have been commercialized and widely used.

The light emitting device includes an active layer that emits energy of light, and the active layer is formed by repeatedly stacking a quantum well having a small energy band gap and a quantum wall having a large energy band gap, and electrons injected from the n-type semiconductor layer and the p-type Holes injected from the semiconductor layer meet each other in the quantum well, combine to emit light, and emit light.

On the other hand, the light emitting device of the prior art has a droop problem in that the luminous efficiency is lowered when the amount of injection current increases, which is a problem that occurs because the injection efficiency of carriers (holes or electrons) into the light emitting layer is not uniform. In order to solve the problem, it is required to develop a technology capable of allowing most of the quantum wells of the light emitting layer to substantially participate in light emission.

In addition, in general, the mobility of holes is lower than that of electrons, so that the injection efficiency into the active layer is low. Accordingly, electrons pass through the active layer to the p-type semiconductor layer region. Such a phenomenon is called an electron overflow, and the electron overflow intensifies as the current density increases. That is, in the light emitting device of the prior art, the external quantum efficiency decreases as the carrier concentration increases as the high current density increases.

The embodiment may provide a light emitting device, a light emitting device package, and a lighting device capable of improving luminous efficiency.

The light emitting device according to the embodiment includes a first conductive semiconductor layer 112; an active layer 114 positioned on the first conductivity-type semiconductor layer; a second conductivity type semiconductor layer 116 disposed on the active layer 114 , wherein the active layer 114 includes a plurality of barrier layers 114QB and a plurality of well layers 114QW, and the plurality of Each of the barrier layers 114QB may include a P-type barrier layer 114PB doped with a P-type dopant and an undoped barrier layer 114UB disposed on the p-type barrier layer 114PB.

The lighting device according to the embodiment may include the light emitting device.

In the light emitting device of the embodiment, a P-type quantum barrier layer is disposed under the undo port quantum barrier layer, so that negative charges are formed on the upper quantum well layer, and positive charges are formed on the lower portion of the quantum well layer. can

1 is a diagram illustrating an energy band of a light emitting device according to an embodiment.
FIG. 2 is a view showing A of FIG. 1 .
3 is a diagram comparing the internal quantum efficiency of a comparative example and an embodiment.
4 is a cross-sectional view illustrating a vertical type light emitting device according to an embodiment.
5 is a cross-sectional view illustrating a horizontal type light emitting device according to an embodiment.
6 is a view showing a light emitting device package according to an embodiment.

In the description of embodiments, each layer (film), region, pattern or structure is “on/over” or “under” the substrate, each layer (film), region, pad or pattern. In the case of being described as being formed on, “on/over” and “under” include both “directly” or “indirectly” formed through another layer. do. In addition, the reference for the upper / upper or lower of each layer will be described with reference to the drawings.

1 is a diagram illustrating an energy band of a light emitting device according to an embodiment, and FIG. 2 is a diagram illustrating A of FIG. 1 .

1 and 2 , the active layer 114 of the light emitting device according to the embodiment is positioned between the first conductivity type semiconductor layer 112 and the second conductivity type semiconductor layer 116 .

The active layer 114 may be a compound semiconductor, for example, the active layer 114 may be composed of a compound semiconductor. The active layer 114 may be implemented, for example, by at least one of a group II-IV group and a group III-V compound semiconductor.

The active layer 114 may include a quantum well layer 114QW and a quantum barrier layer 114QB. When the active layer 114 is implemented as a multi-quantum well structure, the quantum well layer 114QW and the quantum barrier layer 114QB may be alternately disposed. The quantum well layer 114QW and the quantum barrier layer 114QB each have a compositional formula of _{In x} Al _y Ga _{1-xy N (0≤x≤1, 0≤y≤1, 0≤x+y≤1).} It may be disposed as a semiconductor material, or formed into a pair structure of any one or more of AlGaN/GaN, AlGaN/AlGaN, InGaN/GaN, InGaN/InGaN, InAlGaN/GaN, GaAs/AlGaAs, InGaAs/AlGaAs, GaP/AlGaP, InGaP AlGaP may be, but is not limited thereto.

The energy band of the active layer 114 is divided into a conduction band and a valence band, respectively, the conduction band energy level (Ec) and the valence band energy level (Ev) are the energy levels of the quantum well layer 114QW is low, and the energy level of the quantum barrier layer 114QB is high.

As shown in the figure, the conduction band energy level (Ec) and the valence band energy level (Ev) of the active layer 114 have an energy band waveform, such an energy band waveform is a quantum well layer 114QW and a quantum barrier layer ( 114QB) is formed by the wavefunction of holes and electrons in the region.

The active layer 114 _{will be described as an example of a structure composed of an In z} Ga _1-z N (0≤z≤1) quantum well layer 114QW and a GaN-based quantum barrier layer 114QB.

The quantum barrier layer 114QB may include a P-type GaN layer 114PB and an undoped GaN layer 114UB. The P-type GaN layer 114PB may include a P-type dopant. The P-type dopant may include Mg, Zn, Ca, Sr, Ba, or the like. The P-type GaN layer 114PB of the embodiment may include Mg. The P-type GaN layer 114PB may be positioned under the undoped GaN layer 114UB. That is, in the active layer 114 of the embodiment, at least three pairs of the quantum well layer 114QW, the P-type GaN layer 114PB, and the undoped GaN layer 114UB may be alternately disposed, but the present invention is not limited thereto.

The Mg doping concentration of the P-type GaN layer 114PB may be 1×10 ¹⁷ cm ^{−3 or} more, but is not limited thereto. For example, the Mg doping concentration may be 1 x 10 ¹⁷ cm ^-3 to 1 x 10 ¹⁹ cm ^-3 . When the Mg doping concentration of the P-type GaN layer 114PB is ^{less than 1 x 10 17} cm ^-3 _{, the In z} Ga _1-z N (0≤z≤1) quantum well layer 114QW by the activated Mg Since the negative charge (NC) is lower than the interfacial charge of the lower part of the quantum well layer, there is no screening effect, so the internal quantum efficiency may be reduced. When the Mg doping concentration of the P-type GaN layer 114PB is greater than 1 x 10 ¹⁹ cm ^-3 , Mg is diffused into the In _z Ga _1-z N (0≤z≤1) quantum well layer 114QW. Light-emitting characteristics may be deteriorated by non-recombination.

In the quantum barrier layer 114QB, a P-type GaN layer 114PB is disposed under the undoped GaN layer 114UB, and holes in the active layer 114 are formed by holes injected into the lower portion of the quantum barrier layer 114QB. Injection efficiency can be improved. That is, since holes are provided in the active layer 114 by Mg of the p-type GaN layer 114PB, luminous efficiency can be improved. The thickness of the P-type GaN layer 114PB may be 0.3 nm or more. For example, the thickness of the P-type GaN layer 114PB may be 0.3 nm to 5.0 nm. The thickness of the P-type GaN layer 114PB may be 3.0 nm. When the thickness of the P-type GaN layer 114PB is less than 0.3 nm, hole injection efficiency may be reduced. When the thickness of the P-type GaN layer 114PB is greater than 5.0 nm, Mg may diffuse into the undoped GaN layer 114UB and the quantum well layer 114QW, and luminous efficiency may be reduced due to non-luminescent recombination.

For example, the interface charge density of the upper end of the quantum well layer 114QW and the quantum barrier layer 114WB may be 4 x 10 ¹² cm ^-2 , and the thickness of the P-type GaN layer 114PB of the embodiment. When is 3.0 nm, the charge density due to Mg activated by ^{5 x 10 17} cm ^-3 may be ^{-1.5 x 10 12} cm ^-2. That is, the charge density on the quantum well layer 114QW may be lowered to ^{2.5 x 10 12} cm ^-2. In addition, the interfacial charge density of the lower end of the quantum well layer 114QW and the quantum barrier layer 114WB may be -4 x 10 ¹² cm ^-2 , and the quantum well due to holes activated from the quantum well layer 114QW. A positive charge (PC) is formed at the bottom of the layer 114QW, so that the charge density on the upper part of the quantum well layer 114QW may be lowered to ^{-2.5 x 10 12} cm ^-2.

In the light emitting device of the embodiment, a negative charge (NC) is formed _{on the In z} Ga _1-z N (0≤z≤1) quantum well layer 114QW by Mg of the P-type GaN layer 114PB, and P _{in z Ga 1-z N (} 0≤z≤1) in z Ga 1-z N (0≤z≤1) by the holes move to the quantum well layer (114QW) at the bottom of the type GaN layer (114PB) A positive charge PC is formed under the quantum well layer 114QW, and an electric field opposite to that of the piezoelectric field is generated. Therefore, in the light emitting device of the embodiment, the piezoelectric property is relaxed, so that the luminous efficiency can be improved.

3 is a diagram comparing the internal quantum efficiency of a comparative example and an embodiment.

As shown in FIG. 3 , a comparative example is a structure of an InGaN-based quantum well layer and an undoped GaN-based quantum barrier layer. The embodiment is a structure of an InGaN-based quantum well layer and a quantum barrier layer of a P-type GaN layer/undoped GaN layer.

In the light emitting device of the embodiment, the piezoelectricity is relieved by the negative charge (NC) on the upper part of the quantum well layer and the positive charge (PC) on the lower part of the quantum well layer, so that the internal quantum efficiency can be increased by the screening effect.

4 is a cross-sectional view illustrating a vertical type light emitting device according to an embodiment.

As shown in FIG. 4 , the vertical type light emitting device 100 may adopt the technical characteristics of the active layer 114 of FIGS. 1 to 2 .

The vertical type light emitting device may include the light emitting structure 110 having the active layer 114 . The light emitting structure 110 may include a first conductivity type semiconductor layer 112 , an active layer 114 , and a second conductivity type semiconductor layer 116 .

The first conductivity-type semiconductor layer 112 may be implemented with a semiconductor compound, for example, a compound semiconductor such as Group II-IV and Group III-V, and may be doped with a first conductivity-type dopant. For example, the first conductivity type semiconductor layer 112 may include a semiconductor material having a composition formula _{of Al n} Ga _{1-n N (0≤n≤1).} When the first conductivity-type semiconductor layer 112 is an n-type semiconductor layer, the n-type dopant may include Si, Ge, Sn, Se, and Te, but is not limited thereto. The first conductivity-type semiconductor layer 112 may include a light extraction pattern 119 that improves light extraction efficiency.

The active layer 114 may be formed of at least one of a single quantum well structure, a multi quantum well (MQW) structure, a quantum-wire structure, or a quantum dot structure.

The active layer 114 may be formed of a compound semiconductor. The active layer 114 may be implemented, for example, by at least one of a group II-IV group and a group III-V compound semiconductor. The active layer 114 may include a quantum well layer and a quantum barrier layer. When the active layer 114 has a multi-quantum well structure, quantum well layers and quantum barrier layers may be alternately disposed.

The active layer 114 of the embodiment is, for example, _{a quantum barrier including an In z} Ga _1-z N (0≤z≤1) quantum well layer, an undoped GaN layer, and a P-type GaN layer located below the undoped GaN layer. layers may be included. In the active layer 114 of the embodiment _{, a negative charge (NC) is formed on the upper portion of the In z} Ga _1-z N (0≤z≤1) quantum well layer by the P-type dopant of the P-type GaN layer, and is formed below the P-type GaN layer. _{In z} Ga _{1-z N (0 ≤ z} ≤ ₁ ), the positive charge (PC) at the bottom of the In z Ga 1-z N (0 ≤ z ≤ 1) quantum well layer by the holes moved to the quantum well layer An electric field opposite to that of the piezoelectricity is generated. Therefore, in the light emitting device of the embodiment, the piezoelectric property is relaxed, so that the luminous efficiency can be improved.

The second conductivity-type semiconductor layer 116 may be implemented with a semiconductor compound, for example, a compound semiconductor such as group II-IV and group III-V, and may be doped with a second conductivity-type dopant. For example, the second conductivity type semiconductor layer 116 may include a semiconductor material having a composition formula _{of Al p} Ga _{1-p N (0≤p≤1).} When the second conductivity-type semiconductor layer 116 is a p-type semiconductor layer, the second conductivity-type dopant is a p-type dopant and may include Mg, Zn, Ca, Sr, Ba, or the like.

Although the first conductivity-type semiconductor layer 112 is described as an n-type semiconductor layer and the second conductivity-type semiconductor layer 116 as a p-type semiconductor layer, the first conductivity-type semiconductor layer 112 is a p-type semiconductor layer. The layer, the second conductivity type semiconductor layer 116 may be formed of an n-type semiconductor layer, but is not limited thereto. A semiconductor having a polarity opposite to that of the second conductivity type, for example, an n-type semiconductor layer (not shown) may be formed on the second conductivity type semiconductor layer 116 . Accordingly, the light emitting structure 110 may be implemented as any one of an n-p junction structure, a p-n junction structure, an n-p-n junction structure, and a p-n-p junction structure.

The light emitting device of the embodiment may include the first electrode 150 .

The light emitting device of the embodiment may include a current blocking layer 161 , a channel layer 163 , and a second electrode 170 under the light emitting structure 110 .

The second electrode 170 may include a contact layer 165 , a reflective layer 167 , and a bonding layer 169 .

The contact layer 165 may be formed by stacking a single metal, a metal alloy, or a metal oxide in multiple layers to efficiently inject carriers.

The reflective layer 167 may be positioned on the contact layer 165 .

A bonding layer 169 may be formed under the reflective layer 167 .

A support member 173 is formed under the bonding layer 169 , and the support member 173 may be formed of a conductive member.

5 is a cross-sectional view illustrating a horizontal type light emitting device according to an embodiment.

5 , in the horizontal type light emitting device 101 according to the embodiment, the light emitting structure 110 is disposed on the wave wave 111 .

The light emitting structure 110 may employ the technical features of FIGS. 1 to 3 .

In the embodiment, the second electrode 152 is electrically connected to the second conductivity type semiconductor layer 116 on the second conductivity type semiconductor layer 116 , and the second electrode 152 is formed on the first conductivity type semiconductor layer 112 . The first electrode 151 may be electrically connected to the first conductivity type semiconductor layer 112 .

The active layer 114 of the embodiment may include, for example, an undoped GaN layer and a quantum barrier layer including a P-type GaN layer positioned below the undoped GaN layer. In the active layer 114 of the embodiment, negative charges (NC) are formed on the quantum well layer by the P-type dopant of the P-type GaN layer, and the quantum well layer is formed by holes moved to the quantum well layer located below the P-type GaN layer. A positive charge (PC) is formed in the lower part of the Therefore, in the light emitting device of the embodiment, the piezoelectric property is relaxed, so that the luminous efficiency can be improved.

6 is a diagram illustrating a light emitting device package according to an embodiment.

The light emitting device package 200 according to the embodiment includes a package body part 205 , the first lead electrodes 213 and second lead electrodes 214 installed on the package body part 205 , and the package body part ( The light emitting device 100 is installed in 205 and electrically connected to the first lead electrode 213 and the second lead electrode 214 , and a molding member 230 surrounding the light emitting device 100 is included. .

The first lead electrode 213 and the second lead electrode 214 are electrically isolated from each other, and serve to provide power to the light emitting device 100 . In addition, the first lead electrode 213 and the second lead electrode 214 may include a function of increasing light efficiency by reflecting the light emitted from the light emitting device 100 , and the light emitting device 100 . It may include a function of discharging the heat generated in the outside.

The light emitting device 100 may be electrically connected to the first lead electrode 213 or the second lead electrode 214 by any one of a wire method, a flip chip method, or a die bonding method.

The molding member 230 may include a phosphor 232 to form a white light light emitting device package, but is not limited thereto.

The upper surface of the molding member 230 may be flat, concave, or convex, but is not limited thereto.

The light emitting device and the light emitting device package 200 according to the embodiment may be applied to a backlight unit, a lighting device, a display device, an indicator device, a lamp, a street lamp, a vehicle lighting device, a vehicle display device, a smart watch, and the like, but is not limited thereto.

Features, structures, effects, etc. described in the above embodiments are included in at least one embodiment, and are not necessarily limited to only one embodiment. Furthermore, features, structures, effects, etc. illustrated in each embodiment can be combined or modified for other embodiments by those of ordinary skill in the art to which the embodiments belong. Accordingly, the contents related to such combinations and modifications should be interpreted as being included in the scope of the embodiments.

In the above, the embodiment has been mainly described, but this is only an example and does not limit the embodiment, and those of ordinary skill in the art to which the embodiment belongs are provided with several examples not illustrated above within the range that does not deviate from the essential characteristics of the embodiment. It can be seen that variations and applications of branches are possible. For example, each component specifically shown in the embodiment can be implemented by modification. And differences related to such modifications and applications should be construed as being included in the scope of the embodiments set forth in the appended claims.

114: active layer 114QB: quantum barrier layer
114QW: quantum well layer 114PB: P-type GaN layer
114UB: undoped GaN layer

Claims (8)

a first conductivity type semiconductor layer;
an active layer positioned on the first conductivity-type semiconductor layer;
a second conductivity-type semiconductor layer disposed on the active layer;
the active layer comprises a plurality of barrier layers and a plurality of well layers;
Each of the plurality of barrier layers includes a P-type barrier layer doped with a P-type dopant, and an undoped barrier layer disposed on the P-type barrier layer,
The P-type barrier layer is disposed on each of the plurality of well layers, and the undoped barrier layer is disposed under each of the plurality of well layers,
The thickness of the P-type barrier layer is 0.3 nm to 5.0 nm,
The P-type dopant of the P-type barrier layer is Mg, and the Mg doping concentration is 1×10 ¹⁷ cm ^-3 or more,
In the barrier layer disposed between adjacent well layers, the doped P-type barrier layer is disposed under the undoped barrier layer. delete According to claim 1,
The Mg doping concentration of the P-type barrier layer is 1 x 10 ¹⁷ cm ^-3 to 1 x 10 ¹⁹ cm ^-3 A light emitting device. According to claim 1,
The plurality of well layers are InGaN, the P-type barrier layer is P-type GaN, and the undoped barrier layer is undoped GaN. A lighting device comprising the light emitting device of any one of claims 1 to 4. delete delete delete

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