KR101637596B1 - Light emitting device - Google Patents

Abstract

Embodiments relate to a light emitting device, a light emitting device package, and an illumination system.
The light emitting device according to the embodiment includes a first conductivity type semiconductor layer, a second conductivity type semiconductor layer, and a light emitting layer between the first conductivity type semiconductor layer and the second conductivity type semiconductor layer, A quantum well and at least one quantum well between the quantum well and the first quantum well adjacent to the second conductivity type semiconductor layer may be a quantum well doped with a second conductivity type impurity.

Description

[0001] LIGHT EMITTING DEVICE [0002]

Embodiments relate to a light emitting device, a light emitting device package, and an illumination system.

A light emitting device can be produced by combining p-n junction diodes having the characteristic that electric energy is converted into light energy by elements of Group III and Group V on the periodic table. LEDs can be implemented in various colors by controlling the composition ratio of compound semiconductors.

In the light emitting device, electrons supplied from the electron injection layer and holes supplied from the hole injection layer combine with each other in the quantum well to emit light.

However, the conventional nitride semiconductor light emitting device has a problem that the injection efficiency of holes injected from the hole injection layer, for example, P-GaN, into the light emitting layer is very low. This low hole injection efficiency greatly limits the luminous efficiency of the conventional light emitting device.

In addition, in the prior art, electrons injected through an electron injection layer, for example, N-GaN, have inherently high mobility in the nitride semiconductor so that they can easily reach quantum wells and even pass into a hole injection layer, Goes. In order to increase the luminous efficiency of the light emitting device, the loss of electrons passing through the light emitting layer to P-GaN must be minimized.

Embodiments provide a light emitting device, a light emitting device package, and an illumination system capable of achieving high efficiency light emission characteristics by maximizing the hole injection efficiency.

The light emitting device according to the embodiment includes a first conductivity type semiconductor layer, a second conductivity type semiconductor layer, and a light emitting layer between the first conductivity type semiconductor layer and the second conductivity type semiconductor layer, A quantum well and at least one quantum well between the quantum well and the first quantum well adjacent to the second conductivity type semiconductor layer may be a quantum well doped with a second conductivity type impurity.

In addition, the light emitting device package according to the embodiment includes the light emitting element; A package body in which the light emitting device is disposed; And at least one electrode electrically connecting the light emitting device and the package body.

Further, the illumination system according to the embodiment may include a light emitting unit having the light emitting device package.

According to the embodiments, it is expected to provide a light emitting device, a light emitting device package, and an illumination system capable of achieving high efficiency light emission characteristics by maximizing the hole injection efficiency.

For example, by moving the quantum wells from the quantum well adjacent to P-GaN to the center of the multiple quantum well emission layer, more quantum wells can contribute to the emission, The loss of electrons can be minimized.

1 is an exemplary view showing an energy band gap of a light emitting device according to the first embodiment;
FIG. 2 is an exemplary view showing an energy band gap of the light emitting device according to the second embodiment. FIG.
3 is a cross-sectional view of a light emitting device package according to an embodiment.
4 is a perspective view of a lighting unit according to an embodiment;
5 is a perspective view of a backlight unit according to an embodiment.

In the description of the embodiments, each layer (film), region, pattern or structure is referred to as being "on" or "under" the substrate, each layer (film) Quot; on "and" under "are intended to include both" directly "or" indirectly " do. Also, the criteria for top, bottom, or bottom of each layer will be described with reference to the drawings.

The thickness and size of each layer in the drawings are exaggerated, omitted, or schematically shown for convenience and clarity of explanation. Also, the size of each component does not entirely reflect the actual size.

(Example)

Embodiments provide a light emitting device, a light emitting device package, and an illumination system capable of achieving high efficiency light emission characteristics by maximizing the hole injection efficiency.

1 is a diagram illustrating an energy band gap of the light emitting device 100 according to the first embodiment.

The first conductivity type semiconductor layer 110 and the second conductivity type semiconductor layer 130 are formed on the first conductivity type semiconductor layer 110, the second conductivity type semiconductor layer 130, Wherein the light emitting layer comprises at least one quantum well 122 and at least one quantum wall 124 between the quantum well 122 and the second conductivity type semiconductor layer 130 may be a quantum well doped with a second conductivity type dopant.

The second conductive semiconductor layer 130 may be a hole injection layer, and the first conductive semiconductor layer 110 may be an electron injection layer, but the present invention is not limited thereto.

The first quantization energy level (n = 1) of the first quantum well 122a is greater than the first quantization energy n = 1 in another quantum well adjacent to the first conductivity type semiconductor layer 110, It may be above level.

Also, in the embodiment, the first quantum well 122a may be a light emitting layer capable of emitting actual light.

For example, a P-type impurity such as Mg may be doped into the second conductive semiconductor layer 130, for example, a first quantum well 122a adjacent to p-GaN, and a Mg-doped first quantum well 122a are equal in energy state to the first quantized energy levels in the quantum wells 122b, 122c adjacent to each other in the direction of the first conductivity type semiconductor layer 110, for example, in the n-GaN direction The holes injected into the first quantum well 122a can be efficiently injected into the adjacent quantum wells by the quantum mechanical tunneling phenomenon, thereby improving the hole injection efficiency of the light emitting device.

2 is a diagram illustrating an energy band gap of the light emitting device 100b according to the second embodiment.

2, a second conductive type semiconductor layer 130, for example, a second conductive type quantum barrier adjacent to the p-type GaN layer 126, is formed to improve hole injection efficiency, The doping efficiency of the hole can be increased by increasing the mobility of the holes and reducing the non-emission loss probability of the holes by doping a part or all of the p-type impurities, for example, Mg.

A part or the whole of the second conductive type quantum wall 126 is doped with a P type impurity and an energy band gap of the second conductive type quantum wall 126 is larger than an energy of the second conductive type semiconductor layer 130 May be equal to or less than the bandgap.

In the embodiment, the improvement of the hole injection efficiency is achieved by moving the main emission position from the quantum well adjacent to the second conductivity type semiconductor layer 130, for example P-GaN, to the center of the multiple quantum well emission layer, So that the loss of electrons passing in the P-GaN direction can be minimized without contributing to light emission. The improvement of the hole injection efficiency in the light emitting device according to the embodiment can remarkably increase the luminous efficiency of the light emitting device by minimizing the non-emission loss of the injected holes.

According to the embodiments, it is possible to provide a light emitting device, a light emitting device package, and an illumination system capable of achieving high efficiency light emission characteristics by maximizing the hole injection efficiency by overcoming the problem of low hole injection efficiency.

Hereinafter, with reference to FIG. 1, the light emitting device 100 according to the first embodiment will be described in more detail.

The light emitting device 100 according to the first embodiment includes a first conductive semiconductor layer 110, for example, n-GaN and a second conductive semiconductor layer 130, for example, p-GaN, The first quantum well 122a adjacent to the P-GaN among the multiple quantum wells 122 is doped with a P-type impurity, for example, Mg, and the first quantum well 122a of the first quantum well 122a is doped with a P- The energy of the first quantized energy level in the quantum wells 122b and 122c adjacent to each other in the n-GaN direction may be equal to or higher than the energy of the first quantized energy level.

The first embodiment may include an un-acted GaN barrier (not shown) between the first quantum well 122a and the second conductive semiconductor layer 130, but the present invention is not limited thereto.

According to the first embodiment, the holes injected from p-type GaN reach the first quantum well 122a doped with Mg through the undoped GaN barrier and are filled in turn from the low energy level in the quantum well.

The holes occupying the first quantum energy level of the first quantum well 122a are quantum mechanical quantum wells passing through the first quantum well when the first quantization energy level in the second quantum well 122b having the same or lower energy state is empty Tunneling phenomenon. At this time, light may be emitted by the combination of electrons and holes in the first quantum well 122a.

Then, holes injected into the second quantum well 122b are combined with electrons injected through the n-type GaN to emit light. As a result, the holes injected from the P-type GaN can be effectively injected into the second quantum well 122b through the Mg-doped first quantum well 122a. The improvement of the hole injection efficiency reduces the hole loss and can improve the luminous efficiency of the device.

According to the embodiment, it is possible to provide a light emitting device, a light emitting device package, and an illumination system capable of achieving high efficiency light emission characteristics by maximizing the hole injection efficiency.

2 is a diagram illustrating an energy band gap of the light emitting device 100b according to the second embodiment.

The second embodiment can employ the technical features of the first embodiment. The second embodiment differs from the second embodiment in that the second conductivity type semiconductor layer 130, for example, a part of the second conductivity type last barrier 126 adjacent to the p-GaN layer, It is possible to increase the hole injection efficiency by increasing the mobility of holes and reducing the non-emission loss probability of holes by doping the entire P-type impurity, for example, Mg.

At this time, the energy band gap of the second conductive type quantum wall 126 may be equal to or less than the energy band gap of the second conductive type semiconductor layer 130.

According to the second embodiment, the holes injected from the second conductivity type semiconductor layer 130, for example, p-type GaN, are doped with P-type impurities such as Mg-doped second conductivity type quantum wall 126, (Al _x In _y Ga _{1 - x - y} N, 0? _{X, y} ? 1), and then the first quantum well 122a doped with Mg is filled in order from the lowest energy level in the quantum well.

At this time, the holes occupying the first quantized energy level of the first quantum well 122a are quantized by the quantum mechanical tunneling phenomenon when the first quantized energy level in the second quantum well 122b having the same energy level or lower is empty And is moved efficiently.

The holes injected into the second quantum well 122b combine with the electrons injected through the n-type GaN to emit light. At this time, light may be emitted by the combination of electrons and holes in the first quantum well 122a.

As a result, the holes injected from the P-type GaN can be effectively injected into the second quantum well 122b through the Mg-doped second conductivity type quantum wall 126 and the first quantum well 122a. The enhancement of the hole injection efficiency reduces the loss of holes injected into the device, thereby improving the luminous efficiency of the device.

According to the embodiments, it is expected to provide a light emitting device, a light emitting device package, and an illumination system capable of achieving high efficiency light emission characteristics by maximizing the hole injection efficiency.

Hereinafter, a method of manufacturing the light emitting device according to the embodiment will be described.

First, a method of forming the first conductivity type semiconductor layer 110 will be described.

When the first conductive semiconductor layer 110 is an N-type semiconductor layer, the first conductive semiconductor layer 110 may be formed of a Group III-V compound semiconductor doped with a first conductive dopant. The first conductive dopant may include, but is not limited to, Si, Ge, Sn, Se, and Te as an N-type dopant.

The first conductive semiconductor layer 110 may include a semiconductor material having a composition formula of In _x Al _y Ga _{1 -x- y} N (0? X? 1, 0? _Y? 1, 0? _X + .

The first conductive semiconductor layer 110 may be formed of one or more of GaN, InN, AlN, InGaN, AlGaN, InAlGaN, AlInN, AlGaAs, InGaAs, AlInGaAs, GaP, AlGaP, InGaP, AlInGaP and InP.

The first conductive semiconductor layer 110 may be formed by a chemical vapor deposition (CVD) method, a molecular beam epitaxy (MBE) method, a sputtering method, or a vapor phase epitaxy (HVPE) method . The first conductive semiconductor layer 110 may be formed by depositing a silane containing an n-type impurity such as trimethyl gallium gas (TMGa), ammonia gas (NH ₃ ), nitrogen gas (N ₂ ) Gas (SiH ₄ ) may be implanted and formed.

Next, a method for forming a light emitting layer (not shown) will be described.

In the light emitting layer, electrons injected through the first conductive type semiconductor layer 110 and holes injected through the second conductive type semiconductor layer 130 meet to form light having energy determined by the energy band inherent to the light emitting layer material .

The light emitting layer may be formed of a multi quantum well (MQW) structure. For example, the light emitting layer may be formed by implanting trimethyl gallium gas (TMGa), ammonia gas (NH ₃ ), nitrogen gas (N ₂ ), and trimethyl indium gas (TMIn) to form a multiple quantum well structure. It is not.

The well layer / barrier layer of the light emitting layer may be formed of any one or more pairs of InGaN / GaN, InGaN / InGaN, AlGaN / GaN, InAlGaN / GaN, GaAs, / AlGaAs (InGaAs), and GaP / AlGaP But is not limited thereto. The well layer may be formed of a material having a band gap lower than the band gap of the barrier layer.

A conductive clad layer may be formed on and / or below the light emitting layer. The conductive cladding layer may be formed of an AlGaN-based semiconductor and may have a band gap higher than that of the light emitting layer.

At this time, when the thickness of the quantum well 122 of the light emitting layer is reduced, the height of the quantum mechanical energy level is increased and the energy value is increased. When the thickness is increased, the height of the energy level is decreased.

Also, if the indium composition is increased in the quantum well layer, the energy band gap of the quantum well layer becomes smaller and the absolute energy value of the quantum energy level becomes lower. When the indium composition is reduced or the aluminum is mixed, the energy bandgap of the quantum well becomes larger and the absolute energy value of the quantum mechanical energy level becomes larger.

In the embodiment, when the number of energy levels (n = 1, 2, 3, ..) in the quantum well increases, the energy of holes (or electrons) located at the corresponding level means a high state.

In a quantum well, holes are moved from a high energy level state to a low energy level state to stabilize. When there is a quantum wall, when an equivalent energy level is empty or a low energy level is empty in a neighboring quantum well beyond the quantum well, The wall is tunnelled and moved to stabilize it energetically.

If the vacancy energy level of higher energy state is located in the neighboring quantum well beyond the quantum well, it becomes very difficult for the holes to move quantitatively to the corresponding level. Therefore, it is possible to control the movement and distribution of holes efficiently by controlling the energy level of the quantum well.

Embodiments can be achieved by reducing the In composition or reducing the quantum well thickness for the second quantum well, such as the InGaN quantum well, in the first quantum well 122a adjacent to the second conductivity type semiconductor layer 130, for example P-GaN. The energy state of the quantized energy levels in the first quantum well 122a is made higher than the energy levels of other adjacent quantum wells.

Also, the P-type impurity, e.g., Mg doping, for the first quantum well 122a adjacent to P-GaN may have a doping concentration higher than the concentration of electrons supplied by the intrinsic point defects of the InGaN quantum well.

For example, a first quantum well (122a), for example, the concentration of electron caused by the point defects having the InGaN quantum well is about ^{1x10 17 atoms ~ 5x10 17 atoms /} cm 3. As a result, the Mg doping concentration is preferably about 5 x 10 ¹⁷ atoms / cm ³ to 3 x ^{10 20} atoms / cm ³ . Mg doping of ³ x ^{10 20} atoms / cm ³ or more is undesirable because it causes structural defects of crystals.

According to the second embodiment, the P-type impurity, for example, Mg doping in the second conductivity type quantum wall 126 is doped to a part or the whole of the second conductivity type quantum wall 126 at a doping concentration of 5 x 10 ¹⁷ atoms / cm 3 ³ to 3 x ¹⁰ < ²⁰ > atoms / cm < ³ >.

Also, in the embodiment, the energy band gap of the second conductivity type quantum wall 126 is preferably equal to or smaller than the p-GaN energy band gap in order to increase the hole injection efficiency.

According to the embodiments, the light emitting device, the light emitting device package, and the light emitting device package can have high efficiency light emission characteristics by dramatically overcoming the problem of low hole injection efficiency due to the structural problems of the conventional nitride semiconductor light emitting device, It is expected to provide a lighting system.

3 is a cross-sectional view of a light emitting device package according to an embodiment.

3, the light emitting device package 200 according to the embodiment includes a package body 205, a third electrode layer 213 and a fourth electrode layer 214 provided on the package body 205, A light emitting device 100 mounted on the package body 205 and electrically connected to the third electrode layer 213 and the fourth electrode layer 214 and a molding member 240 surrounding the light emitting device 100 .

The package body 205 may be formed of a silicon material, a synthetic resin material, or a metal material, and the inclined surface may be formed around the light emitting device 100.

The third electrode layer 213 and the fourth electrode layer 214 are electrically isolated from each other and provide power to the light emitting device 100. The third electrode layer 213 and the fourth electrode layer 214 may function to increase light efficiency by reflecting the light generated from the light emitting device 100, And may serve to discharge heat to the outside.

The light emitting device 100 illustrated in FIG. 1 may be applied to the light emitting device 100, but the light emitting device 100b illustrated in FIG. 2 may also be used.

The light emitting device 100 may be mounted on the package body 205 or on the third electrode layer 213 or the fourth electrode layer 214.

The light emitting device 100 may be electrically connected to the third electrode layer 213 and / or the fourth electrode layer 214 through a wire 230. In an exemplary embodiment, the vertical light emitting device 100 may include, for example, And one wire 230 is used, but the present invention is not limited thereto.

The molding member 240 surrounds the light emitting device 100 to protect the light emitting device 100. In addition, the molding member 240 may include a phosphor to change the wavelength of light emitted from the light emitting device 100.

The light emitting device package according to the embodiment can be applied to the illumination system. The illumination system includes the illumination unit shown in Fig. 4, the back-ride unit shown in Fig. 5, and may include a traffic light, a vehicle headlight, a signboard, and the like.

4 is a perspective view 1100 of a lighting unit according to an embodiment.

4, the lighting unit 1100 includes a case body 1110, a light emitting module unit 1130 installed in the case body 1110, and a power supply unit 1130 installed in the case body 1110, And may include a connection terminal 1120 to be provided.

The case body 1110 is preferably formed of a material having a good heat dissipation property, and may be formed of, for example, a metal material or a resin material.

The light emitting module unit 1130 may include a substrate 1132 and at least one light emitting device package 200 mounted on the substrate 1132.

The substrate 1132 may be a circuit pattern printed on an insulator. For example, the PCB 1132 may be a printed circuit board (PCB), a metal core PCB, a flexible PCB, a ceramic PCB . ≪ / RTI >

Further, the substrate 1132 may be formed of a material that efficiently reflects light, or may be formed of a color whose surface is efficiently reflected, for example, white, silver, or the like.

The at least one light emitting device package 200 may be mounted on the substrate 1132. Each of the light emitting device packages 200 may include at least one light emitting diode (LED) 100. The light emitting diode 100 may include a colored light emitting diode that emits red, green, blue, or white colored light, and a UV light emitting diode that emits ultraviolet (UV) light.

The light emitting device 100 illustrated in FIG. 1 may be applied to the light emitting device 100, but the light emitting device 100b illustrated in FIG. 2 may also be used.

The light emitting module unit 1130 may be arranged to have a combination of various light emitting device packages 200 to obtain color and brightness. For example, a white light emitting diode, a red light emitting diode, and a green light emitting diode may be arranged in combination in order to secure a high color rendering index (CRI).

The connection terminal 1120 may be electrically connected to the light emitting module 1130 to supply power. 4, the connection terminal 1120 is coupled to the external power source by being inserted in a socket manner, but the present invention is not limited thereto. For example, the connection terminal 1120 may be formed in a pin shape and inserted into an external power source or may be connected to an external power source through a wiring.

5 is an exploded perspective view 1200 of a backlight unit according to an embodiment.

The backlight unit 1200 according to the embodiment includes a light guide plate 1210, a light emitting module unit 1240 for providing light to the light guide plate 1210, a reflection member 1220 below the light guide plate 1210, But the present invention is not limited thereto, and may include a bottom cover 1230 for housing the light emitting module unit 1210, the light emitting module unit 1240, and the reflecting member 1220.

The light guide plate 1210 serves to diffuse light into a surface light source. The light guide plate 1210 may be made of a transparent material such as acrylic resin such as PMMA (polymethyl methacrylate), polyethylene terephthalate (PET), polycarbonate (PC), cycloolefin copolymer (COC), and polyethylene naphthalate Resin. ≪ / RTI >

The light emitting module part 1240 provides light to at least one side of the light guide plate 1210 and ultimately acts as a light source of a display device in which the backlight unit is installed.

The light emitting module 1240 may be in contact with the light guide plate 1210, but is not limited thereto. Specifically, the light emitting module 1240 includes a substrate 1242 and a plurality of light emitting device packages 200 mounted on the substrate 1242. The substrate 1242 is mounted on the light guide plate 1210, But is not limited to.

The substrate 1242 may be a printed circuit board (PCB) including a circuit pattern (not shown). However, the substrate 1242 may include not only a general PCB, but also a metal core PCB (MCPCB), a flexible PCB (FPCB), and the like.

The plurality of light emitting device packages 200 may be mounted on the substrate 1242 such that a light emitting surface on which the light is emitted is spaced apart from the light guiding plate 1210 by a predetermined distance.

The reflective member 1220 may be formed under the light guide plate 1210. The reflection member 1220 reflects the light incident on the lower surface of the light guide plate 1210 so as to face upward, thereby improving the brightness of the backlight unit. The reflective member 1220 may be formed of, for example, PET, PC, or PVC resin, but is not limited thereto.

The bottom cover 1230 may receive the light guide plate 1210, the light emitting module 1240, and the reflective member 1220. For this purpose, the bottom cover 1230 may be formed in a box shape having an opened upper surface, but the present invention is not limited thereto.

The bottom cover 1230 may be formed of a metal material or a resin material, and may be manufactured using a process such as press molding or extrusion molding.

According to the embodiments, the light emitting device, the light emitting device package, and the light emitting device package can have high efficiency light emission characteristics by dramatically overcoming the problem of low hole injection efficiency due to the structural problems of the conventional nitride semiconductor light emitting device, It is expected to provide a lighting system.

The features, structures, effects and the like described in the embodiments are included in at least one embodiment and are not necessarily limited to only one embodiment. Furthermore, the features, structures, effects and the like illustrated in the embodiments can be combined and modified by other persons skilled in the art to which the embodiments belong. Accordingly, the contents of such combinations and modifications should be construed as being included in the scope of the embodiments.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention. It can be seen that the modification and application of branches are possible. For example, each component specifically shown in the embodiments can be modified and implemented. It is to be understood that the present invention may be embodied in many other specific forms without departing from the spirit or essential characteristics thereof.

Claims (8)

A first conductivity type semiconductor layer, a second conductivity type semiconductor layer, and a light emitting layer between the first conductivity type semiconductor layer and the second conductivity type semiconductor layer,
Wherein the light emitting layer comprises at least one quantum well and at least one quantum wall between the quantum wells,
The first quantum well adjacent to the second conductivity type semiconductor layer is a quantum well into which the second conductivity type impurity is implanted,
Wherein the second conductivity type semiconductor layer is a hole injection layer, and the first conductivity type semiconductor layer is an electron injection layer. The method according to claim 1,
The first quantum well
And the doping concentration of the second conductive impurity is 5 x 10 ¹⁷ atoms / cm ³ to 3 x ^{10 20} atoms / cm ³ . The method according to claim 1,
Wherein the first quantum energy level of the first quantum well is equal to or higher than a first quantization energy level in another quantum well adjacent to the first conductivity type semiconductor layer. The method according to claim 1,
The first quantum well
A light emitting element which is a light emitting layer capable of emitting light. A first conductivity type semiconductor layer, a second conductivity type semiconductor layer, and a light emitting layer between the first conductivity type semiconductor layer and the second conductivity type semiconductor layer,
Wherein the light emitting layer comprises at least one quantum well and at least one quantum wall between the quantum wells,
The first quantum well adjacent to the second conductivity type semiconductor layer is a quantum well into which the second conductivity type impurity is implanted,
The first quantum well
And the doping concentration of the second conductive impurity is 5 x 10 ¹⁷ atoms / cm ³ to 3 x ^{10 20} atoms / cm ³ . A first conductivity type semiconductor layer, a second conductivity type semiconductor layer, and a light emitting layer between the first conductivity type semiconductor layer and the second conductivity type semiconductor layer,
Wherein the light emitting layer comprises at least one quantum well and at least one quantum wall between the quantum wells,
The first quantum well adjacent to the second conductivity type semiconductor layer is a quantum well into which the second conductivity type impurity is implanted,
And a second conductivity type quantum wall in which a second conductivity type impurity is injected between the first quantum well and the second conductivity type semiconductor layer. The method according to claim 6,
The second conductivity type quantum wall
And the energy band gap of the second conductivity type quantum wall is equal to or smaller than the energy band gap of the second conductivity type semiconductor layer. The method according to claim 6,
And a doping concentration is 5 x 10 ¹⁷ atoms / cm ³ to 3 x ^{10 20} atoms / cm ³ in a part or the whole of the second conductivity type quantum wall.

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