KR20170082738A - Light emitting device - Google Patents

Abstract

One embodiment of the light emitting device includes a first conductivity type semiconductor layer; An active layer disposed on the first conductivity type semiconductor layer and comprising a plurality of quantum well layers and a plurality of quantum barrier layers alternately stacked; And a second conductive semiconductor layer disposed on the active layer, wherein at least one of the quantum barrier layers is formed with a doping layer doped with In.

Description

[0001]

The embodiment relates to a light emitting device having a structure in which the movement of holes progresses smoothly and the polarization is relaxed.

The contents described in this section merely provide background information on the embodiment and do not constitute the prior art.

GaN, and AlGaN are widely used for optoelectronics and electronic devices due to many advantages such as wide and easy-to-adjust energy band gap.

Particularly, a light emitting device such as a light emitting diode or a laser diode using a semiconductor material of a 3-5 group or a 2-6 group compound semiconductor has been widely used in various fields such as red, green, blue and ultraviolet rays It can realize various colors, and it can realize efficient white light by using fluorescent material or color combination. It has low power consumption, semi-permanent lifetime, fast response speed, safety, and environment compared to conventional light sources such as fluorescent lamps and incandescent lamps Affinity.

Therefore, a transmission module of the optical communication means, a light emitting diode backlight replacing a cold cathode fluorescent lamp (CCFL) constituting a backlight of an LCD (Liquid Crystal Display) display device, a white light emitting element capable of replacing a fluorescent lamp or an incandescent lamp Diode lighting, automotive headlights, and traffic lights.

The light emitting device may have a structure that generates light by energy generated in a recombination process of electrons and holes.

However, in general, the mobility of holes is lower than that of holes, which causes a problem that the luminous efficiency and the light output of the light emitting device are lowered.

In addition, in the light emitting device, polarization may be generated which interferes with the recombination of electrons and holes. This polarization also lowers the luminous efficiency and optical output of the optical device.

Therefore, the embodiment relates to a light emitting device having a structure in which the movement of holes progresses smoothly and the polarization is relaxed.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.

One embodiment of the light emitting device includes a first conductivity type semiconductor layer; An active layer disposed on the first conductivity type semiconductor layer and comprising a plurality of quantum well layers and a plurality of quantum barrier layers alternately stacked; And a second conductive semiconductor layer disposed on the active layer, wherein at least one of the quantum barrier layers is formed with a doping layer doped with In.

Wherein the quantum barrier layer comprises: a first layer on which the doped layer is formed; And a second layer formed on the first layer and having the doping concentration of In non-uniformly along the stacking direction.

Wherein the first layer comprises: a doping layer; And a first barrier layer disposed on top and bottom of the doped layer.

The doping layer may have a lower energy band gap than the first barrier layer and an energy band gap higher than the quantum well layer.

The first barrier layer may be one in which electrons or holes are tunneled.

The thickness of the first layer may be in the range of 20 Å to 40 Å.

The thickness of the second layer may be in the range of 10 Å to 15 Å.

The thickness of the doping layer may be in the range of 10 Å to 15 Å.

The thickness of the quantum well layer may be 15 ANGSTROM to 25 ANGSTROM.

The doping layer may have an In doping concentration lower than the quantum well layer and higher than the first barrier layer.

The doping layer may have a composition of In _x Ga _{1 - x} N (0.01 _{? X} ? 0.02).

Another embodiment of the light emitting device includes: a first conductivity type semiconductor layer; An active layer formed between the first conductivity type semiconductor layers and including a plurality of quantum well layers and a plurality of quantum barrier layers alternately stacked; And a second conductive semiconductor layer disposed on the active layer, wherein the quantum barrier layer is doped with In and doped with a higher energy band gap than the well layer; And a first barrier layer disposed above and below the doped layer and having a higher energy bandgap than the doped layer and through which electrons or holes are tunneled.

In the embodiment, electrons or holes are tunneled through the first barrier layer and injected smoothly into each quantum well layer, so that uniform light is generated throughout the active layer, thereby increasing the luminous efficiency and light output of the light emitting device.

In the embodiment, the doping layer can increase the luminous efficiency and the light output of the light emitting device by reducing the polarization of electrons and holes in the active layer and increasing the frequency of recombination of electrons and holes.

In the embodiment, the energy band gap is gently changed at the boundary between the quantum barrier layer and the quantum well layer, so that the polarization of electrons and holes in the active layer can be relaxed.

1 is a cross-sectional view illustrating a light emitting device according to an embodiment.
2 is a diagram showing an energy band gap of the light emitting device shown in FIG.
3 is a diagram showing an energy band gap of a light emitting device according to another embodiment.
4 is a view illustrating a light emitting device package according to one embodiment.

Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. The embodiments are to be considered in all aspects as illustrative and not restrictive, and the invention is not limited thereto. It is to be understood, however, that the embodiments are not intended to be limited to the particular forms disclosed, but are to include all modifications, equivalents, and alternatives falling within the spirit and scope of the embodiments. The sizes and shapes of the components shown in the drawings may be exaggerated for clarity and convenience.

The terms "first "," second ", and the like can be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. In addition, terms specifically defined in consideration of the constitution and operation of the embodiment are only intended to illustrate the embodiments and do not limit the scope of the embodiments.

In the description of the embodiments, when it is described as being formed on the "upper" or "on or under" of each element, the upper or lower (on or under Quot; includes both that the two elements are in direct contact with each other or that one or more other elements are indirectly formed between the two elements. Also, when expressed as "on" or "on or under", it may include not only an upward direction but also a downward direction with respect to one element.

It is also to be understood that the terms "top / top / top" and "bottom / bottom / bottom", as used below, do not necessarily imply nor imply any physical or logical relationship or order between such entities or elements, But may be used only to distinguish one entity or element from another entity or element.

1 is a cross-sectional view illustrating a light emitting device according to an embodiment. 1, the light emitting device of the embodiment includes a substrate 400, a first conductive semiconductor layer 100, an active layer 200, a second conductive semiconductor layer 300, a first electrode 810, And may include a second electrode 820.

Here, the first conductive semiconductor layer 100, the active layer 200, and the second conductive semiconductor layer 300 may form a light emitting structure.

The substrate 400 may support the light emitting structure. The substrate 400 may be formed of a template in which at least one of GaN, InGaN, AlGaN, and AlInGaN is stacked on a sapphire substrate 400, silicon (Si), zinc oxide (ZnO) Lt; / RTI >

The light emitting structure may be disposed on the substrate 400 and may serve to generate light. At this time, stress may be generated at the interface between the substrate 400 and the light emitting structure due to the difference in lattice constant, thermal expansion coefficient, and the like between the substrate 400 and the light emitting structure.

A buffer layer (not shown) may be interposed between the substrate 400 and the light emitting structure to mitigate such stress. In order to improve the crystallinity of the first conductivity type semiconductor layer 100, an undoped semiconductor layer (not shown) may be interposed. However, a small amount of unintended impurities may be doped in the manufacturing process.

At this time, the buffer layer can be grown at a low temperature, and the material may be a GaN layer or an AlN layer, but the present invention is not limited thereto. The n-type dopant is not doped in the un- And may be the same as the first conductivity type semiconductor layer 100 except that it has low electrical conductivity.

1, the first electrode 810 may be disposed on an exposed stepped portion of the first conductive type semiconductor layer 100, and the second electrode 820 may be disposed on the exposed portion of the first conductive type semiconductor layer 100, Type semiconductor layer 300 on the upper surface. When a current is applied through the first electrode 810 and the second electrode 820, the light emitting device of the embodiment emits light.

Although FIG. 1 illustrates a horizontal type light emitting device, it may be a vertical type light emitting device or a flip chip light emitting device.

As described above, the light emitting structure may include the first conductive semiconductor layer 100, the active layer 200, and the second conductive semiconductor layer 300.

The first conductive semiconductor layer 100 is disposed on the substrate 400 and may be formed of, for example, a nitride semiconductor.

That is, the first conductive semiconductor layer 100 may be formed of a semiconductor having a composition formula of In _x Al _y Ga _{1 -x- y} N (0? X? 1, 0? _Y? 1, 0? _X + A material such as GaN, AlN, AlGaN, InGaN, InN, InAlGaN, AlInN or the like and an n-type dopant such as Si, Ge, Sn, Se or Te can be doped.

The active layer 200 is disposed on the first conductivity type semiconductor layer 100 and includes electrons and holes provided from the first conductivity type semiconductor layer 100 and the second conductivity type semiconductor layer 300, It is possible to generate light by the energy generated in the recombination process.

When the active layer 200 has a quantum well structure, for example, it has a composition formula of In _x Al _y Ga _{1 -x- y} N (0? X? 1, 0? _Y? 1, 0? _X + y? 1) A quantum barrier layer 220 having a composition formula of a quantum well layer 210 and In _a Al _b Ga _{1 -a b} N (0? A? 1, 0? _B ? 1, 0? A + And may have a single or multiple quantum well structure.

At this time, the quantum well layer 210 may be provided to have an energy band gap lower than the energy band gap of the quantum barrier layer 220.

1, the active layer 200 includes a multi quantum well (MQW) structure in which a plurality of quantum well layers 210 and a plurality of quantum barrier layers 220 are alternately stacked A light emitting device having a light emitting layer is disclosed.

The quantum well layers 210 may be disposed in the direction of the second conductivity type semiconductor layer 300 from the first conductivity type semiconductor layer 100 and between the adjacent quantum well layers 210, (220) may be disposed. Hereinafter, only a light emitting device having a multiple quantum well structure will be described for the sake of simplicity.

1, the active layer 200 of the embodiment may have a structure in which a plurality of quantum well layers 210 and a plurality of quantum barrier layers 220 are alternately arranged. At this time, at least one of the quantum barrier layers 220 may be formed with a doping layer 221a doped with indium (In).

Although only two quantum well layers 210 and one quantum barrier layer 220 are illustrated in FIG. 1, only the quantum well layer 210 and the quantum barrier layer 220 are illustrated as a plurality of It is of course possible to be provided.

The quantum barrier layer 220 may include a doping layer 221a and a first barrier layer 221b. At this time, the doping layer 221a may be formed at the center of the quantum barrier layer 220, and the first barrier layer 221b may be formed at the top and bottom of the doping layer 221a.

The structure of the quantum barrier layer 220 will be described in detail with reference to FIGS. 2 and 3. FIG.

The second conductive semiconductor layer 300 may be disposed on the active layer 200. That is, the second conductive semiconductor layer 300 may be disposed on the quantum well layer 210 of the active layer 200. At this time, the second conductive semiconductor layer 300 may be formed of, for example, a nitride semiconductor.

That is, the second conductivity type semiconductor layer 300 may be a semiconductor having a composition formula of In _x Al _y Ga _{1 -x- y} N (0? X? 1, 0? _Y? 1, 0? _X + And may be doped with a p-type dopant such as Mg, Zn, Ca, Sr, Ba, or the like, for example, GaN, AlN, AlGaN, InGaN, InN, InAlGaN and AlInN.

2 is a diagram showing an energy band gap of the light emitting device shown in FIG. 2, electrons are injected from the first conductive semiconductor layer 100, holes are injected from the second conductive semiconductor layer 300, and the active layer 200 is injected from the first conductive semiconductor layer 100 And the second conductive type semiconductor layer 300. The second conductive type semiconductor layer 300 may be formed of a conductive material.

In the multiple quantum well structure, the active layer 200 may include at least two quantum well layers 210 and at least one quantum barrier layer 220. In FIG. 3, four quantum well layers 210 and three quantum barrier layers 220 are shown, but are not limited thereto.

At this time, the energy band gap of the quantum barrier layer 220 is larger than the energy band gap E3 of the quantum well layer 210.

When a current is applied to the light emitting device, since the mobility of holes is generally lower than that of electrons, the holes may not be uniformly injected into the entire multi-quantum well.

Therefore, light emission can mainly occur in the last quantum well nearest to the second conductivity type semiconductor layer 300 in which holes are injected, that is, the quantum well layer 210 located on the rightmost side in FIG.

For this reason, uniform light emission does not occur in the entire region of the active layer 200, and the light emitting efficiency and the light output of the light emitting device can be reduced. In an embodiment, a doping layer 221a may be formed on the quantum barrier layer 220 to solve this problem. Hereinafter, the doping layer 221a will be described in detail.

2, in an embodiment, the quantum barrier layer 220 may include a doping layer 221a and a first barrier layer 221b. The doping layer 221a may be disposed at a central portion of the quantum barrier layer 220 and the first barrier layer 221b may be disposed at an upper portion and a lower portion of the doping layer 221a.

The doping layer 221a may have a lower energy band gap than the first barrier layer 221b and an energy band gap higher than that of the quantum well layer 210. [ That is, the energy band gap may be reduced in the order of the first barrier layer 221b, the doping layer 221a, and the quantum well layer 210. That is, the relationship E2> E1> E3> can be formed. At this time, E1, E2 and E3 represent the energy band gap of each layer.

At this time, the energy band gap size can be adjusted by doping each layer. The dopant used herein may be, for example, In. The larger the doping concentration of In, the smaller the energy band gap can be.

Accordingly, the doping concentration of the doped layer 221a may be lower than the quantum well layer 210 and higher than the first barrier layer 221b. At this time, the doping layer 221a may have a composition of In _x Ga _{1 - x} N (0.01 _{? X} ? 0.02).

Due to such a structure, the first barrier layer 221b may tunnel electrons or holes through a tunneling path. Electrons or holes may be tunneled through the first barrier layer 221b and electrons or holes may be smoothly injected into each quantum well layer 210. [

Accordingly, electrons or holes are uniformly distributed in each of the plurality of quantum well layers 210, uniform light can be generated throughout the active layer 200, and as a result, the luminous efficiency and light output of the light emitting device can be increased .

Electrons or holes are tunneled in the first barrier layer 221b and are smoothly injected into each quantum well layer 210 to generate uniform light throughout the active layer 200, The output can be increased.

Meanwhile, in order for the tunneling effect to occur in the first barrier layer 221b, it is appropriate that the first barrier layer 221b is formed to a thickness at which tunneling occurs. For example, when the first barrier layer 221b is formed of GaN, the thickness of the first barrier layer 221b where tunneling occurs is experimentally less than 30 ANGSTROM, It is appropriate to set the thickness of each of the electrodes 221a and 221b.

Meanwhile, the doping layer 221a may mitigate the polarization of electrons and holes in the active layer 200. [ Polarization refers to a phenomenon in which electrons and holes are not recombined, and electrons are electrons and holes are separated from each other.

When such a polarization becomes remarkable, the recombination frequency of electrons and holes becomes remarkably low, so that the luminous efficiency and light output of the light emitting device can be lowered.

This polarization may become more significant as the magnitude of the energy band gap between the quantum barrier layer 220 and the quantum well layer 210 becomes larger. In the embodiment, the doping layer 221a reduces the energy band gap of the quantum barrier layer 220, so that the polarization phenomenon can be alleviated.

Accordingly, in the embodiment, the doping layer 221a can relax the polarization of electrons and holes in the active layer 200, increase the recombination frequency of electrons and holes, and increase the luminous efficiency and light output of the light emitting device.

3 is a diagram showing an energy band gap of a light emitting device according to another embodiment. As shown in FIG. 3, the light emitting device of the embodiment may include a first layer 221 and a second layer 222 in the quantum barrier layer 220.

The first layer 221 may include the doped layer 221a. The first layer 221 may include a doping layer 221a and a first barrier layer 221b disposed on top and bottom of the doping layer 221a. Since the doping layer 221a and the first barrier layer 221b have already been described in the embodiment shown in FIGS. 1 and 2, the repetitive description will be omitted.

The second layer 222 is formed on the first layer 221, and the doping density of In may be unevenly distributed along the stacking direction. 3, the energy band gap of the second layer 222 may be reduced from the first conductivity type semiconductor layer 100 toward the second conductivity type semiconductor layer 300, have.

This energy bandgap structure can be achieved by adjusting the doping concentration of In to the vertical direction of the active layer 200. That is, the In doping concentration of the second layer 222 is made smaller at a portion adjacent to the first barrier layer 221b, the In doping concentration is gradually increased toward the upper side, and at the point where it reaches the quantum well layer 210, The energy bandgap structure of the second layer 222 shown in FIG. 3 can be made by making the concentration the same as that of the quantum well layer 210.

When the second layer 222 having such an inclined energy band gap structure is formed, the polarization of electrons and holes in the active layer 200 can be relaxed. As described above, this polarization can become more significant as the magnitude of the energy band gap between the quantum barrier layer 220 and the quantum well layer 210 becomes larger.

Also, the energy band gap at the boundary between the quantum barrier layer 220 and the quantum well layer 210 may be abruptly changed. In the embodiment of FIG. 3, the energy band gap at the boundary between the quantum barrier layer 220 and the quantum well layer 210 is gently changed, so that polarization of electrons and holes in the active layer 200 can be mitigated.

In an embodiment, the thickness T1 of the first layer 221 may be in the range of 20 to 40 angstroms, more preferably about 30 angstroms. The thickness T2 of the second layer 222 may be in the range of 10 to 15 Angstroms.

In addition, the thickness T3 of the doped layer 221a may be 10 Å to 15 Å, more preferably 13 Å. In addition, the thickness T4 of the quantum well layer 210 may be 15 ANGSTROM to 25 ANGSTROM, more preferably 20 ANGSTROM.

As described above, when the first barrier layer 221b is formed of GaN, the thickness of the first barrier layer 221b where tunneling occurs is experimentally less than 30 ANGSTROM, It is preferable that the sum of the thickness of the first barrier layer 221b and the thickness T2 of the second layer 222 be 30 angstroms or less.

The following Table 1 shows experimental results of the light emitting device having the structure shown in FIG. The thickness T1 of the first layer 221 is about 30 ANGSTROM and the thickness T4 of the quantum well layer 210 is about 20 ANGSTROM and the thickness T3 of the doped layer 221a is about 13 ANGSTROM to be.

The thickness T2 of the second layer 222 is arbitrarily selected within the range of 10 to 15 angstroms, and each data is an average value of the results obtained by repeating the experiment several times.

Table 1 shows experimental results for a lateral chip having a rated current of 95 mA and 65 mA applied to the light emitting device.

Sample 1 is a case in which a light emitting device without the doping layer 221a is used in the light emitting device of the embodiment shown in FIG. 3, and sample 2 is a case where the light emitting device of the embodiment shown in FIG. 3 is used.

Sample 1 is identical or very similar in structure, specification and experimental conditions to sample 2 except that the doping layer 221a is not formed.

Rated output (mA) 95 65 Optical output of sample 1 (mW) 142.2 98.2 Optical power of sample 2 (mW) 143.2 99.0

3, it can be seen that the light output of the chip using the light emitting element of the embodiment shown in FIG. 3 is higher than that of the sample 1, and therefore, the light emitting element of the embodiment shown in FIG. 1, the light emitting efficiency and the light output are improved.

However, in the sample 1, the light emitting device having the light emitting device of the embodiment, that is, the second layer 222 having the oblique energy bandgap structure is formed. 3, that is, the light emitting element of the embodiment shown in FIG. 3, and the light emitting element including the general active layer 200 without the doped layer 221a and the second layer 222 having the inclined energy band gap structure Comparing the devices, it is clear that the luminous efficiency and the light output of the light emitting device of the embodiment shown in Fig. 3 are much higher than the experimental results shown in Table 1 above.

Considering the experimental results, the light emitting device of the embodiment can improve the light emitting efficiency and the light output by providing the doping layer 221a and / or the second layer 222.

4 is a view illustrating a light emitting device package 10 according to one embodiment.

A light emitting device package 10 according to an embodiment includes a body 11 including a cavity, a first lead frame 12 and a second lead frame 13 mounted on the body 11, A light emitting device 20 mounted on the body 11 and electrically connected to the first lead frame 12 and the second lead frame 13 according to the above embodiment and a molding part 16 formed in the cavity, .

The body 11 may be formed of a silicon material, a synthetic resin material, or a metal material. When the body 11 is made of a conductive material such as a metal material, an insulating layer is coated on the surface of the body 11 to prevent an electrical short between the first and second lead frames 12 and 13 . A cavity may be formed in the package body 11, and a light emitting device 20 may be disposed on a bottom surface of the cavity.

The first lead frame 12 and the second lead frame 13 are electrically disconnected from each other and supply current to the light emitting element 20. The first lead frame 12 and the second lead frame 13 can reflect the light generated by the light emitting device 20 to increase the light efficiency and reduce the heat generated from the light emitting device 20 to the outside It may be discharged.

The light emitting device 20 may be electrically connected to the first lead frame 12 and the second lead frame 13 through the wires 14 according to the above embodiment.

The light emitting device 20 may be fixed to the bottom surface of the package body 11 with a conductive paste (not shown), and the molding part 16 may surround and protect the light emitting device 20, The phosphor 17 may be included in the portion 16 and the phosphor 17 may be excited by the light of the first wavelength range emitted from the light emitting device 20 to emit light in the second wavelength region.

The light emitting device package 10 may include one or more light emitting devices according to the above-described embodiments, but the present invention is not limited thereto.

The light emitting device to the light emitting device package may be used as a light source of an illumination system, for example, a light emitting device such as an image display device of an image display device and an illumination device.

May be used as a backlight unit of an edge type when used as a backlight unit of a video display device or as a backlight unit of a direct-type type and may be used for a light source of a built-in type or a register when used in a lighting device.

While only a few have been described above with respect to the embodiments, various other forms of implementation are possible. The technical contents of the embodiments described above may be combined in various forms other than the mutually incompatible technologies, and may be implemented in a new embodiment through the same.

100: a first conductivity type semiconductor layer
200: active layer
210: quantum well layer
220: Quantum barrier layer
221: First Floor
221a: doping layer
221b: first barrier layer
222: Second layer
300: second conductive type semiconductor layer
400: substrate
810: first electrode
820: second electrode

Claims (12)

A first conductive semiconductor layer;
An active layer disposed on the first conductivity type semiconductor layer and comprising a plurality of quantum well layers and a plurality of quantum barrier layers alternately stacked; And
And a second conductive type semiconductor layer disposed on the active layer,
Wherein at least one of the quantum barrier layers is formed with a doping layer doped with In. The method according to claim 1,
Wherein the quantum barrier layer comprises:
A first layer on which the doped layer is formed;
A second layer formed on the first layer and having a doping concentration of In non-uniformly along the stacking direction,
. 3. The method of claim 2,
Wherein the first layer comprises:
The doping layer; And
And a first barrier layer disposed on top and bottom of the doped layer. The method of claim 3,
The doping layer
Wherein the first barrier layer has a lower energy band gap than the first barrier layer and has an energy band gap higher than that of the quantum well layer. The method of claim 3,
Wherein the first barrier layer comprises:
A light emitting device in which electrons or holes are tunneled. The method of claim 3,
Wherein the thickness of the first layer is 20 to 40 ANGSTROM. The method of claim 3,
And the thickness of the second layer is 10 to 15 ANGSTROM. The method of claim 3,
Wherein the doping layer has a thickness of 10 to 15 ANGSTROM. The method of claim 3,
Wherein the quantum well layer has a thickness of 15 ANGSTROM to 25 ANGSTROM. The method of claim 3,
The doping layer
The In doping concentration being lower than the quantum well layer and higher than the first barrier layer. 11. The method of claim 10,
The doping layer
Wherein the composition is In _x Ga _{1 - x} N (0.01 _{? X} ? 0.02). A first conductive semiconductor layer;
An active layer formed between the first conductivity type semiconductor layers and including a plurality of quantum well layers and a plurality of quantum barrier layers alternately stacked; And
And a second conductive type semiconductor layer disposed on the active layer,
Wherein the quantum barrier layer comprises:
A doping layer doped with In and having a higher energy band gap than the well layer;
A first barrier layer disposed at upper and lower portions of the doped layer and having a higher energy bandgap than the doped layer and tunneling electrons or holes,
.

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