KR101662242B1 - A light emitting device and a light emitting device package - Google Patents

Abstract

The light emitting device includes a first conductivity type semiconductor layer, an active layer formed on the first conductivity type semiconductor layer and having a well layer and a barrier layer alternately stacked at least once, and a second conductivity type semiconductor layer Wherein the barrier layer comprises a relaxation layer having an energy band gap that decreases from a first energy band gap to a second energy band gap and a blocking layer that retains the first energy band gap, The band gap is equal to the energy band gap of the first conductivity type semiconductor layer, and the second energy band gap is greater than the energy band gap of the well layer and smaller than the first energy band gap.

Description

[0001] The present invention relates to a light emitting device and a light emitting device package,

The present invention relates to a light emitting device and a light emitting device package.

Light emitting devices such as light emitting diodes and laser diodes using semiconductor materials of Group 3-5 or Group 2-6 compound semiconductors can realize various colors such as red, green, blue and ultraviolet rays through the development of thin film growth techniques and device materials, By using fluorescent materials or by combining colors, it is possible to realize a white light beam having high efficiency.

With the development of such technology, not only display devices but also transmission modules of optical communication means, light-emitting diode backlights replacing CCFL (Cold Cathode Fluorescence Lamp) constituting the backlight of LCD (Liquid Crystal Display) White light emitting diodes (LED) lighting devices, automotive headlights, and traffic lights.

Here, the structure of the LED is such that the p-type semiconductor layer, the light emitting layer, and the n-type semiconductor layer are sequentially laminated on the substrate, and the substrate and the n-type semiconductor layer are wire-bonded.

When a current is applied to the substrate, current is supplied to the p-type semiconductor layer and the n-type semiconductor layer, holes (+) are emitted from the p-type semiconductor layer to the light emitting layer, Is released. Therefore, the energy level is lowered as the holes and electrons are combined in the light emitting layer, and the energy level is lowered, and the emitted energy is emitted in the form of light.

Embodiments provide a light emitting device and a light emitting device package capable of improving light emitting efficiency.

The light emitting device according to the embodiment includes a first conductivity type semiconductor layer, an active layer formed on the first conductivity type semiconductor layer, the active layer having a quantum well layer and a quantum barrier layer alternately stacked at least once, Wherein the quantum barrier layer includes a relaxation layer having an energy band gap that decreases from a first energy band gap to a second energy band gap and a barrier layer that retains the first energy band gap, Wherein the first energy band gap is equal to the energy band gap of the first conductivity type semiconductor layer and the second energy band gap is greater than the energy band gap of the quantum well layer and smaller than the first energy band gap.

The light emitting device according to another embodiment includes a first conductivity type semiconductor layer, an active layer formed on the first conductivity type semiconductor layer, the active layer having a quantum well layer and a quantum barrier layer alternately stacked at least once, Wherein the quantum barrier layer has a composition of In _x Ga _{1 -x} N (0? X? K <1), and the indium content ratio increases as the distance from the quantum well layer And a blocking layer having a composition of In _y Ga _{1- y} N (0? _Y <k), where k means the finally increased indium content ratio for the relaxed layer formation.

The light emitting device package according to the embodiment includes a package body, a first metal layer and a second metal layer disposed on the package body, and a light emitting element mounted on the package body to be electrically connected to the first metal layer and the second metal layer. And an encapsulating layer surrounding the light emitting element.

The embodiment can improve the luminous efficiency.

1 shows a light emitting device according to an embodiment.
2 shows a light emitting device according to another embodiment.
3 shows a band diagram of an active layer according to an embodiment.
4 shows a band diagram of an active layer according to another embodiment.
5 shows a band diagram of an active layer according to another embodiment.
6A shows a band diagram for driving a general light emitting device.
FIG. 6B is a graph showing the carrier concentration when driving a general light emitting device.
FIG. 7A shows a band diagram for driving the light emitting device according to the embodiment.
FIG. 7B shows a graph of carrier concentration during driving of the light emitting device according to the embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other features and advantages of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which: FIG. In the drawings, dimensions are exaggerated, omitted, or schematically illustrated for convenience and clarity of illustration. Also, the size of each component does not entirely reflect the actual size. The same reference numerals denote the same elements throughout the description of the drawings. Hereinafter, a light emitting device, a method of manufacturing the same, and a light emitting device package according to embodiments will be described with reference to the accompanying drawings.

1 shows a light emitting device according to an embodiment. Referring to FIG. 1, a light emitting device includes a substrate 110, a light emitting structure 120, a conductive layer 125, a first electrode 130, and a second electrode 140.

The substrate 110 may be any one of a sapphire substrate, a silicon substrate, a zinc oxide (ZnO) substrate, a nitride semiconductor substrate, or a template substrate in which at least one of GaN, InGaN, AlGaN, and AlInGaN is stacked. have.

The light emitting structure 120 is a multilayer structure in which a first conductive semiconductor layer 122, an active layer 124, and a second conductive semiconductor layer 126 are sequentially stacked on a substrate 110. The first conductivity type may be N-type and the second conductivity type may be P-type. Although not shown in the drawing, at least one buffer layer (buffer layer) is formed between the first conductive semiconductor layer 122 and the substrate 110 to mitigate lattice mismatch between the substrate 110 and the semiconductor layer 120 due to lattice mismatching. layer may be formed.

The first conductive semiconductor layer 122 may be a nitride semiconductor layer. For example, the first conductive semiconductor layer 122 may be selected from InAlGaN, GaN, AlGaN, InGaN, AlN, and InN, and may be doped with an N-type dopant such as Si, Ge, or Sn.

The active layer 124 is formed on the first conductivity type semiconductor layer 122 and is formed by recombination of electrons provided from the first conductivity type semiconductor layer 122 and holes provided from the second conductivity type semiconductor layer 126. [ ) Can produce light by the energy generated in the process. The active layer 124 may be a single or multiple quantum well structure made of a GaN-based material such as GaN and / or InGaN.

The active layer 124 has a quantum well layer (hereinafter referred to as a "well layer") and a quantum barrier layer (hereinafter referred to as "barrier layer") alternately stacked at least once. The active layer 124 may be in the form of a stack of a single well layer (e.g., 18-1) and a barrier layer (e.g., 19-1), or alternatively stacked well layers 18-1 through 18- N, N > 1) and barrier layers 19-1 to 19-N.

For example, each of the well layers 18-1 to 18-N may be formed of InGaN, and each of the barrier layers 19-1 to 19-N may be formed of well layers 18-1 to 18-N (Al, In, Ga) N-type group III nitride semiconductor layer having a larger bandgap than the N-type nitride semiconductor layer. For example, an InGaN layer or a GaN layer.

Each of the barrier layers 19-1 to 19-N includes a relaxation layer a1 and a barrier layer b1. The relaxation layer a1 is formed of a material having an energy band gap ranging from the first energy band gap E1 to the second energy band gap E2 in order to reduce the deformation of the energy band due to naturally occurring polarization, And the blocking layer b1 is a layer which maintains the first energy band gap E1 in order to prevent tunneling of electrons or holes.

The first energy band gap E1 may be the same as the energy band gap of the first conductivity type semiconductor layer 122 and the second energy band gap E2 may be the same as the energy band gap of the well layers 18-1 to 18- (Hereinafter referred to as "third energy band gap E3") and smaller than the first energy band gap E1 (E3 < E2 &lt; E1).

For example, the relaxation layer a1 may have an energy band that decreases linearly from the first energy band gap E1 to the second energy band gap E2. Or the relaxed layer a1 may have an energy band that decreases nonlinearly from the first energy band gap E1 to the second energy band gap E2. Or the relaxed layer a1 may have an energy band that gradually decreases from the first energy band gap E1 to the second energy band gap E2.

3 shows a band diagram of an active layer according to an embodiment. 3, the active layer 124 is a single or multiple quantum well structure in which a well layer and a barrier layer are alternately stacked, and the well layers 18-1 to 18-N have a third energy band gap E3, Respectively.

The barrier layers 19-1 to 19-N are formed of a relaxation layer a1 having an energy band gap linearly decreasing from a first energy band gap E1 to a second energy band gap E2, And a blocking layer b1 for retaining the band gap E1.

For example, In _z Ga _{1 -z} N (0 <z <1) having a constant indium (In) content ratio is grown on the first conductivity type semiconductor layer 122 for a first time t 1 to form a first well layer 18 -1). At this time, the content ratio (z) of indium contained in the well layer (18-1) is referred to as "first indium content ratio &quot;. For example, the first indium content ratio (z) may be 0.13.

Next, in order to increase the indium content ratio x linearly over time without including indium (In) at first, it is preferable that In _x Ga _{1 -x} N (0? X? K <1) may be grown to form the relaxed layer a1 having a linearly decreasing energy band gap on the first well layer 18-1.

That is, the distance from the well layer 18-1, increases linearly. The finally increased indium content ratio for forming the relaxed layer (a1) is referred to as "second indium content ratio (k) ".

At this time, the second indium content ratio (k) may be smaller than or equal to the first indium content ratio (k? Z). For example, it is possible to grow In _x Ga _{1 -x} N (0? X? K <1) while increasing the indium content ratio (x) from 0 to 0.03 to form the relaxed layer (a1) The ratio (k) becomes 0.03.

Next, that does not contain indium _{In y Ga 1 - y N (} y = 0) or to the growth, the constant 3 In _y Ga ₁ to contain the indium content ratio _{(y) -y N (0≤y <} k) The barrier layer (b1) can be formed. At this time, the third indium content ratio (y) may be smaller than the second content ratio (k).

The thickness ratio of the well layer to the barrier layer may be 1: 4 to 5, and the thickness ratio of the barrier layer (b1) to the relaxed layer (a1) may be 1: 2 to 4. For example, the thickness of each of the well layers 18-1 to 18-N may be 2.5 nm, the thickness of the barrier layer may be 10 nm, the thickness of the relaxed layer a1 may be 7 nm, Lt; / RTI &gt;

4 shows a band diagram of an active layer according to another embodiment. Referring to FIG. 4, unlike FIG. 3, the energy band gap of the relaxation layer a1 shown in FIG. 4 decreases non-linearly.

In _x Ga _{1 -x} N (0 < = x &lt; = k &lt; 1) is grown for a second time (t2) while non-linearly increasing indium content ratio (x) The relaxed layer a1 having a non-linearly reduced energy band gap can be formed on the first well layer 18-1. The remaining parts are the same as those described in Fig.

5 shows a band diagram of an active layer according to another embodiment. Referring to FIG. 5, unlike FIG. 3 and FIG. 4, the energy band gap of the relaxation layer a1 shown in FIG. 5 is steadily reduced.

Initially, while we do not include the indium (In), over time, increasing system exemplifies the content ratio (x) of indium second time _{(t2) In x Ga 1 -x} N (0≤x≤k <1) The relaxed layer a1 in which the energy band gap gradually decreases on the first well layer 18-1 can be formed. The remaining parts are the same as those described in Fig.

The second conductive semiconductor layer 126 may be formed on the active layer 120 and may be a nitride semiconductor layer. For example, it may be selected from InAlGaN, GaN, AlGaN, InGaN, AlN and InN, and may be doped with a P-type dopant such as Mg, Zn, Ca, Sr and Ba.

The light emitting structure 120 may include a structure in which the second conductive semiconductor layer 126, the active layer 120, and a portion of the first conductive semiconductor layer 122 are etched to expose a portion of the first conductive semiconductor layer 122 to be.

The conductive layer 125 is formed on the second conductive semiconductor layer 126 and is formed of ITO (Indium Tin Oxide), TO (Tin Oxide), IZO (Indium Zinc Oxide), ITZO (Indium Tin Zinc Oxide) Zinc Oxide).

The first electrode 130 is formed on the conductive layer 125 and the second electrode 140 is formed on the first conductive semiconductor layer 122 exposed by etching. The first and second electrodes 130 and 140 may be formed of one of a metal selected from the group consisting of Cr, Ni, Au, Al, Ti, and Pt, And the like.

2 shows a light emitting device according to another embodiment. 2, the light emitting device includes a support layer 210, a diffusion prevention layer 220, a reflective layer 225, an ohmic contact layer 230, a light emitting structure 240, a first passivation layer 235, A second protective layer 250, and an electrode 260.

The support layer 210 may be made of a metal substrate or a semiconductor. For example, the support layer 210 may be formed of a metal material such as Cu, Cr, Ni, Ag, Au, Mo, Pd, W, or Al.

The diffusion barrier layer 220 is formed on the support layer 210 to prevent metal ion diffusion of the support layer 210 and may be formed of Ni, Ti, TiN, or the like.

The reflective layer 225 is disposed on the diffusion barrier layer 220 to improve the effective luminance and may be made of Au, Ni, Ag, Al, or an alloy thereof.

The light emitting structure 240 has a structure in which the second conductivity type semiconductor layer 242, the active layer 244, and the first conductivity type semiconductor layer 246 are stacked on the reflective layer 225. At this time, the second conductive type may be P type and the first conductive type may be N type.

The ohmic contact layer 230 is positioned between the reflective layer 225 and the second conductive semiconductor layer 220 for ohmic contact between the reflective layer 225 and the light emitting structure 240. At this time, the ohmic contact layer 230 may be formed of a transparent conductive oxide composed of at least one of indium tin oxide (ITO), ZnO, RuOx, TiOx, and IrOx.

The second conductive semiconductor layer 242 may be a nitride semiconductor layer positioned on the reflective layer 225 and selected from InAlGaN, GaN, AlGaN, InGaN, AlN, InN and AlInN. Type dopant can be doped.

The active layer 244 is disposed on the second conductive semiconductor layer 242 and includes a single well layer and barrier layer as described in FIG. 1 or alternately stacked well layers 18-1 to 18-N, And includes the barriers 19-1 to 19-N. Each of the barrier layers 19-1 to 19-N also includes a relaxation layer a1 and a barrier layer b1. The description will be omitted in order to avoid redundancy.

The first passivation layer 235 is formed on the diffusion prevention layer 220 adjacent to the side surface of the light emitting structure 240 and has one side adjacent to the ohmic contact layer 215. The second passivation layer 250 covers the side surface of the light emitting structure 240. The first passivation layer 235 and the second passivation layer 250 may be formed of a silicon oxide film (SiO 2), a silicon nitride film (Si ₃ N ₄ ), or AlN. The first electrode 260 is formed on the first conductive semiconductor layer 246. At this time, the first electrode 260 may be N-type.

Generally, in a light emitting device including an active layer having a multilayer quantum structure based on GaN, the luminous efficiency of the light emitting device is lowered due to the deformation of the energy band of the active layer due to spontaneous polarization.

FIG. 6A shows a band diagram when driving a general light emitting device, and FIG. 6B shows a graph of a carrier concentration when a general light emitting device is driven. Here, the driving voltage is 3 V, the solid line in Figure 6 (b) represents the electron, and the dotted line represents the hole.

Referring to FIG. 6A, the energy band profile of the barrier layer in the active layer has a serrated shape 610, which interferes with the movement of the carrier. Referring to FIG. 6B, in the case of holes, the injection efficiency falls into the active layer.

Embodiments can improve the luminous efficiency by changing the energy band occurring naturally in the light emitting device, particularly by changing the energy band profile of the barrier layer formed in the active layer in a state where a bias is applied to the light emitting device.

In addition, the embodiment does not increase indium over the entire region of the barrier layer formed in the active layer, but does not include indium or retain a certain thickness of the barrier layer in the barrier layer, Or a carrier overflow in which the holes are separated from the active layer can be prevented.

FIG. 7A shows a band diagram for driving the light emitting device according to the embodiment, and FIG. 7B shows a graph of the carrier concentration at the time of driving the light emitting device according to the embodiment. 6A and 7A, the ordinate axis represents the energy (eV) and the abscissa axis represents the distance. In Figs. 6B and 7B, the vertical axis represents the concentration and the horizontal axis represents the distance.

Referring to FIG. 7A, the energy band profile of the barrier layer in the active layer of the light emitting device according to the embodiment has a relaxed shape as compared with FIG. 6A. That is, the carrier of the carrier in the active layer is less disturbed.

Also, referring to FIG. 7B, it can be seen that the holes are more smoothly moved in the active layer, thereby improving the efficiency of injecting holes into the active layer.

8 illustrates a light emitting device package including a light emitting device according to an embodiment. 8, a light emitting device package according to an embodiment includes a package body 810, a first metal layer 812, a second metal layer 814, a light emitting device 820, a reflector 825, at least one wire 830, and an encapsulation layer 840.

The package body 810 has a cavity in which a cavity is formed. At this time, the side wall of the cavity may be formed to be inclined. The package body 810 may be formed of a substrate having good insulating or thermal conductivity, such as a silicon based wafer level package, a silicon substrate, silicon carbide (SiC), aluminum nitride (AlN) Or may be a structure in which a plurality of substrates are stacked. The embodiments are not limited to the material, structure, and shape of the body described above.

The first metal layer 812 and the second metal layer 814 are disposed on the surface of the package body 810 so as to be electrically separated from each other in consideration of heat dissipation or mounting of the light emitting device. The light emitting device 820 may be electrically connected to the first metal layer 812 and / or the second metal layer 814 through at least one wire.

The reflection plate 825 is formed on the cavity side wall of the package body 810 so as to direct light emitted from the light emitting element in a predetermined direction. The reflector 825 is made of a light reflecting material, for example, a metal coating or a metal flake.

The encapsulation layer 840 surrounds the light emitting element 820 located in the cavity of the package body 810 to protect the light emitting element 820 from the external environment. The sealing layer 840 is made of a colorless transparent polymer resin material such as epoxy or silicone. The sealing layer 840 may include a phosphor to change the wavelength of the light emitted from the light emitting device 820. The light emitting device package can mount at least one of the light emitting elements of the above-described embodiments, but is not limited thereto.

A plurality of light emitting device packages according to embodiments may be arranged on a substrate, and a light guide plate, a prism sheet, a diffusion sheet, and the like may be disposed on the light path of the light emitting device package. The light emitting device package, the substrate, and the optical member may function as a backlight unit.

Still another embodiment may be implemented as a display device, an indicating device, and a lighting system including the light emitting device or the light emitting device package described in the above embodiments. For example, the lighting system may include a lamp and a streetlight.

The features, structures, effects and the like described in the embodiments are included in at least one embodiment of the present invention 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. Therefore, it should be understood that the present invention is not limited to these combinations and modifications.

110: substrate, 120,240: light emitting structure, 122, 242: first conductivity type semiconductor layer,
124, 244: an active layer, 125: a conductive layer, 126, 246: a second conductive semiconductor layer,
130: first electrode, 140: second electrode, 210: supporting layer, 220: diffusion preventing layer,
225: reflection layer, 230: ohmic contact layer, 235: first protection layer, 250: second protection layer,
260: electrode, 18-1 to 18-N: relaxation layers, 19-1 to 19-N: barrier layers.

Claims (15)

A first conductive semiconductor layer;
An active layer formed on the first conductivity type semiconductor layer and having a well layer and a barrier layer stacked alternately at least once; And
And a second conductivity type semiconductor layer formed on the active layer,
Wherein the barrier layer comprises
And a barrier layer sequentially disposed in a direction from the first conductivity type semiconductor layer to the second conductivity type semiconductor layer,
Wherein the relaxed layer has an energy band gap that decreases from a first energy band gap to a second energy band gap in a direction from the first conductivity type semiconductor layer toward the second conductivity type semiconductor layer,
Wherein the blocking layer has an energy band W that maintains the first energy band gap,
And the second energy band gap is equal to the energy band gap of the well layer. The method according to claim 1,
Wherein the first energy band gap is equal to the energy band gap of the first conductivity type semiconductor layer and the second energy band gap is greater than or equal to the energy band gap of the well layer and smaller than the first energy band gap. The method of claim 1,
And an energy band gap that linearly decreases from the first energy band gap to the second energy band gap. The method of claim 1,
And an energy band that decreases nonlinearly from the first energy band gap to the second energy band gap. The method of claim 1,
And an energy band that gradually decreases from the first energy band gap to the second energy band gap. The method according to claim 1,
Wherein the first conductivity type semiconductor layer is an n-type semiconductor layer, and the second conductivity type semiconductor layer is a p-type semiconductor layer. A first conductive semiconductor layer;
An active layer formed on the first conductivity type semiconductor layer and having a well layer and a barrier layer stacked alternately at least once; And
And a second conductivity type semiconductor layer formed on the active layer,
Wherein the well layer has a composition of In _z Ga _1-z N (0 < z < 1)
Wherein the barrier layer comprises
And a barrier layer sequentially disposed in a direction from the first conductivity type semiconductor layer to the second conductivity type semiconductor layer,
Wherein the relaxed layer has a composition of In _x Ga _{1 -x} N (0? _X ? K <1), wherein the indium content ratio increases from the first conductivity type semiconductor layer toward the second conductivity type semiconductor layer,
Wherein the barrier layer has a composition of In _y Ga _1-y N (0? _Y <k)
Here, k represents the indium content ratio finally increased for forming the relaxed layer,
Wherein the indium content ratio of the well layer is equal to the indium content ratio ultimately increased for forming the relaxed layer. 8. The method of claim 7,
A conductive layer disposed on the second conductive type semiconductor layer; And
A first electrode disposed on the conductive layer; And
And a second electrode disposed on the first conductive type semiconductor layer. 8. The method of claim 7,
Wherein the first conductivity type semiconductor layer is an n-type semiconductor layer, and the second conductivity type semiconductor layer is a p-type semiconductor layer. 8. The method of claim 7,
Wherein the indium content ratio (x) increases linearly with distance from the well layer. 8. The method of claim 7,
Wherein the indium content ratio (x) increases non-linearly with distance from the well layer. 8. The method of claim 7,
Wherein the indium content ratio (x) is gradually increased as being further away from the well layer. 8. The method of claim 7,
Wherein the indium content ratio increases from 0 to 0.03. 8. The method of claim 7,
Wherein the ratio of the thickness of the well layer to the thickness of the barrier layer is 1: 4 to 5, and the ratio of the thickness of the barrier layer to the thickness of the relaxation layer is 1: 2 to 4. A package body;
A first metal layer and a second metal layer disposed in the package body;
The light emitting device according to any one of claims 1 to 14, which is mounted on the package body so as to be electrically connected to the first metal layer and the second metal layer. And
And a sealing layer surrounding the light emitting device.

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