KR101745996B1 - Light emitting device - Google Patents

Abstract

A light emitting device according to an embodiment includes a substrate and a first semiconductor layer, a second semiconductor layer, and a second semiconductor layer disposed on the substrate so as to have a structure that can easily increase external quantum efficiency with respect to light generated in the active layer. And a light emitting structure including an active layer between the first and second semiconductor layers, wherein the thickness of the light emitting structure is 0.3 to 1 times the thickness of the substrate.

Description

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting device, and more particularly, to a light emitting device having a structure capable of easily increasing external quantum efficiency for light generated in an active layer.

In general, a light emitting diode (LED), which is one of light emitting devices, is a semiconductor device that emits light based on the recombination of electrons and holes, and is widely used as a light source in optical communication, electronic devices, and the like.

In a light emitting diode, the frequency (or wavelength) of light to be emitted is a band gap function of a material used in a semiconductor device. When a semiconductor material having a small band gap is used, photons with low energy and long wavelength are generated, When a semiconductor material having a gap is used, short wavelength photons are generated.

For example, AlGaInP materials generate light at a red wavelength, and silicon carbide (SiC) and Group III nitride-based semiconductors, particularly GaN, emit blue or ultraviolet light.

Among them, since a light-emitting diode can not form a bulk monocrystal of GaN, a substrate suitable for growth of GaN crystal should be used, and a sapphire substrate is typically used.

In recent years, in order to use a light emitting element as an illumination light source, a higher brightness has been required. In order to achieve such high brightness, research is underway to manufacture a light emitting element capable of increasing the light emitting efficiency by uniformly diffusing a current.

It is an object of the present invention to provide a light emitting device having a structure that can easily increase the external quantum efficiency with respect to light generated in the active layer.

A light emitting device according to an embodiment includes a substrate and a light emitting structure disposed on the substrate, the light emitting structure including a first semiconductor layer, a second semiconductor layer, and an active layer between the first and second semiconductor layers, The thickness may be 0.3 to 1 times the thickness of the substrate.

The light emitting device according to the embodiment has an advantage that the external quantum efficiency can be increased by making the thickness of the light emitting structure to be a multiple of 2.2 to 2.5 占 퐉 or 0.3 to 1 times the thickness of the substrate.

The thickness of the first semiconductor layer may be 1/3 to 1/2 times the thickness of the light emitting structure or the thickness of the second semiconductor layer may be a multiple of 0.075 mu m to 0.09 mu m, There is an advantage that the quantum efficiency can be maximized.

1A and 1B are cross-sectional views illustrating the structure of a light emitting device according to an embodiment.
2 is an enlarged view showing the structure of the light emitting structure shown in FIG.
3 to 5 are graphs showing changes in luminous intensity depending on the thicknesses of the light emitting structure and the first and second semiconductor layers.

Before describing the embodiments, it is to be understood that the terms "on "," below ", " on "quot;, " on ", and " under " includes everything that is "directly" or "indirectly formed" In addition, the criteria for above or below each layer will be described with reference to the drawings.

In the drawings, the thickness and size of each layer are exaggerated, omitted, or schematically illustrated for convenience and clarity. Therefore, the size of each component does not entirely reflect the actual size.

Further, the angle and direction mentioned in the description of the structure of the light emitting device in the embodiment are based on those shown in the drawings. In the description of the structure of the light emitting device in the specification, reference points and positional relationship with respect to angles are not explicitly referred to, refer to the related drawings.

1A is a cross-sectional view illustrating a structure of a vertical light emitting device according to an embodiment.

Referring to FIG. 1A, a light emitting device 100 may include a light emitting structure 150 on a substrate 110 and a substrate 110.

The substrate 110 may be formed using a material having a high thermal conductivity, or may be formed of a conductive material. The substrate 110 may be formed of a single layer, and may be formed of a dual structure or a multiple structure.

In an embodiment, the substrate 110 is described as having conductivity, but may not be conductive, but is not limited thereto.

That is, the substrate 110 may be formed of gold (Au), nickel (Ni), tungsten (W), molybdenum (Mo), copper (Cu), copper-tungsten (Cu-W)

For example, the carrier wafer may be formed of Si, Ge, GaAs, ZnO, SiC, SiGe, GaN, Ga2O3, or the like.

The substrate 110 facilitates the emission of heat generated in the light emitting device 100, thereby improving the thermal stability of the light emitting device 100.

In the embodiment shown in FIG. 1A, the substrate 110 is described as sapphire (Al ₂ O ₃ ), and a pattern (PSS, Patterned Sapphire Substrate) is formed on the substrate 110.

A predetermined concavo-convex pattern (a) may be integrally or partially formed on the substrate 110.

Here, the shape of the concavo-convex pattern (a) may be a lens shape, a polygonal shape, or a branched shape spaced apart by a predetermined angle, and the concavo-convex pattern (a) in the embodiment is described as having a triangular shape.

At this time, the concavo-convex pattern (a) may be periodically formed regularly or irregularly, but is not limited thereto.

The concavo-convex pattern (a) may be formed in a step structure (step structure) on at least one surface, and a metal such as a diffusing material capable of refracting light on an end face of the concavo- , It is possible to improve the optical characteristics of the light emitting device 100 by increasing the pattern density.

An adhesive layer 112 may be disposed on the substrate 110 to mitigate lattice mismatch between the substrate 110 and the second semiconductor layer 156. The adhesive layer 112 can be formed in a low-temperature atmosphere, and can be selected from materials such as AlGaN, GaN, InN, AlN, AlInN, InGaN, and InAlGaN.

The adhesive layer 112 is formed to minimize the electromigration phenomenon in which the atoms of the electrode layer 130 move due to the electric field during the application of the electric current. Further, the adhesive layer 112 can be formed using a metal material having excellent adhesion to the lower material.

The adhesive layer 112 may include at least one of Ti, Au, Sn, Ni, Cr, Ga, In, Bi, Cu, Ag and Ta, , But is not limited thereto.

The adhesive layer 112 may be formed by bonding different metal materials to form a plurality of layers, but is not limited thereto.

The reflective film 120 reflects the light generated from the active layer 154 of the light emitting structure 150 toward the upper portion of the light emitting device 100 when the light is directed to the substrate 110 and the adhesive layer 112, 100 can be improved.

Therefore, it is preferable that the reflective film 120 is formed of a material having a high light reflectivity such as Ag, Al, Pt, or Rh.

The electrode layer 130 may be formed of any one of Ni, Pt, Ru, Ir, Rh, Ta, Mo, Ti, Ag, W, Cu, Cr, Pd, V, Co, Nb, Zr, ITO, AZO, It can be used in the form of alloy.

The reflective layer 120 and the electrode layer 130 may be formed to have the same width and the reflective layer 120 and the electrode layer 130 are formed through a simultaneous firing process.

The channel layer 140 may be formed in contact with the outer peripheral side surface of at least one of the electrode layer 130 and the reflective film 120. The channel layer 140 serves to prevent the light emitting structure 150 from being etched when the reflective layer 120 and the electrode layer 130 are dry-etched.

Also, the channel layer 140 is formed of at least one of a metal material and an insulating material.

The light emitting structure 150 is in contact with the electrode layer 130 and the channel layer 140 and may include a first semiconductor layer 152, an active layer 154 and a second semiconductor layer 156, And the active layer 154 is interposed between the second semiconductor layer 152 and the second semiconductor layer 156.

The first semiconductor layer 152 may be an n-type semiconductor layer, for example, In _x Al _y Ga _(1-xy) N (0? X? 1, 0? _Y? for example, InAlGaN, GaN, AlGaN, InGaN, AlN, InN, AlInN or the like and may be doped with an n-type dopant such as Si, Ge or Sn.

An electrode pad 160 may be formed on the first semiconductor layer 152 with nickel or the like and a portion of the surface of the first semiconductor layer 152 on which the electrode pad 160 is not formed, The irregularities 158 for improving the light extraction efficiency can be formed on the region by a predetermined etching method.

The active layer 154 may be formed under the first semiconductor layer 152.

The active layer 154 is a region where electrons and holes are recombined. As the electrons and the holes are recombined, the active layer 154 transitions to a low energy level and light having a wavelength corresponding thereto can be generated.

When the active layer 154 is formed of a quantum well structure, for example, a well having a composition formula of In _x Al _y Ga _(1-xy) N (0? X? 1, 0? Y? 1, 0? X + And a barrier layer having a composition formula of In _a Al _b Ga _(1-ab) N (0? A? 1, 0? B? 1, 0? A + b? 1) have. The well layer may be formed of a material having a band gap lower than the band gap of the barrier layer.

A conductive cladding layer may be formed on and / or below the active layer 154. The conductive clad layer may be formed of an AlGaN-based semiconductor and may have a band gap higher than that of the active layer 154.

A second semiconductor layer 156 may be formed under the active layer 154. The second semiconductor layer 156 is formed of a p-type semiconductor layer, and holes can be injected into the active layer 154. For example, the p-type semiconductor layer may be a semiconductor material having a composition formula of In _x Al _y Ga _(1-xy) N (0 x 1, 0 y 1, 0 x + y 1) GaN, AlN, AlGaN, InGaN, InN, InAlGaN, AlInN and the like, and p-type dopants such as Mg, Zn, Ca, Sr and Ba can be doped.

A third semiconductor layer (not shown) may be formed under the second semiconductor layer 156. Here, the third semiconductor layer may be implemented as an n-type semiconductor layer.

The first semiconductor layer 152, the active layer 154 and the second semiconductor layer 156 may be formed using a metal organic chemical vapor deposition (MOCVD) method, a chemical vapor deposition (CVD) method, a plasma May be formed by a method such as chemical vapor deposition (PECVD), molecular beam epitaxy (MBE), hydride vapor phase epitaxy (HVPE), sputtering, or the like But is not limited thereto.

In addition, the first semiconductor layer 152 may be implemented as a p-type semiconductor layer and the second semiconductor layer 156 may be implemented as an n-type semiconductor layer, but the present invention is not limited thereto.

1B is a cross-sectional view illustrating the structure of a horizontal light emitting device according to an embodiment

Referring to FIG. 1B, the light emitting device 200 of the embodiment may include a light emitting structure 150 on a substrate 210 and a substrate 210.

The substrate 210 is preferably made of a transparent material including sapphire. In addition to sapphire, the substrate 110 may be formed of zinc oxide (ZnO), gallium nitride (GaN) gallium nitride (GaN), silicon carbide (SiC), silicon and aluminum nitride (AlN). In addition, it is assumed that a predetermined pattern (PSS, Patterned Sapphire Substrate) is formed on the substrate 210.

The light emitting structure 150 includes a first semiconductor layer 152, an active layer 154 and a second semiconductor layer 156. The first semiconductor layer 152 is disposed adjacent to the substrate 210, Is the same as that described in the vertical light emitting device 100 described above.

A buffer layer 211 may be disposed on the substrate 210 to mitigate lattice mismatch between the substrate 210 and the first semiconductor layer 152. The buffer layer 211 can be formed in a low-temperature atmosphere and can be selected from materials such as GaN, InN, AlN, AlInN, InGaN, AlGaN, and InAlGaN.

A first electrode 260 may be formed on the first semiconductor layer 152.

The first electrode 260 may be formed in a plurality of positions in consideration of the size of the light emitting device 200 and the like. Preferably, the second semiconductor layer 156 and a part of the active layer 154 A portion of the first semiconductor layer 152 is exposed, and a first electrode 260 may be formed on the exposed top surface of the first semiconductor layer 152. The substrate 210 and the buffer layer 211 may be removed and the first electrode 260 may be formed on the exposed surface of the first semiconductor layer 152.

A second electrode 270 may be formed on the second semiconductor layer 156.

The first electrode 260 and the second electrode 270 are in ohmic contact with the semiconductor layer to supply power to the light emitting structure 150 smoothly. The first electrode 260 and the second electrode 270 may be made of a transparent conductive layer and a metal. For example, ITO (indium tin oxide), IZO (indium zinc oxide), IZTO (indium zinc tin oxide , Indium aluminum zinc oxide (IAZO), indium gallium zinc oxide (IGZO), indium gallium tin oxide (IGTO), aluminum zinc oxide (AZO), antimony tin oxide (ATO), gallium zinc oxide (GZO) (Ru), RuOx / ITO, Ni, Pt, Ru, Ir, Rh, Ta, Mo, Tungsten, copper, chromium, palladium, vanadium, cobalt, niobium, zirconium, Ni / IrOx / Au, or Ni / IrOx / Au / ITO, and carbon nanotubes. However, the present invention is not limited thereto.

The vertical and horizontal light emitting devices shown in FIG. 1 have been described, but the present invention is not limited thereto, and they can be formed by a flip chip method. Hereinafter, the vertical type light emitting device will be described as a reference.

FIG. 2 is an enlarged view showing the structure of the light emitting structure shown in FIG. 1A, and FIGS. 3 to 5 are graphs showing changes in light intensity according to the thicknesses of the light emitting structure and the first and second semiconductor layers.

Fig. 2 is illustrated in Fig. 1A, but can also be described in Fig. 1B, but is not limited thereto.

2, the light emitting structure 150 may include an active layer 154 formed between the first semiconductor layer 152, the second semiconductor layer 156, and the first and second semiconductor layers 152 and 156 And may include other semiconductor layers.

At this time, the thickness dt of the light emitting structure 150 may be thinner than the thickness of the substrate 110. That is, the thickness dt of the light emitting structure 150 is preferably 0.3 to 1 times the thickness (not shown) of the substrate 110.

That is, the thickness dt of the light emitting structure 150 is preferably 3 to 8.5 μm when the wavelength λ of the light emitted from the active layer 154 is 400 to 500 nm, 150 may be formed to have a thickness of a multiple of 2.2 탆 to 2.5 탆.

The thickness dt of the light emitting structure 150 is designed to have a multiple of 2.2 탆 to 2.5 탆 in order to prevent the loss of light in accordance with the interference condition of the wavelength λ of light emitted from the active layer 154 in all directions.

After the thickness dt of the light emitting structure 150 is determined, the thicknesses d1 and d2 of the first and second semiconductor layers 152 and 154 are determined.

That is, the first thickness d1 of the first semiconductor layer 152 may preferably be 1/3 to 1/2 times the thickness dt of the light emitting structure 150, and the second semiconductor layer 156 (D2) of the first thickness (d2).

As a result, the first and second thicknesses d1 and d2 of the first and second semiconductor layers 152 and 156 are determined in accordance with the doped material, the flow rate of the material, and the lattice defect existing in the semiconductor layer, The external quantum efficiency can be increased.

Here, FIG. 3 shows a change in luminous intensity with respect to the thickness dt of the light emitting structure 150.

3 is a graph showing the luminous intensity lm according to the thickness dt of the light emitting structure 150 when the wavelength? Of the light of the active layer 154 is 455 nm.

Here, FIG. 3 shows experimental data p and simulation data s.

The thickness dt of the light emitting structure 150 varies from 3 탆 to 8.5 탆 and the change in the luminous intensity lm with the change in the thickness dt can be known.

3, the thickness dt of the light emitting structure 150 is 19.13 (lm) and 19.1 (lm) in the first and second experimental data p1 and p2 of the experimental data P at 4.50 and 7, respectively lm and a luminous intensity of 19 (lm) and 19.08 (lm) at the adjacent first and second peak values s1 and s2 in the simulation data s, respectively.

At this time, it can be seen that the thickness dt of the light emitting structure 150 shows a large light intensity at a thickness dt having a multiple of 2.2 to 2.5 탆.

That is to say, the thickness dt of the light emitting structure 150 may cause an error of the light intensity lm between the experimental data p and the simulation data s of 0.25 mu m to 0.3 mu m, .

The thickness dt of the light emitting structure 150 according to the wavelength λ of the light emitted from the active layer 154 is designed to be increased to have a periodicity of 2.2 μm to 2.5 μm after 4.50 μm, lm < / RTI >

4 also shows the change in luminous intensity with respect to the thickness dt of the light emitting structure and the first thickness dl of the first semiconductor layer 152. [

4, the experimental data p and the simulation data s are shown in the same manner as in Fig. 3, and the experiment data p and the simulation date s are located on the same line.

When the thickness dt of the light emitting structure 150 is 4.7 μm, 5.6 μm, and 6.5 μm, the first thickness d 1 of the first semiconductor layer 152 is 3.8 μm, 8.85 μm, and 5.7 μm, It can be seen that the luminous intensities lm are 18.7 (lm), 18.95 (lm) and 18.75 (lm), respectively.

Thus, it can be seen that the first thickness d1 of the first semiconductor layer 152 has a periodicity of 0.93 (mu m) or 1.12 (mu m).

That is, the first semiconductor layer 152 has a periodicity of 1/3 to 1/2 with respect to the period of 2.2 占 퐉 to 2.5 占 퐉 with respect to the thickness dt of the light emitting structure 150 illustrated in FIG. .

The first thickness d1 of the first semiconductor layer 152 for compensation of the first semiconductor layer 152 according to the wavelength λ of the light emitted from the active layer 154 can be determined by the first thickness d1 of the light emitting structure 150 By having 1/3 to 1/2 times the thickness dt, the luminous intensity lm can be improved.

5 shows a change in the luminous intensity with respect to the thickness dt of the light emitting structure 150 and the second thickness d2 of the second semiconductor layer 156. FIG.

5, the experiment data p and the simulation data s are shown in the same manner as in Figs. 3 and 4, and the experiment data p and the simulation data s are located on the same line.

When the second thickness d2 of the second semiconductor layer 156 is 0.25 (mu m), 0.319 (mu m), 0.38 mu m and 0.46 mu m, the luminous intensities lm are 18.8 (lm) 18.6 (lm), 18.5 (lm) and 18.7 (lm), the experimental data (p) and the simulation date (s) have peak values.

3 and 4, the second thickness d2 of the second semiconductor layer 156 is in a range of about 0.062 m to about 0.07 m, 0.082 占 퐉, and it is preferable to have a multiple of 0.075 占 퐉 to 0.090 占 퐉 according to the experimental error.

As described above, the thickness dt of the light emitting structure 150 is determined by the first and second thicknesses d1 and d2 of the first and second semiconductor layers 152 and 156 in accordance with the wavelength? Of light generated in the active layer 154, And adjusts the compensation interference according to the wavelength? Of the light, thereby improving the light efficiency.

Although a vertical type light emitting device has been described in the embodiment, the present invention is not limited thereto and can be applied to a horizontal type light emitting device.

The light emitting device 100 according to the embodiment can be mounted in a package, and a plurality of light emitting device packages are arrayed on a substrate, and a light guide plate, a prism sheet, a diffusion sheet, .

Such a light emitting device package, a substrate, and an optical member can function as a light unit. Another embodiment may be implemented with a display device, an indicating device, a lighting system including the light emitting diode or the light emitting device package described in the above embodiments, for example, the lighting system may include a lamp, 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 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.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of example, It will be understood that various modifications and applications are possible without departing from the scope of the present invention. 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 (7)

Board; And
And a light emitting structure disposed on the substrate and including a first semiconductor layer, a second semiconductor layer, and an active layer between the first and second semiconductor layers,
The thickness of the light-
0.3 to 1 times the thickness of the substrate,
The thickness of the light-
Emitting element is a multiple of 2.2 탆 to 2.5 탆. delete The semiconductor device according to claim 1, wherein the thickness of the first semiconductor layer
And the second semiconductor layer is thicker than the first semiconductor layer. The semiconductor device according to claim 1, wherein the thickness of the first semiconductor layer
And the thickness of the second semiconductor layer is 1.1 to 1.7 times the thickness of the second semiconductor layer. The semiconductor device according to claim 1, wherein the thickness of the first semiconductor layer
Wherein the thickness of the light emitting structure is 1/3 to 1/2 times the thickness of the light emitting structure. The semiconductor device according to claim 1, wherein the thickness of the second semiconductor layer
0.0 > um, < / RTI > The substrate processing apparatus according to claim 1,
A light emitting device comprising a patterned sapphire substrate (PSS).

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