KR20150117816A - Light Emitting Device comprising light extraction layer with graded refractive index and Method of preparing the same - Google Patents

Abstract

The present invention relates to a light emitting device having a high transmittance light extracting layer in which the refractive index is gradually decreased by varying the temperature during the deposition of a beam, and a method of manufacturing the same.
Since the light emitting device of the present invention includes the light extraction layer whose refractive index gradually changes, the reflectance due to the difference in refractive index between the semiconductor light emitting device and the atmosphere can be lowered and the light emission efficiency can be increased.
Since the light extraction layer of the present invention controls the refractive index in the deposition layer by controlling the temperature during the deposition of the beam, it is simpler and more efficient than the method of forming the refractive index gradient by changing the composition in the conventional multi-component system.
The light extracting layer of the present invention is highly effective in light extraction because there is no rapid change in the refractive index because the refractive index continuously changes in the layer composed of a single component.

Description

TECHNICAL FIELD [0001] The present invention relates to a light emitting device having a light extracting layer having a refractive index continuously changing, and a method of manufacturing the light emitting device.

The present invention relates to a light emitting device having a light extracting layer with a continuously changing refractive index and a method of manufacturing the same, and more particularly, to a light emitting device having a refractive index gradually increasing through a process effect such as a temperature change of the beam deposition or an ion beam treatment And a method of manufacturing the light emitting device.

BACKGROUND ART In general, semiconductor light emitting diodes (LEDs) are widely used as light sources in full color displays, image scanners, various signal systems, and optical communication devices. These LEDs generate and emit light in the active layer, which utilizes the recombination principle of electrons and holes. Particularly, nitride semiconductors are receiving the spotlight as a constituent material of a light emitting device capable of covering a wide wavelength including blue and green light bands according to the composition ratio thereof.

The light efficiency of such a semiconductor light emitting device is determined by internal quantum efficiency and light extraction efficiency (also referred to as "external quantum efficiency"). In particular, the light extraction efficiency is greatly influenced by the optical factor of the light emitting device, that is, the refractive index of each structure and / or the flatness of the interface.

Since the semiconductor layer constituting the semiconductor light emitting element has a larger refractive index than the outer atmosphere or the sealing material or the substrate, the critical angle that determines the range of incidence angle at which light can be emitted is reduced. As a result, So that the light extraction efficiency is low due to propagation in a substantially undesired direction or loss in the total reflection process.

1 is a schematic view showing a cross-sectional view of a conventional light emitting diode. 1, the light emitting diode includes a buffer layer 11, an n-type semiconductor layer 12, a multiple quantum well layer (MQW) 13, a p-type semiconductor layer 14 And a p-electrode 20 formed on the p-type semiconductor layer and an n-electrode 22 formed on the n-type semiconductor layer exposed to a predetermined region through etching. In the light emitting diode having the above structure, light emitted from the active layer is emitted not only in the upper direction but also in the forward direction, and is partially reflected by the substrate emitted in the downward direction, that is, in the substrate direction, There is a problem that the light intensity of the light emitting diode is lowered because most of the light generated in the light emitting diode can not go out of the light emitting diode and is mostly reflected and absorbed inside.

2 is a schematic view showing a cross-sectional view of a conventional flip chip structure light emitting diode. The light emitting diode of Fig. 1 is reversed, and the p-electrode 23 and the n-electrode 22 are fixed by solder to emit light generated in the active layer toward the upper direction. This structure also emits light in all directions. In this process, other than the light reflected or transmitted vertically from the upper and lower layers due to the refractive index difference of the sapphire substrate, the remainder is reabsorbed after the reflection or partial reflection of the light, There is a problem that the light intensity of the light emitting diode is lowered.

There is an attempt to improve the light extraction efficiency of such a light emitting device. Korean Patent Laid-Open No. 10-2010-50430 discloses a light emitting device having a fine pattern of a graded refractive index layer, WO 2007-136064GH38214 discloses a light emitting device having an inclined refractive index layer, and US Pat. No. 2,011-147773 A multilayered film is laminated to form a refractive index gradient.

The above-mentioned patents disclose that a refractive index gradient is formed by forming a refractive index gradient by adhering multiple layers or changing the composition of source gases upon deposition. However, a method of manufacturing a light emitting device having a refractive index gradient which can be continuously formed, Is still required.

The present invention provides a light emitting device capable of reducing total internal reflection caused by a difference in refractive index between a semiconductor light emitting device and the atmosphere and increasing light transmission efficiency.

The present invention provides a light emitting device which can easily form a refractive index gradient in a single layer while being easily manufactured, and a method of manufacturing the same.

In one aspect, the present invention provides a light emitting device comprising a first conductive semiconductor layer, an active layer, a second conductive semiconductor layer, a first electrode, and a second electrode,

The light emitting device includes a light extracting layer formed on a light emitting surface from which light generated in the active layer is emitted, and the light extracting layer is gradually reduced as the density in the layer is further away from the active layer .

In another aspect, the present invention provides a method of manufacturing a light emitting device, including: forming a first conductive semiconductor layer, an active layer, a second conductive semiconductor layer, a first electrode, and a second electrode;

And forming a light extracting layer on the light emitting surface on which the light generated in the active layer is emitted by using an e-beam deposition method, wherein the light extracting layer forming step includes: Emitting layer is continuously decreased as the distance from the active layer increases.

Since the light emitting device of the present invention includes the light extraction layer whose refractive index gradually changes, the reflectance due to the difference in refractive index between the semiconductor light emitting device and the atmosphere can be lowered and the light emission efficiency can be increased.

Since the light extraction layer of the present invention controls the refractive index in the deposition layer by controlling the temperature during the deposition of the beam, it is simpler and more efficient than the method of forming the refractive index gradient by changing the composition in the conventional multi-component system.

The light extracting layer of the present invention is highly effective in light extraction because there is no rapid change in the refractive index because the refractive index continuously changes in the layer composed of a single component.

1 is a schematic view showing a cross-sectional view of a conventional light emitting diode.
2 is a schematic view showing a cross-sectional view of a conventional flip chip structure light emitting diode.
3 is a side sectional view of a semiconductor light emitting device according to an embodiment of the present invention.
4 shows a light emitting device having a flip chip structure according to an embodiment of the present invention.
5 shows that a second light extracting layer is additionally provided between the light extracting layer and the light emitting surface.
Figure 6 shows an EBEAM Evaporater equipment used in the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. 3 and 4 are side cross-sectional views of a semiconductor light emitting device according to an embodiment of the present invention.

Referring to FIG. 3, the light emitting device of the present invention includes a substrate 110, a first conductive semiconductor layer 120, an active layer 130, a second conductive semiconductor layer 140, a first electrode 150, Two electrodes 160 are formed.

The substrate 110 may be any substrate that can be used as a substrate of a semiconductor light emitting device. For example, a double-side polished sapphire substrate or a silicon substrate may be used.

The first conductive semiconductor layer 120 may be a n-type nitride semiconductor material, for example, an n-GaN layer. The second conductive semiconductor layer 140 may be a p-GaN layer or a p-GaN / AlGaN layer, for example.

The active layer 130 may be a GaN-based nitride semiconductor layer of InxAlyGa1-x-yN (0 = x <1, 0 = y <1 and 0 = x + y <1) multi-quantum well (MQW), or a single quantum well. Preferably, it may be a GaN / InGaN / GaN MQW or GaN / AlGaN / GaN MQW structure.

First and second electrodes 150 and 160 connected to the first and second conductive semiconductor layers 120 and 140 are formed, respectively.

The first electrode 150 may be formed of a metal material such as Ti / Al, Ti / Au, Ti / Ag, Cr / Au, Cr / Al, Cr / Ag, Ag alloy, Au alloy, Al alloy, Au, Or a transparent conductive material.

The second electrode 160 may be a transparent conductive oxide (TCO) that can transmit light or a transparent conductive nitride (TCN). Any transparent conductive material of the oxide series may be used. For example, ITO (indium-tin-oxide ), IZO (indium-zinc-oxide), GZO (gallium-zinc-oxide), AZO (aluminium-zinc-oxide), Ga 2 O 3 (gallium oxide), SnO ₂ there is a substance such as _{(tin-oxide), in 2} O 3 (indium-oxide), IGZO (indium-galliumzinc-oxide) may be used.

A Bonding-electrode (B-electrode) 161 for electrical contact is formed on the second electrode.

A u-GaN layer 111 may be formed on the substrate 110 as a buffer layer. When the semiconductor layer is grown on the buffer layer 111, the interfacial energy is reduced as compared with the case where the semiconductor layer is directly grown on the heterogeneous substrate, so that nucleation of a high density can be performed. Further, This has the advantage of promoting planar growth, which can alleviate the lattice mismatch to some extent.

When a predetermined voltage is applied between the first electrode 150 and the second electrode 160, electrons and electrons are emitted from the first conductive semiconductor layer 120 and the second conductive semiconductor layer 140, respectively. Holes are injected into the active layer 130 and recombined, whereby light can be generated from the active layer 130.

A light extracting layer 170 is formed on the light emitting surface of the light emitting device. Here, the light emitting surface refers to a specific surface of the light emitting device that emits light generated from the active layer 130 and emits outside the ceramic or metal electrode layer.

For example, in FIG. 3, the light emitting surface on which light is emitted in the upward direction may correspond to the second electrode 160, and light may also be emitted from the side surfaces of the respective layers constituting the device, It may correspond to a light emitting surface.

4 has a substrate 210, a first conductive semiconductor layer 220, an active layer 230, a second conductive semiconductor layer 240, a first electrode 250, Two electrodes 260 are formed.

In the light emitting device of the flip chip structure of FIG. 4, since light can be emitted even to the substrate 210 on which light is emitted in the upward direction and the side surfaces of the respective layers constituting the device, . &Lt; / RTI &gt;

As the substrate, a transparent substrate such as Al ₂ O ₃ , ZnO, GaN, or LiAl ₂ O ₃ is used. In this embodiment, a sapphire substrate is used.

As the second electrode 260, a reflective electrode is formed of at least one of Ni, Ru, Pt, Ir, Cu, W, Ag, Al, Ni alloy, Ag alloy and Al alloy.

A u-GaN layer 211 may be formed on the substrate 210 as a buffer layer.

Referring to FIGS. 3 and 4, the light extracting layers 170 and 270 formed on the light emitting surface gradually decrease as the density in the layer is further away from the active layer.

The expression &quot; progressive &quot; used in the present invention indicates that the refractive index is continuously decreased. For example, when a plurality of layers having different refractive indexes are bonded to each other, the refractive index is uniform and maintained at a constant value in each layer, and the refractive index varies abruptly in the form of a step in the joint surface. &Quot; is continuously decreased in each thin film layer in a curved shape, and the refractive index is gradually changed by minimizing the variation width of the refractive index even at the bonding surfaces where a plurality of thin film layers are in contact with each other. Particularly, the refractive index gradually changes even in a single layer It is used as a term to indicate. The light extracting layer may be non-uniform in density within a single layer. Here, the heterogeneity of the density is used in a broad sense to mean that the density is not the same within a single layer.

F compounds, such as the light extraction layer is _{MgF 2, CaF 2, LiF,} BaF 2, PbF 2, ITO, ZnO, SnO 2, Ga 2 O 3, In 2 O 3, SiO 2, MgO, Al 2 O 3, TiO _{2 , and} Ta ₂ O ₅ , and a compound layer such as ZnS.

The density of the light extracting layer can be represented by a change in refractive index, and the refractive index gradually decreases from 2.4 to 1.1.

The refractive index of the light extracting layer gradually decreases as the density decreases.

The refractive index of the light extracting layer may be gradually reduced between the refractive index of the semiconductor layer and the air. For example, since the refractive index of the gallium nitride layer forming the semiconductor layer is 2.4 and the air is 1, the light extracting layer can be gradually reduced in the above range.

The light extracting layer may have a thickness of 0.01-100 탆, preferably 0.5-2 탆.

The light extracting layer may be formed in a patterned structure to increase the light extraction efficiency. For example, a part of the light extracting layer may be etched to be patterned, and the light extracting layer may have a vertical section, a convex upper section, or a trapezoidal section.

A dielectric layer having a refractive index in a range of less than 2.4, preferably in a range of 1.8 to 1.4 may be additionally formed between the light extracting layer and the light emitting surface. For example, the dielectric layer can be formed by e-beam evaporation of SiO ₂ having a refractive index of 1.46.

The light extracting layer may be a multi-layer, and the at least one monolayer constituting the multi-layer is continuously reduced in refractive index in the layer.

As an example, FIG. 5 shows a multi-layered light extraction layer further comprising a second light extraction layer 180 between the light extraction layer 170 and the light exit surface in FIG. The refractive index of the second light extracting layer 180 may gradually decrease to a range of 1.4-1.2 according to the density change. When the light extracting layer is MgF ₂ , the refractive index of the second light extracting layer 180 can be adjusted to 1.4 to 1.2.

The refractive index of the second light extracting layer 180 may be gradually reduced, for example, between the refractive index of the gallium nitride layer 2.4 and the maximum refractive index of the light extracting layer 170.

The light extracting layer may be formed on the upper layer of the nitride electrode structure as shown in FIGS.

In another aspect, the present invention provides a method of manufacturing a light emitting device, comprising: forming a first conductive semiconductor layer, an active layer, a second conductive semiconductor layer, a first electrode, and a second electrode; To form a layer.

The light extraction layer forming step gradually decreases the density of the light extracting layer as the deposition temperature is changed, as the distance from the active layer increases.

The light extracting layer forming step is a step of reducing the deposition temperature from a temperature between 1000 캜 and 100 캜 at a rate of 30 캜 / min to 50 캜 / min. For example, the deposition can be performed by reducing the deposition temperature at a rate of from 500 캜 to 30 캜 / min and reaching room temperature.

The formation of the first conductive semiconductor layers 120 and 220, the active layers 130 and 230, the buffer layers 111 and 211 and the second conductive semiconductor layers 140 and 240 may be performed by a conventional method, (MOCVD), molecular beam growth (MBE), hydride vapor phase growth (HVPE) and the like can be exemplified. Typical examples thereof include organic metal Chemical vapor deposition may be applied. The layer forming method can be easily achieved by those skilled in the art.

The method of forming the first and second electrodes is not particularly limited, and any known CVD method, sputtering method, reactive evaporation method, or the like can be used without any particular limitation.

The light extraction layer forming step may be formed using at least one of e-beam deposition and ion-beam.

The light extracting layer forming step may be formed using e-beam deposition using an ion beam.

The light extracting layer (170, 270)) and the second light extraction layer 180 is _{MgF 2, CaF 2, LiF,} BaF 2, PbF 2, ITO, ZnO, SnO 2, Ga 2 O 3, In 2 O 3 _{, SiO 2, MgO, Al 2} O 3, TiO 2 Ta 2 O 5 And And ZnS is formed by beam evaporation. That is, the metal oxide is deposited by an E-BEAM evaporator to form a light extracting layer.

The light extraction layer forming method may deposit the light extracting layer forming compound by beam irradiation while irradiating Ar or O ₂ gas onto the light emitting surface through an ion beam accelerator. If the ion beam irradiation and the beam deposition are performed at the same time, the crystallinity of the interface can be improved.

The thickness of the light extracting layers 170 and 270 may be 0.01-100 μm, preferably 0.5-2 μm.

6 is a view showing an embodiment of an EBEAM Evaporater equipment used in the present invention. 6, the E-BEAM Evaporater equipment 300 includes a wafer carousel 310, a substrate 320, a crucible 330, a vacuum pump 330, A valve 340, and a filament 350. 6, an ion-beam accelerator 360 is installed in an E-BEAM evaporator 300 and irradiated with Ar or O ₂ gas through an ion beam accelerator, Can be performed.

First, argon ions are irradiated to the second electrode layer 160 through an ion beam accelerator. At this time, the voltage may be 100 to 200 V and the flow rate may be 1 to 5 sccm. Subsequently, the substrate 320 is mounted on the wafer carousel 320, the metal oxide deposited on the first substrate 110 is inserted into the groove (not shown) on the crucible 330, and the vacuum pump valve 310 The wafer carousel 310 mounted on the substrate 320 is rotated, and a very high voltage is applied to the filament 350 to radiate heat electrons from the filament 350 to collide with the metal oxide. The metal oxide is deposited on the substrate 320 to a thickness of 0.001 to 3 mu m to form a light extracting layer.

The deposition condition of the beam is briefly described as follows.

The base vacuum is about 3 × 10 ^-6 Torr and the working pressure is 1.6 × 10 ^-4 Torr. The deposition rate is in the range of 2 A / sec. Since the annealing temperature is 550 ° C, the deposition time can be up to max 500 ° C. The annealing temperature can be maintained at 300 ° C or 200 ° C or 100 ° C, and the time to reduce to 24 ° C (room temperature) , And the deposition proceeds. The method of decreasing can be a stepwise method, and a method of continuously decreasing can be used, but in the present embodiment, a method of continuously decreasing is applied.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments.

110, 210: substrate 120, 220: first conductivity type semiconductor layer
130, 230: an active layer 140, 240: a second conductivity type semiconductor layer
150, 250: first electrode 160, 260: second electrode
170, 270: light extracting layer 180: second light extracting layer

Claims (18)

1. A light emitting device comprising a first conductivity type semiconductor layer, an active layer, a second conductivity type semiconductor layer, a first electrode, and a second electrode,
Wherein the light emitting device includes a light extracting layer formed on a light emitting surface from which light generated in the active layer is emitted, and the light extracting layer gradually decreases in density as the distance from the active layer increases. device. The method of claim 1, wherein the light extraction layer is MgF _2, CaF _2, LiF, BaF _2, PbF _2, NaF, AlF, BaF _2, BeF _2, CdF _2, CsF, ThF _4, YF _3, ITO, ZnO, TiO ₂ , AgO, AgO ₂ , NiO, MgO, Al ₂ O ₃ , TiO ₂ , SnO ₂ , Ga ₂ O ₃ , BeO, In ₂ O ₃ , SiO ₂ , Si ₃ N ₄ , CuO, Cu ₂ O, WO ₃ , ₂ Ta ₂ O ₅ And ZnS, and a compound semiconductor layer. The semiconductor light emitting device according to claim 1, wherein the density of the light extracting layer is continuously reduced in a single layer. The semiconductor light emitting device according to claim 1, wherein the refractive index of the light extracting layer is continuously decreased as the density is reduced. The semiconductor light emitting device according to claim 1, wherein the refractive index of the light extracting layer has a refractive index between the semiconductor layer and air. The semiconductor light emitting device according to claim 1, further comprising a dielectric layer between the light extracting layer and the light emitting surface, the dielectric layer having a refractive index in a range of less than 2.4. The semiconductor light emitting device according to claim 1, wherein the light extracting layer is patterned into a predetermined shape. The semiconductor light emitting device according to claim 1, wherein the light extracting layer has a uniform density in a single layer. The semiconductor light emitting device according to claim 1, wherein the light extracting layer has a thickness of 0.5 to 2 占 퐉. 2. The semiconductor light emitting device of claim 1, wherein the light extracting layer may be a multi-layered structure, and the at least one single layer constituting the multi-layer may continuously decrease the refractive index in the layer. The semiconductor light emitting device of claim 1, wherein the light extracting layer is formed on an upper layer of the nitride electrode structure. Forming a first conductive semiconductor layer, an active layer, a second conductive semiconductor layer, a first electrode, and a second electrode;
And forming a light extracting layer on a light emitting surface from which light generated in the active layer is emitted, wherein the light extracting layer forming step changes the deposition temperature to gradually increase the density of the light extracting layer as it moves away from the active layer Wherein the thickness of the semiconductor light emitting device is reduced. 13. The method of claim 12, wherein the light extraction layer forming step is performed using at least one of e-beam deposition and ion-beam. The method of claim 12, wherein the light extraction layer is MgF _2, CaF _2, LiF, BaF _2, PbF _2, NaF, AlF, BaF _2, BeF _2, CdF _2, CsF, ThF _4, YF _3, ITO, ZnO, TiO ₂ , AgO, AgO ₂ , NiO, MgO, Al ₂ O ₃ , TiO ₂ , SnO ₂ , Ga ₂ O ₃ , BeO, In ₂ O ₃ , SiO ₂ , Si ₃ N ₄ , CuO, Cu ₂ O, WO ₃ , ₂ Ta ₂ O ₅ And ZnS, and combinations thereof. The method for manufacturing a semiconductor light-emitting device according to claim 1, 14. The method of claim 13, wherein the forming of the light extracting layer comprises reducing the deposition temperature at a rate of about 30 DEG C / min to about 50 DEG C / min. 14. The method of claim 13, wherein the method further comprises patterning the light extraction layer into a predetermined shape. 15. The method according to claim 14, wherein the method comprises the step of irradiating Ar or O ₂ gas onto the light emitting surface through an ion beam accelerator and subjecting the light extracting layer compound material to ion beam deposition. 18. The method of claim 17, wherein the method comprises irradiating Ar or O ₂ gas at a flow rate of 0.1 sccm to 500.

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