KR100891827B1 - Vertical nitride semiconductor light emitting device and manufacturing method of the same - Google Patents

Abstract

The present invention relates to a vertical structure nitride semiconductor light emitting device and a method for manufacturing the same, and an aspect of the present invention, a light emitting structure comprising a first conductive nitride layer and a second conductive nitride layer and an active layer formed therebetween; An electrode portion formed on one surface of the exposed surface of the first conductive nitride layer in the light emitting structure, a highly reflective ohmic contact layer and the highly reflective ohmic contact formed on the exposed surface of the second conductive nitride layer in the light emitting structure And a conductive substrate formed on the layer, wherein the first conductivity type nitride layer includes a plurality of delta-doped films delta-doped with a first conductivity type impurity. Another aspect of the present invention provides a method of manufacturing a vertical nitride semiconductor light emitting device having the above structure. According to the present invention, the operating voltage is lowered and the electrostatic withstand voltage is improved, and thus, a vertical nitride semiconductor light emitting device having improved optical characteristics and reliability and a method of manufacturing the same can be obtained.

Vertical structure, nitride semiconductor, light emitting device, LED, delta doping, electrostatic breakdown voltage, current dispersion

Description

Vertical structure nitride semiconductor light emitting device and manufacturing method {VERTICAL NITRIDE SEMICONDUCTOR LIGHT EMITTING DEVICE AND MANUFACTURING METHOD OF THE SAME}

1 is a cross-sectional view showing a vertical nitride semiconductor light emitting device according to one embodiment of the present invention.

2A to 2E are cross-sectional views showing processes according to an embodiment of the manufacturing process of the vertical nitride semiconductor light emitting device of FIG.

<Code Description of Main Parts of Drawing>

11: n-type nitride semiconductor layer 12: active layer

13: p-type nitride semiconductor layer 14: reflective metal layer

15: metal barrier layer 16: conductive substrate

17a: n-side electrode 17b: p-side bonding electrode

delta delta film 20 sapphire substrate

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vertical structure nitride semiconductor light emitting device and a method of manufacturing the same. More particularly, the vertical structure has a low operating voltage and improved electrostatic breakdown voltage without deterioration of crystallinity, and thus the optical characteristic and reliability are improved. A structure nitride semiconductor light emitting device and a method of manufacturing the same.

BACKGROUND A light emitting diode (LED) is a semiconductor device capable of generating light of various colors based on recombination of electrons and holes at a junction portion of a p and n type semiconductor when current is applied thereto. These LEDs have a number of advantages over filament based light emitting devices, such as long life, low power, excellent initial driving characteristics, high vibration resistance, and high tolerance for repetitive power interruptions. In recent years, group III nitride semiconductors capable of emitting light in a blue short wavelength region have been in the spotlight.

The nitride single crystal constituting the light emitting device using the group III nitride semiconductor is formed on a specific single crystal growth substrate, such as a sapphire or SiC substrate. However, in the case of using an insulating substrate such as sapphire, the arrangement of electrodes is greatly limited. That is, in the conventional nitride semiconductor light emitting device, since the electrodes are generally arranged in the horizontal direction, the current flow becomes narrow. Due to such a narrow current flow, the forward voltage Vf of the light emitting device increases, resulting in a decrease in current efficiency, and also a problem of being vulnerable to electrostatic discharge.

In order to solve the above problem, a nitride semiconductor light emitting device having a vertical structure is required. However, even in the vertical nitride light emitting device according to the prior art, when the doping concentration of the n-type nitride semiconductor layer is increased to improve the electrical conductivity and the electrostatic withstand voltage, crystallinity and light transmittance may be deteriorated. Therefore, the crystallinity of the active layer and the p-type nitride semiconductor layer grown on the n-type nitride semiconductor layer whose crystallinity is lowered also decreases, resulting in deterioration of optical characteristics and reliability of the final light emitting device.

Accordingly, there is a need for a vertical nitride semiconductor light emitting device that increases the n-type impurity doping concentration and does not reduce crystallinity and light transmittance in order to improve electrical conductivity and static pressure resistance.

The present invention has been made to solve the above-mentioned problems of the prior art, one object of which is that the operating voltage is low, the electrostatic breakdown voltage is improved without deterioration in crystallinity and light transmittance, and thus, optical characteristics and reliability It is to provide an improved vertical structure nitride semiconductor light emitting device. Another aspect is to provide a method of manufacturing the vertical nitride semiconductor light emitting device.

In order to achieve the above technical problem, an aspect of the present invention,

A light emitting structure including a first conductive type nitride layer and a second conductive type nitride layer, and an active layer formed therebetween; an electrode portion formed in one region of an exposed surface of the first conductive type nitride layer in the light emitting structure; The light emitting structure includes a highly reflective ohmic contact layer formed on the exposed surface of the second conductivity type nitride layer and a conductive substrate formed on the highly reflective ohmic contact layer, wherein the first conductivity type nitride layer is formed of a first conductivity type impurity. Provided is a vertical nitride semiconductor light emitting device comprising a plurality of delta-doped delta-doped films.

Additionally, it is preferable to further include a metal barrier layer formed between the reflective metal layer and the conductive substrate.

In this case, the metal barrier layer is preferably made of tungsten (W) or a tungsten-based alloy.

The delta dope film included in the first conductivity type nitride layer employed in the present invention has a function of improving electrical conductivity and improving current dispersing effect.

Preferably, the first conductivity type nitride layer may be a nitride semiconductor layer doped with n-type impurities, and the second conductivity type nitride layer may be a nitride semiconductor layer doped with p-type impurities. In this case, the n-type impurity is preferably made of a material selected from the group consisting of Si, Ge, Se, Te and C.

In addition, it is preferable that the distance between adjacent delta dope films among the plurality of delta dope films is 180 to 220 mW.

Meanwhile, the concentration of n-type impurities in the n-type nitride semiconductor layer is 3 × 10 ¹⁸ to 5 × 10 ¹⁸ / cm ³ , and the concentration of n-type impurities in the delta-doped film is 7 × 10 ¹⁸ to 1 × 10 ¹⁹ / cm Is preferably.

Preferably, the number of the delta doped films included in the first conductivity type nitride layer may be 65 to 80.

In a preferred embodiment of the present invention, the conductive substrate may be made of a material selected from the group consisting of Si, Cu, Ni, Au, W and Ti.

In addition, the thickness of the conductive substrate is preferably in the range of 50 to 100 µm.

The highly reflective ohmic contact layer employed in the present invention may be made of a material selected from the group consisting of Ag, Ni, Al, Rh, Pd, Ir, Ru, Mg, Zn, Pt, Au, and combinations thereof.

Another aspect of the invention,

Sequentially growing a first conductivity type nitride layer, an active layer, and a second conductivity type nitride layer on the nitride single crystal growth preliminary substrate, and forming a highly reflective ohmic contact layer on the second conductivity type nitride layer; Forming a conductive substrate on the highly reflective ohmic contact layer, removing the preliminary substrate so that the first conductive nitride layer is exposed, and a part of the exposed region of the first conductive nitride layer. And forming an electrode portion, wherein growing the first conductivity type nitride layer comprises forming a plurality of delta-doped films delta-doped with a first conductivity type impurity. Provided is a method of manufacturing a semiconductor light emitting device.

In this case, the step of removing the preliminary substrate is preferably by a laser lift-off process.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the present invention.

1 is a cross-sectional view showing a vertical nitride semiconductor light emitting device according to one embodiment of the present invention.

Referring to Fig. 1, the vertical nitride semiconductor light emitting element 10 according to the present embodiment is composed of an n-type nitride semiconductor layer 11 and a p-type nitride semiconductor layer 13 and an active layer 12 formed therebetween. A light emitting structure, wherein the electrode portion 17a is formed at one region of the exposed surface of the n-type nitride semiconductor layer 11 in the light emitting structure and the exposed surface of the p-type nitride semiconductor layer 13 in the light emitting structure. The high reflective ohmic contact layer 14, the metal barrier layer 15, the conductive substrate 16, and the p-side bonding electrode 17b which are sequentially formed are included. In the present invention, the 'light emitting structure' refers to a structure formed by sequentially stacking the n-type nitride semiconductor layer 11, the active layer 12, and the p-type nitride semiconductor layer 13.

The n-type nitride semiconductor layer 11 and the p-type nitride semiconductor layer 13 are Al _x In _y Ga _(1-xy) N composition formula (where 0≤x≤1, 0≤y≤1, 0≤x + n? impurity and p type impurity doped with a semiconductor material doped with y ≦ 1), and typically GaN, AlGaN, InGaN. In addition, Si, Ge, Se, Te or C may be used as the n-type impurity, and the p-type impurity may be representative of Mg, Zn or Be.

In particular, the n-type nitride semiconductor layer 11 employed in the present embodiment includes a plurality of delta-doped films δ doped with n-type impurities. That is, as shown in FIG. 1, the delta-doped film δ is in the form of a film in which the n-type impurity is highly two-dimensionally doped in the n-type nitride semiconductor layer 11. Therefore, in the n-type nitride semiconductor layer 11 having a structure including a plurality of highly doped delta doped films δ, high electrical conductivity and current dispersion effect can be expected. Accordingly, the operating voltage of the vertical nitride semiconductor light emitting device 10 can be reduced and the static breakdown voltage can be enhanced.

In order to achieve the above-mentioned lowering of the operating voltage and strengthening of the static withstand voltage efficiently, in this embodiment, it is preferable that the distance between the delta-doped films δ adjacent to each other among the plurality of delta-doped films δ is 180 to 220 kV. In this case, the distance between the adjacent delta-doped films δ may be defined as the thickness of the layer sandwiched between the adjacent delta-doped films δ. In addition, in FIG. 1, although the intervals of the plurality of delta-doped films δ are shown to be the same, the present invention is not limited thereto, and the delta-doped films δ adjacent to the delta-doped films δ are not limited thereto. The spacing between may be different.

On the other hand, although not shown, the delta-doped film δ is very thin, so that the crystallinity and light transmittance of the n-type nitride semiconductor layer 11 are not significantly reduced, and the preferred thickness thereof is about 10 GPa. In addition, as in the n-type nitride semiconductor layer 11, n-type impurities doped in the delta-doped film δ may be Si, Ge, Se, Te or C, etc., of which Si is representative.

In addition, in consideration of the effective current spreading effect, the concentration of n-type impurities in the n-type nitride semiconductor layer 11 is 3 × 10 ¹⁸ to 5 × 10 ¹⁸ / cm ³ , and the n-type impurities of the delta-doped film δ. The concentration of is preferably 7 × 10 ¹⁸ to 1 × 10 ¹⁹ / cm, and in addition, the first conductivity type nitride layer 11 preferably contains 65 to 80 delta dopants δ. .

Meanwhile, the n-type and p-type nitride semiconductor layers 11 and 13 may be grown by organometallic vapor deposition (MOCVD), molecular beam growth (MBE), hybrid vapor deposition (HVPE), and the like. The formation process of the dope film (delta) is demonstrated in FIG.

The active layer 12 may be a layer for emitting visible light (a wavelength range of about 350 to 680 nm), and is formed of an undoped nitride semiconductor layer having a single or multiple quantum well structure. Like the n-type and p-type nitride semiconductor layers 11 and 13, the active layer may be grown by organometallic vapor deposition (MOCVD), molecular beam growth (MBE), hybrid vapor deposition (HVPE), and the like.

The highly reflective ohmic contact layer 14 preferably has a reflectance of 70% or more and forms an ohmic contact with the p-type nitride semiconductor layer 13. The highly reflective ohmic contact layer 14 may be formed of at least one layer made of a material selected from the group consisting of Ag, Ni, Al, Rh, Pd, Ir, Ru, Mg, Zn, Pt, Au, and combinations thereof. have. Preferably, the highly reflective ohmic contact layer 14 is formed of Ni / Ag, Zn / Ag, Ni / Al, Zn / Al, Pd / Ag, Pd / Al, Ir / Ag. It may be formed of Ir / Au, Pt / Ag, Pt / Al or Ni / Ag / Pt.

The metal barrier layer 15 is adopted as a layer for preventing the lowering of ohmic contact properties (particularly, reflectance and contact resistance) by being fused at the interface between the bonding electrode material and the ohmic contact layer material. The metal barrier layer 15 may be made of tungsten or a tungsten-based alloy, and specifically, may be made of TiW or Ti / TiW.

In particular, in the case where the highly reflective ohmic contact layer 14 includes Ag, there is an advantage in that leakage current due to migration of Ag can be effectively prevented. In addition, the metal barrier layer 15 having a predetermined reflectance may serve to assist the reflective role of the highly reflective ohmic contact layer 24.

The conductive substrate 16 is an element included in the final light emitting device, and serves as a support for supporting the light emitting structure together with the p-side electrode of the vertical nitride semiconductor light emitting device 10. The conductive substrate 16 may be made of a material selected from the group consisting of Si, Cu, Ni, Au, W, and Ti.

Finally, the bonding electrode 17b is the outermost electrode layer and is generally made of Au or an alloy containing Au. The p-side bonding electrode 17b may be formed by a deposition method or a sputtering process, which is a conventional metal layer growth method.

An embodiment of the manufacturing process of the present invention having the above structure will be described with reference to Figs. 2A to 2E.

2A to 2E are cross-sectional views showing processes according to an embodiment of the manufacturing process of the vertical nitride semiconductor light emitting device of FIG.

First, as shown in FIG. 2A, an n-type nitride semiconductor layer 11 including a plurality of delta-doped films δ is grown on a sapphire substrate 20, which is a preliminary substrate for nitride single crystal growth.

The sapphire substrate 20 is a crystal having hexagonal-Rhombo R3c symmetry and has a lattice constant of 13.001Å in the c-axis direction and 4.765 4. in the a-axis direction, and has a sapphire plane direction. An orientation plane includes a C (0001) plane, an A (1120) plane, an R (1102) plane, and the like. The C surface of the sapphire substrate 20 is relatively easy to grow a nitride thin film, and is mainly used as a nitride growth substrate because it is stable at high temperatures. However, in the present invention, the nitride single crystal growth preliminary substrate 20 is not limited to the sapphire substrate, SiC, MgAl ₂ O ₄ , MgO, LiAlO ₂ and LiGaO ₂ A substrate made of or the like may be employed.

The growth process of the n-type nitride semiconductor layer 11 and the delta-doped film δ will be described. First, trimethylgallium and ammonia are respectively introduced into the n-type nitride semiconductor layer 11 on the sapphire substrate 20. Grow to 20 nm thick. Next, the supply of trimethylgallium is stopped for 10 to 30 seconds to introduce an n-type delta-doped source gas in a state where an ammonia gas atmosphere is formed, thereby forming an n-type delta-doped film δ. In this case, the organometallic chemical field Vapor deposition, molecular beam growth, or the like. In this case, as described above, Si, Ge, Se, Te, C, etc. may be used as the n-type delta doping impurity. However, in the present embodiment, silicon tetrahydride (SiH ₄₎ is used as an impurity source gas by employing Si. ) Was used. Next, according to the number of delta-doped films δ to be included in the n-type nitride semiconductor layer 11, the supply of the n-type delta-doped source gas is stopped and trimethylgallium is supplied again, thereby providing the n-type nitride semiconductor described above. The process of growing the layer 11 and the process of forming the delta doped film δ may be repeated.

Next, as shown in FIG. 2B, the active layer 12 and the p-type nitride semiconductor layer 13 are sequentially grown on the n-type nitride semiconductor layer 11. As described above, the active layer 12 and the p-type nitride semiconductor layer 13 may be grown by a known nitride growth process such as organometallic vapor deposition, molecular beam growth, and hydride vapor deposition.

Next, as shown in FIG. 2C, the highly reflective ohmic contact layer 14 and the metal barrier layer 15 are sequentially formed on the p-type nitride semiconductor layer 13. The highly reflective ohmic contact layer 14 is generally made of Ag. In this case, the highly reflective ohmic contact layer 14 may be formed by a deposition method or a sputtering process, which is a conventional metal layer growth method. In addition, the metal barrier layer 15 may also be formed by a deposition method or a sputtering process.

In particular, the highly reflective ohmic contact layer 14 may be heat treated at a temperature of about 400 to 900 ° C. in order to improve ohmic contact characteristics. In addition, the metal barrier layer 25 is formed by a conventional deposition method or a sputtering process like other electrodes, and may be heat treated for several tens of seconds to several minutes at a temperature of about 300 ° C. in order to improve adhesion.

Subsequently, as shown in FIG. 2D, the conductive substrate 16 is formed on the metal barrier layer 15. The conductive substrate 16 is made of Si, Cu, Ni, Au, Ti, W, and the like. In the case of a metal, plating, vapor deposition, sputtering, or the like may be performed, but a plating process is preferable in terms of process efficiency. The plating process includes a known plating process used to form a metal layer, such as electroplating, non-plating, and deposition plating, and among these, it is preferable to use an electroplating method that requires a short plating time. However, the method of forming the conductive substrate in the present invention is not limited thereto, and the conductive substrate 16 may be bonded to the metal barrier layer 15 through wafer bonding.

Next, as shown in FIG. 2E, the laser lift-off process, that is, the laser beam L is irradiated to the lower surface of the sapphire substrate 20 to remove the sapphire substrate 20 from the light emitting structure. The laser beam L is not irradiated to the entire surface of the sapphire substrate 20, but is preferably irradiated a plurality of times aligned with each of the light emitting structures separated by the size of the final light emitting device formed on the sapphire substrate 20. . The step of removing the sapphire substrate 20 is most preferably a laser lift-off process as in the present embodiment, but the present invention is not limited thereto and may be separated through other mechanical or chemical processes.

Lastly, although not shown, an electrode portion 17a is formed on a first surface of the light emitting structure, that is, on an area of the n-type nitride semiconductor layer 11, and a bonding electrode is formed on the bottom surface of the conductive substrate 16. 17b). In this case, the formation process of the electrode structure, metal thin film deposition using APCVD, LPCVD, PECVD, etc. may be used. The final light emitting device that has undergone the electrode forming process as described above has the structure shown in FIG.

It is intended that the invention not be limited by the foregoing embodiments and the accompanying drawings, but rather by the claims appended hereto. Accordingly, various forms of substitution, modification, and alteration may be made by those skilled in the art without departing from the technical spirit of the present invention described in the claims, which are also within the scope of the present invention. something to do.

As described above, according to the present invention, the operating voltage is lowered and the electrostatic breakdown voltage is improved without deterioration of crystallinity, thereby obtaining a vertical structure nitride semiconductor light emitting device having improved optical characteristics and reliability and a method of manufacturing the same. Can be.

Claims (23)

a light emitting structure comprising n-type and p-type nitride layers and an active layer formed therebetween; An electrode part formed in one region of an exposed surface of the n-type nitride layer in the light emitting structure; A highly reflective ohmic contact layer formed on the exposed surface of the p-type nitride layer in the light emitting structure; And A conductive substrate formed on the highly reflective ohmic contact layer, The n-type nitride layer includes a plurality of delta-doped films delta-doped with n-type impurities, the distance between adjacent delta-doped films of the plurality of delta-doped films is 180-220 kV, and the number of delta-doped films is 65-80. Vertical structure nitride semiconductor light emitting device characterized in that the individual. The method of claim 1, The vertical nitride semiconductor light emitting device of claim 1, further comprising a metal barrier layer formed between the highly reflective ohmic contact layer and the conductive substrate. The method of claim 2, The metal barrier layer is a vertical nitride semiconductor light emitting device, characterized in that made of tungsten (W) or tungsten-based alloy. delete The method of claim 1, The n-type impurity is a vertical structure nitride semiconductor light emitting device, characterized in that made of a material selected from the group consisting of Si, Ge, Se, Te and C. delete The method of claim 1, The n-type impurity concentration of the n-type nitride semiconductor layer is 3 × 10 ¹⁸ ~ 5 × 10 ¹⁸ / cm ³ , the concentration of the n-type impurity of the delta dope film is 7 × 10 ¹⁸ ~ 1 × 10 ¹⁹ / cm A vertical structure nitride semiconductor light emitting device. delete The method of claim 1, And the conductive substrate is made of a material selected from the group consisting of Si, Cu, Ni, Au, W and Ti. The method of claim 1, Vertical conductive nitride semiconductor light emitting device, characterized in that the thickness of the conductive substrate is 50 ~ 100㎛. The method of claim 1, The highly reflective ohmic contact layer includes at least one layer made of a material selected from the group consisting of Ag, Ni, Al, Rh, Pd, Ir, Ru, Mg, Zn, Pt, Au, and combinations thereof. Vertical structure nitride semiconductor light emitting device. Sequentially growing an n-type nitride layer, an active layer and a p-type nitride layer on the nitride single crystal growth preliminary substrate; Forming a highly reflective ohmic contact layer on the p-type nitride layer; Forming a conductive substrate on the highly reflective ohmic contact layer; Removing the preliminary substrate to expose the n-type nitride layer; And Forming an electrode part in a portion of the exposed region of the n-type nitride layer, In the growing of the n-type nitride layer, a plurality of delta-doped delta-doped films are formed, wherein a distance between the delta-doped films adjacent to each other among the plurality of delta-doped films is 180 to 220 Å, The manufacturing method of the vertical structure nitride semiconductor light emitting device, characterized in that the number is carried out so as to be 65 to 80. The method of claim 12, And forming a metal barrier layer on the highly reflective ohmic contact layer between the forming of the highly reflective ohmic contact layer and the forming of the conductive substrate. Manufacturing method. The method of claim 13, The metal barrier layer is made of tungsten (W) or a tungsten-based alloy, characterized in that the vertical nitride semiconductor light emitting device manufacturing method. delete The method of claim 12, The n-type impurity is a method of manufacturing a vertical nitride semiconductor light emitting device, characterized in that made of a material selected from the group consisting of Si, Ge, Se, Te and C. delete The method of claim 12, The concentration of n-type impurities in the n-type nitride semiconductor layer is 3 × 10 ¹⁸ to 5 × 10 ¹⁸ / cm ³ , and the concentration of n-type impurities in the delta-doped film is 7 × 10 ¹⁸ to 1 × 10 ¹⁹ / cm. A vertical structure nitride semiconductor light emitting device manufacturing method characterized in that. delete The method of claim 12, The conductive substrate is a method of manufacturing a vertical nitride semiconductor light emitting device, characterized in that made of a material selected from the group consisting of Si, Cu, Ni, Au, W and Ti. The method of claim 12, The forming of the conductive substrate may include manufacturing a vertical nitride semiconductor light emitting device according to claim 1, wherein the thickness of the conductive substrate is 50 to 100 μm. The method of claim 12, The forming of the highly reflective ohmic contact layer may include forming at least one layer of a material selected from the group consisting of Ag, Ni, Al, Rh, Pd, Ir, Ru, Mg, Zn, Pt, Au, and combinations thereof. A vertical structure nitride semiconductor light emitting device manufacturing method comprising the step of. The method of claim 12, The removing of the preliminary substrate may be performed by a laser lift-off process.

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