KR20070047047A - Nitride semiconductor light emitting device and method of of manufacturing the same - Google Patents

Abstract

The present invention relates to a nitride semiconductor light emitting device, comprising: a substrate for nitride single crystal growth, an n-type nitride semiconductor layer formed on the substrate, an active layer formed on the n-type nitride semiconductor layer, and a p-type formed on the active layer A nitride semiconductor layer and an ohmic contact layer formed on said p-type nitride semiconductor layer, distributed over said p-type nitride semiconductor layer, and having a single crystal such that a contact resistance with said ohmic contact layer is 10 ⁻² Pa · cm 2 or more. A nitride semiconductor light emitting device is provided which has a large number of damaged Schottky junction regions.

According to the present invention, the current crowding phenomenon is alleviated, a high reliability flip chip nitride semiconductor light emitting device having a lower forward voltage and a high luminous efficiency can be expected.

Flip-chip, nitride semiconductor light emitting diode, current crowding

Description

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

1A and 1B are side cross-sectional and top plan views showing a conventional nitride light emitting device.

2A to 2D are cross-sectional views illustrating a method of manufacturing the nitride light emitting device according to the present invention, respectively.

3 is a top plan view of the nitride light emitting device of FIG. 2D.

Fig. 4A is a side sectional view showing a flip chip light emitting device according to another embodiment of the present invention.

4B is a side sectional view showing a flip chip light emitting device employing the nitride light emitting device shown in FIG. 4A.

<Code Description of Main Parts of Drawing>

30: nitride light emitting element 31: sapphire substrate

32: n-type nitride semiconductor layer 33: active layer

34: p-type nitride semiconductor layer 35: Schottky junction region

37: ohmic contact layer 39a: n-side electrode

39b: p-side electrode

The present invention relates to a nitride semiconductor light emitting device, and more particularly to a nitride semiconductor light emitting device having excellent electrical characteristics and excellent brightness.

Recently, a nitride semiconductor light emitting device is a light emitting device for obtaining light in a blue or green wavelength band, and has an Al _x In _y Ga _(1-xy) N composition formula (where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1).

The nitride semiconductor crystal is grown on a nitride single crystal growth substrate such as a sapphire substrate in consideration of lattice matching. Since the sapphire substrate is an electrically insulating substrate, the final nitride semiconductor light emitting device has a structure in which the p-side electrode and the n-side electrode are formed on the same surface. Therefore, the current flow between the electrodes is formed laterally, there is a problem that the current is not uniformly distributed as a whole, and concentrated in the area therebetween.

In order to solve this problem of current concentration, in Korean Patent Publication No. 2005-76140 filed by the present applicant (published: July 26, 2005, the invention name: nitride semiconductor light emitting device for flip chip), the ohmic contact layer is formed in a mesh form By doing so, a method of distributing current more uniformly over the entire area was proposed. 1A and 1B are a side sectional view and a top plan view of a nitride light emitting device according to the above document.

Referring to FIG. 1A, the nitride semiconductor light emitting device 10 for flip chip includes a nitride semiconductor growth substrate 11 such as a sapphire substrate, an n-type nitride semiconductor layer 12, an active layer 13 and sequentially stacked on the upper surface thereof. The p-type nitride semiconductor layer 14 is included.

The n-side electrode 19a of the nitride semiconductor light emitting device 10 is formed on the upper surface of the n-type nitride semiconductor layer 12 exposed through mesa etching. The p-side electrode structure employed in the nitride semiconductor light emitting device 10 includes a highly reflective ohmic contact layer 15, a metal barrier layer 16, and a p-side bonding electrode 19b.

Here, the highly reflective ohmic contact layer 15 is formed on the p-type nitride semiconductor layer 14, and has a mesh structure having a plurality of open regions so that the p-type nitride semiconductor layer 14 is partially exposed. . Therefore, the current traveling along the highly reflective ohmic contact layer 15 having a low specific resistance has a long path (for example, an arrow of FIG. 1B) to reach the n-side electrode 19a, and thus, as shown in FIG. 2A. Likewise, the specific gravity of the current directly directed to the p-type nitride semiconductor layer 14 may be relatively increased.

However, this method of changing the electrode structure is cumbersome, involving a complicated electrode patterning process. In particular, when such a semiconductor light emitting device is employed in a flip chip structure, it is difficult to obtain a sufficient reflection effect as a mesh structure, and thus there is a problem that an additional reflective layer is required.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and an object thereof is to form a nitride semiconductor forming a Schottky junction region distributed in the p-type nitride semiconductor layer itself so that current crowding phenomenon is alleviated without changing the p-side electrode structure. It is to provide a light emitting device.

Another object of the present invention is to provide a method of manufacturing the nitride semiconductor light emitting device.

In order to achieve the above technical problem, the present invention,

A substrate for nitride single crystal growth, an n-type nitride semiconductor layer formed on the substrate, an active layer formed on the n-type nitride semiconductor layer, a p-type nitride semiconductor layer formed on the active layer, and the p-type nitride semiconductor layer An ohmic contact layer formed on the p-type nitride semiconductor layer and having a plurality of Schottky junction regions where the single crystal is damaged so that the contact resistance with the ohmic contact layer is 10 ⁻² Pa · cm 2 or more. A nitride semiconductor light emitting device is provided.

Preferably, an upper surface region, that is, an ohmic junction region of the p-type nitride semiconductor layer except for the plurality of Schottky junction regions may be a mesh or stripe.

Preferably, the thickness of the plurality of Schottky junction regions is smaller than the thickness of the p-type nitride semiconductor layer. The area in which the plurality of Schottky junction regions are formed is preferably 10 to 50% of the upper surface area of the p-type nitride semiconductor.

The ohmic contact layer may be formed of a material having a light transmittance, and in order to implement the flip chip form, the ohmic contact layer may be a highly reflective ohmic contact layer. The highly reflective ohmic contact layer may be at least one layer made of a material selected from the group consisting of Ag, Ni, Al, Ph, Pd, Ir, Ru, Mg, Zn, Pt, Au, and combinations thereof.

The present invention provides a method for manufacturing a nitride semiconductor light emitting device. The manufacturing method includes the steps of providing a substrate for nitride single crystal growth, sequentially forming an n-type nitride semiconductor layer, an active layer and a p-type nitride semiconductor layer on the substrate, and on the p-type nitride semiconductor layer Selectively plasma-processing the upper surface of the p-type nitride semiconductor layer to form a plurality of distributed Schottky junction regions with damaged single crystals, having a plurality of Schottky junction regions and a Schottky junction and an ohmic junction with other regions Forming an ohmic contact layer on the p-type nitride semiconductor layer using a material. Here, the ohmic contact layer has a contact resistance of the plurality of Schottky junction regions of 10 ⁻² Pa · cm 2 or more.

Preferably, the plasma treatment may be performed using a plasma generated from an inert gas. Here, Ar, He, N ₂ , CF ₄ And H ₂ may be used as the inert gas.

Forming a mask having a plurality of open regions on the p-type nitride semiconductor layer, and plasma treating the single crystal of the upper surface region of the p-type nitride semiconductor layer exposed in the open region to be damaged. Here, the mask may be a mesh or stripe.

The main feature of the present invention is to form a large number of Schottky junction regions by selectively degrading the crystallinity through the plasma treatment on the p-type nitride semiconductor layer without modifying the p-type ohmic contact structure itself. The Schottky junction region employed in the present invention serves as a high resistance region, acting as an open region of the mesh type ohmic contact layer in the prior art. In the present invention, the Schottky junction region refers to a high resistance region which intentionally damaged crystallinity by plasma treatment.

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

2A to 2D are cross-sectional views for explaining one example of the method for manufacturing the nitride light emitting device according to the present invention.

First, in the method of manufacturing a nitride light emitting device according to the present invention, as shown in FIG. 2A, an n-type nitride semiconductor layer 32, an active layer 33, and a p-type nitride semiconductor layer are formed on a substrate 31 for nitride single crystal growth. Beginning step 34 to form sequentially. The substrate 31 may be a sapphire substrate.

Subsequently, as shown in FIG. 2B, a mask M having a plurality of open regions is formed for selective plasma processing, and plasma processing is performed. The open area of the mask M defines a region where a Schottky junction region is to be formed. Preferably, the mask M may be implemented in a mesh shape or a stripe shape. For example, when the mask M is implemented in a mesh shape, the Schottky junction region is formed in a dot pattern while the ohmic contact region may be obtained in a mesh form. A suitable range for the total area of the open area for the Schottky junction region may vary depending on the pattern shape, but is preferably formed to point 10 to 50% of the upper surface area of the p-type nitride semiconductor layer 34. If less than 10% it is difficult to obtain a sufficient current distribution effect, if more than 50% may have a problem that the actual ohmic contact area is excessively reduced to increase the series resistance.

Plasma treatment used in the present process does not use reactive ions, unlike conventional dry etching using plasma, and forms plasma using an inert gas. For example, Ar, He, N ₂ , CF ₄ and H ₂ may be used as the inert gas.

Next, as shown in Fig. 2D, after forming a plurality of Schottky junction regions 35 by plasma processing, the mask M is removed. The Schottky junction region 35 employed in the present invention can be understood as a crystal damage region in which an N ₂ component is released from a GaN single crystal by plasma, and a void is formed in N sites. Such a Schottky junction region 35 greatly impairs crystallinity and exhibits high specific resistance. The depth of the region 35 may be controlled by the plasma treatment time and the plasma forming conditions (RF power, pressure, etc.), and the contact resistance of the ohmic contact layer to be formed in a subsequent process may be 10 ⁻² Pa · cm 2 or more. Satisfaction is as deep as possible. However, it is preferable not to exceed at least the thickness of the p-type nitride semiconductor layer 34 so as not to damage the active layer 33 region.

Finally, as shown in FIG. 2D, the ohmic contact layer 37 and the p-side bonding electrode 39b are formed on the p-type nitride semiconductor layer 34, and the n-side electrode ( A desired nitride semiconductor light emitting element is completed by forming 39a). Before the n-side electrode 39a is formed, a mesa etching process is performed to expose the upper surface region of the n-type nitride semiconductor layer 32. Further, the ohmic contact layer 37 has a schottky junction with the plurality of schottky junction regions 35 and is formed of a suitable material having an ohmic junction with another region. Fortunately, the Schottky junction region 35 whose crystal is damaged by the plasma has a high resistance, and therefore, a known conventional material can be used as the ohmic contact layer 37 material. In the present embodiment, the ohmic contact layer 37 may be a light transmissive ohmic contact layer. For example, it may be a heat treated Ni / Au bilayer, or alternatively, a transparent conductive oxide layer such as ITO may be used.

In the light emitting device shown in Fig. 2D, a current flow (indicated by an arrow) between the p-side electrode 39b and the n-side electrode 39a is a Schottky junction region 35 having a high contact resistance with the ohmic contact layer 37. Is hardly formed, and is formed along another portion of the p-type nitride semiconductor layer 34 which is not damaged, so that the current can be uniformly distributed as a whole.

3 is a top plan view illustrating the nitride semiconductor light emitting device of FIG. 2D, and the nitride semiconductor light emitting device illustrated in FIG. 3 may be understood to omit the ohmic contact layer for easier description.

The nitride semiconductor light emitting device 30 is obtained from a manufacturing process in which a mask is formed in a mesh shape in the process of FIG. 2B. In the region between the p-side and n-side electrodes 39a and 39b, a longer current path is formed by the Schottky junction region 35 having a higher contact resistance (see arrow), and a Schottky junction region 35 having a higher resistance. Due to the distribution of, more uniform current flow can be obtained over the entire area.

The nitride semiconductor light emitting device shown in FIGS. 2A to 2D illustrates a planar structure in which p-side and n-side electrodes are formed on surfaces of the same direction of the light-emitting device, but the present invention is not limited thereto. It can be usefully employed also in the formed vertical structure.

The present invention effectively disperses the current by forming a Schottky junction region having a constant pattern directly on the p-type nitride semiconductor layer, so that there is no need to change the electrode structure. Therefore, since the ohmic contact layer is formed in almost the entire area of the upper surface of the electrode structure without employing a mesh shape, the reflection effect by the highly reflective ohmic contact layer employed in the flip chip structure can be enhanced. This is explained in more detail in FIGS. 3A and 3B.

4A is a side cross-sectional view showing a nitride light emitting device 50 for flip chips according to another embodiment of the present invention.

As shown in FIG. 4A, the flip chip nitride semiconductor light emitting device 50 includes a nitride semiconductor growth substrate 51, such as a sapphire substrate, an n-type nitride semiconductor layer 52, an active layer 53, and sequentially stacked on an upper surface thereof. The p-type nitride semiconductor layer 54 is included.

A plurality of Schottky junction regions 55 are distributed on the upper surface of the p-type nitride semiconductor layer 54. The Schottky junction region 55 is a region of high resistance in which crystallinity is damaged by plasma and where current flow is suppressed. As described above, the schottky junction region 55 allows current to be uniformly distributed throughout.

In addition, the n-side electrode 59a of the nitride semiconductor light emitting device 50 is formed on the upper surface of the n-type nitride semiconductor layer 52 exposed through mesa etching, and the p-side employed in the nitride semiconductor light emitting device 50 is provided. The electrode structure includes a highly reflective ohmic contact layer 57, a metal barrier layer 58, and a bonding electrode 59b. The metal barrier layer 58 may have a structure formed to surround the top surface and the side surfaces of the highly reflective ohmic contact layer 57.

The highly reflective ohmic contact layer 57 preferably has a reflectance of 70% or more and forms an ohmic junction with the p-type nitride semiconductor layer 54 except for the Schottky junction region. The highly reflective ohmic contact layer 57 may be formed of at least one layer made of a material selected from the group consisting of Ag, Ni, Al, Ph, Pd, Ir, Ru, Mg, Zn, Pt, Au, and combinations thereof. have. Preferably, the highly reflective ohmic contact layer 57 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.

In this embodiment, since the highly reflective ohmic contact layer 57 can be formed in the entire upper surface region, a reflection effect can be expected in almost the entire upper surface of the p-type nitride semiconductor layer. Accordingly, the reflection effect can be expected on the entire upper surface while uniformly distributing the current through the Schottky junction region distributed on the p-type nitride semiconductor layer, so that the luminance can be greatly improved as compared with the conventional form (Fig. 1A). .

The metal barrier layer 58 prevents mixing of Au components at the interface between the p-side bonding electrode 59b and the highly reflective ohmic contact layer 57, and the elements of the highly reflective ohmic contact layer 57 move to leak. Function to prevent the generation of current. In particular, the present embodiment can be advantageously applied when using the highly reflective ohmic contact layer 57 containing Ag having high mobility.

FIG. 3B is a side sectional view showing the chip structure 60 on which the nitride light emitting device 50 of FIG. 3A is mounted.

As shown in FIG. 3B, the nitride semiconductor light emitting device 50 includes the lead patterns 62a and 62b through the conductive bumps 64a and 64b through the electrodes 69a and 69b on the support substrate 61. It can be mounted by fusing onto a phase. As described above, in the flip chip light emitting device 60, the sapphire substrate 51 of the light emitting device 50 is light-transmitting and thus used as a light emitting surface. In addition, as described above, the highly reflective ohmic contact layer 57 is formed in almost the entire area, thereby improving the reflection performance, and thus high luminance characteristics can be expected.

The above-described embodiments and the accompanying drawings are merely illustrative of preferred embodiments, and the present invention is intended to be limited by the appended claims. In addition, it will be apparent to those skilled in the art that the present invention may be substituted, modified, and changed in various forms without departing from the technical spirit of the present invention described in the claims.

As described above, according to the present invention, in the p-side electrode structure, a Schottky junction region is formed on the upper surface of the p-type nitride semiconductor layer, which is a high-resistance region where crystals are selectively damaged. As a result, the current concentrated in the portion adjacent to the n-side electrode can be reduced, and the luminance can be greatly improved by uniformly distributing the current in the entire area of the p-type nitride semiconductor layer.

Claims (17)

Substrates for nitride single crystal growth; An n-type nitride semiconductor layer formed on the substrate; An active layer formed on the n-type nitride semiconductor layer; A p-type nitride semiconductor layer formed on the active layer; And An ohmic contact layer formed on the p-type nitride semiconductor layer, And a plurality of Schottky junction regions distributed on the p-type nitride semiconductor layer and damaged by a single crystal such that the contact resistance with the ohmic contact layer is 10 ⁻² Pa · cm 2 or more. The method of claim 1, And a top surface region of the p-type nitride semiconductor layer except for the plurality of Schottky junction regions is a mesh or stripe. The method of claim 1, The thickness of the plurality of Schottky junction regions is smaller than the thickness of the p-type nitride semiconductor layer. The method of claim 1, The area in which the plurality of Schottky junction regions are formed is 10 to 50% of the upper surface area of the p-type nitride semiconductor. The method of claim 1, The ohmic contact layer is a nitride semiconductor light emitting device, characterized in that made of a material having a light transmittance The method of claim 1, The ohmic contact layer is a nitride semiconductor light emitting device, characterized in that the highly reflective ohmic contact layer. The method of claim 6, The highly reflective ohmic contact layer includes at least one layer made of a material selected from the group consisting of Ag, Ni, Al, Ph, Pd, Ir, Ru, Mg, Zn, Pt, Au, and combinations thereof. Nitride semiconductor light emitting device. Preparing a substrate for nitride single crystal growth; Sequentially forming an n-type nitride semiconductor layer, an active layer, and a p-type nitride semiconductor layer on the substrate; Selectively plasma treating an upper surface of the p-type nitride semiconductor layer to form a plurality of Schottky junction regions distributed on the p-type nitride semiconductor layer and damaged single crystals; And Forming an ohmic contact layer on the p-type nitride semiconductor layer using a material having a plurality of Schottky junction regions and a Schottky junction and having an ohmic junction with another region, And a contact resistance of the ohmic contact layer and the plurality of schottky junction regions is 10 ⁻² Pa · cm 2 or more. The method of claim 8, The plasma treatment is performed by using a plasma generated from an inert gas. The method of claim 9, The inert gas is Ar, He, N ₂ , CF ₄ And H ₂ characterized in that the nitride semiconductor light emitting device manufacturing method. The method of claim 8, Forming a mask having a plurality of open regions on the p-type nitride semiconductor layer, and plasma treating the single crystal of the upper surface region of the p-type nitride semiconductor layer exposed in the open region to be damaged. A nitride semiconductor light emitting device manufacturing method. The method of claim 11, The mask is a method of manufacturing a nitride semiconductor light emitting device, characterized in that the mesh or stripe. The method of claim 8, And a thickness of the plurality of Schottky junction regions is smaller than a thickness of the p-type nitride semiconductor layer. The method of claim 8, The area in which the plurality of Schottky junction regions are formed is 10 to 50% of the upper surface area of the p-type nitride semiconductor. The method of claim 8, The ohmic contact layer is a nitride semiconductor light emitting device manufacturing method, characterized in that made of a material having a light transmittance. The method of claim 8, The ohmic contact layer is a nitride semiconductor light emitting device manufacturing method, characterized in that the highly reflective ohmic contact layer. The method of claim 8, The highly reflective ohmic contact layer includes at least one layer made of a material selected from the group consisting of Ag, Ni, Al, Ph, Pd, Ir, Ru, Mg, Zn, Pt, Au, and combinations thereof. Nitride semiconductor light emitting device manufacturing method.

Images