KR101360966B1

KR101360966B1 - Nitride semiconductor light emitting device and fabrication method of the same

Info

Publication number: KR101360966B1
Application number: KR1020070112841A
Authority: KR
Inventors: 서승범; 한상헌; 정명구
Original assignee: 삼성전자주식회사
Priority date: 2007-11-06
Filing date: 2007-11-06
Publication date: 2014-02-11
Also published as: KR20090046602A

Abstract

The present invention provides a substrate for growing a nitride single crystal, a lower nitride single crystal layer grown on the substrate, and a plurality of fine metal structures formed on an upper surface of the lower nitride single crystal layer and having a curved surface; And a light emitting laminate including a first conductivity type nitride semiconductor layer, an active layer, and a second conductivity type nitride semiconductor layer sequentially grown on the lower nitride single crystal.

Nitride single crystal, reflective layer, light emitting device (LED), aluminum (Al)

Description

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

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nitride semiconductor light emitting device, and more particularly to a nitride semiconductor light emitting device having improved light extraction efficiency by using a novel type of reflective structure.

The nitride semiconductor light emitting device is a light emitting device comprising a semiconductor single crystal having an Al _x In _y Ga _(1-xy) N composition formula, where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, and 0 ≦ x + y ≦ 1. It is attracting much attention because it can generate light in a wide wavelength band including short wavelength light such as blue or green light.

In general, the light efficiency of a nitride semiconductor light emitting device is determined by an internal quantum efficiedncy and a light extraction efficiency (also called an external quantum efficiency).

In terms of light extraction efficiency, nitride semiconductor light emitting devices have fundamental limitations. That is, since the semiconductor layer constituting the semiconductor light emitting device has a larger refractive index than the external atmosphere or the substrate, the critical angle that determines the range of incidence angles of light emission becomes small, and as a result, a large portion of the light generated from the active layer It is totally reflected and propagated in a substantially undesired direction or lost in the total reflection process, so the light extraction efficiency is low.

In order to solve such a problem, a technique of increasing the surface roughness or employing an uneven pattern and a technique of increasing the light extraction effect by applying a photonic crystal structure have been actively used.

In addition, the light generated by the recombination of electrons and holes from the active layer proceeds in all directions. As such, the light directed to the undesired surface accounts for 20-30% of the total generated light. In order to prevent light loss and improve light efficiency, the semiconductor light emitting device may employ a highly reflective metal layer for extracting light in a desired direction.

However, the conventional light extraction efficiency improvement method described above has an disadvantage that it is difficult to be applied in-situ since an etching process and an additional metal film deposition technique are applied and implemented. That is, since the process must be performed outside the chamber separately from the growth process of the nitride thin film structure, the process itself is troublesome.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems of the prior art, and an object thereof is to provide a nitride semiconductor light emitting device having a new type of reflective structure that can be formed in a chamber during or after a thin film growth process.

Another object of the present invention is to provide a method of manufacturing a nitride semiconductor light emitting device having the above-described reflective structure of the new type.

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

A plurality of fine metal structures formed of a metal material having a substrate for nitride single crystal growth, a lower nitride single crystal layer grown on the substrate, and an upper surface of the lower nitride single crystal layer and having a curved surface; And a light emitting laminate including a first conductivity type nitride semiconductor layer, an active layer, and a second conductivity type nitride semiconductor layer sequentially grown on the lower nitride single crystal.

Preferably, the plurality of fine metal structures may have a nitrided surface.

In addition, the plurality of fine metal structures are preferably Al, which may be formed from a source gas such as trimethlyaluminum (TMAl), which has high reflectivity and can be used in the nitride growth process.

These fine metal structures may be formed to have hemispherical shapes, respectively. Although not limited thereto, the planar diameter of each fine metal structure may range from 10 nm to 500 nm.

In certain embodiments, the lower nitride single crystal layer can be an undoped nitride single crystal layer. In addition, in order to prevent deterioration of crystallinity due to the fine metal structure, the first conductivity type nitride semiconductor layer preferably has a thickness in the range of 1.5 μm to 3 μm larger than the thickness normally used.

The present invention also provides a method for manufacturing a nitride semiconductor light emitting device. The fabrication step may include preparing a substrate for nitride single crystal growth, growing a lower nitride single crystal layer on the substrate, and forming a plurality of fine metals on the upper surface of the lower nitride single crystal layer to be curved. Forming a structure, and forming a light emitting stack by sequentially growing a first conductivity type nitride semiconductor layer, an active layer, and a second conductivity type nitride semiconductor layer on the lower nitride single crystal.

Preferably, the method may further include nitriding a surface of the plurality of fine metal structures between the forming of the plurality of fine metal structures and the forming of the light emitting stack.

In the forming of the plurality of fine metal structures, it is preferable to grow at a high temperature so as not to spread from the surface of the nitride single crystal layer. The formation temperature of the fine metal structure may be the same temperature as the growth temperature of the lower nitride single crystal layer or the lower nitride single crystal layer.

The present invention may be easily applied to nitride semiconductor light emitting devices having other structures. That is, in another aspect, the present invention includes a light emitting stack having at least first and second conductivity type nitride semiconductor layers and an active layer formed therebetween, wherein the light emitting stack is intended to emit light based on the active layer. It provides a nitride semiconductor light emitting device comprising a plurality of fine metal structures formed on the same plane of the laminate region on the opposite side of the surface, the outer surface of the plurality of fine metal structures form a curved surface, and is nitrided .

According to the present invention, a reflection structure for reflecting light generated from the active layer in a desired direction to improve the effective light extraction efficiency is provided during or after the nitride growth process using a source gas that can be used in a nitride growth process such as TMAl. Through a more simplified in-situ process can provide a nitride semiconductor light emitting device having excellent luminous efficiency.

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

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

Referring to FIG. 1, the nitride semiconductor light emitting device 10 includes a sapphire substrate 11 having a buffer layer 12 for nitride single crystal growth and a lower nitride single crystal layer 13 formed on the sapphire substrate 11. do.

Here, the sapphire substrate 11 may be replaced with another nitride single crystal growth substrate such as SiC. The lower nitride single crystal layer 13 may be an undoped layer as a layer introduced to improve crystallinity of a nitride light emitting stack to be subsequently grown, but is not limited thereto.

Further, an n-type nitride semiconductor layer 16, an active layer 17, and a p-type nitride semiconductor layer 18 are included on the upper surface of the lower nitride single crystal on which a plurality of fine metal structures having curved surfaces are formed. The nitride semiconductor light emitting element 10 has an n-side electrode 19a and a p-side electrode 19b formed to be connected to the n-type nitride semiconductor layer 16 and the p-type nitride semiconductor layer 18, respectively.

The fine metal structure 15 employed in the present invention has a curved surface and may be formed of a highly reflective metal. Such highly reflective metal may preferably be aluminum (Al). Al may be formed from a source gas such as trimethylaluminum (TMAl) used in nitride single crystal growth processes (e.g., MOCVD processes).

The fine metal structure 15 employed in the present embodiment is a new type of reflective structure made of a highly reflective metal. The fine metal structure 15 may improve light efficiency by reflecting light directed toward the bottom surface toward the desired light emission direction.

In particular, the fine metal structure 15 is located inside the semiconductor light emitting device 10 and has a curved reflective surface, thereby effectively extracting light that can be trapped inside the device 10 through the diffuse reflection inside. You can also expect the effect.

It can be understood that the plurality of fine metal structures 15 each have a shape such as a droplet. That is, it can be formed into a structure having a nearly hemispherical shape having a curved surface by providing a condition having low wettability to form a predetermined contact angle. Although not limited thereto, the planar diameter of each fine metal structure 15 may range from 10 nm to 500 nm.

Preferably, as shown in Fig. 1, by applying a nitriding treatment to the surface, the nitride film N can be formed to maintain its shape in a subsequent growth process. This nitride film N can be obtained by supplying a nitrogen source gas. However, the nitriding treatment step is preferably carried out for a short time so as not to cause loss of the reflective structure due to excessive formation of the nitride film N such as AlN (that is, AlN formation of the Al droplet itself).

As such, the nitride single crystal layer 13 is exposed between the plurality of fine metal structures 15, and the n-type nitride semiconductor layer 16 may be further grown based on the exposed surface.

The fine metal structure 15 employed in the present embodiment has a great advantage in that the forming process can be made in an in-situ process. That is, the fine metal bath 15 uses the source gas used in the nitride growth process such as MOCVD as described above, while the conditions having the curved drooplet shape are obtained under similar growth conditions (especially growth temperature). Since it can be made, it is possible to easily form the desired reflective structure without the addition or additional modification of a separate process.

Advantages associated with the process of forming such a fine metal structure will be described in more detail with reference to FIG. 3.

The new type of fine metal structure employed in the above-described embodiment can be advantageously applied to nitride semiconductor light emitting devices having various other structures. 2A and 2B are side cross-sectional views showing nitride semiconductor light emitting devices according to various application examples of the present invention, respectively.

In the nitride semiconductor light emitting device 20 shown in FIG. 2A, similar to FIG. 1, an n-type nitride semiconductor sequentially formed on the sapphire substrate 21 and the sapphire substrate 21 on which the buffer layer 22 for nitride single crystal growth is formed. A layer 26, an active layer 27, and a p-type nitride semiconductor layer 28 are included. The nitride semiconductor light emitting device 20 has an n-side electrode 29a and a p-side electrode 29b formed to be connected to the n-type nitride semiconductor layer 26 and the p-type nitride semiconductor layer 28, respectively.

The nitride semiconductor light emitting device 20 shown in FIG. 2A has a flip chip structure to emit light to the lower surface of the substrate 21 as opposed to the embodiment of FIG. 1. In this case, the plurality of fine metal structures 25 may be provided on the p-type nitride semiconductor layer. Except that the fine metal structure (15 of FIG. 1) is provided on the upper surface of the p-type nitride semiconductor layer 28, the description related to the fine metal structure 25 described above can be referred to. That is, the fine metal structure 25 employed in the present embodiment can also be formed by an in situ process.

The nitride semiconductor light emitting device 30 shown in FIG. 2B has an n-type nitride semiconductor layer sequentially formed on the n-type GaN substrate 31 and the n-type GaN substrate 31 on which the buffer layer 32 for nitride single crystal growth is formed. 36), an active layer 37 and a p-type nitride semiconductor layer 38. The nitride semiconductor light emitting device 30 is vertical having an n-side electrode 39a and a p-side electrode 39b formed on the bottom surface of the n-type GaN substrate 31 and the top surface of the p-type nitride semiconductor layer 38, respectively. Structure.

In this embodiment, it can be understood as a structure which emits light to the upper surface of the nitride semiconductor light emitting element 30. That is, the micro reflective structure 35 is located under the active layer. In particular, as in the present embodiment, it can be introduced during the growth of the n-type nitride semiconductor layer 36. 2B shows a fine metal structure 35 on the n-type lower nitride semiconductor layer 36a as a resultant device structure, and an n-type upper nitride semiconductor layer 36b is formed on the upper surface thereof.

Even in this case, the plurality of fine metal structures 35 can be provided on the p-type nitride semiconductor layer. Reference may be made to the description relating to the above-described fine metal structure 15 (FIG. 1). That is, the fine metal structure 35 employed in the present embodiment can also be formed by an in situ process.

As such, the present invention may be easily applied to nitride semiconductor light emitting devices having other structures. That is, the present invention includes a light emitting stack having at least first and second conductivity type nitride semiconductor layers and an active layer formed therebetween, wherein the light emitting stack is opposite to a surface to which light is to be emitted based on the active layer. Comprising a plurality of fine metal structures formed on the same plane of the laminate region, the outer surface of the plurality of fine metal structures to form a curved surface, it can provide a nitrided nitride semiconductor light emitting device.

3A to 3D are cross-sectional views for each process for explaining the method for manufacturing the nitride semiconductor light emitting device according to the present invention, respectively. This process can be understood as a method of manufacturing a nitride semiconductor light emitting device similar to the structure shown in FIG.

As shown in Fig. 3A, after the nitride single crystal growth substrate 51 is provided, the lower nitride single crystal layer 53 is grown on the substrate 51.

The nitride single crystal growth substrate 51 is mainly a sapphire substrate, but may be another nitride single crystal growth substrate such as SiC and GaN. In addition, as shown in the illustrated embodiment, the buffer layer 52 may be further formed on the substrate as the nitride single crystal nucleus growth layer before the lower nitride single crystal layer 53 is grown. The lower nitride single crystal layer 53 may be an undoped layer.

As shown in FIG. 3B, a plurality of fine metal structures 55 made of a metal material are formed on the upper surface of the lower nitride single crystal layer 52 such that the surface thereof is curved.

The process may utilize additional other metal source gases. Specifically, the MOCVD process may be obtained by stopping ammonia (NH ₃ ) supply and supplying a TMAl source to pre-seeding Al.

In this process, in order to obtain a microstructure 55 having a curved surface by using a metal on the surface of the nitride single crystal layer 53, wetting of the Al single nitride crystal surface must be lowered. To this end, it is necessary to provide a metal source under high temperature conditions. In low temperature, metal such as Al generally spreads on the surface due to the low contact angle, but when grown at high temperature, the kinetic energy of metal element such as Al increases on the surface of nitride single crystal 53 and moves on the surface to form a drooplet-like structure. To be provided as a plurality of microstructures 55 having a curved surface.

Preferably, the temperature for forming the fine metal structure 55 having a desired shape may be at least 900 ° C or more. Advantageously, this temperature is very similar to the growth temperature of the lower nitride single crystal layer 53 or the growth temperature of the n-type nitride semiconductor layer (56 in FIG. 3D) to be subsequently grown, so that it can be easily realized during growth. Specifically, the temperature for forming the fine metal structure 55 is the same as the growth temperature of the lower nitride single crystal layer 53 or the growth temperature of the n-type nitride semiconductor layer 56 to be subsequently grown, or the temperature is different. In that case it may be a temperature in the range between.

Next, as shown in FIG. 3C, after forming a plurality of fine metal structures 55 having a droplet shape, a nitride film N is formed on the surface of the fine metal structure 53 by nitriding. Can be formed to maintain its shape and facilitate the subsequent growth process.

The nitriding treatment process can be performed by stopping a metal source gas such as Al and supplying a nitrogen source such as NH ₃ .

For example, when the fine metal structure 55 is Al, the coating N may be AlN. If the AlN is too large, the reflection effect due to the fine metal structure cannot be expected to be high, and in view of this, it is preferable to perform the nitriding treatment process for a short time so as to form a thin film. Depending on the flow rate of the nitrogen source, it may be performed in the range of about 1 to about 30 seconds to prevent excessive film formation.

Finally, as shown in FIG. 3D, the n-type nitride semiconductor layer 56, the active layer 57, and the p-type nitride semiconductor layer 58 are sequentially grown on the lower nitride single crystal layer 53. In addition, the n-side electrode 59a and the p-side electrode 59b formed to be connected to the partial region of the n-type nitride semiconductor layer 56 exposed through mesa etching and the p-type nitride semiconductor layer 58 are formed, respectively. do.

Here, in order to prevent the lowering of the crystallinity of the light emitting laminate to be subsequently grown due to the fine metal structure 55, the n-type nitride semiconductor layer 56 is preferably grown to be about 1 μm thicker than the normal thickness. That is, the thickness t of the n-type nitride semiconductor layer 56 is preferably 1.5 µm to 3 µm.

As described above, the process may be continuously performed with the lower nitride single crystal layer growth process and the fine metal structure. Therefore, since the temperature in the chamber is controlled in a nearly similar range over the entire process, it is possible to prevent the process time delay due to the ramping time. The process of forming the fine metal structure is performed in situ, thereby simplifying the overall process.

The present invention is not limited by the above-described embodiments and the accompanying drawings, but is defined by the appended claims. It will be apparent to those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined in the appended claims, As will be described below.

2A and 2B are side cross-sectional views showing nitride semiconductor light emitting devices according to various application examples of the present invention, respectively.

3A to 3D are cross-sectional views for each process for explaining the method for manufacturing the nitride semiconductor light emitting device according to the present invention, respectively.

Claims

Nitride single crystal growth substrate;

A lower nitride single crystal layer grown on the substrate;

A plurality of fine metal structures formed on an upper surface of the lower nitride single crystal layer and having a curved surface and made of a metal material; And

And a light emitting laminate having a first conductivity type nitride semiconductor layer, an active layer, and a second conductivity type nitride semiconductor layer sequentially grown on the lower nitride single crystal.

The method of claim 1,

The plurality of fine metal structures are nitride semiconductor light emitting device, characterized in that having a nitrided surface.

The method of claim 1,

The plurality of fine metal structures are nitride semiconductor light emitting device, characterized in that made of Al.

The method of claim 1,

The plurality of fine metal structures are nitride semiconductor light emitting device, characterized in that having a hemispherical shape.

The method of claim 1,

A nitride semiconductor light emitting element, characterized in that the planar diameter of each of the fine metal structures is 10 nm to 500 nm.

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The method of claim 1,

The first conductive nitride semiconductor layer is a nitride semiconductor light emitting device, characterized in that 1.5㎛ 3㎛.

Preparing a substrate for nitride single crystal growth;

Growing a lower nitride single crystal layer on the substrate;

Forming a plurality of fine metal structures made of a metal material on the upper surface of the lower nitride single crystal layer such that a surface thereof is curved; And

And forming a light emitting stack by sequentially growing a first conductivity type nitride semiconductor layer, an active layer, and a second conductivity type nitride semiconductor layer on the lower nitride single crystal.

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9. The method of claim 8,

The plurality of fine metal structures are made of Al,

Forming the plurality of fine metal structures,

And supplying an Al source gas at a temperature of 900 ° C. or higher to form a fine metal structure having a curved surface.

12. The method of claim 11,

The fine metal structure is a nitride semiconductor light emitting device manufacturing method, characterized in that formed in the temperature range between the growth temperature of the lower nitride single crystal layer and the growth temperature of the first conductivity type nitride semiconductor layer.

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A light emitting laminate having at least first and second conductivity type nitride semiconductor layers and an active layer formed therebetween,

The light emitting stack includes a plurality of fine metal structures formed on the same plane of the stack area on the opposite side of the plane from which light is to be emitted based on the active layer.

The outer surface of the plurality of fine metal structures form a curved surface, the nitride semiconductor light emitting device, characterized in that the nitrided.