KR100892740B1 - Light emitting device of a nitride compound semiconductor and the fabrication method thereof - Google Patents

Abstract

A light emitting device of a nitride compound semiconductor and a fabrication method thereof are provided to reduce the interface blank and the crystallization stress of the substrate and the semiconductor layer. A substrate is located inside a reaction chamber(S1). An InGaN buffer layer is formed on the upper part of substrate(S2). The InGaN buffer layer is formed by using a MOCVD(Metal Organic Chemical Vapor Deposition), a HVPE(Hydride Vapor Phase Epitaxial) or a MBE(Molecular Beam Epitaxial), a MOCVPE(Metal-Organic Chemical Vapor Phase Epitaxial) etc. The InGaN buffer layer has the content on In smaller than the active layer. The u- GaN(undoped-GaN) layer is formed on the top of the InGaN buffer layer(S3). The semiconductor layer of the GaN series having P-N junction is formed in the u-GaN layer(S4). The compound semiconductor layer consisting of the first conductivity type semiconductor layer, the active layer, and the second electrical conduction semiconductor layer is formed(S4). An emitting device is manufactured by forming electrodes on the first conductivity type semiconductor layer and the second electrical conduction semiconductor layer(S5).

Description

LIGHT EMITTING DEVICE OF A NITRIDE COMPOUND SEMICONDUCTOR AND THE FABRICATION METHOD THEREOF

The present invention relates to a nitride semiconductor light emitting device and a method for manufacturing the same. More particularly, the lattice constant and thermal expansion of a substrate and a semiconductor layer are realized by implementing a buffer layer interposed between the substrate and the semiconductor layer as an InGaN buffer layer having an IN content of 5 atomic% or less. The present invention relates to a nitride semiconductor light emitting device for reducing the occurrence of cracks or the like due to a difference in coefficient and a method of manufacturing the same.

In general, nitrides of Group III elements, such as gallium nitride (GaN) and aluminum nitride (AlN), have excellent thermal stability and have a direct transition energy band structure. As a lot of attention. In particular, blue and green light emitting devices using gallium nitride (GaN) have been used in various applications such as large-scale color flat panel display devices, traffic lights, indoor lighting, high density light sources, high resolution output systems, and optical communications.

The nitride semiconductor layer of the group III element has a metal organic chemical vapor deposition (MOCVD) or a molecular beam epitaxy (MBE) on a heterogeneous substrate such as sapphire or silicon carbide (SiC) having a hexagonal structure. Is grown through the process. However, when a nitride semiconductor layer of a group III element is formed on a dissimilar substrate, cracks or warpage occur in the semiconductor layer due to a difference in lattice constant and thermal expansion coefficient between the semiconductor layer and the substrate, and a potential (dislocation) is generated. Cracks, distortions and dislocations in the semiconductor layer deteriorate the characteristics of the light emitting device. Therefore, a buffer layer is generally used to relieve stress due to the lattice constant and thermal expansion coefficient difference between the substrate and the semiconductor layer.

According to the prior art, by forming a buffer layer between the semiconductor layer and the substrate, it is possible to reduce the occurrence of cracks due to the difference in lattice constant and thermal expansion coefficient between the substrate and the semiconductor layer.

However, the buffer layer grown at low temperature mainly grows perpendicularly to the substrate and thus has a columnar structure. On the other hand, the semiconductor layer is affected by the crystal structure, crystalline and column size distribution of the buffer layer located below. That is, crystal defects of the buffer layer are transferred to the semiconductor layer on the buffer layer. Therefore, crystal defects in accordance with the columnar structure of the buffer layer appear as crystal defects in the semiconductor layer.

SUMMARY OF THE INVENTION An object of the present invention is to provide a nitride semiconductor light emitting device comprising a buffer layer capable of reducing crystal defects of a semiconductor layer grown thereon when a buffer layer is formed between a substrate and a semiconductor layer to fabricate a nitride semiconductor light emitting device. It is to provide an element and a method of manufacturing the same.

In order to accomplish these problems, according to an aspect of the present invention, there is provided a method of preparing a substrate, forming an InGaN buffer layer on the substrate, and forming a first conductive semiconductor layer, an active layer, and a second conductive type on the InGaN buffer layer. Forming a GaN-based semiconductor layer having a semiconductor layer, the In content of the InGaN buffer layer provides a method for manufacturing a nitride semiconductor light emitting device, characterized in that less than the In content of the active layer and greater than zero.

Preferably, the InGaN buffer layer has an In content of 2 to 3 atomic%.

Preferably, the forming of the InGaN buffer layer, InGaN buffer layer is formed in a multi-layer on the substrate, each layer of the InGaN buffer layer is reduced in the content of In closer to the first conductive semiconductor layer from the substrate Has characteristics.

According to another aspect of the present invention, there is provided a substrate, an InGaN buffer layer formed on the substrate, and a GaN-based semiconductor layer having a first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer on the InGaN buffer layer. The In content of the buffer layer is smaller than the In content of the active layer and provides a nitride semiconductor light emitting device, characterized in that greater than zero.

Preferably, the InGaN buffer layer has an In content of 2 to 3 atomic%.

Preferably, the InGaN buffer layer includes InGaN buffer layers formed in multiple layers on the substrate, wherein each layer of the InGaN buffer layers is characterized in that the content of In decreases as it approaches the first conductive semiconductor layer from the substrate. .

The nitride semiconductor light emitting device may further include an undoped GaN layer formed between the GaN buffer layer and a GaN based semiconductor layer having the P-N junction.

According to an embodiment of the present invention, in the intervening buffer layer between the substrate and the semiconductor layer, the buffer layer is embodied as an InGaN buffer layer smaller than the In content of the active layer, for example, having an In content of greater than 0 and less than 5 atomic%. By reducing the interfacial gap and crystal stress between the semiconductor layer and the semiconductor layer, it is possible to effectively reduce the occurrence of cracks due to the difference in lattice constant and thermal expansion coefficient between the substrate and the semiconductor layer.

In addition, the semiconductor layer is influenced by the crystal structure, crystalline and column size distribution of the buffer layer disposed below. That is, crystal defects of the buffer layer are transferred to the semiconductor layer on the buffer layer. According to the exemplary embodiment of the present invention, as the crystal defects of the buffer layer are reduced, the crystal defects of the semiconductor layer are also reduced, thereby improving the light yield of the nitride light emitting device.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are provided as examples to ensure that the spirit of the invention to those skilled in the art can fully convey.

Accordingly, the present invention is not limited to the embodiments described below and may be embodied in other forms. In the drawings, widths, lengths, thicknesses, and the like of components may be exaggerated for convenience. Like numbers refer to like elements throughout.

1 is a process flowchart illustrating a method of forming a nitride semiconductor light emitting device according to an embodiment of the present invention, Figure 2 is a cross-sectional view for explaining a method for manufacturing a light emitting device according to an embodiment of the present invention. .

1 and 2, the substrate 100 is prepared and placed in the reaction chamber (S1). The substrate 100 has a lattice constant similar to that of the nitride semiconductor layer to be formed thereon. The substrate 100 may be a sapphire, spinel, Si substrate, SiC substrate, ZnO substrate, GaAs substrate, GaN substrate, or the like.

An InGaN buffer layer 200 is formed on the substrate 100 (S2).

The InGaN buffer layer 200 may be formed of metal organic chemical vapor deposition (MOCVD), hydride vapor phase epitaxy (HVPE) or molecular beam growth (MBE), metal organic chemical vapor deposition. It can be formed using a growth method (metalorganic chemical vapor phase epitaxy, MOCVPE) and the like. In this case, the InGaN buffer layer 200 may have an In content smaller than the In content of the active layer 420, for example, 5 atomic% or less, and optimally have an In content of 2 to 3 atomic%.

The InGaN buffer layer 200 may be grown using any one of the above-described crystal growth methods at a pressure of about 10 torr to about 780 torr at 400 ° C to 500 ° C.

The source gas for forming the InGaN buffer layer 200 uses trimethyl indium (TMI, In (CH ₃ ) ₃ ), gallium, trimethylgallium (TMG), and / or triethyl gallium (TEG). Ammonia (NH ₃ ) is used as the reaction gas. These source gases and reactants are introduced into the reaction chamber, and an InGaN buffer layer 200 having an In content of 5 atomic% or less is formed at 400 to 500 ° C.

Thereafter, for example, a u-GaN (undoped-GaN) layer 300 is formed on the InGaN buffer layer 200 having an In content of 5 atomic percent or less (S3). The In content of the InGaN buffer layer 200 is set smaller than the In content of the active layer 420 and greater than zero in consideration of the In content of the active layer 420.

The u-GaN 300 is to enable the GaN-based semiconductor layer 400 formed of GaN-based material to be formed thereon with high quality, and may be selectively adopted.

After forming the u-GaN layer 300, the temperature of the reaction chamber is 900-1200 ° C., and the GaN-based semiconductor layer 400 having a PN junction on the u-GaN layer 300 is formed by using a MOCVD or MBE process. To form (S4).

A compound semiconductor layer 400 including the first conductive semiconductor layer 410, the active layer 420, and the second conductive semiconductor layer 430 is sequentially formed (S4).

The first conductive semiconductor layer 410 may be a GaN-based implanted N-type impurity, for example, an N-type Al _x In _y Ga _1-xy N (0 <x, y, x + y <1) film, but is not limited thereto. Can be formed of various semiconductor layers. In addition, the second conductivity-type semiconductor layer 143 may be a GaN series, for example, a P-type Al _x In _y Ga _{1- xy} N (0 <x, y, x + y <1) film, into which a P-type impurities are injected. However, the present invention is not limited thereto and may be formed of various semiconductor layers.

The first conductivity-type semiconductor layer 141 and the second conductivity-type semiconductor layer 160 may be formed of an In _x Ga _{1- x} N (0 <x <1) film or Al _x Ga _{1- x} N (0 <x <1). It may be a film.

The first conductivity type semiconductor layer 141 may be formed by doping silicon (Si), and the second conductivity type semiconductor layer 143 may be formed by doping zinc (Zn) or magnesium (Mg). have.

The active layer 142 is an area where electrons and holes are recombined, and includes InGaN. The content of In in the active layer 142 may be 10 to 20 atomic%. The emission wavelength emitted from the light emitting cell may be determined according to the type of material constituting the active layer 142. The active layer 142 may be a multilayer film in which a quantum well layer and a barrier layer are repeatedly formed. The barrier layer and the well layer may be binary to quaternary compound semiconductor layers represented by general formula Al _x In _y Ga _1-xy N (0 ≦ x, y, x + y <1).

Thereafter, electrodes are formed on the first conductive semiconductor layer 410 and the second conductive semiconductor layer 430 to manufacture a light emitting device (S5).

3 is a graph showing crystallinity of a semiconductor layer formed according to an embodiment of the present invention and a semiconductor layer formed according to a comparative example. In the graph, one embodiment of the present invention uses an InGaN buffer layer having an In content of 5 atomic% or less, and a comparative example uses an AlN buffer layer.

In order to show the crystallinity improvement of the semiconductor layer according to an embodiment of the present invention, a semiconductor layer formed using an InGaN buffer layer having an In content of 5 atomic% or less according to one embodiment of the present invention, and an AlN buffer layer according to a comparative example The degree of crystal distortion was measured for the semiconductor layer formed by using X-ray.

Referring to FIG. 3, the FWHM-Full Width Half Maximum, which is a measure of crystallinity, is displayed on the Y axis in order to compare the crystallinity of semiconductor layers according to an embodiment of the present invention and a comparative example. The full width at half maximum indicates crystallinity, and the smaller the value is, the smaller the defects are and the better the crystallinity is. In the graph, 002 and 201 indicate crystal directions. The X axis represents the content of In.

As described through the graph, the semiconductor layer formed using the InGaN buffer layer having an In content of 5 atomic% or less according to an embodiment of the present invention can be confirmed that the crystallinity is improved compared to the AlN buffer layer according to the comparative example. The crystallinity is determined by the number of defects, which in turn affects the luminous intensity. The smaller the half width, the smaller the number of defects, which means that the luminous intensity can be improved.

The present invention has been described with reference to preferred embodiments. However, those skilled in the art will understand that many other embodiments other than those specifically described also fall within the spirit and scope of the invention.

For example, in an embodiment of the present invention, the InGaN buffer layer having an In content of 5 atomic% or less formed on a substrate has been described as a single layer, but may be implemented as a plurality of layers. In addition, the plurality of layers may reduce the In content as the substrate approaches the semiconductor layer.

1 is a process flowchart illustrating a method of manufacturing a nitride semiconductor light emitting device according to an embodiment of the present invention.

2 is a cross-sectional view illustrating a method of manufacturing a nitride semiconductor light emitting device according to an embodiment of the present invention.

3 is a graph showing crystallinity of a semiconductor layer formed according to an embodiment of the present invention and a semiconductor layer formed according to a comparative example.

<Description of the symbols for the main parts of the drawings>

100 substrate 200 InGaN buffer layer

300: u-GaN layer 400: semiconductor layer

Claims (6)

Preparing a substrate; Forming an InGaN buffer layer on the substrate; Forming a GaN-based semiconductor layer having a first conductivity type semiconductor layer, an active layer including InGaN, and a second conductivity type semiconductor layer on the InGaN buffer layer, The In content of the InGaN buffer layer is a nitride semiconductor light emitting device manufacturing method, characterized in that less than the In content of the active layer and greater than zero. The method of claim 1, wherein the InGaN buffer layer has an In content of 2 to 3 atomic%. The method according to claim 1, Forming the InGaN buffer layer, To form a multi-layer InGaN buffer layer on the substrate, And each layer of the InGaN buffer layer is characterized in that the content of In decreases as it approaches the first conductive semiconductor layer from the substrate. Substrate, An InGaN buffer layer formed on the substrate, A GaN-based semiconductor layer having a first conductivity type semiconductor layer, an active layer including InGaN, and a second conductivity type semiconductor layer on the InGaN buffer layer, The In content of the InGaN buffer layer is a nitride semiconductor light emitting device, characterized in that less than the In content of the active layer and greater than zero. The nitride semiconductor light emitting device of claim 4, wherein the InGaN buffer layer has an In content of 2 to 3 atomic%. The method according to claim 4, wherein the InGaN buffer layer, InGaN buffer layers formed in multiple layers on the substrate, Each layer of the InGaN buffer layer is characterized in that the content of In decreases toward the first conductive semiconductor layer from the substrate.

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