KR20080041796A - Method for forming gan type semiconductor light emitting device - Google Patents

Abstract

A method for forming a GaN type semiconductor light emitting device is provided to reduce defects by re-growing a second n type GaN layer on an etched surface. A substrate(100) for growing a GaN type semiconductor material is prepared. A first n type GaN layer(120a) is formed on the substrate. An etch process is performed to etch an upper surface of the first n type GaN layer. A second n type GaN layer(120b) is formed by performing a re-grow process on the etched part of the first n type GaN layer. An active region(130) is formed on the second n type GaN layer. A p type GaN layer(140) is formed on the active layer. A buffer layer forming process is performed to form a buffer layer(110) on the substrate before the first n type GaN layer is formed on the substrate.

Description

Method for manufacturing gallium nitride-based semiconductor light emitting device {Method for forming GaN type semiconductor Light Emitting device}

1A to 1D are cross-sectional views sequentially illustrating a GaN layer growth method by a conventional LEO method.

Fig. 2 is a state diagram showing generation of dislocations in a GaN layer grown by a conventional LEO method.

3A to 3G are process perspective views sequentially illustrating a method of manufacturing a gallium nitride-based semiconductor light emitting device according to an embodiment of the present invention.

4 is a view showing a crystal structure of a second n-type GaN layer of a gallium nitride-based semiconductor light emitting device manufactured according to an embodiment of the present invention.

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

100 substrate 110 buffer layer

120a: first n-type GaN layer 120b: second n-type GaN layer

130: active layer 140: p-type GaN layer

150: p-type electrode 160: n-type electrode

170: p-type bonding electrode

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a gallium nitride (GaN) semiconductor light emitting device, and more particularly, to reduce defects such as Ga vacancies of a gallium nitride layer grown on a substrate and defects due to lattice mismatch. The present invention relates to a method for manufacturing a gallium nitride-based semiconductor light emitting device that can improve the characteristics and optical characteristics.

Recently, LED (light emitting device) display boards, which are emerging as a transmission medium for new image information, began with simple character or numeric information and have now reached the level of providing moving images such as various CF images, graphics, and video screens. The color range was limited to red and yellow-green LEDs from the existing monochromatic screen, and recently, with the emergence of high-brightness blue LEDs using nitride semiconductors, the display of all natural colors using red, yellow-green, and blue became possible. .

On the other hand, since the yellow-green LED is lower in brightness than the red LED and blue LED and the emission wavelength is 565 nm, it is not the green color of the wavelength necessary for the three primary colors of light, so it is impossible to express natural full color. This was solved by producing semiconductor LEDs.

Such a nitride semiconductor uses a nitride semiconductor material having an Al x In y Ga (1-xy) N composition formula, where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, and 0 ≦ x + y ≦ 1. Research on semiconductor light emitting devices using cerium (GaN) has been actively conducted.

In the nitride semiconductor light emitting device, since there is no commercial substrate having the same crystal structure and lattice matching as the nitride semiconductor material such as GaN, a sapphire substrate or the like which is an insulating substrate is used.

However, since a difference in lattice constant and coefficient of thermal expansion occurs between the sapphire substrate and the GaN layer grown on the sapphire substrate, crystal defects are generated. Thus, a GaN buffer layer, which is grown at low temperature, is conventionally formed on the sapphire substrate. The GaN layer was grown at high temperature on the buffer layer. This is to reduce the difference in lattice constant between the sapphire substrate and the GaN layer.

However, the GaN buffer layer grown at low temperature has a large amount of crystalline defects, and is more amorphous than amorphous. Therefore, when the GaN layer is directly grown at a high temperature on the low temperature growth buffer layer, a large amount of crystalline defects propagate to the high temperature growth GaN layer, thereby generating a defect called dislocation.

Conventionally, to grow such a dislocation free GaN layer, it is used the LEO (Lateral Epitaxial Overgrowth) method (also known as ELOG; Epitaxial Of Lateral Overgrowth method) or Pendio-Epitaxy (PE) method. It was.

Both of the above methods are methods of growing the GaN layer laterally to suppress the movement of defects formed at the interface between the sapphire substrate and the GaN layer to the upper layer portion. The LEO method is a method in which a dielectric mask is formed on a sapphire substrate or on an upper surface of a GaN epitaxial layer grown first, and then GaN is grown on the upper surface of the mask so that GaN is laterally grown. In addition, similar to the LEO method, the Pendio-epitaxial method first grows a GaN epitaxial layer on a sapphire substrate, forms a mask on the upper surface of the first grown GaN epitaxial layer, and then etches a portion of the groove. ) To grow the GaN epitaxial layer again on the groove.

1A to 1D sequentially illustrate a method of growing a GaN layer using such a conventional LEO method. In the LEO method, the GaN epitaxial layer 11 is first grown on the top surface of the sapphire substrate 10 as shown in FIG. 1A, and then the silicon oxide film is formed on the top surface of the first growth epitaxial layer 11 as shown in FIG. 1B. Alternatively, a mask 12 having a predetermined pattern is formed of a silicon nitride film or the like.

Then, GaN is regrown again at the portion where the mask 12 is not formed as shown in FIG. 1C. At this time, GaN 13 is grown on the mask 12 laterally as indicated by arrows in FIG. 1C. When the lateral growth of GaN is completed, the growth of the GaN layer 13 is completed as shown in FIG. 1D.

The Pendo epitaxy method is an addition of an etching process for removing a GaN epilayer without a mask after forming a mask in the LEO method as described above.

GaN layers formed by the LEO method or the Pedio epitaxy method are generally known to reduce the propagation potential.

In the portion where the first growth epitaxial layer 11 is exposed as shown in FIG. 2, the potential B existing below propagates to the GaN layer 13 which is subsequently regrown, but is covered by the mask 12. Since the growth is caused by lateral growth, there is no dislocation propagating below, so defects are reduced.

However, in the case of growing GaN in this manner, the problem of dislocation A of regions not covered by the mask propagates upwards and high density dislocation B at the adhesion surface where the GaN layer 13 which is laterally regrown meet each other. There is a problem that occurs.

In addition, there is a problem that a defect occurs due to the stress formed between the mask 12 material and the regrown GaN layer 13. Such defects such as potentials cause problems in that the electrical and optical characteristics of the nitride semiconductor element are degraded and the yield is lowered.

In addition, the conventional LEO method or the pendio epitaxy method increases the manufacturing cost because a process of manufacturing a mask is used, and since the GaN epitaxial layer is first grown, patterning and regrowth are added. There is a complicated additional problem.

As described above, even if the LEO method or the Pendo epitaxy method is used to reduce the defects due to lattice mismatch, defects such as dislocations cannot be significantly reduced, and the process is complicated by the addition of the process and the manufacturing cost is increased. There is a rising problem.

Accordingly, there is a need in the art for a new gallium nitride-based semiconductor light emitting device having excellent electrical and optical characteristics and preventing a defect such as dislocation caused by lattice mismatch between a sapphire substrate and a nitride semiconductor material such as GaN and a manufacturing method thereof. It's happening.

Accordingly, an object of the present invention is to reduce the defects such as Ga vacancy of the gallium nitride layer growing on the substrate and the defects due to lattice mismatch to improve the electrical and optical properties to solve the above problems. The present invention provides a method for manufacturing a gallium nitride-based semiconductor light emitting device.

In order to achieve the above object, the present invention is to provide a substrate for growing a gallium nitride-based semiconductor material, forming a first n-type GaN layer on the substrate, and the first n-type GaN layer Etching a top surface of the substrate to a predetermined thickness, forming a second n-type GaN layer through the regrowth process on the etched first n-type GaN layer, and forming an active layer on the second n-type GaN layer It provides a method of manufacturing a gallium nitride-based semiconductor light emitting device comprising the step and forming a p-type GaN layer on the active layer.

In addition, in the method of manufacturing the gallium nitride-based semiconductor light emitting device of the present invention, it is preferable to further include the step of forming a buffer layer on the substrate before the step of forming the first n-type GaN layer.

In the method for manufacturing a gallium nitride-based semiconductor light emitting device of the present invention, it is preferable that the first n-type GaN layer is formed to a thickness of 1 μm to 10 μm.

In addition, in the method of manufacturing the gallium nitride-based semiconductor light emitting device of the present invention, the step of etching a predetermined thickness of the upper surface of the first n-type GaN layer, the first n-type GaN layer through a dry or wet etching process It is preferable to etch the entire surface of the upper surface of the substrate to a uniform thickness, more specifically, to etch within 50% of the total thickness of the first n-type GaN layer.

Further, in the method of manufacturing the gallium nitride-based semiconductor light emitting device of the present invention, the step of etching a predetermined thickness of the upper surface of the first n-type GaN layer, forming a mask for forming a pattern on the first n-type GaN layer And etching a portion of the surface of the first n-type GaN layer using the pattern forming mask and removing the pattern forming mask. In this case, the pattern forming mask may be formed of one or more linear and one or more polygons or a combination thereof.

Further, in the method of manufacturing the gallium nitride-based semiconductor light emitting device of the present invention, the step of etching the portion of the surface of the first n-type GaN layer using the pattern forming mask, the whole of the first n-type GaN layer It is preferable to etch to within 50% of the thickness.

In addition, in the method for manufacturing a gallium nitride-based semiconductor light emitting device of the present invention, the first and second n-type GaN layer is formed by growing in the temperature range of 850 ℃ to 1200 ℃ to excellent crystallinity of GaN It is preferable.

In the method of manufacturing the gallium nitride-based semiconductor light emitting device of the present invention, Al _X In _Y Ga _{1 -X- Y} N (0≤X, Y≤1, X + Y≤1) in the second n-type GaN layer. It is preferable to further form a nitride semiconductor layer consisting of a) composition, the band gap is larger or smaller than GaN.

In the method of manufacturing the gallium nitride-based semiconductor light emitting device of the present invention, after forming the p-type GaN layer on the active layer, a portion of the active layer and the p-type GaN layer is removed to remove the second n-type GaN. Exposing a layer, forming a p-type electrode on the p-type GaN layer, and forming a p-type bonding electrode on the p-type electrode and an n-type electrode on the exposed second n-type GaN layer It is preferred to further comprise a step.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. In the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity.

Now, a method of manufacturing a gallium nitride-based semiconductor light emitting device according to an embodiment of the present invention will be described in detail with reference to FIGS. 3A to 3G.

3A to 3G are process perspective views sequentially illustrating a method of manufacturing a gallium nitride-based semiconductor light emitting device according to an embodiment of the present invention.

First, as shown in FIG. 3A, a buffer layer 110 is formed on a substrate 100.

The substrate 100 is a substrate suitable for growing a nitride semiconductor single crystal, and may be a heterogeneous substrate such as a sapphire substrate and a silicon carbide (SiC) substrate or a homogeneous substrate such as a nitride substrate.

The buffer layer 110 is a layer for improving lattice matching with the substrate 100 before growing an n-type GaN layer, which will be described later. Generally, the buffer layer 110 is formed of a nitride including GaN or Ga, which is not essential. The furnace may be omitted depending on the characteristics of the device and the process conditions.

3B, a first n-type GaN layer 120a is formed on the buffer layer 110. The first n-type GaN layer 120a is preferably formed in a thickness of 1 μm to 10 μm by growing in a temperature range of 850 ° C. to 1200 ° C. in order to improve the crystallinity of GaN.

3C, the entire surface of the upper surface of the first n-type GaN layer 120a is removed by a predetermined thickness through dry or wet etching. In this case, the thickness of the first n-type GaN layer 120a to be etched is preferably etched within 50% of the total thickness of the first n-type GaN layer 120a.

Next, a second n-type GaN layer 120b is formed on the etched first n-type GaN layer 120a through a regrowth process, thereby forming first and second n-type GaN layers on the buffer layer 110. The n-type GaN layer 120 formed of 120a and 120b is formed. At this time, the second n-type GaN layer 120b, like the first n-type GaN layer 120a, is also grown in the temperature range of 850 ℃ to 1200 ℃ to improve the crystallinity of GaN.

In addition, the second n-type GaN layer 120b is a layer in contact with an n-type electrode to be described later. In order to have excellent ohmic characteristics, the second n-type GaN layer 120b has n-type impurities in the range of 1 × 10 ¹⁶ cm ^-3 to It is preferable to form a high concentration by doping about 5 × 10 ¹⁹ cm ^-3 , which can be adjusted according to the thickness of the second n-type GaN layer (120b).

In particular, the n-type GaN layer 120 may be formed of a semiconductor material having an In _X Al _Y Ga _{1 -X- Y} N composition formula (where 0 ≦ X, 0 ≦ Y, and X + Y ≦ 1). For example, a single GaN layer or a GaN / AlGaN layer doped with n-type conductivity impurities may be used. For example, Si, Ge, Sn, etc. may be used as the n-type conductivity impurities. Si is mainly used.

As such, when the upper surface of the first n-type GaN layer 120a is etched and the second n-type GaN layer 120b is regrown from the etched surface of the first n-type GaN layer 120a, the As the upper surface of the first n-type GaN layer 120a has an crystalline structure similar to GaN as shown in FIG. 4 through an etching process, the second n-type GaN layer 120b regrown thereon is lattice matched. By doing so, defects such as a conventional dislocation caused by lattice mismatch can be minimized. That is, the surface of the first n-type GaN layer 120a etched according to the present invention serves to minimize defects caused by lattice mismatch between the substrate 100 and a nitride semiconductor material such as GaN.

In addition, an upper surface of the first n-type GaN layer 120a may be formed with a pattern forming mask (not shown) on the first n-type GaN layer 120a and then used as an etching mask. A portion of the surface of the first n-type GaN layer 1200 may be selectively etched to have a crystal structure similar to GaN as shown in FIG. 4. In this case, the pattern forming mask may be made of one or more linear and one or more polygons or a combination thereof, and the thickness of the first n-type GaN layer to be etched is preferably etched within 50% of the total thickness. .

Although not shown, an Al _X In _Y Ga ₁ -X _{- Y} N (0≤X, Y≤1, X + Y≤1) composition is formed in the second n-type GaN layer 120a. The nitride semiconductor layer with a large or small band gap may be further formed to improve the current diffusion effect.

3E, an active layer 130 and a p-type GaN layer 140 are sequentially stacked on the n-type GaN layer 120b, that is, the second n-type GaN layer 120. To form.

More specifically, the active layer 130 and the p-type GaN layer 140 have an In _X Al _Y Ga _{1 -X - Y} N composition formula (where 0 ≦ X, 0 ≦ Y, and X + Y ≦ 1). It may be made of a semiconductor material. That is, the active layer 130 may be formed of an InGaN / GaN layer having a multi-quantum well structure, and the p-type GaN layer 140 may be a single GaN layer or GaN doped with p-type conductive impurities. It may be made of / AlGaN layer, for example, as the p-type conductive impurities, Mg, Zn, Be, etc. are used, preferably Mg is mainly used.

Subsequently, as illustrated in FIG. 3F, mesa etching removes a portion of the p-type GaN layer 140 and the active layer 130 so that a portion of the second n-type GaN layer 120b is exposed. Proceed with the process.

Then, as illustrated in FIG. 3G, the p-type electrode 150 is formed on the p-type GaN layer 140. In this case, the p-type electrode 150 is made of a transparent oxide material having a high transmittance with respect to the light emission wavelength of the light emitting device in order to increase the current diffusion effect to improve the brightness, for example, ITO (Indium Tin Oxide), TO (Tin Oxide), Indium Zinc Oxide (IZO), Indium Tin Zinc Oxide (ITZO), Zinc Oxide (ZnO), etc. are used, and preferably ITO is mainly used.

Then, the p-type bonding electrode 170 and the n-type electrode 160 are formed on the p-type electrode 150 and the exposed second n-type GaN layer 120b, respectively.

Although the preferred embodiments of the present invention have been described in detail above, those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. Accordingly, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concept of the present invention as defined in the following claims also fall within the scope of the present invention.

As described above, according to the present invention, the upper surface of the first n-type GaN layer is etched by a predetermined thickness, and then the second n-type GaN layer is regrown on the etched surface, thereby reducing defects due to lattice misalignment such as dislocations. The crystallinity of the light emitting structure made of gallium nitride semiconductor can be improved.

In addition, by using a conventional wet or dry etching process, there is an effect that it is possible to ensure high-quality crystal growth at low cost without adopting a costly process such as the LEO method or the Pedio-epitaxial method.

Accordingly, the present invention not only can improve the electrical and optical characteristics of the gallium nitride semiconductor light emitting device, but also has the effect of improving the production yield of the gallium nitride semiconductor light emitting device.

Claims (11)

Providing a substrate for growing a gallium nitride based semiconductor material; Forming a first n-type GaN layer on the substrate; Etching a top surface of the first n-type GaN layer by a predetermined thickness; Forming a second n-type GaN layer on the etched first n-type GaN layer through a regrowth process; Forming an active layer on the second n-type GaN layer; And Forming a p-type GaN layer on the active layer; method of manufacturing a gallium nitride-based semiconductor light emitting device comprising a. The method of claim 1, Before forming the first n-type GaN layer, A method of manufacturing a gallium nitride-based semiconductor light emitting device further comprising the step of forming a buffer layer on the substrate. The method of claim 1, The first n-type GaN layer is formed with a thickness of 1 μm to 10 μm. The method of claim 1, Etching a predetermined thickness of the upper surface of the first n-type GaN layer, A method of manufacturing a gallium nitride-based semiconductor light emitting device, characterized in that for etching the entire surface of the upper surface of the first n-type GaN layer to a uniform thickness through a dry or wet etching process. The method of claim 4, wherein The etching of the upper surface of the first n-type GaN layer by a predetermined thickness may include etching the gallium nitride-based semiconductor light emitting device within 50% of the total thickness of the first n-type GaN layer. The method of claim 1, Etching a predetermined thickness of the upper surface of the first n-type GaN layer, Forming a pattern forming mask on the first n-type GaN layer; Etching a portion of the surface of the first n-type GaN layer using the pattern forming mask; And Removing the pattern forming mask; and manufacturing a gallium nitride based semiconductor light emitting device. The method of claim 6, The pattern forming mask is made of at least one linear and at least one polygon or a combination thereof. The method of claim 6, The etching of a portion of the surface of the first n-type GaN layer using the pattern forming mask may include etching the gallium nitride-based semiconductor light emitting device within 50% of the total thickness of the first n-type GaN layer. Manufacturing method. The method of claim 1, The first and second n-type GaN layer is formed by growing in the temperature range of 850 ℃ to 1200 ℃ method of manufacturing a gallium nitride-based semiconductor light emitting device. The method of claim 1, A nitride semiconductor layer composed of Al _X In _Y Ga ₁ -X _{- Y} N (0≤X, Y≤1, X + Y≤1) composition in the second n-type GaN layer, and having a band gap larger or smaller than GaN. Method for producing a gallium nitride-based semiconductor light emitting device, characterized in that further forming. The method of claim 1, After forming a p-type GaN layer on the active layer, Exposing the second n-type GaN layer by removing a portion of the active layer and a p-type GaN layer; Forming a p-type electrode on the p-type GaN layer; And Forming an n-type electrode on the p-type electrode and the exposed second n-type GaN layer on the p-type electrode; and manufacturing a gallium nitride-based semiconductor light emitting device.

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