KR101189165B1 - Light emitting device and method of making semiconductor layer therefor - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting device, and more particularly, to a light emitting device capable of manufacturing a high quality nitride semiconductor thin film having a low dislocation density and a method of manufacturing the semiconductor thin film. Such a method of manufacturing a semiconductor thin film using semiconductor growth equipment, the method comprising: forming a first semiconductor layer on a substrate; Forming a first nitride layer on the first semiconductor layer; Forming islands of semiconductor material over the nitride layer; Forming a second nitride layer over said nitride layer and islands; It is preferably configured to include the step of forming a second semiconductor layer on the second nitride layer.

Potential, LED, nitride, GaN, semiconductor.

Description

Light emitting device and method for manufacturing the semiconductor thin film {Light emitting device and method of making semiconductor layer therefor}

1 to 4 are diagrams showing a first embodiment of the present invention.

1 is a cross-sectional view showing a step of forming a first nitride layer of the present invention.

2 is a cross-sectional view showing growth of a gallium nitride island of the present invention.

3 is an electron microscope image of the gallium nitride islands of FIG. 2.

4 is a cross-sectional view showing a step of forming a first semiconductor layer of the present invention.

5 to 11 are diagrams illustrating a second embodiment of the present invention.

5 is a cross-sectional view showing growth of a gallium nitride island of the present invention.

6 is an electron microscope image of gallium nitride islands of FIG. 5.

7 is a cross-sectional view showing a step of forming a second nitride layer of the present invention.

8 is a cross-sectional view illustrating a step of forming a second semiconductor layer of the present invention.

9 is a cross-sectional view illustrating a step in which a second semiconductor layer of the present invention is grown.

10 is a cross-sectional view showing a step of forming a light emitting device structure of the present invention.

11 is a cross-sectional view showing an example of the light emitting element of the present invention.

<Brief description of the main parts of the drawing>

10: substrate 20: first conductive layer

21 gallium nitride island 30 first nitride layer

40: second semiconductor layer 50: nitride semiconductor island

60 second nitride layer 71 first conductive semiconductor layer

72 emitting layer 73 second conductive semiconductor layer

80 electrode

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting device, and more particularly, to a light emitting device capable of manufacturing a light emitting device having a high quality nitride semiconductor thin film having a low dislocation density and a method of manufacturing the semiconductor thin film.

Light Emitting Diodes (LEDs) are well-known semiconductor light emitting devices that convert current into light.In 1962, red LEDs using GaAsP compound semiconductors were commercialized, along with GaP: N series green LEDs. It has been used as a light source for display images of electronic devices, including.

The wavelength of light emitted by such LEDs depends on the semiconductor material used to make the LEDs. This is because the wavelength of the emitted light depends on the band-gap of the semiconductor material, which represents the energy difference between the valence band electrons and the conduction band electrons.

Gallium nitride compound semiconductors (Gallium Nitride: GaN) have high thermal stability and wide bandgap (0.8 to 6.2 eV), which has attracted much attention in the development of high-power electronic components including LEDs.

One reason for this is that GaN can be combined with other elements (indium (In), aluminum (Al), etc.) to produce semiconductor layers that emit green, blue and white light.

In this way, the emission wavelength can be adjusted to match the material's characteristics to specific device characteristics. For example, GaN can be used to create a white LED that can replace the blue LEDs and incandescent lamps that are beneficial for optical recording.

Due to the advantages of these GaN-based materials, the GaN-based LED market is growing rapidly. Therefore, since commercial introduction in 1994, GaN-based optoelectronic device technology has rapidly developed.

However, there are many limitations in the application of GaN-based nitride semiconductors, among which the fundamental limitations are crystal defects occurring in the nitride semiconductor thin film.

Nitride semiconductors are not currently commercially available for homogeneous substrates. Therefore, heterogeneous substrates are currently used, and representative ones of them are sapphire (Al ₂ O ₃ ), silicon (Si), silicon carbide (SiC) and the like.

When the nitride semiconductor thin film is formed using such a hetero substrate, crystal defects may be formed in the thin film due to a mismatch of crystal lattice constants between the substrate and the thin film or during the growth process.

Of these crystal defects, the most fundamental, difficult to remove, and critical to device characteristics is threading dislocation.

Therefore, many researchers have been researching and developing various techniques to obtain high quality thin films by reducing the density of these threading dislocations.

The nitride semiconductor thin film growth techniques reported to date can be largely classified into in-situ growth and ex-situ growth.

When a process or technique is performed in a growth device during thin film growth, such a growth method is called an in-situ growth method.

Ex-situ growth, on the other hand, refers to any process or technique being performed outside the thin film growth equipment.

Since the in-situ growth method is performed in the growth equipment, it is mainly a method to lower the dislocation density by controlling the growth variables. Therefore, there is no additional cost increase, but there is a certain limit to the dislocation density reduction simply by controlling the growth variable.

The aforementioned limitations are mainly due to the inherent nature of dislocations that do not break in the crystal. Therefore, the researchers developed an ex-situ technique.

The ex-situ method grows a thin film of a certain thickness, removes the specimen from the growth equipment, performs the mask patterning process and the etching process, and then re-grows the growth equipment.

In this case, since the potential is artificially blocked by the silicon oxide mask used, there is an advantage that the dislocation density can be greatly reduced.

However, this ex situ method requires an additional mask pattern and etching process outside the growth equipment, and thus has a high additional cost.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide a light emitting device having a nitride semiconductor thin film having a low crystal defect density and a method of manufacturing the semiconductor thin film.

As a first aspect for achieving the above technical problem, the present invention is a method of manufacturing a semiconductor thin film using a semiconductor growth equipment, comprising: forming a first semiconductor layer on a substrate; Forming a first nitride layer on the first semiconductor layer; Forming islands of semiconductor material over the nitride layer; Forming a second nitride layer over said nitride layer and islands; It is preferably configured to include the step of forming a second semiconductor layer on the second nitride layer.

It is preferable that the first nitride layer or the second nitride layer uses silicon nitride, and the first nitride layer and the second nitride layer are preferably formed in the thin film growth equipment.

The first nitride layer may use porous silicon nitride, and the second nitride layer may be formed thicker than the first nitride layer and use a nonporous nitride.

Islands of the semiconductor material may be formed at regular intervals. These islands are preferably formed vertically on the side, so that the second nitride layer is formed only on the upper side of the first nitride layer and the island.

Meanwhile, when the sides of the islands are not perpendicular to each other, the forming of the first nitride layer may be further included between forming the second nitride layer and forming the second semiconductor layer.

As a 2nd viewpoint for achieving the said technical subject, this invention is a board | substrate; A first semiconductor layer on the substrate; A first nitride layer positioned on the first semiconductor layer; Located on the first nitride layer, preferably comprises a crystal defect blocking layer formed of a mixture of semiconductor and nitride in at least one layer.

The layer of the semiconductor and the nitride of the blocking layer is composed of two layers, and the two layers are preferably formed at a position where the semiconductor and the nitride cross each other.

More specifically, the blocking layer comprises: a plurality of islands formed of a semiconductor material on the first nitride layer; A second nitride layer formed around the island; A second semiconductor layer formed on the plurality of islands and second nitride layers; A third nitride layer positioned on the second semiconductor layer; It is preferably configured to include a third semiconductor layer located on the third nitride layer.

In this case, the third nitride layer may be formed only on an upper portion of the island.

A first conductive semiconductor layer on the blocking layer; A light emitting layer on the first conductive semiconductor layer; A second conductive semiconductor layer on the light emitting layer; An electrode in contact with the first conductive semiconductor layer and the second conductive semiconductor layer may be further included to form a light emitting device.

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

As shown in FIG. 1, a first semiconductor layer 20 of gallium nitride (GaN) is formed on a substrate 10, and a first nitride layer made of porous silicon nitride is formed on the first semiconductor layer 20 ( 30).

Since the first semiconductor layer 20 is formed on a heterogeneous substrate 10 such as sapphire (Al ₂ O ₃ ), silicon (Si), silicon carbide (SiC), the substrate 10 and the first semiconductor layer 20. Crystal defects such as dislocations (a) may be formed in the thin film due to a mismatch of crystal lattice constants between the thin films or during the growth process.

In this case, the first nitride layer 30 made of silicon nitride may be used as a spontaneous mask that can be used in the thin film growth equipment. That is, the ex-situ method for forming such a silicon nitride layer as a mask may be combined with the in-situ growth method for forming in the thin film growth equipment.

The first nitride layer 30 formed of the porous thin silicon nitride layer exposes a substantial portion of the first nitride layer 30 without completely covering the substrate 10 or the first semiconductor layer 20.

As such, when the gallium nitride semiconductor layer is formed on the porous first nitride layer 30 again, as shown in FIG. 2, the gallium nitride islands 21 start to grow in the exposed portions.

3 shows an electron microscope image of gallium nitride islands 21 grown in portions exposed to the porous first nitride layer 30. These gallium nitride islands 21 grow not only in the vertical direction but also in the transverse direction.

At this time, the growth in the vertical direction does not block the potential a. The blocking effect of the potential (a) occurs when the gallium nitride islands 21 grow laterally, and since the lateral growth takes place on the first nitride layer 30, the first nitride layer 30 as a silicon nitride mask 30 The blocked potential a cannot penetrate the upper layer.

Also, the lateral growth can bend some dislocations (a) penetrated into the top layer in the lateral growth direction. These bent dislocations (a) may not interact with dislocations (a) coming from the opposite side and may not grow into the top layer.

Subsequently, when the thin film growth is continued, the initial islands 21 continue to grow laterally and eventually meet each other, thereby forming the second semiconductor layer 40 of the single flat thin film as shown in FIG. 4.

The above-described method can effectively reduce the dislocation density by using a mask material using the first nitride layer 30 while being an in-situ method.

However, for this method, the dislocation density can still be high compared to the ex-situ method. The reason is that the method requires the use of an inherently porous thin mask layer.

In other words, through many exposed portions in the mask layer, the dislocations a may penetrate into the second semiconductor layer 40 thin film that continues to grow and regrow.

Therefore, as described below, by using the nitride layer secondaryly, crystal defects can be more effectively removed. Hereinafter, this will be described in detail.

As shown in FIG. 5, a first semiconductor layer 20 of gallium nitride (GaN) is formed on the substrate 10, and a first nitride layer made of porous silicon nitride is formed on the first semiconductor layer 20 ( 30).

The first semiconductor layer 20 and the first nitride layer 30 of silicon nitride are grown in thin film growth equipment, and the first nitride layer 30 is preferably porous so that the lower layer may be partially exposed. .

Thereafter, nitride semiconductor islands 50 having a flat top surface are formed on the first nitride layer 30. At this time, the islands 50 are formed on the portion exposed by the porous first nitride layer 30.

FIG. 6 is an electron microscope image of these islands 50, which, unlike FIG. 2, are preferably allowed to grow primarily in the vertical direction.

This is possible by controlling growth conditions, and usually, by increasing the growth temperature, decreasing the growth pressure, or increasing the amount of source gas, it is possible to control the islands 50 to grow in the vertical direction.

Next, as shown in FIG. 7, a second nitride layer 60 made of silicon nitride is deposited. In this case, the second nitride layer 60 is covered with a sufficient thickness on the porous first nitride layer 30 so that the lower first nitride layer 30 or the first semiconductor layer 20 is not exposed.

The second nitride layer 60 is also deposited on the flat top surfaces of the nitride semiconductor islands 50. Unlike the first nitride layer 30, the second nitride layer 60 is not porous.

The non-porous second nitride layer 60 may be formed by increasing the growth time than the first nitride layer 30 to form a thicker thickness or by controlling growth conditions.

The second nitride layer 60 completely covers the portion of the first semiconductor layer 20 exposed by the first nitride layer 30, thereby preventing potential defects generated from the lower layer from penetrating into the upper nitride semiconductor layer during regrowth. Can be.

In addition, the second nitride layer 60 may be thickly deposited on the flat top of the nitride semiconductor island 50 to completely block the penetration of the upper layer of the potential through the island 50.

Accordingly, the second nitride layer 60 has a relatively thicker thickness and no porosity than the first nitride layer 30.

In addition, the second nitride layer 60 is preferably not deposited on the side surface of the nitride semiconductor island 50. As described above, since the side of the island 50 is ideally perpendicular to the substrate 10, the formation of the second nitride layer 60 is limited to the side of the island 50.

However, in some cases, when the side surface of the island 50 is inclined, it is preferable that the thin porous first nitride layer 30 is deposited once more.

Thereafter, a second semiconductor layer 40 made of nitride semiconductor is deposited. At this time, the second semiconductor layer 40 begins to be deposited from the side of the islands 50, as shown in FIG. If this growth continues, the islands 50 continue to grow from the side and eventually encounter neighboring islands 50.

Once the islands 50 are in contact with each other, a two-dimensional thin film is formed and subsequent growth of the nitride semiconductor causes the thin film to grow vertically, thereby forming the second semiconductor layer 40.

Subsequently, when the thin film continues to grow vertically and grows higher than the second nitride layer 60 covering the upper layer of the flat island 50, the thin film growth is accompanied by lateral growth.

This lateral growth proceeds by covering the second nitride layer 60 layer covering the top layer of the flat island 50. If growth continues, as in FIG. 9, the nitride semiconductor completely covers the second nitride layer 60 covering the flat top layer of the island 50, eventually forming a second semiconductor layer 40 of generally flat thin film. Done.

As a result, many of the dislocations starting from the upper side of the substrate 10 cannot be connected to the upper side of the second semiconductor layer 40, so that a higher quality semiconductor layer having a lower dislocation density on the upper side of the second semiconductor layer 40. This can be formed.

As such, the structure formed on the first nitride layer 30 is a blocking layer 100 that blocks crystal defects such as dislocations starting from the first semiconductor layer 20 above the substrate 10 so that they do not lead to the upper side. Can work.

As shown in FIG. 9, the blocking layer 100 has a structure in which a semiconductor and a nitride are mixed with each other to form one layer 110 and 130.

That is, an island-type semiconductor is formed on the upper surface of the first nitride layer 30, and the second nitride layer 60, which is positioned at the same thickness as that of the semiconductor, is formed in the first layer of the blocking layer 100. Layer 110 is formed.

In addition, a second layer 120 having a portion of the second semiconductor layer 40 formed on the upper side of the first layer 110 formed of a portion of the island-type semiconductor and the second nitride layer 60 is located. .

On the second layer 120, a nitride formed in the upper portion of the island-type semiconductor and a third layer 130 formed around and on the nitride are positioned.

The structure of the light emitting device may be formed on the semiconductor layer thus formed.

That is, as shown in FIG. 10, the first conductive semiconductor layer 71, the light emitting layer 72, and the second conductive semiconductor layer 73 are sequentially formed on the second semiconductor layer 40 or the blocking layer 100. Can be.

The first conductive semiconductor layer 71 may be an n-type gallium nitride semiconductor layer, wherein the second conductive semiconductor layer 73 becomes a p-type gallium nitride semiconductor layer.

In contrast, the first conductive semiconductor layer 71 may be a p-type gallium nitride semiconductor layer, and in this case, the second conductive semiconductor layer 73 may be an n-type gallium nitride semiconductor layer.

In this structure, as shown in FIG. 11, the electrode 80 is formed on the first conductive semiconductor layer 71 and the second conductive semiconductor layer 73 after being etched to expose the first conductive semiconductor layer 71. Thus, the structure of the horizontal light emitting device is achieved.

Meanwhile, after the substrate 10 is removed from the structure of FIG. 10, and then the second semiconductor layer 40 is removed, the surface of the first conductive semiconductor layer 71 is exposed by removing the second semiconductor layer 40. By forming an electrode in the structure, it is possible to manufacture a vertical light emitting device.

This invention can completely block the penetration of dislocations from the lower layer to the upper layer. In addition, the nitride semiconductor thin film can start growing from the side of the island, thereby providing a method for growing a nitride semiconductor thin film that is ideally free of electric potential.

The present invention can overcome the fundamental problems of the conventional in-situ lateral growth method using silicon nitride can provide a nitride semiconductor thin film having a low crystal defect density.

The present invention can overcome the additional external process step and the high production cost increase problem, which is a fundamental problem of the conventional ex-situ Pentio growth method can provide a high quality nitride thin film at low cost .

As a result, the dislocation density of the nitride semiconductor thin film grown on the dissimilar substrate can be effectively reduced significantly, and the reliability and device performance of the optical device and the electronic device formed thereon can be greatly improved.

The above embodiment is an example for explaining the technical idea of the present invention in detail, and the present invention is not limited to the above embodiment, various modifications are possible, and various embodiments of the technical idea are all of the present invention. Naturally, it belongs to the scope of protection.

The present invention as described above has the following effects.

First, the present invention makes it possible to produce a nitride semiconductor thin film that is ideally free of electric potential since the nitride semiconductor thin film starts to grow from the side of the island.

Second, the present invention can overcome the fundamental problems of the in-situ lateral growth method using a conventional silicon nitride can provide a nitride semiconductor thin film having a low crystal defect density.

Third, the present invention can overcome the additional external process step, which is a fundamental problem of the conventional ex-situ Pentio growth method and the resulting high production cost increase problem to provide a high quality nitride thin film at low cost Can be.

Claims (14)

In the manufacturing method of a semiconductor thin film using a semiconductor growth equipment, Forming a first semiconductor layer on the substrate; Forming a first nitride layer on the first semiconductor layer; Forming islands of semiconductor material over the nitride layer; Forming a second nitride layer over said nitride layer and islands; Forming a second semiconductor layer on the second nitride layer, characterized in that it comprises a semiconductor thin film manufacturing method. The method of manufacturing a semiconductor thin film according to claim 1, wherein the first nitride layer or the second nitride layer is silicon nitride. The method of manufacturing a semiconductor thin film according to claim 1, wherein the first nitride layer is porous. The method of manufacturing a semiconductor thin film according to claim 1, wherein the first nitride layer and the second nitride layer are formed in the semiconductor growth equipment. The method of claim 1, wherein the second nitride layer is formed thicker than the first nitride layer. The method of claim 1, wherein the islands of the semiconductor material are formed at regular intervals. The method of claim 1, wherein the second nitride layer is formed on an upper surface of the first nitride layer and the island. The method of claim 1, further comprising forming the first nitride layer between the forming of the second nitride layer and the forming of the second semiconductor layer. A substrate; A first semiconductor layer on the substrate; A first nitride layer positioned on the first semiconductor layer; And a crystal defect blocking layer disposed on the first nitride layer and formed by mixing semiconductor and nitride in at least one layer. 10. The light emitting device of claim 9, wherein the semiconductor and nitride layers of the blocking layer are composed of two layers, and the two layers are formed at positions where the semiconductor and nitride cross each other. The method of claim 9, wherein the blocking layer, A first layer comprising a plurality of islands formed of a semiconductor material on the first nitride layer, and a nitride formed around the island; A second layer formed of a semiconductor material on the first layer; And a third layer formed on the second layer and formed of a nitride located on an upper portion of the island and a semiconductor material formed around and on the nitride. 10. The light emitting device of claim 9, wherein the blocking layer blocks crystal defects of the first semiconductor layer. The method of claim 9, wherein the blocking layer, A first conductive semiconductor layer; A light emitting layer on the first conductive semiconductor layer; A second conductive semiconductor layer on the light emitting layer; The light emitting device further comprises an electrode in contact with the first conductive semiconductor layer and the second conductive semiconductor layer. 10. The light emitting device of claim 9, wherein the nitride of the blocking layer is formed thicker than the first nitride layer.

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