KR20120060368A - Nitride semiconductor light emitting device - Google Patents

Abstract

PURPOSE: A nitride semiconductor light emitting device is provided to obtain high efficiency with long wavelengths and a high current by minimizing the diffusion of indium at a quantum barrier layer and a quantum well layer. CONSTITUTION: An undoped nitride semiconductor layer(20) is formed on a substrate(10). An n-type nitride semiconductor layer(30) is formed on the undoped nitride semiconductor layer. An active layer(40) is formed on the n-type nitride semiconductor layer. A p-type nitride semiconductor layer(50) is formed on the active layer. A p-type electrode(70) is formed on the p-type nitride semiconductor layer.

Description

Nitride-based semiconductor light emitting device

The present invention relates to a semiconductor light emitting device, and more particularly to a nitride-based semiconductor light emitting device.

Light Emitting Diode (LED) is a well-known semiconductor light emitting device that converts electric current into light.In 1962, a red LED using GaAsP compound semiconductor was commercialized. It has been used as a light source for display images of electronic devices, including.

Nitride compound semiconductors, represented by gallium nitride (GaN), have high thermal stability and wide bandgap (0.8 to 6.2 eV), attracting much attention in the field of high-power electronic component development including LEDs. come.

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 white LEDs that can replace incandescent and blue LEDs that are beneficial for optical recording.

Accordingly, nitride semiconductors are currently used as basic materials for the fabrication of blue / green laser diodes and light emitting diodes (LEDs). In particular, high-power LED is attracting attention as a light source for white lighting, foretelling the era of LED lighting.

An object of the present invention is to provide a nitride-based semiconductor light emitting device that can implement an efficient nitride-based semiconductor light emitting device by providing a light emitting device having an active layer having a high quality.

In order to achieve the above technical problem, a nitride-based semiconductor light emitting device, the first conductive semiconductor layer; A second conductive semiconductor layer; An active layer disposed between the first conductive semiconductor layer and the second conductive semiconductor layer and including at least one quantum barrier layer and a quantum well layer; And a diffusion barrier layer positioned between the quantum barrier layer and the quantum well layer to prevent the atoms included in the quantum well layer or the quantum barrier layer from diffusing.

The present invention has the following effects.

In the III-V nitride semiconductor light emitting device, the InGaN state or bonding structure used in the quantum well layer in the active layer is more unstable than GaN, so that In atoms are easily desorbed even at low energy, and are easily diffused into the quantum barrier layer. Many of these phenomena occur in the case of high In composition or at high currents.

The out-diffusion phenomenon of In may cause defects between the quantum well layer and the quantum barrier layer, and may cause the emission or non-emission of unwanted energy, thereby reducing the efficiency of the light emitting device. By minimizing the diffusion of In in the quantum barrier layer and the quantum well layer, a nitride semiconductor light emitting device capable of obtaining high efficiency even at a long wavelength and a high current can be provided.

1 is a cross-sectional view showing an example of a horizontal nitride semiconductor light emitting device.
2 is an enlarged view of the active layer.
3 is a cross-sectional view showing an example of a vertical nitride semiconductor light emitting device.
4 is an enlarged view of the active layer.
5 is a cross-sectional view showing another example of the vertical nitride semiconductor light emitting device.

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

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. However, it is not intended to be exhaustive or to limit the invention to the precise forms disclosed, but rather the invention includes all modifications, equivalents, and alternatives consistent with the spirit of the invention as defined by the claims.

It will be appreciated that when an element such as a layer, region or substrate is referred to as being present on another element "on," it may be directly on the other element or there may be an intermediate element in between .

Although the terms first, second, etc. may be used to describe various elements, components, regions, layers, and / or regions, such elements, components, regions, layers, and / or regions It will be understood that it should not be limited by these terms.

As shown in FIG. 1, the horizontal nitride semiconductor light emitting device includes an n-type nitride semiconductor layer 30, an active layer 40, a p-type nitride semiconductor layer 50, and the like sequentially on the substrate 10. The p-type electrode 70 is located. The n-type nitride semiconductor layer 30 may be an n-type GaN layer having a thickness of 0.1 μm to 10 μm, and the p-type nitride semiconductor layer 50 may have a p-type between 0.03 μm and 1 μm. GaN layer may be used.

In addition, an n-type electrode 80 electrically connected to the n-type nitride semiconductor layer 30 is positioned in the opening 31 opened to expose the n-type nitride semiconductor layer 30.

An undoped nitride semiconductor layer 20 may be positioned between the substrate 10 and the n-type nitride semiconductor layer 30 as a buffer layer.

In addition, the transparent electrode 60 may be further positioned between the p-type nitride semiconductor layer 50 and the p-type electrode 70. The transparent electrode 60 may be a transparent metal or a transparent conductive oxide.

The substrate 10 is a substrate for growing a gallium nitride-based semiconductor layer, but may be sapphire, SiC, spinel, and the like, but is not limited thereto. In particular, the substrate 10 may include a sapphire substrate (PSS) patterned to improve light extraction efficiency; patterned sapphire substrate).

The active layer 40 includes at least one quantum barrier layer 41 and a quantum well layer 42, wherein the quantum well layer 42 is positioned between the quantum barrier layer 41 and is banded than the quantum barrier layer 41. The gap energy is low, and a confining energy level is created in this quantum well layer 42.

2 is an enlarged view of the active layer 40, and a diffusion barrier layer 43 is positioned between the quantum barrier layer 41 and the quantum well layer 42. The diffusion barrier layer 43 may serve to prevent the atoms included in the quantum well layer or the quantum barrier layer from diffusing to the adjacent layer.

The quantum barrier layer 41 or the quantum well layer 42 formed in the active layer 40 of the nitride semiconductor light emitting device may include an InGaN material. Of these, the quantum well layer 42 may include more In components to control the energy band gap.

As described above, the InGaN material used in the active layer 40 is unstable in its state or bonded state, so that In atoms escape and diffuse into the adjacent layer even at low energy.

That is, In atoms contained in the quantum well layer 42 easily escape and diffuse into the quantum barrier layer 41. In particular, this phenomenon may occur a lot during the temperature increase during the growth of the active layer 40, and this phenomenon may appear more at high In or high current.

The out-diffusion phenomenon of In may cause defects between the quantum well layer 42 and the quantum barrier layer 41, and may cause emission or non-emission of unwanted energy, thereby improving the luminous efficiency of the light emitting device. Can be reduced.

At this time, the diffusion barrier layer 43 located between the quantum barrier layer 41 and the quantum well layer 42 can prevent this phenomenon to produce a light emitting device having a high quality active layer 40, which improves the luminous efficiency You can.

As the diffusion barrier layer 43, a material containing an atom having a smaller lattice constant than InGaN included in the quantum well layer 42 may be used.

As an example, AlGaN can be used as the diffusion barrier layer 43 for preventing the diffusion of In. Then, it is difficult to move the In atoms of the quantum well layer 42 to the quantum barrier layer 41 because a large amount of energy is required to replace the unstable In valence Al atoms with a small lattice constant. In this case, the quantum barrier layer 41 may include an InGaN or GaN material containing less In.

As such, the diffusion barrier layer 43 may be positioned between the quantum well layer 42 including InGaN and the quantum barrier layer 41 including GaN or InGaN, and as shown in FIG. 2, the quantum well layer 42. Located at the lower side and the upper side of), it is possible to prevent In atoms of the quantum well layer 42 from diffusing into the quantum barrier layer 41.

According to the present embodiment, the lattice constant of the diffusion barrier layer 43 located between the quantum barrier layer 41 and the quantum well layer 42 has a value between the lattice constants of GaN and InGaN. More specifically, for InGaN, it is advantageous that the lattice constant is smaller than the lattice constant of InGaN (In _x Ga _1-x N (0.10≤x≤0.30)) in which the In component has a value between 0.10 and 0.30.

In addition, the composition of AlGaN included in the diffusion barrier layer 43 may be AlGaN (Al _x Ga _{1 - x} N (0.01≤x≤1.00)) in which the Al component has a value between 0.01 and 1.00. That is, AlGaN having a very small Al component may be used, and AlN may be used.

The AlGaN layer used as the diffusion barrier layer 43 is advantageously a thickness through which an n-type or p-type carrier can tunnel, and the thickness may be 0.1 nm or more and 2 nm or less.

If the diffusion barrier layer 43 containing the AlGaN material is too thick, it can act as a high barrier for electrons and hole carriers, so it is advantageous that the thickness thereof is as thin as possible.

The In composition of the quantum barrier layer 41 and the quantum well layer 42 in the active layer 40 and the number of repetitions of each layer can be arbitrarily set according to the target emission wavelength.

On the other hand, the diffusion barrier layer 43 may be conductive. That is, the diffusion barrier layer 43 may include a p-type dopant or an n-type dopant.

That is, the entire diffusion barrier layer 43 may be doped n-type or p-type, and in some cases, the diffusion barrier layer 43 close to the n-type nitride semiconductor layer 30 may be doped n-type. The diffusion barrier layer 43 close to the p-type nitride semiconductor layer 50 may be doped in a p-type.

Such doping may use delta doping in which only a single atomic layer or equivalent thin layer is doped. That is, n-type doping may use Si delta doping, and p-type doping may use Mg delta doping.

Meanwhile, a cap layer (not shown) made of AlGaN may be disposed directly on the active layer 40, and the cap layer may prevent evaporation of InGaN or diffusion of n-type impurities introduced into the p-type nitride semiconductor layer 50. Can function. The AlGaN layer can be arbitrarily set in thickness and composition, and can be omitted.

3 illustrates an example of a vertical nitride light emitting device, and the p-type electrode 200, the p-type nitride semiconductor layer 300, the active layer 400, and the n− are sequentially formed on the conductive substrate 100. The structure in which the type nitride semiconductor layer 500 and the n-type electrode 600 are located is shown.

Similar to the horizontal nitride based light emitting device described above, the n-type nitride semiconductor layer 500 may use an n-type GaN layer having a thickness of 0.1 μm to 10 μm, and the p-type nitride semiconductor layer 300 may be P-type GaN layers between 0.03 μm and 1 μm may be used.

The active layer 400 may include at least one quantum barrier layer 410 and a quantum well layer 420.

The semiconductor structure including the p-type nitride semiconductor layer 300, the active layer 400, and the n-type nitride semiconductor layer 500 may be protected by the passivation layer 800 and form n as the main emission surface. The light extraction structure 700 may be positioned on the top surface of the -type nitride semiconductor layer 500.

As shown in FIG. 4, in the active layer 400, a diffusion barrier layer 430 is positioned between the quantum barrier layer 410 and the quantum well layer 420. The diffusion barrier layer 430 may serve to prevent the atoms included in the quantum well layer 420 or the quantum barrier layer 410 from diffusing to the adjacent layer, and the diffusion barrier layer 430 may be formed as described above. Since they may be the same, they are omitted below.

On the other hand, the conductive substrate 100 may be made of a metal or a semiconductor, in the case of including a semiconductor, as shown in Figure 5, the contact layer 120 includes a conductive semiconductor layer 110 located on the upper and lower sides It can be done by.

Referring to the characteristics of the manufacturing process of the light emitting device described above are as follows.

In FIG. 1, trimethylgallium (TMG) and / or triethyl gallium (TEG) may be used as a gallium (Ga) source gas to form the semiconductor layers 20, 30, 40, and 50 on the substrate 10. As the nitrogen (N) source gas, ammonia (NH 3) or dimethylhydrazine (DMHy) may be used.

In addition, trimethyl indium (TMI, In (CH ₃ ) ₃ ) may be used as the In source gas, and trimethyl aluminum (TMAl, Al (CH ₃ ) ₃ ) may be used as the Al source gas.

The semiconductor layers 20, 30, 40, and 50 may be metal organic chemical vapor deposition (MOCVD), hydride vapor phase epitaxy (HVPE), or molecular beam epitaxy (Molecular beam epitaxy). MBE), metalorganic chemical vapor phase epitaxy (MOCVPE), or the like.

The undoped nitride semiconductor layer 20 used as the buffer layer is a layer for alleviating the occurrence of defects such as dislocations between the substrate 10 and the n-type nitride semiconductor layer 30, and is grown at a relatively high temperature.

The n-type nitride semiconductor layer 30 is a layer on which the n-type electrode 80 is formed, and may be doped with n-type impurities such as Si or Ge, for example, GaN or AlGaN. The n-type nitride semiconductor layer 30 may be a single layer, but is not limited thereto and may be a multilayer in some cases.

Meanwhile, a nuclear layer (not shown) may be formed on the substrate 10 to form the undoped nitride semiconductor layer 20. The nucleus layer may be formed of (Al, Ga) N at a low temperature of 400 to 600 ° C. to grow the undoped nitride semiconductor layer 20 on the substrate 10, and may be formed of AlN. This nuclear layer can be formed to a thickness of about 25 nm.

As described above, the active layer 40 may have a multi-quantum well structure in which a quantum barrier layer 41 and a quantum well layer 42 are alternately stacked, and the quantum well layer 42 includes a GaN or InGaN layer. can do.

The quantum barrier layers 41 in the multi-quantum well structure may include relatively thicker barrier layers, wider bandgap barrier layers, or barrier layers doped with p-type impurities.

In addition, a transparent electrode 16 such as Ni / Au or an indium tin oxide film (ITO) is formed on the p-type nitride semiconductor layer 50, and the p-type electrode 70 is formed thereon, for example, by a lift-off process. Can be. In addition, an n-type electrode 80 made of Ti / Al or the like may be formed on the n-type nitride semiconductor layer 30 by a lift-off process.

Also in the structure of the vertical nitride semiconductor light emitting device having the structure as shown in FIG.

However, the vertical structure separates the growth substrate after fabricating the conductive substrate 100 on the p-type electrode 200 positioned on the semiconductor layers 300, 400, and 500 fabricated on the growth substrate (not shown). The formation of the n-type electrode 600 on the surface of the n-type nitride semiconductor layer 500 thus separated is different.

In this case, the light extraction structure 700 for light extraction may be formed on the outer surface of the n-type nitride semiconductor layer 500 where the n-type electrode 600 is formed, that is, the main emission surface by etching. It is.

The diffusion barrier layer of the quantum well structure described above can provide a nitride semiconductor light emitting device capable of obtaining high efficiency even at a long wavelength or a high current by minimizing out-diffution of In between the quantum barrier layer and the quantum well layer. .

The out-diffusion phenomenon of In may cause defects between the quantum well layer and the quantum barrier layer, and may cause the emission or non-emission of unwanted energy, thereby reducing the efficiency of the light emitting device. By minimizing In diffusion of the barrier layer and the quantum well layer, it is possible to provide a nitride semiconductor light emitting device capable of obtaining high efficiency even at a long wavelength and a high current.

While some embodiments of the present invention have been described by way of example, those skilled in the art will appreciate that various modifications and variations can be made without departing from the essential features thereof.

Therefore, the embodiments described above should not be construed as limiting the technical spirit of the present invention but merely for better understanding.

The scope of the present invention is not limited by these embodiments, and should be interpreted by the following claims, and the technical spirit within the scope equivalent thereto should be interpreted as being included in the scope of the present invention.

10 substrate 20 undoped nitride semiconductor layer
30: n-type nitride semiconductor layer 40: active layer
50: p-type nitride semiconductor layer 60: transparent electrode
70: p-type electrode 80: n-type electrode

Claims (13)

In a nitride semiconductor light emitting device,
A first conductive semiconductor layer;
A second conductive semiconductor layer;
An active layer disposed between the first conductive semiconductor layer and the second conductive semiconductor layer and including at least one quantum barrier layer and a quantum well layer; And
Located between the quantum barrier layer and the quantum well layer, nitride-based semiconductor light emitting device comprising a diffusion prevention layer for preventing the atoms contained in the quantum well layer or quantum barrier layer. The nitride-based semiconductor light emitting device of claim 1, wherein the quantum well layer comprises In. The nitride-based semiconductor light emitting device according to claim 2, wherein the diffusion barrier layer contains atoms having a smaller lattice constant than the In atoms. The nitride-based semiconductor light emitting device according to claim 1, wherein the diffusion barrier layer comprises Al. The nitride-based semiconductor light emitting device according to claim 1, wherein the composition of Al is expressed by Al _x Ga _{1 - x} N (0.01≤x≤1.00). The nitride-based semiconductor light emitting device according to claim 1, wherein the diffusion barrier layer has a thickness of 0.1 nm or more and 2 nm or less. The nitride-based semiconductor light emitting device according to claim 1, wherein a lattice constant of the diffusion barrier layer is between a lattice constant of GaN and a lattice constant of InGaN. The nitride-based semiconductor light emitting device according to claim 1, wherein a lattice constant of the diffusion barrier layer is between a lattice constant of GaN and a lattice constant of In _x Ga _{1- x} N (0.10 ≦ _x ≦ 0.30). The nitride-based semiconductor light emitting device according to claim 1, wherein the diffusion barrier layer is conductive. The nitride-based semiconductor light emitting device of claim 1, wherein the diffusion barrier layer comprises a first conductive dopant or a second conductive dopant. The diffusion barrier layer of claim 10, wherein the diffusion barrier layer relatively close to the first conductive semiconductor layer comprises the first conductive dopant, and the diffusion barrier layer relatively close to the second conductive semiconductor layer is the second conductive dopant. Nitride-based semiconductor light emitting device comprising a. The nitride-based semiconductor light emitting device of claim 1, wherein the diffusion barrier layer prevents atoms contained in the quantum well layer from diffusing into the quantum barrier layer. The nitride-based semiconductor light emitting device of claim 1, wherein the diffusion barrier layer is positioned above and below the quantum well layer.

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