KR20120135821A - Light emitting diode and its manufacturing method - Google Patents

Abstract

PURPOSE: A light emitting diode and a manufacturing method thereof are provided to reduce internal reflection of light by including an anti-reflective structure having a cycle smaller than a multi-layer and a light emitting wavelength. CONSTITUTION: A barrier layer is formed on the upper end of a bottom contact layer. An active layer(120) has single and multiple quantum well structures. A top contact layer(130) is formed on the upper end of the active layer. A multi-layer(133) has a thickness smaller than a light emitting wavelength at an external part of the top contact layer and the bottom contact layer. The size of an anti-reflective structure is smaller than the light emitting wavelength of a light emitting diode.

Description

LIGHT EMITTING DIODE AND ITS MANUFACTURING METHOD}

The present invention relates to a light emitting diode and a method of manufacturing the same. More specifically, the upper contact layer of the light extraction region of the light emitting diode has a thickness smaller than that of the light emitting wavelength and has a smaller period than that of a multi-layer or light emitting wavelength which gradually varies in refractive index. A light emitting diode having an antireflective structure and a method of manufacturing the same.

In general light emitting diodes, the internal quantum efficiency is nearly 100% (I. Schnitzer et al., Appl. Phys. Lett. 78, 3379), but the external quantum efficiency outside the actual device is less than 30% (MG Craford, Semiconductor and semimetals, 64 (Academic press, 2000)). This is due to the total reflection caused by the difference in refractive index at the interface between the device and the air when the light produced in the multi-quantum well structure comes out of the device. Due to this physical phenomenon, the light extraction efficiency of the conventional light emitting diode is very low.

In order to overcome this problem, the surface roughness is formed through p-type gallium nitride through a non-selective etching process without a mask, so that when the light traveling upward reaches a rough surface, the incident angle is smaller than the critical angle so that the light is easily emitted to the outside of the light emitting diode. There is an example of increasing the light extraction efficiency by allowing it to exit. And dry etching the p-type gallium nitride using a mask to form a protrusion to increase the light extraction efficiency by allowing the light to escape easily outside the light emitting diode by making the incident angle smaller than the critical angle when reaching the protrusion proceeding to the upper surface There is an example. In US Pat. No. 6,842,403, there is an example of improving the light extraction efficiency of light by making a photonic band gap formed photonic crystal by giving a difference in periodic refractive index on the p-type gallium nitride surface of the light emitting diode.

However, this technique may cause a problem that light of a certain angle enters again and is reabsorbed in the active layer or the defect of epi. As a solution to the above, the present invention reduces the Fresnel reflection caused by the refractive index difference rather than simply increasing the critical angle in order to increase the light extraction efficiency. To create an antireflective structure. However, research on improving the LED efficiency using the same has not been made much, and in particular, there is no example applied to the vertical light emitting diode which is a recent issue.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has a thickness smaller than the light emission wavelength on the outer side of at least one of an upper contact layer, a lower contact layer, or a substrate, which is a light extraction region of a light emitting diode, and gradually varies the refractive index. The present invention provides a light emitting diode and a method of manufacturing the same, which reduce internal reflection by having an antireflective structure having a period smaller than that of a multi-layer or light emitting wavelength.

The present invention for achieving the technical problem, the lower contact layer consisting of n-type or p-type Al _x Ga _y In _z N (0 ≤ x, y, z ≤ 1); A barrier layer formed on top of the lower contact layer and formed of Al _x Ga _y In _z N (0 ≦ x, y, z ≦ 1) and Al _x Ga _y In _z N (0 ≦ x, y, z ≦ 1). An active layer having a single or multi-quantum well structure including at least one well layer formed thereon; An upper contact layer formed on top of the active layer and formed of p-type or n-type Al _x Ga _y In _z N (0 ≦ x, y, z ≦ 1); It includes, and characterized in that the outer side of the upper contact layer or the lower contact layer has a thickness less than the light emitting wavelength and has a non-reflective structure of a periodicity less than the multi-layer or light emitting wavelength with gradually different refractive index.

Also preferably, the anti-reflective structure is any one of a multi-layer having a size smaller than the light emitting wavelength of the light emitting diode and gradually decreasing the refractive index, nanocones, nanorods, nanotips, or nanospheres having a pyramid structure with a period smaller than the light emitting wavelength. It is characterized by having a structure of.

Also preferably, a substrate made of any one of aluminum oxide, silicon (Si), gallium nitride (GaN), gallium arsenide (GaAs), silicon carbide (SiC), zinc oxide (ZnO), or a metal at the bottom of the lower contact layer; Further comprising:

In addition, the outer surface of the substrate is characterized in that it has a thickness less than the light emitting wavelength and has a non-reflective structure of a periodicity less than the multi-layer or light emitting wavelength having a different refractive index gradually.

Also preferably, the antireflective structure may include a 3-4 component oxide including gallium nitride, zinc oxide, and zinc oxide, and a 3-4 component oxide including tin and thio oxide (ITO) and tin oxide or oxide. Characterized in that made of any one of magnesium.

Also preferably, (a) sequentially growing a lower contact layer, an active layer and an upper contact layer made of n-type or p-type Al _x Ga _y In _z N (0 ≦ x, y, z ≦ 1) on the substrate; And (b) forming a non-reflective structure having a thickness smaller than the light emitting wavelength and gradually reducing the refractive index of at least one of the lower contact layer, the upper contact layer, or the substrate with a different refractive index. And a control unit.

And, preferably, the step (b) has a thickness smaller than the light emission wavelength by using any one of a method using this beam (E-beam) lithography, a method using a hologram of laser light or a method using a nanoimprint. It is characterized by forming a non-reflective structure of a period smaller than the multi-layer or the light emitting wavelength having a different refractive index gradually.

According to the present invention as described above, at least one of the upper contact layer, the lower contact layer, or the substrate, which is the light extraction region of the light emitting diode, has a thickness smaller than that of the light emitting wavelength and gradually increases the refractive index of the multilayer or the light emitting wavelength. Light extraction efficiency is improved compared to the prior art by reducing the internal reflection of light, including a small period of antireflection structure.

1 is a block diagram of a light emitting diode according to an embodiment of the present invention.
2 is a block diagram of a light emitting diode having a multi-layer according to an embodiment of the present invention.
Figure 3 is an exemplary view of a cylindrical anti-reflective structure according to an embodiment of the present invention.
4 is an exemplary view of a stepped cylindrical anti-reflective structure according to an embodiment of the present invention.
5 is an exemplary view of a pyramidal antireflection structure according to an embodiment of the present invention.
6 is a flow chart of a method of manufacturing a light emitting diode according to an embodiment of the present invention.

Specific features and advantages of the present invention will become more apparent from the following detailed description based on the accompanying drawings. It is to be noted that the detailed description of known functions and constructions related to the present invention is omitted when it is determined that the gist of the present invention may be unnecessarily blurred.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to the accompanying drawings.

A light emitting diode 100 and a method of manufacturing the same according to the present invention will be described with reference to FIGS. 1 to 6.

1 is a configuration diagram of a light emitting diode 100 according to an embodiment of the present invention, as shown in the light emitting diode 100, the lower contact layer 110, the active layer 120, and the upper contact to the substrate 10. Layer 130.

The substrate 10 is made of any one of aluminum oxide (sapphire), silicon (Si), gallium nitride (GaN), gallium arsenide (GaAs), silicon carbide (SiC), zinc oxide (ZnO), or a metal. After forming the light emitting diode 100 on one side of the (10) and the light emitting diode 100 is formed may be separated from the light emitting diode (100).

The lower contact layer 110 may include n-type or p-type Al _x Ga _y In _z N (0 ≦ x, y, z ≦ 1) on one side of the substrate 10.

The active layer 120 is formed on top of the lower contact layer 110 and has a barrier layer made of Al _x Ga _y In _z N (0 ≤ x, y, z ≤ 1) and Al _x Ga _y In _z N (0 ≤). It has a single or multi-quantum well structure comprising at least one well layer consisting of x, y, z ≤ 1).

The upper contact layer is formed on the active layer 120 and is formed of p-type or n-type Al _x Ga _y In _z N (0 ≦ x, y, z ≦ 1).

In addition, the outer portion of the upper contact layer 130 or the lower contact layer 110 in one embodiment, as shown in Figure 2 or 3, a multi-layer 133 having a thickness smaller than the emission wavelength and gradually vary the refractive index Or an antireflection structure 131 having a period smaller than the light emission wavelength. When the substrates are combined, the substrate 10 may have a multi-layer 133 having a thickness smaller than the light emission wavelength and gradually varying the refractive index, or an antireflection structure 131 having a period smaller than the light emission wavelength.

The antireflective structure 131 is a subwavelength grating structure having a period smaller than a light emission wavelength and may have various types of antireflective structures 131 such as pyramidal nanocones, nanorods, nanotips, or nanospheres. . At this time, the antireflective structure 131 is a 3-4 component oxide including gallium nitride, zinc oxide, zinc oxide, a 3-4 component oxide including ithio (ITO) and ithio (ITO), tin oxide or magnesium oxide The reflectance characteristics can be calculated using either rigorous coupled-wave analysis (RCWA).

The multi-layer 133 includes a plurality of layers having a thickness smaller than the light emission wavelength, and each layer gradually varies in refractive index.

In general, the light emitting diode 100 has a red wavelength of 700 nm, a green wavelength of 550 nm, and a blue wavelength of 450 nm, so the antireflective structure 131 has a size smaller than several hundred nm of the light emitting wavelength. In this case, the anti-reflective structure 131 may have a shape in which a simple cylindrical structure is repeated as shown in FIG. 3 in the form of a moth eye, and a stepped cylindrical or pyramidal structure as shown in FIG. 4 or 5. Not only may have a repeated form, but various modifications may be made depending on the emission wavelength and the type and situation of the upper contact layer 130 or the lower contact layer 110.

Accordingly, the antireflective structure 131 increases the light extraction efficiency by reducing the Fresnel reflection caused by the difference in refractive index so that the light can be directly exited without internal reflection when the light exits.

Hereinafter, a manufacturing method of the light emitting diode 100 having the above configuration will be described.

6 is a flow chart of a method of manufacturing a light emitting diode 100 according to an embodiment of the present invention, as shown in the substrate 10, n-type or p-type Al _x Ga _y In _z N (0 ≤ x, y, A step (S100) of sequentially growing the lower contact layer 110, the active layer 120 and the upper contact layer 130 made of z ≤ 1) and the outside of the lower contact layer 110 or the upper contact layer 130 And forming a non-reflective structure 131 having a period smaller than a light emission wavelength on the surface (S200).

Specifically, the S100 process may include a lower contact layer 110, an active layer 120, and an upper contact layer 130 formed of Al _x Ga _y In _z N (0 ≦ x, y, z ≦ 1) on the substrate 10. Growing sequentially. In this case, the lower contact layer 110, the active layer 120, and the upper contact layer 130 may be grown and separated from the substrate 10.

The S200 process may include a multi-layer 133 or a light emitting wavelength having a thickness smaller than a light emitting wavelength on one or more of the lower contact layer 110, the upper contact layer 130, or the substrate 10 and gradually varying the refractive index. A smaller period antireflection structure 131 is formed. In this case, the anti-reflective structure 131 having a smaller size than the emission wavelength may be formed by various methods such as using the E-beam lithography, using the hologram of the laser light, or using the nanoimprint.

The anti-reflective structure 131 reduces the Fresnel reflection caused by the difference in refractive index so that the light can be directly exited without internal reflection when the light exits, thereby increasing the light extraction efficiency.

While the present invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by 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 by the appended claims. It will be appreciated by those skilled in the art that numerous changes and modifications may be made without departing from the invention. Accordingly, all such appropriate modifications and changes, and equivalents thereof, should be regarded as within the scope of the present invention.

10 substrate 100 light emitting diode
110: lower contact layer 120: active layer
130: upper contact layer 131: antireflective structure
133: multi-layer

Claims (7)

a bottom contact layer consisting of n-type or p-type Al _x Ga _y In _z N (0 ≦ x, y, z ≦ 1);
A barrier layer formed on top of the lower contact layer and formed of Al _x Ga _y In _z N (0 ≦ x, y, z ≦ 1) and Al _x Ga _y In _z N (0 ≦ x, y, z ≦ 1). An active layer having a single or multi-quantum well structure including at least one well layer formed thereon; And
An upper contact layer formed on the active layer and formed of p-type or n-type Al _x Ga _y In _z N (0 ≦ x, y, z ≦ 1); Including,
A light emitting diode having an antireflective structure having a thickness smaller than a light emitting wavelength and having a smaller refractive index than a light emitting wavelength and having a period smaller than a light emitting wavelength.
The method of claim 1,
The antireflective structure,
A light emitting diode having a structure smaller than a light emitting wavelength of a light emitting diode and having a smaller refractive index and a structure of any one of a nanocone, a nanorod, a nanotip, or a nanosphere having a pyramid structure having a cycle smaller than the light emitting wavelength. diode.
The method of claim 1,
A substrate made of any one of aluminum oxide, silicon (Si), gallium nitride (GaN), gallium arsenide (GaAs), silicon carbide (SiC), zinc oxide (ZnO), or a metal under the lower contact layer; Light emitting diodes further comprising.
The method of claim 3, wherein
A light emitting diode having a thickness less than a light emitting wavelength on the outside of the substrate and having an anti-reflective structure with a period smaller than that of the light emitting wavelength or a multi-layer having a different refractive index.
The method of claim 1,
The antireflective structure,
3-4 component oxides including gallium nitride, zinc oxide, and zinc oxide, and 3-4 component oxides including ithio (ITO) and Ithio (ITO), tin oxide or magnesium oxide Light emitting diode.
(a) sequentially growing a lower contact layer, an active layer, and an upper contact layer including n-type or p-type Al _x Ga _y In _z N (0 ≦ x, y, z ≦ 1) on the substrate; And
(b) forming a non-reflective structure having a thickness smaller than the light emitting wavelength and gradually changing the refractive index of at least one of the lower contact layer, the upper contact layer, or the substrate and having a period smaller than that of the light emitting wavelength; Light emitting diode manufacturing method comprising a.
The method of claim 5, wherein
The step (b)
Multi-layer or light-emitting wavelengths having a thickness smaller than the light-emitting wavelength and gradually varying in refractive index by using any one of the method using the E-beam lithography, the method using the hologram of the laser light, or the method using the nanoimprint. A method of manufacturing a light emitting diode, characterized by forming an antireflective structure with a smaller cycle.

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