KR20120029660A - Semiconductor light emitting device and method for manufacturing thereof - Google Patents

Abstract

PURPOSE: A semiconductor light emitting device and a manufacturing method thereof are provided to enhance light output efficiency by forming metal particles on a transparent electrode layer or a semiconductor layer. CONSTITUTION: A first semiconductor layer is formed on a substrate. An active layer is formed on the first semiconductor layer. A second semiconductor layer is formed on the active layer. A metal layer is formed on the second semiconductor layer. A metal particle(410) is formed on the second semiconductor layer by adding heat to the metal layer. A transparent electrode layer(370) is formed on the second semiconductor layer in order to cover the metal particle. A part of the first semiconductor layer is exposed. A first electrode is formed on the first semiconductor layer which is exposed. A second electrode is formed on the transparent electrode layer.

Description

Semiconductor Light Emitting Device and Method for Manufacturing Thereof}

The present invention relates to a semiconductor light emitting device, and more particularly, to a semiconductor light emitting device using a metal particle and a method of manufacturing the same.

The nitride semiconductor light emitting device has a light emitting area covering ultraviolet, blue and green areas. In particular, GaN-based nitride semiconductor light emitting device is a high-speed switching such as optical devices of blue / green LED (Light Emitting Diode), metal semiconductor field effect transistor (MESFET) or hetero junction field effect transistors (HEMT) It is applied to electronic devices which are high output devices.

FIG. 1 is a cross-sectional view schematically illustrating a structure of a general semiconductor light emitting device, and FIG. 2 is a view illustrating total reflection of internal light of a general semiconductor light emitting device.

As shown in FIG. 1, the general nitride semiconductor light emitting device 100 includes a substrate 110, a buffer layer 120, an undoped semiconductor layer 130, an N-type nitride semiconductor layer 140, an active layer 150, The N-type nitride semiconductor layer 140 exposed by etching the P-type nitride semiconductor layer 160, the transparent electrode layer 170, the P-type electrode 180, and the active layer 150 and a portion of the P-type nitride semiconductor layer 160. N-type electrode 190 is formed on the ().

In the semiconductor light emitting device 100, when a voltage is applied to the P-type electrode 180 and the N-type electrode 190, a forward bias is performed between the P-type nitride semiconductor layer 160 and the N-type nitride semiconductor layer 140. Bias), and electrons and holes are recombined in the active layer 150 to emit light.

The nitride semiconductor light emitting device is an important problem how to efficiently extract the light generated in the active layer to the outside, in the case of a general nitride semiconductor light emitting device, the material constituting the nitride semiconductor light emitting device as shown in FIG. Because the refractive index of is larger than the refractive index of the material surrounding the outside of the device (e.g., air, resin, substrate, etc.), photons generated inside the device do not escape to the outside and are totally reflected inside. There is a problem in that light extraction efficiency (Extraction Efficiency) is lowered by reabsorption.

That is, in the conventional semiconductor light emitting device (LED), when light is generated by the combination of electrons and holes between the N-type semiconductor and the P-type semiconductor, the light exits through a transparent electrode such as ITO formed on the upper surface, As shown, since the refractive indices of the semiconductor material and the transparent electrode are larger than the refractive indices of the free space, the light incident on the light emitting surface at an angle greater than the critical angle is totally reflected and proceeds inside the absorbed light. Accordingly, in the conventional semiconductor light emitting device, a phenomenon in which light emission efficiency is deteriorated is generated, and heat may be generated because heat generated in the process of absorbing the light that has not escaped from the inside may occur.

In order to solve this problem, a method of extracting the lateral light generated in the active layer in the longitudinal direction has been proposed by forming a predetermined angle on the sidewall of the stacked structure of the semiconductor light emitting device and forming the sidewall as a reflective surface. This makes it difficult to manufacture a semiconductor light emitting device, thereby increasing the manufacturing cost of the semiconductor light emitting device.

SUMMARY OF THE INVENTION An object of the present invention for solving the above problems is to provide a semiconductor light emitting device and a method of manufacturing the same, wherein metal particles are formed in a transparent electrode layer or a semiconductor layer.

The semiconductor light emitting device according to the present invention for achieving the above technical problem, the substrate; A first semiconductor layer formed on the substrate; An active layer formed on the first semiconductor layer; A second semiconductor layer formed on the active layer; A transparent electrode layer formed on the second semiconductor layer; A first electrode formed on the first semiconductor layer on which the active layer, the second semiconductor layer, and the transparent electrode layer are not formed; A second electrode formed on the transparent electrode; And metal particles formed in one of the first semiconductor layer, the second semiconductor layer, and the transparent electrode layer.

According to an aspect of the present invention, there is provided a method of manufacturing a semiconductor light emitting device, including sequentially forming a first semiconductor layer, an active layer, and a second semiconductor layer on a substrate; Forming a metal layer on the second semiconductor layer; Applying heat to the metal layer to form metal particles on the second semiconductor layer; Forming a transparent electrode layer on the second semiconductor layer to cover the metal particles; Exposing a portion of the first semiconductor layer; And forming a first electrode on the exposed first semiconductor layer, and forming a second electrode on the transparent electrode layer.

Another method of manufacturing a semiconductor light emitting device according to the present invention for achieving the above-described technical problem, comprising the steps of sequentially forming a first semiconductor layer and an active layer on a substrate; Forming a metal layer on the active layer; Applying heat to the metal layer to form metal particles on the active layer; Forming a second semiconductor layer on the active layer to cover the metal particles; Forming a transparent electrode layer on the second semiconductor layer; Exposing a portion of the first semiconductor layer; And forming a first electrode on the exposed first semiconductor layer, and forming a second electrode on the transparent electrode layer.

According to the above solution, the present invention provides the following effects.

That is, the present invention provides the effect that light is emitted to the outside by scattering of the metal particles by forming the metal particles in the transparent electrode layer or the semiconductor layer, thereby increasing the light emission efficiency.

In addition, the present invention provides an effect that can solve the heat generation problem by letting the light that is not escaped to the outside due to total reflection phenomenon to the outside by the heat by using the scattering of the metal particles.

1 is a cross-sectional view schematically showing the structure of a general semiconductor light emitting device.
2 is a view showing that the internal light of the general semiconductor light emitting device is totally reflected.
3 is a view schematically showing a state in which the internal light of the semiconductor light emitting device according to the present invention is scattered by the metal particles.
Figure 4 is a graph showing the scattering and absorption efficiency according to the Mie theory of silver particles applied to the semiconductor light emitting device according to the present invention.
5 is an exemplary view showing a FDTD simulation result for a semiconductor light emitting device according to the present invention.
6 is a cross-sectional view showing the structure of a semiconductor light emitting device according to the present invention.
7A to 7E illustrate a method of manufacturing a semiconductor light emitting device according to the present invention.

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

3 is a view schematically showing a state in which the internal light of the semiconductor light emitting device according to the present invention is scattered by the metal particles, Figure 4 is a scattering by the Mie theory of silver particles applied to the semiconductor light emitting device according to the present invention; 5 is a graph showing absorption efficiency, and FIG. 5 is an exemplary diagram showing a FDTD simulation result for a semiconductor light emitting device according to the present invention.

That is, the present invention is one of methods for minimizing the total reflection phenomenon inside a semiconductor light emitting device (LED), by using scattering of metal particles, thereby maximizing light extraction efficiency.

To this end, as shown in FIG. 3, the present invention is configured to apply metal particles to the inside of the semiconductor light emitting device so that light is emitted to the outside by scattering of the metal particles.

Metal particles of the semiconductor light emitting device according to the present invention may be located in various places such as a transparent electrode (ITO) layer, a P-type semiconductor layer, an N-type semiconductor layer. In addition, gold particles or silver (Ag) particles may be applied as the metal particles.

On the other hand, the calculation of the scattering efficiency of the 60 nm-spherical silver (Ag) particles according to the Mie theory is shown as shown in Figure 4, it can be seen that the scattering occurs a lot around 450nm by the plasmon resonance (plasmon) resonance .

Therefore, the present invention, in the above region, it is preferable that the light is scattered by using the metal particles, reducing the total reflection light is designed so that most of the light is emitted to the outside. That is, in the semiconductor light emitting device according to the present invention, a spherical silver (Ag) having a radius of 50 to 70 nm is used as a metal particle and is applied to a blue semiconductor light emitting device (Blue LED) having a wavelength of 350 to 500 nm. In this case, the light extraction efficiency is maximized. In particular, in consideration of a manufacturing process, it is preferable to be positioned on the transparent electrode ITO.

Meanwhile, FDTD (Finite-Difference) is a method of total reflection between the interior and free space of a conventional semiconductor light emitting device and light extraction by preventing total reflection using metal particles (Ag) in the semiconductor light emitting device according to the present invention. The simulation result using the Time-Domain method is shown in FIG. 5. Assuming that the index of refraction inside the semiconductor is 2, the critical angle at which total reflection occurs is 30 degrees, and FIG. 5 simulates a case where incident light proceeds to the boundary surface at 43 degrees, which is an angle at which total reflection occurs. One result is shown. At this time, the radius of the silver (Ag) particles is 60nm, assuming a light of 450nm wavelength. That is, in the case of the conventional semiconductor light emitting device (LED), as can be seen in Figure 5 (a), it can be seen that all the light is totally reflected back into the semiconductor light emitting device, in the case of the semiconductor light emitting device according to the present invention As shown in (b) of FIG. 5, it is possible to confirm that a part of the light exits outside the semiconductor light emitting device due to the scattering of the metal particles (silver particles) 410.

That is, the present invention uses the scattering, reflection, and plasmon of the metal particles contained in the semiconductor light emitting device to escape the light generated inside the semiconductor light emitting device to the outside, thereby increasing the light emission efficiency of the semiconductor light emitting device. In this case, the internal light efficiency is enhanced by coupling of plasmon and excitons in the metal particles and the light emitting layer.

6 is a cross-sectional view showing the structure of a semiconductor light emitting device according to the present invention.

As shown in FIG. 6, the semiconductor light emitting device 300 according to the present invention includes a substrate 310, a buffer layer 320, an undoped semiconductor layer 330, an N-type nitride semiconductor layer 340, and an active layer 350. , A P-type nitride semiconductor layer 360, a metal particle 410, a transparent electrode layer 370, a P-type electrode 380, and an N-type electrode 390.

Since the substrate 310 has the same crystal structure as that of the nitride semiconductor material grown thereon and there is no commercial substrate forming a lattice match, a sapphire substrate is generally used in consideration of lattice matching.

The sapphire substrate is a Hexa-Rhombo R3c symmetric crystal with a lattice constant of 13.001Å in the c-axis direction and 4.765Å in the a-axis direction, and in the sapphire orientation plane. Has a C (0001) plane, an A (1120) plane, an R (1102) plane, and the like.

Since the c plane of the sapphire substrate is relatively easy to grow a nitride semiconductor material and stable at high temperature, a sapphire substrate is mainly used as a substrate for a blue or green light emitting device.

The buffer layer 320 is to reduce the lattice constant difference between the substrate 310 and the N-type nitride semiconductor layer 340, and is formed on the substrate 310, for example, an AlInN structure, an InGaN / GaN superlattice structure, and InGaN / GaN. The stacking structure may be selected from a stacking structure of AlInGaN / InGaN / GaN.

The undoped semiconductor layer 330 is formed on the buffer layer 320 and may be formed of GaN. The undoped semiconductor layer 330 may be formed by, for example, supplying NH ₃ and trimetal gallium (TMGa) on the buffer layer 320 at a growth temperature of 1500 ° C.

In the above-described embodiment, both the buffer layer 320 and the undoped semiconductor layer 330 are described as being included. However, in the modified embodiment, only one of the buffer layer 320 and the undoped semiconductor layer 330 is included. It may or may not be all included.

The N-type nitride semiconductor layer 340 is formed on the undoped semiconductor layer 330 and is made of a semiconductor material such as GaN, AlGaN, InGaN, AlN, or AlInGaN doped with N-type impurities. N-type impurities include Si, Ge, Sn, Se, Te and the like.

The N-type nitride semiconductor layer 340 may include the above-mentioned semiconductor material by metal organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), or hydride vapor deposition (Hydride Vapor). It is formed by growing on the substrate 310 or the undoped semiconductor layer or buffer layer using a deposition process such as Phase Epitaxy (HVPE).

The active layer 350 is a layer for emitting light, and is usually formed by forming an InGaN layer as a well and growing an (Al) GaN layer as a barrier layer to form a multi-quantum well structure (MQW). In the blue light emitting diode, multiple quantum well structures such as InGaN / GaN are used, and in the ultraviolet light emitting diode, multiple quantum well structures such as GaN / AlGaN, InAlGaN / InAlGaN, and InGaN / AlGaN are used.

For the improvement of the efficiency of the active layer 350, the internal quantum efficiency of the light emitting diode is improved by controlling the wavelength of light by changing the composition ratio of In or Al, or by changing the depth of the quantum wells, the number and thickness of the active layers in the active layer. I'm making it. The active layer 350 is formed on the N-type nitride semiconductor layer 340 by using a deposition process such as an organometallic vapor deposition method, a molecular beam growth method, or a hydride vapor deposition method as in the N-type nitride semiconductor layer 340 described above. Can be.

The P-type nitride semiconductor layer 360 is formed on the active layer 350 and is made of a semiconductor material such as GaN, AlGaN, InGaN, AlN, or AlInGaN doped with P-type impurities. P-type impurities include Mg, Zn, or Be.

The P-type nitride semiconductor layer 360 described above is formed by growing the semiconductor material on the active layer 350 using a deposition process such as organometallic vapor deposition, molecular beam growth, or hydride vapor deposition.

The transparent electrode layer 370 is formed on the P-type nitride semiconductor layer 360. The transparent electrode layer 370 is suitable for lowering contact resistance with the P-type nitride semiconductor layer 360 having a relatively high energy band gap, and at the same time, has a good light transmittance for light emitted from the active layer 350 to be emitted upward. It is preferable to form. In general, the transparent electrode layer 370 mainly uses a double layer structure of Ni / Au, and has a relatively high contact resistance, but indium tin oxide (ITO), cadmium tin oxide (CTO), or titanium tungsten nitride (TiWN) to ensure good light transmittance. ) Can be used as a material.

The transparent electrode layer 370 may be formed by a deposition method such as chemical vapor deposition (CVD) and an e-beam evaporator, or a process such as sputtering, and the like may be used. It may be heat treated at a temperature of about 400 to 900 ℃ to improve.

The P-type electrode 380 is formed on the transparent electrode layer 370. The P-type electrode 380 may be formed by a deposition method such as a chemical vapor deposition method or an electron beam evaporation method, or a sputtering process, generally using Au or an alloy containing Au.

The N-type electrode 390 may be formed on the mesa-etched N-type nitride semiconductor layer 340 as a single layer or a plurality of layers made of a material selected from the group consisting of Ti, Cr, Al, Cu, and Au. Can be. The N-type electrode 390 may be formed on the N-type nitride semiconductor layer 340 by a deposition method such as chemical vapor deposition and electron beam evaporation, or a process such as sputtering.

Meanwhile, the semiconductor light emitting device according to the present invention includes the metal particles 410 in at least one of the transparent electrode layer 370, the P-type nitride semiconductor layer 360, and the N-type nitride semiconductor layer 340. 6 illustrates a semiconductor light emitting device in which metal particles 410 are disposed in the transparent electrode layer 370.

Here, gold or silver may be applied as the metal particles, but as described above, the semiconductor light emitting device according to the present invention uses a spherical silver (Ag) having a radius of 50 to 70 nm as the metal particles, and has a wavelength. When applied to a blue semiconductor light emitting device (Blue LED) that is between 350 ~ 500nm, it is characterized by maximizing the light extraction efficiency, the semiconductor light emitting device according to the present invention is configured to have the conditions as described above It is preferable.

Therefore, below, the manufacturing method of the semiconductor light emitting element which concerns on this invention with the conditions as mentioned above with reference to FIG. 7 is demonstrated in detail.

7A to 7E are views illustrating a method of manufacturing a semiconductor light emitting device according to the present invention.

First, referring to FIG. 7A, a buffer layer 320, an undoped semiconductor layer 330, an N-type nitride semiconductor layer 340, an active layer 350, and a P-type nitride semiconductor layer 360 are formed on a substrate 310. Form sequentially. In this case, at least one layer of the buffer layer 320 and the undoped semiconductor 330 may be formed, or both layers may not be formed.

Next, as shown in FIG. 7B, the metal layer 400 is formed on the P-type nitride semiconductor layer 360. Here, the metal layer may be laminated using gold or silver. However, as can be seen from the simulation using the FDTD in the above description, it is advantageous to use silver particles rather than gold particles in order to use effective scattering using metal particles having a radius of 50 to 70 nm for light in the region of 350 to 500 nm. In this embodiment, the metal layer 400 is formed of silver.

Next, as shown in Figure 7c, the metal layer is heated to a high temperature to melt and then maintained at a constant temperature to form a metal particle 410. That is, when the metal layer 400 formed of silver is heated to a high temperature of 961.9 ° C. or more, which is the melting point of silver, the metal layer melts and turns into a liquid state. Aggregate in the form of metal particles of the same shape. Therefore, when the metal particles are formed, the metal particles 410 may be formed on the P-type nitride semiconductor layer 360 by lowering the temperature thereafter.

Next, as shown in FIG. 7D, the transparent electrode layer 370 is formed on the P-type nitride semiconductor layer 360 on which the metal particles are formed to cover the metal particles.

Next, as shown in FIG. 7E, mesa etching is performed from the transparent electrode layer 370 to the N-type nitride semiconductor layer 340 to form the N-type electrode.

Finally, as shown in FIG. 7F, the P-type electrode 380 is formed on the transparent electrode layer 370 on which the metal particles 410 are formed, and the N-type electrode 390 is formed on the N-type nitride semiconductor layer 340. ).

Subsequently, although not shown, in order to improve the reliability of the semiconductor light emitting device, an insulating film is formed on the entire surface of the semiconductor light emitting device using an oxide such as SiO _2, and the substrate is thinned through lapping and polishing processes. After the thinning, the semiconductor light emitting device is cut using a laser or diamond to be separated into individual chips.

Through the above process, the semiconductor light emitting device according to the present invention can be manufactured.

Meanwhile, in the above description, the present invention has been described in that the metal particles 410 are included in the transparent electrode layer 370 on the upper portion of the P-type nitride semiconductor layer 360. However, the present invention describes the metal particles 410 as described above. May be formed in the N-type nitride semiconductor layer 340 or the P-type nitride semiconductor layer 360. However, in the case of the active layer 360, defects may occur due to the metal particles, and as a result, light emission efficiency of the active layer may be lowered, which is not suitable as a layer capable of forming metal particles.

The present invention as described above relates to a high efficiency semiconductor light emitting device (LED) using metal particles, and has the feature of improving the light extraction efficiency. That is, in the present invention, as one of methods for minimizing the total reflection phenomenon inside the semiconductor light emitting device, a method of maximizing light extraction efficiency using scattering of metal particles is used.

In detail, the present invention, in order to minimize the total reflection between the inside and the free space of the semiconductor light emitting device, the metal particles are applied to the inside of the semiconductor light emitting device by the reflection, scattering, plasmon of the metal particles to the outside light It is configured to come out.

Here, the metal particles may be located at various places such as a transparent electrode (ITO) layer, a P-type nitride semiconductor layer, an N-type nitride semiconductor layer, and the like.

On the other hand, the calculation of the scattering efficiency of the 60nm radius silver (Ag) particles according to the Mie theory is shown as shown in Figure 4, it can be seen that the scattering occurs a lot around 450nm by the plasmon resonance. Therefore, it is preferable that the semiconductor light emitting device according to the present invention is designed to emit light to the outside by scattering light using scattering in this area (Blue area) to reduce total reflection.

Those skilled in the art to which the present invention pertains will understand that the present invention can be implemented in other specific forms without changing the technical spirit or essential features. Therefore, it is to be understood that the embodiments described above are exemplary in all respects and not restrictive. The scope of the present invention is shown by the following claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts should be construed as being included in the scope of the present invention. do.

310: substrate 320: buffer layer
330: undoped semiconductor layer 340: N-type nitride semiconductor layer
350: active layer 360: P-type nitride semiconductor layer
370: transparent electrode layer 380: P-type electrode
390: N-type electrode 400: metal layer
410 metal particles

Claims (11)

Board;
A first semiconductor layer formed on the substrate;
An active layer formed on the first semiconductor layer;
A second semiconductor layer formed on the active layer;
A transparent electrode layer formed on the second semiconductor layer;
A first electrode formed on the first semiconductor layer on which the active layer, the second semiconductor layer, and the transparent electrode layer are not formed;
A second electrode formed on the transparent electrode; And
And a metal particle formed inside one of the first semiconductor layer, the second semiconductor layer, and the transparent electrode layer. The method of claim 1,
The metal particles,
A semiconductor light emitting device, characterized in that formed of gold or silver. The method of claim 1,
The active layer,
A semiconductor light emitting device, characterized in that for emitting a wavelength of 350 to 500nm. The method of claim 1,
The metal particles,
A semiconductor light emitting device having a radius in the range of 50 to 70 nm. The method of claim 1,
The metal particles,
And emitting light emitted from the active layer to the outside of the transparent electrode by reflection, scattering, or plasmon resonance. The method of claim 1,
At least one of a buffer layer and an undoped semiconductor layer is further included between the substrate and the first semiconductor layer. Sequentially forming a first semiconductor layer, an active layer, and a second semiconductor layer on the substrate;
Forming a metal layer on the second semiconductor layer;
Applying heat to the metal layer to form metal particles on the second semiconductor layer;
Forming a transparent electrode layer on the second semiconductor layer to cover the metal particles;
Exposing a portion of the first semiconductor layer; And
Forming a first electrode on the exposed first semiconductor layer, and forming a second electrode on the transparent electrode layer. Sequentially forming a first semiconductor layer and an active layer on the substrate;
Forming a metal layer on the active layer;
Applying heat to the metal layer to form metal particles on the active layer;
Forming a second semiconductor layer on the active layer to cover the metal particles;
Forming a transparent electrode layer on the second semiconductor layer;
Exposing a portion of the first semiconductor layer; And
Forming a first electrode on the exposed first semiconductor layer, and forming a second electrode on the transparent electrode layer. The method according to claim 7 or 8,
The metal particles,
Method for manufacturing a semiconductor light emitting device, characterized in that formed of gold or silver. The method according to claim 7 or 8,
Forming the metal particles,
A method of manufacturing a semiconductor light emitting device, characterized in that the metal layer formed of silver is heated above the melting point of the silver to cause the silver in the liquid state to aggregate into a spherical shape. The method according to claim 7 or 8,
And forming at least one of a buffer layer and an undoped semiconductor layer between the substrate and the first semiconductor layer.

Images