KR101189162B1 - Light emitting diode and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a structure and a manufacturing method capable of improving the brightness of a high-brightness red light emitting diode. To this end, embodiments of the present invention do not remove the GaAs layer, which is an opaque absorbing substrate, or change the structure thereof, By growing a reflective layer consisting of layers of light and then sequentially growing a light emitting diode structure on top of it, it is possible to further form a reflective layer instead of deformation of the absorbing substrate which may cause damage to the device, thereby emitting toward the absorbing substrate. Reflecting most of the light to the front has the effect that can greatly increase the efficiency of the front light.

Description

LIGHT EMITTING DIODE AND MANUFACTURING METHOD THEREOF

1 is a cross-sectional view showing the structure of a conventional side current type light emitting diode.

Figure 2 is a cross-sectional view showing a light emitting diode structure of one embodiment of the present invention.

Description of the Related Art [0002]

110: absorbing substrate 120: reflective layer

130: n contact layer 140: active layer

150: p contact layer 160: p electrode

170: n electrode

The present invention relates to a light emitting diode and a method for manufacturing the same, and more particularly, to a structure and a manufacturing method capable of improving the brightness of a high brightness red light emitting diode.

Light Emitting Diode is basically a semiconductor PN junction diode. As a result of research on a wide variety of materials and structures, light emitting diodes of various wavelengths with high brightness are gradually commercialized. It is rapidly replacing other kinds of light emitting means with a long life.

The largest factor for classifying light emitting diodes is the emission spectrum, which can be broadly divided into infrared (IR), visible (UV), and ultraviolet (UV) light, depending on the center emission wavelength. The GaAs (infrared), AlGaAs (red), GaAsP (yellow to red), GaP (green to red), AlInGaP (yellow green to red), and AlInGaN (green, blue, purple, white, and ultraviolet) , AlGaInP (amber to red) and the like, AlGaAs, AlInGaP, AlInGaN, AlGaInP and the like is a material system that has recently attracted particular attention as a high brightness light emitting diode.

Among the light emitting diodes in the visible region, the light emitting diodes having a prominent utility are red light emitting diodes, and since they have excellent visibility at the same luminance as green or yellow, they are useful for traffic lights, vehicle stop lights, and various display displays. The use area is rapidly spreading.

In general, GaP, GaAsP, AlGaAs, AlGaInP, etc. may be used as a material system used for fabricating a red light emitting diode, and AlInGaP has the highest luminous efficiency according to the material (20lm / A at 10mA).

In the GaP red light emitting diode, the Zn-O pair formed in the p-type crystal becomes the main body of light emission, but there is a limit in luminance even when a large current flows due to the concentration limit of the Zn-O pair in the p-type crystal, and the peak wavelength is around 700 nm.

GaAsP red light-emitting diode because it is a direct transition type to form a ternary compound semiconductor, GaAs P _{0 0 .6 .4} pn junction crystal can be manufactured from a highly efficient light-emitting diode and the peak wavelength is near 650nm. In general, GaAsP crystals are grown on GaAs by forming a buffer layer using vapor phase growth.

This AlGaAs heterojunction of Al _{0 .35} Ga _{0 .65} As and Al _{0 .5} Ga _{0 .5} As a basic structure, possible to manufacture high efficiency light emitting diode and the peak wavelength is about 660nm. Sometimes also Al _{0 .5} Ga _{0 .5} an As layer as an active layer, and a barrier layer control the peak wavelength with the Al _{0 .65} Ga _{0 .35} As to 630nm. Direct and indirect transition bands are controlled according to the AlAs composition ratio.

The AlGaAs red light emitting diode uses a method of growing an AsGaAs structure on a GaAs substrate. Since the GaAs substrate is opaque and light is absorbed into the substrate, a method of removing the GaAs substrate is limited.

Recently, a high efficiency red light emitting diode using AlGaInP as an active layer has been developed, which has a color range from amber to red.

The AlGaInP having an _{(Al x Ga 1 -x) 0.5} In 0 .5 directly in value between the P to grow, in the Al composition ratio x = 0 x = 0.53 transition type band gap of the lattice constant matching on the GaAs substrate, This region has visible light spectrum from red (1.9eV, x = 0) to yellow green (2.2eV, x = 0.53). However, if the high Al composition ratio changes the indirect transition type band structure, the actual commercialization is limited to red, orange and amber.

1 is a cross-sectional view showing a structure of a general AlGaInP light emitting diode, and has a side current injection type light emitting diode.

As illustrated, the p-contact is formed after the n-AlGaInP n contact layer 20, the AlGaInP active layer 30, and the p-AlGaInP p contact layer 40 are sequentially formed on the n-type doped GaAs substrate 10. A portion of the layer 40, the active layer 30, and the n contact layer 20 are sequentially removed to expose the n-GaAs substrate 10, and an upper portion of the p contact layer 40 and the exposed n-GaAs substrate ( 10) p electrodes 50 and n electrodes 60 are formed on the upper portions, respectively.

The AlGaInP layers are grown using low pressure organometallic chemical vapor deposition (MOVCD), which is grown in consideration of mixing order, hydrogen deposition of acceptor ions, and bonding of oxygen.

The AlGaInP layers are grown on the GaAs substrate 10 to match the lattice constant. However, since the GaAs substrate 10 is opaque, the photons emitted from the active layer 30 are absorbed to lower light efficiency. Therefore, in order to solve this problem, a method of increasing the efficiency of light emitted in the direction of the n contact layer 20 by removing the GaAs substrate 10 and replacing it with a transparent substrate such as GaP or using the AlGaInP layer has been proposed. have. However, such a method requires a process of removing the GaAs substrate 10 by a lift-off method and flattening the surface of the exposed AlGaInP layer, and the process is complicated. A problem arises. In addition, a method of using the back light as a method of changing the structure of the substrate to an inverted trapezoidal shape, etc. has been proposed. However, since the physical processing of the substrate impacts the device, the reliability may be lowered, and a fine and complicated processing process may be performed. The cost is high because it is required.

In contrast to the prior art as described above, the embodiment of the present invention does not remove or change the structure of the GaAs layer, which is an opaque absorbing substrate, and grows a reflective layer composed of a plurality of layers thereon, and a light emitting diode structure thereon. It is an object of the present invention to provide a light emitting diode and a method of manufacturing the same to increase the efficiency of the front light by reflecting all the light emitted in the direction of the absorbing substrate toward the front to grow sequentially.

In order to achieve the above object, an embodiment of the present invention is formed on an absorbent substrate in which the material system to be grown and the lattice structure is matched, and a reflective layer made of a stack of transparent thin films having different refractive indices; A light emitting diode structure having a first contact layer, an active layer, and a second contact layer structure formed on the reflective layer; And electrodes formed on the absorbing substrate and the second contact layer, respectively.

In addition, another embodiment of the present invention and the n-AlAs / AlGaInP repeating structure formed on the n-GaAs absorption substrate; An n-AlGaInP layer formed on the reflective layer; An active layer formed on the n-AlGaInP layer; A p-AlGaInP layer formed on the active layer; A p electrode formed on the p-AlGaInP layer; Characterized in that the n electrode formed on the n-GaAs layer.

In addition, another embodiment of the present invention comprises the steps of forming a reflective layer by alternately growing a plurality of thin films having different refractive index on the absorbent substrate; Sequentially forming a first contact layer, an active layer, and a second contact layer based on the same material on the reflective layer; And forming an electrode on the absorbing substrate and the second contact layer.

When described in detail with reference to the accompanying drawings and embodiments of the present invention as follows.

2 is a cross-sectional view illustrating a light emitting diode structure according to an exemplary embodiment of the present invention. As illustrated, a plurality of reflective layers 120, an n contact layer 130, an active layer 140, and a p contact layer may be disposed on an absorber substrate 110. 150 has a mesa structure, a p-type electrode 160 is formed on the p contact layer 150, and an n-type electrode 170 is formed on the absorber substrate 110.

In the present exemplary embodiment, the absorber substrate 110 is n-GaAs, and the n contact layer 130, the active layer 140, and the p contact layer 150 forming the light emitting diode structure are formed of AlGaInP material system exhibiting the highest efficiency to date. Formed by growing, only the basic structure is shown, if necessary, a cladding layer or superlattice structure layer for electron, hole injection may be further formed, the structure of the active layer 140 is also a single layer, quantum well structure, multiple A quantum well structure may be applied.

The absorber substrate 110 is made of GaAs, which is most widely used among materials matching the lattice structure of the semiconductor layer to be formed thereon, using the GaAs as a substrate to form a semiconductor layer thereon, and the GaAs substrate After removal, the transparent substrate may be bonded to each other by a wave bonding method. However, in the exemplary embodiment of the present invention, the reflective layer may be applied such that the substrate is opaque and absorbs light in a corresponding direction, such as GaAs, thereby lowering light efficiency. 120 is formed on the absorbing substrate 110 to reflect all the light in the corresponding direction to increase the brightness of the front light.

The reflective layer 120 uses the same kind of material system as the material structure of the semiconductor structure, and has to have the same conductive property as that of the contact layer grown thereon, and have high reflective properties. Therefore, it has a lamination form of AlAs / AlGaInP here. The stack structure of AlAs / AlGaInP utilizes the fact that two transparent materials having different refractive indices are alternately stacked in multiple layers to reflect light of a predetermined wavelength.

The stacked structure of the reflective layer 12 is made of AlAs and Al _x Ga _y In _(1-xy) P material, each thickness is nλ / 4 (λ is the wavelength), the reflectance (R) is Equation 1

In order to increase the reflectance, it is possible to increase the number of layers or increase the ratio of nH / nL (H is a high refractive index transparent thin film and L is a low refractive index transparent thin film). At this time, the amount of light absorbed by the GaAs substrate is 1-R.

A characteristic of the present embodiment is that the reflective layer 120, the n contact layer 130, the active layer 140, and the p contact layer 150 all have the same material composition while using the plurality of reflective layers 120. Is done. That is, in consideration of the manufacturing process of the growth-type light emitting diode layers, a distributed Bragg reflector used in optical communication, not a metal reflecting layer, is formed by a method of growing the same lattice structure layer, so as to facilitate crystal growth. Only the same material composition is used to complete the formation of the structure.

Referring to the formation of the structure shown above, first, a plurality of n-AlAs / AlGaInP layers are sequentially grown on an n-type GaAs layer 110 to form a reflective layer 120, and an n-AlGaInP layer 130 thereon. Grow to the n contact layer. Then, the active layer 140 using AlGaInP is also grown thereon. It is also possible to form a quantum well structure that forms AlGaInP between two charge confinement layers. Then, the p-type AlGaInP layer 150 is grown as a p-contact layer thereon. Each crystal growth can use low pressure organometallic chemical vapor deposition (MOVCD) and can be implanted with impurities during growth to have n-type or p-type characteristics.

Subsequently, it is determined whether the structure of the light emitting diode is a vertical type or a horizontal type. When the light emitting diode is formed in a horizontal structure having a side current injection type, the upper portion of the n-GaAs absorption substrate 110 is illustrated as shown. The p contact layer 150, the active layer 140, the n contact layer 130, and the reflective layer 120 are sequentially etched to form a mesa structure, and the upper part of the n-GaAs absorbing substrate 110 exposed through the above process. The n electrode 170 and the p electrode 160 are formed on the p contact layer 150, respectively.

In the case of forming a vertical structure, the p-electrode 160 may be formed on the p-contact layer 150, and the n-electrode may be formed below the n-GaAs absorption substrate 110.

As described in the above-described embodiments of the present invention and the description thereof, when manufacturing a red light emitting diode, a plurality of layers having different refractive indices are formed on a GaAs layer, which is a base, and used as a reflective layer, and a light emitting diode structure thereon. By forming the same material system, it is possible to reflect the light in the GaAs layer direction to greatly increase the amount of front emission light. The light emitting diode may use a material system such as GaP, GaAsP, AlGaAs, or AlGaInP.

As described above, the light emitting diode of the present invention and the method of manufacturing the same do not remove or change the structure of the GaAs layer, which is an opaque absorbing substrate, and grow a reflective layer composed of a plurality of layers thereon, and sequentially light emitting diode structure thereon. The light emitted in the absorbing substrate direction is mostly reflected to the front surface, thereby increasing the efficiency of the front light.

The material composition for forming the light emitting diode structure according to the embodiment of the present invention is based on A lGaInP, and the reflection layer is made of a stack of AlAs / AlGaInP to facilitate crystal growth.

The reflective layer according to the embodiment of the present invention stacks transparent thin films having different refractive indices, and the light reflectance can be adjusted according to the number of laminations and the refractive ratio of each stack, thereby controlling the increase in the amount of front light.

Claims (10)

A reflection layer formed on the absorber substrate in which the material system to be grown and the lattice structure coincide with each other, and a stack of transparent thin films having different refractive indices; A light emitting diode structure having a first contact layer, an active layer, and a second contact layer structure formed on the reflective layer; Electrodes formed on the absorber substrate and the second contact layer, respectively; The light emitting diode structure has a composition of AlGaInP, and the reflective layer has a multilayer structure of AlAs / AlGaInP. The light emitting diode of claim 1, wherein the reflective layer is formed of a laminate in which two kinds of thin films having different refractive indices are repeatedly formed, and has the same conductivity as the first contact layer. The light emitting diode of claim 1, wherein the absorbing substrate, the reflective layer, and the first contact layer all have n-type conductivity, and the second contact layer has a p-type conductivity. delete a reflection layer having an n-AlAs / AlGaInP repeating structure formed on the n-GaAs layer; An n-AlGaInP layer formed on the reflective layer; An active layer formed on the n-AlGaInP layer; A p-AlGaInP layer formed on the active layer; A p electrode formed on the p-AlGaInP layer; A light emitting diode comprising an n electrode formed on the n-GaAs layer. The method of claim 5, wherein the reflective layer, the n-AlGaInP layer, the active layer, the p-AlGaInP layer, and the p electrode formed on the n-GaAs layer have a mesa structure in a part of an upper portion of the n-GaAs layer. A light emitting diode in which an n electrode is formed on an exposed n-GaAs layer. Alternately growing a plurality of thin films having different refractive indices on the absorbent substrate to form a reflective layer; Sequentially forming a first contact layer, an active layer, and a second contact layer based on AlGaInP material on the reflective layer; Forming an electrode on the absorbent substrate and the second contact layer; The reflective layer is a light emitting diode manufacturing method comprising the step of repeatedly growing a multi-layer structure of AlAs / AlGaInP. The method of claim 7, wherein the absorbing substrate uses a substrate having the same conductivity as that of the first contact layer, and the reflective layer is doped during growth to have the same conductivity as that of the first contact layer. The method of claim 7, wherein the reflective layer and the first contact layer are both doped during growth to have an n-type conductivity, and the second contact layer is doped during growth to have a p-type conductivity. delete

Images