KR100722818B1 - Method of manufacturing light emitting diode - Google Patents

Abstract

The present invention includes forming an N-type semiconductor layer on a substrate, forming an active layer on the N-type semiconductor layer, and forming a P-type semiconductor layer on the active layer, the P-type semiconductor layer The forming step provides a method of manufacturing a light emitting diode, comprising forming an impurity layer doped with a high concentration of impurities during growth such that irregularities are formed on a surface thereof.

The present invention also includes forming an N-type semiconductor layer on a substrate, forming an active layer on the N-type semiconductor layer, and forming a P-type semiconductor layer on the active layer. Forming the layer provides a method of manufacturing a light emitting diode comprising increasing the flow rate of hydrogen and nitrogen gas at a growth temperature of 650 to 800 ° C. during the growth to form grooves on the surface.

Light Emitting Diode, LED, Semiconductor, GaN, Uneven

Description

Method of manufacturing light emitting diodes

1 is a schematic cross-sectional view showing a conventional nitride semiconductor light emitting diode.

2A to 2D are cross-sectional views illustrating a manufacturing process of the first embodiment of the light emitting diode according to the present invention.

3A and 3B are cross-sectional views illustrating a manufacturing process of a second embodiment of the light emitting diode according to the present invention.

4a to 4b are conceptual cross-sectional views for explaining the effect of the light emitting diode according to the present invention.

<Explanation of symbols for the main parts of the drawings>

110, 210: substrate 120, 220: buffer layer

130, 230: N-type semiconductor layer 140, 240: active layer

150, 250: P-type semiconductor layer

The present invention relates to a method of manufacturing a light emitting diode, and more particularly, to a method of manufacturing a light emitting diode for improving luminous efficiency and brightness in a nitride semiconductor light emitting diode.

The light emitting diode has a smaller power consumption and a longer lifespan than a conventional light bulb or a fluorescent lamp, and can be installed in a narrow space and is strong in vibration. Such light emitting diodes are used as display devices and backlights because they have excellent characteristics in terms of power consumption and durability, and active research is being conducted to apply them to general lighting applications.

Among the compound semiconductors, nitride-based semiconductor materials exhibit excellent luminescent properties for visible and UV regions, and are also used in high power, high frequency electronic devices. In particular, gallium nitride (GaN) has a direct transition bandgap of 3.4 eV at room temperature and is combined with materials such as indium nitride (InN) and aluminum nitride (AlN) at 1.9 eV (InN) to 3.4 eV (GaN). It has a direct energy bandgap of up to 6.2eV (AlN), which is a material with great potential for application of optical devices due to the wide wavelength range from visible light to ultraviolet light.

1 is a schematic cross-sectional view showing a conventional nitride semiconductor light emitting diode.

Referring to FIG. 1, a light emitting diode includes a substrate 10, a buffer layer 20 formed on the substrate 10, an N-type semiconductor layer 30 formed sequentially on the buffer layer 20, and an active layer 40. ) And a P-type semiconductor layer 50.

P-type and N-type semiconductor layers 50 and 30 formed on the upper and lower portions of the active layer 40 respectively supply current to the active layer 40 to emit light. In general, in the gallium nitride semiconductor light emitting diode, a GaN semiconductor compound doped with magnesium (Mg) is used as the P-type semiconductor layer 50, and silicon (Si) is used as the N-type semiconductor layer 30. Doped GaN semiconductor compounds are used.

Indicators indicating the performance of light emitting diodes include light emission efficiency (lm / W), internal quantum efficiency (%), external quantum efficiency (%), and extraction efficiency (%). And the ratio of photons emitted out of the light emitting diode. The higher the extraction efficiency, the brighter the light emitting diode. The extraction efficiency of the light emitting diode is greatly influenced by the shape or surface shape of the chip, the structure of the chip, and the packaging type, so it is necessary to pay close attention when designing the light emitting diode. Light generated in the active layer of the light emitting diode is emitted from six sides of the chip, and the light extraction efficiency is generally determined by the critical angle of the light.

However, in the conventional light emitting diodes as described above, a large amount of photons generated in the light emitting layer does not easily escape to the outside of the light emitting device, and causes a total reflection inside to absorb and disappear. That is, there is a problem that the luminous efficiency of the electrical energy is converted into the light energy to escape to the outside of the device is low.

The present invention relates to a method of manufacturing a light emitting diode, and more particularly, to a method of manufacturing a light emitting diode for improving luminous efficiency and brightness in a nitride semiconductor light emitting diode.

The light emitting diode has a smaller power consumption and a longer lifespan than a conventional light bulb or a fluorescent lamp, and can be installed in a narrow space and is strong in vibration. Such light emitting diodes are used as display devices and backlights because they have excellent characteristics in terms of power consumption and durability, and active research is being conducted to apply them to general lighting applications.

Among the compound semiconductors, nitride-based semiconductor materials exhibit excellent luminescent properties for visible and UV regions, and are also used in high power, high frequency electronic devices. In particular, gallium nitride (GaN) has a direct transition bandgap of 3.4 eV at room temperature and is combined with materials such as indium nitride (InN) and aluminum nitride (AlN) at 1.9 eV (InN) to 3.4 eV (GaN). It has a direct energy bandgap of up to 6.2eV (AlN), which is a material with great potential for application of optical devices due to the wide wavelength range from visible light to ultraviolet light.

1 is a schematic cross-sectional view showing a conventional nitride semiconductor light emitting diode.

Referring to FIG. 1, a light emitting diode includes a substrate 10, a buffer layer 20 formed on the substrate 10, an N-type semiconductor layer 30 formed sequentially on the buffer layer 20, and an active layer 40. ) And a P-type semiconductor layer 50.

P-type and N-type semiconductor layers 50 and 30 formed on the upper and lower portions of the active layer 40 respectively supply current to the active layer 40 to emit light. Generally, in the gallium nitride semiconductor light emitting diode, a GaN semiconductor compound doped with magnesium (Mg) is used as the P-type semiconductor layer 50, and silicon (Si) is doped as the N-type semiconductor layer 30. A GaN semiconductor compound is used.

Indicators indicating the performance of light emitting diodes include light emission efficiency (lm / W), internal quantum efficiency (%), external quantum efficiency (%), and extraction efficiency (%). And the ratio of photons emitted out of the light emitting diode. The higher the extraction efficiency, the brighter the light emitting diode. The extraction efficiency of the light emitting diode is greatly influenced by the shape or surface shape of the chip, the structure of the chip, and the packaging type, so it is necessary to pay close attention when designing the light emitting diode. Light generated in the active layer of the light emitting diode is emitted from six sides of the chip, and the light extraction efficiency is generally determined by the critical angle of the light.

However, in the conventional light emitting diodes as described above, a large amount of photons generated in the light emitting layer does not easily escape to the outside of the light emitting device, and causes a total reflection inside to absorb and disappear. That is, there is a problem that the luminous efficiency of the electrical energy is converted into the light energy to escape to the outside of the device is low.

The present invention includes the steps of forming an N-type semiconductor layer on the substrate, forming an active layer on the N-type semiconductor layer and forming a P-type semiconductor layer on the active layer in order to achieve the above object The forming of the P-type semiconductor layer may include forming an impurity layer doped with a high concentration of impurities during growth such that irregularities are formed on a surface thereof.

The forming of the P-type semiconductor layer includes growing a first P-type semiconductor layer by injecting TMGa, NH ₃ gas and a gas for supplying P-type impurities onto the substrate, and stopping the injection of the TMGa gas Forming an impurity layer doped with a high concentration of impurities by injecting a source for supplying an N-type or N-type impurity and again injecting TMGa, NH ₃ gas and a gas for supplying P-type impurities onto the unevenness Growing a layer.

The gas for supplying the P-type impurity includes CP ₂ Mg gas, and the gas for supplying the N-type impurity is silane (SiH ₄ ), disilane (Si ₂ H ₆ ) or tetraethoxysilane (Si (OEt)). ₄ ) may be included.

The present invention includes forming an N-type semiconductor layer on a substrate, forming an active layer on the N-type semiconductor layer, and forming a P-type semiconductor layer on the active layer, the P-type semiconductor layer Forming step provides a method of manufacturing a light emitting diode comprising the step of forming a groove on the surface by increasing the flow rate of hydrogen and nitrogen gas at a growth temperature of 650 to 800 ℃ during growth.

Forming the P-type semiconductor layer, characterized in that it comprises the step of increasing the flow rate of the hydrogen and nitrogen gas by 10 to 40%.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various forms, and only the present embodiments are intended to complete the disclosure of the present invention and to those skilled in the art to fully understand the scope of the invention. It is provided to inform you.

According to the present invention, in a semiconductor light emitting diode in which an N-type semiconductor layer, an active layer, and a P-type semiconductor layer are sequentially formed, irregularities or grooves are formed on the P-type semiconductor layer, thereby changing the critical angle of the light and easily extracting the light. The luminous efficiency of the light emitting diode can be improved.

2A to 2D are cross-sectional views illustrating a manufacturing process of a first embodiment of a light emitting diode according to the present invention.

As the deposition and growth method of semiconductor, metal organic chemical vapor deposition (MOCVD), chemical vapor deposition (CVD), plasma enhanced chemical vapor deposition (PECVD), molecular beam growth method Various methods including (MBE; Molecular Beam Epitaxy) and Hydride Vapor Phase Epitaxy (HVPE) can be used. In this embodiment, organometallic chemical vapor deposition (MOCVD) is used.

Referring to FIG. 2A, a buffer layer, an N-type semiconductor layer, and an active layer are sequentially formed on a substrate.

The substrate 110 refers to a conventional wafer for fabricating a light emitting diode and includes at least one of Al ₂ O ₃ , SiC, ZnO, Si, GaAs, GaP, LiAl ₂ O ₃ , BN, AlN, and GaN. The substrate 110 is used. This embodiment uses a crystal growth substrate 110 composed of sapphire (Al ₂ O ₃ ).

The buffer layer 120 is to reduce lattice mismatch between the substrate and subsequent layers during crystal growth on the substrate, and may include GaN, InN, or AlN, which is a semiconductor material.

The N-type semiconductor layer 120 is a layer in which electrons are generated, and uses a nitride semiconductor layer doped with N-type impurities. In this embodiment, a GaN layer doped with silicon (Si) atoms is formed on the N-type semiconductor layer 120.

The active layer 130 is a region where a predetermined band gap and a quantum well are made to recombine electrons and holes, and may include InGaN. In addition, the emission wavelength generated by the combination of electrons and holes is changed according to the type of material constituting the active layer 130. Therefore, it is preferable to adjust the semiconductor material included in the active layer 130 according to the target wavelength.

Referring to FIG. 2B, in order to form the P-type semiconductor layer 150 having predetermined irregularities on its surface, first, the first P-type semiconductor layer 150a is formed on the active layer 140 through a conventional process. . At this time, it is formed to about 50 to 80% of the thickness of the P-type semiconductor layer 150 to be formed.

The P-type semiconductor layer 150 is a layer in which holes are generated, and uses a nitride semiconductor layer doped with P-type impurities. In this embodiment, a GaN layer doped with Mg is formed as the P-type semiconductor layer 150. Here, trimethylgallium (TMGa) or triethyl gallium (TEGa) may be used as a source gas for Ga, and ammonia (NH ₃ ), monomethylhydrazine (MMHy), or dimethylhydrazine (DMHy) may be used as a source gas for N. CP ₂ Mg may be used as the source gas for Mg.

Referring to FIG. 2C, an impurity layer 155 doped with a high concentration of impurities is formed on the first P-type semiconductor layer 150a. At this time, it is preferable that the doping concentration is 1 × 10 ²⁰ to 1 × 10 ²¹ . The impurity layer 155 is preferably 1000 to 2000 microns thick, and the high concentration impurity serves to induce formation of a predetermined roughness on the surface.

To this end, after forming the first P-type semiconductor layer 150a using TMGa, NH ₃ , and CP ₂ Mg gas, the injection of a source for supplying P-type or N-type impurities is stopped after stopping injection of TMGa for several minutes. The surface shape as shown in the figure can be obtained. For example, a source for supplying Mg or Si is implanted to form an impurity layer 155 doped with impurities at a high concentration. Here, as the source gas for Si, silane (SiH ₄ ), disilane (Si ₂ H ₆ ) or tetraethoxysilane (Si (OEt) ₄ ) may be used.

Referring to FIG. 2D, the second P-type semiconductor layer 150b is continuously grown on the impurity layer 155 formed as described above to form the P-type semiconductor layer 150 having irregularities on the surface thereof. That is, as described above, after forming the impurity layer 155 doped with a high concentration impurity having a predetermined roughness on the surface and injecting TMGa, NH ₃ , CP ₂ Mg gas again, growth is performed along the impurity layer 155. Thus, the P-type semiconductor layer 150 having irregularities on the surface thereof may be formed.

As described above, according to the present invention, an impurity layer doped with a high concentration of impurities may be formed during the growth of a P-type semiconductor layer, thereby manufacturing a light emitting diode including a P-type semiconductor layer having irregularities on its surface.

The method of manufacturing the light emitting diode of the present invention described above is not limited thereto, and various processes and manufacturing methods may be changed or added according to the characteristics of the device and the convenience of the process. For example, in order to increase light efficiency, a P-type cladding layer such as AlGaN having a larger energy band gap may be further configured between the active layer 140 and the P-type semiconductor layer 150.

As described above, the present embodiment can improve the luminous efficiency compared to the conventional light emitting device by forming irregularities on the surface of the P-type semiconductor layer through the above-described process. This is because photons that have been reflected on conventional flat surfaces exit outside without being reflected by various angle surfaces.

3A and 3B are cross-sectional views illustrating a manufacturing process of a second embodiment of a light emitting diode according to the present invention.

Referring to FIG. 3A, the buffer layer 220, the N-type semiconductor layer 230, and the active layer 240 are sequentially formed on the substrate 210. This is the same as the case of the first embodiment, and overlapping description is omitted.

Referring to FIG. 3B, a P-type semiconductor layer 250 including a groove 255 is formed on the active layer 240. To this end, during the process for forming a conventional P-type semiconductor layer, it is characterized by growing by lowering the temperature and increasing the injection amount of hydrogen (H ₂ ) and nitrogen (N ₂ ) gas used as a carrier gas.

That is, the P-type semiconductor layer 250 is formed at a growth temperature of 800 to 1000 ° C. using TMGa, NH ₃ and CP ₂ Mg gas simultaneously with the injection of hydrogen (H ₂ ) and nitrogen (N ₂ ) gases as carrier gases. To grow. During this growth, preferably 50 to 80% growth, and then increase the injection amount of the hydrogen (H ₂ ) and nitrogen (N ₂ ) 10 to 40% and lower the temperature to 650 to 800 ℃ to grow as shown Grooves 255 may be formed. The hydrogen (H ₂ ) gas serves to etch lattice defect sites such as dislocations present on the surface of the P-type semiconductor layer 250. This is because the lattice defect areas are thermodynamically unstable and preferentially etched relative to other areas. The groove 255 is formed in a hexagonal pyramid shape, and in cross section is formed in a V-shape that narrows toward the lower side.

The method of manufacturing the light emitting diode of the present invention described above is not limited thereto, and various processes and manufacturing methods may be changed or added according to the characteristics of the device and the convenience of the process.

As described above, according to the present exemplary embodiment, the groove 255 is formed on the P-type semiconductor layer 250 through the above-described process, thereby improving luminous efficiency as compared with the conventional light emitting device. This is because photons that have been reflected on a conventional flat surface exit outside without being reflected by various angle surfaces.

The present invention can be applied to light emitting diodes having various structures such as horizontal, vertical, or flip chip structures, and various processes and manufacturing methods can be changed or added according to the characteristics of the device and the convenience of the process. For example, in the case of a horizontal light emitting diode, the P-type semiconductor layer including the N-type semiconductor layer, the active layer, the unevenness or the groove is formed on the substrate through the above-described process, and then the P-type semiconductor is formed through a predetermined etching process. A portion of the layer and the active layer are removed to expose a portion of the N-type semiconductor layer, and a P-type electrode and an N-type electrode are formed on the P-type semiconductor layer and the exposed N-type semiconductor layer.

4A to 4B are conceptual cross-sectional views for explaining the effect of the light emitting diode according to the present invention.

The light efficiency of the light emitting diode can be represented by internal quantum efficiency and external quantum efficiency, and the internal quantum efficiency is determined according to the design and quality of the active layer. In the case of external quantum efficiency, the amount of photons generated in the active layer comes out of the light emitting diode. Referring to FIG. 4A, when the upper surface of the P-type semiconductor layer has a flat surface, some photons do not penetrate at the interface between the semiconductor layers and are reflected. It does not penetrate into. However, in the case where irregularities are formed or grooves are formed on the surface of the P-type semiconductor layer as shown in FIG. 4B, the surfaces having various angles change the critical angle of the light to help extract light more easily. Accordingly, the probability that light generated in the active layer is emitted to the outside of the light emitting diode without total reflection is increased, thereby significantly improving the external quantum efficiency.

As mentioned above, although this invention was demonstrated in detail using the preferable Example, the scope of the present invention is not limited to a specific Example and should be interpreted by the attached Claim. In addition, those skilled in the art should understand that many modifications and variations are possible without departing from the scope of the present invention.

The method of manufacturing a light emitting diode according to the present invention improves the characteristics such as light emission efficiency, external quantum efficiency, extraction efficiency, and the like by forming irregularities or grooves on the surface of the P-type semiconductor layer to ensure reliability, and emit light of high brightness and high brightness. There is an advantage to this.

Claims (5)

Forming an N-type semiconductor layer on the substrate; Forming an active layer on the N-type semiconductor layer; And Forming a P-type semiconductor layer on the active layer; The forming of the P-type semiconductor layer may include forming an impurity layer doped with a high concentration of impurities during growth such that irregularities are formed on a surface thereof. The method according to claim 1, Forming the P-type semiconductor layer, Growing a first P-type semiconductor layer by injecting TMGa, NH ₃ gas and a gas for supplying P-type impurities onto the substrate; Stopping the injection of the TMGa gas and injecting a source for supplying P-type or N-type impurities to form an impurity layer doped with a high concentration of impurities; And And growing a second P-type semiconductor layer by injecting TMGa, NH ₃ gas and a gas for supplying P-type impurities onto the unevenness. The method according to claim 2, The gas for supplying the P-type impurity includes CP ₂ Mg gas, and the gas for supplying the N-type impurity is silane (SiH ₄ ), disilane (Si ₂ H ₆ ) or tetraethoxysilane (Si (OEt)). ₄ ) manufacturing method of a light emitting diode comprising a. Forming an N-type semiconductor layer on the substrate; Forming an active layer on the N-type semiconductor layer; And Injecting a source gas and a carrier gas at a first flow rate at a first growth temperature onto the active layer to form a P-type semiconductor layer, During the formation of the P-type semiconductor layer, lowering the temperature to a second growth temperature lower than the first growth temperature and increasing the flow rate of the carrier gas to a second flow rate to form grooves on the surface. Method for manufacturing a light emitting diode. The method according to claim 4, And a second flow rate of the carrier gas is increased by 10 to 40% from the first flow rate.

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