KR20080024788A - Nitride semiconductor light-emitting device and manufacturing method thereof - Google Patents

Abstract

A nitride semiconductor light emitting device and a manufacturing method thereof are provided to prevent the back drift of a dopant in a p-type semiconductor layer to an active layer by forming a supper lattice layer on the active layer. An n-type semiconductor layer(120) is formed on a substrate(105). An active layer(125) is formed over the n-type semiconductor layer. An LD(Low Doped) p-type semiconductor layer and an un-doped semiconductor layer are alternatively laminated to form a super lattice layer(130) over the active layer. A p-type semiconductor layer(140) is formed on the super lattice layer. The un-doped semiconductor layer of the super lattice layer is alternatively laminated with a super lattice structure under the temperature change of 500 ‹C to 1000 ‹C. The supper lattice layer has an amorphous shape. The un-doped semiconductor layer of the supper lattice layer is Um-GaN layer.

Description

Nitride semiconductor light emitting device and manufacturing method thereof

1 is a side cross-sectional view illustrating a structure of a general nitride semiconductor light emitting device by way of example.

Figure 2 is a side cross-sectional view showing the structure of a nitride semiconductor light emitting device according to an embodiment of the present invention.

3 is a flowchart illustrating a method of manufacturing a nitride semiconductor light emitting device according to an embodiment of the present invention.

<Explanation of symbols for main parts of drawing>

100 nitride semiconductor light emitting device 105 substrate

110: buffer layer 115: undoped semiconductor layer

120: n-type semiconductor layer 125: active layer

130: superlattice layer 140: p-type semiconductor layer

150: p-side electrode 160: n-side electrode

The present invention relates to a nitride semiconductor light emitting device and a method for manufacturing the nitride semiconductor light emitting device.

In general, a semiconductor light emitting device (LED) is a light emitting diode (LED), which is used to send and receive signals by converting electrical signals into infrared, visible or light forms using the characteristics of compound semiconductors. It is an element.

The use range of LED is used in home appliances, remote controllers, electronic signs, indicators, and various automation devices, and the types are divided into IRED (Infrared Emitting Diode) and VLED (Visible Light Emitting Diode).

In general, miniaturized LEDs are made of a surface mount device type for direct mounting on a printed circuit board (PCB) board. Accordingly, LED lamps, which are used as display elements, are also being developed as surface mount device types. These surface-mount devices can replace the existing simple lighting lamps, which are used for lighting indicators of various colors, character display and image display.

As the area of use of LEDs becomes wider as described above, required luminances such as electric lamps used for living, electric lamps for rescue signals, and the like become higher and higher, and in recent years, development of high output light emitting diodes is actively underway.

In particular, many researches and investments have been made on semiconductor optical devices using Group 3 and Group 5 compounds such as GaN (gallium nitride), AlN (aluminum nitride), and InN (indium nitride). This is because the nitride semiconductor light emitting device has a very wide band gap ranging from 1.9 eV to 6.2 ev, and the band gap engineering using the same has the advantage of realizing three primary colors of light on one semiconductor.

Recently, the development of blue and green light emitting devices using nitride semiconductors has revolutionized the optical display market and is considered as one of the promising industries that can create high added value in the future. However, as mentioned above, in order to pursue more industrial use in such a nitride semiconductor optical device, increasing light emission luminance is also a problem to be taken first.

1 is a side cross-sectional view showing the structure of a general nitride semiconductor light emitting device.

Referring to FIG. 1, a general nitride semiconductor light emitting device 10 includes a substrate 11, a buffer layer 12, an undoped semiconductor layer 13, an n-type semiconductor layer 14, an active layer 15, and a p-type. The semiconductor layer 16, the p-side electrode 17, the n-side electrode 18, and the like.

The substrate 11 is made of sapphire or SiC, and a buffer layer 12 having a polycrystalline thin film structure of, for example, an Al _y Ga _1-y N layer is grown on the substrate 11 at a low temperature. When the buffer layer 12 is grown, an undoped semiconductor layer 13 such as Undoped-GaN is grown thereon to increase lattice agreement, and an n-type semiconductor layer (GaN layer) 14 doped with Si (silicon) is formed. Is formed.

An active layer 15 is stacked on the n-type semiconductor layer 14, and a p-type semiconductor layer (GaN layer) 16 doped with Mg (magnesium) is formed on the active layer 15. As a multiple quantum well (MQW) structure, holes flowing through the p-type semiconductor layer 16 and electrons flowing through the n-type semiconductor layer 14 are combined to generate light. At this time, light of energy corresponding to the excitation level or the energy band gap difference of the quantum well is emitted.

The n-side electrode 18 and the p-side electrode 17 are formed on the n-type semiconductor layer 14 and the p-type semiconductor layer 16, respectively, to form a semiconductor light emitting device 10.

However, first of all, since the difference in crystal lattice constant between the buffer layer 12 and the substrate 11 is large, the buffer layer 12 may have a dislocation or attacker between the layer grown on the substrate 11 and the buffer layer 12. Lattice defects such as vacancy occur.

These phenomena cause problems on the interface such as the generation of dislocation defects at the interface, the formation of pinholes and thermal pit, and the flow of electrons is not smooth and the optical and electrical characteristics of the semiconductor device are reduced. Results in deterioration.

The present invention provides a nitride semiconductor light emitting device capable of forming a semiconductor layer of high quality by minimizing the influence of lattice defects and crystal defects, and facilitating the bonding and conductivity control of holes and electrons, thereby improving luminous efficiency.

In addition, the present invention improves the quality of the active layer by preventing the dopant of the p-type semiconductor layer from being diffused into the active layer, and a surface recovery layer function to minimize the effects of strain and stress phenomena transferred from the lower layer. Provided is a nitride semiconductor light emitting device.

According to the present invention, a nitride semiconductor light emitting device capable of realizing a high quality thin film by reducing a dislocation generation, a pinhole and a thermal pit, which are deteriorated in electrical and optical characteristics of a semiconductor device can be realized. It provides a method for producing.

The nitride semiconductor light emitting device according to the present invention comprises a substrate; An n-type semiconductor layer formed on the substrate; An active layer formed on the n-type semiconductor layer; A superlattice layer in which a low doped p-type semiconductor layer and an undoped semiconductor layer are alternately stacked and formed on the active layer; And a p-type semiconductor layer formed on the superlattice layer.

In addition, the undoped semiconductor layer of the superlattice layer of the nitride semiconductor light emitting device according to the present invention is alternately stacked in a superlattice structure by giving a temperature change in the range of 500 ° C to 1000 ° C.

In addition, the superlattice layer of the nitride semiconductor light emitting device characterized in that it has a superlattice structure having 3 to 100 cycles, and is formed to a thickness of 10 Å to 500 Å.

A method of manufacturing a nitride semiconductor light emitting device according to 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; Forming a superlattice layer by alternately stacking an LD p-type semiconductor layer and an undoped semiconductor layer on the active layer; And forming a p-type semiconductor layer on the superlattice layer.

Hereinafter, a method of manufacturing a nitride semiconductor light emitting device and a nitride semiconductor light emitting device according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings, together with the structure of the nitride semiconductor light emitting device and a method of manufacturing the same. This will be explained.

2 is a side cross-sectional view showing the structure of the nitride semiconductor light emitting device 100 according to the embodiment of the present invention, Figure 3 is a flow chart showing a manufacturing method of the nitride semiconductor light emitting device 100 according to an embodiment of the present invention. to be.

Referring to FIG. 2, the nitride semiconductor light emitting device 100 according to the exemplary embodiment of the present invention may include a substrate 105, a buffer layer 110, an undoped semiconductor layer 115, an n-type semiconductor layer 120, and an active layer 125. And a superlattice layer 130, a p-type semiconductor layer 140, a p-side electrode 150, and an n-side electrode 160.

First, the buffer layer 110 is stacked on the substrate 105 (S100), the buffer layer 110 may be formed of a multi-buffer layer, the substrate 105 may be made of a silicon (Si) material.

In general, a silicon substrate is characterized by firstly, a high lattice mismatch with a semiconductor layer, secondly, thermal durability (increased diffusivity) of Si degraded at a high temperature of 1050 ° C. or higher, and thirdly, a crystal structure different from that of the semiconductor layer ( hexagonal / cubic) and the like, the nitride semiconductor light emitting device 100 according to the present invention solves this problem.

That is, according to the present invention, since the structure of the conventional active layer 15 is improved, the influence of the substrate 105 and the buffer layer 110 on the semiconductor layer can be minimized. Eliminating the effects of materials, easy to process monolithic array (Monolithic array), and can lay the foundation for mass production of low-cost semiconductor devices.

The buffer layer 110 serves to relieve stress between the substrate 105 and the semiconductor layer 120, such as to prevent melt-back etching due to the chemical action of the substrate 105. / GaN stacked structure, In _x Ga _1-x N / GaN laminated structure, it may be formed of a structure such as a lamination structure of Al _x In _y Ga _1-xy N / In _x Ga _1-x N / GaN.

Subsequently, an undoped semiconductor layer (which may be formed of a u-GaN layer) 115 is formed on the buffer layer 110, and the NH ₃ (4.0 × 10 ⁻² mol / min) and a growth temperature of about 700 ° C. Trimetal gallium (TMGa) (1.0 × 10 ⁻⁴ mol / min) is supplied to form a thickness of about 300 nm (S105).

When the undoped semiconductor layer 115 is formed, the n-type semiconductor layer 120 is formed (S110).

The n-type semiconductor layer 122 may be formed of a silicon-doped n-GaN layer to lower the driving voltage, for example, NH ₃ (3.7 × 10 ⁻² mol / min), TMGa (1.2 × 10 ⁻⁴ mol) Per minute) and a silane gas (6.3 × 10 ^-9 moles / minute) containing an n-type dopant such as Si is supplied to grow an n-GaN layer.

When the n-type semiconductor layer 120 is grown, an active layer 125 having a multi-quantum well (MQW) structure composed of InGaN / GaN is formed using, for example, a metal organic chemical vapor deposition (MOCVD) method. (S115).

Subsequently, a superlattice layer 130 is formed on the active layer 125. The superlattice layer 130 alternates between a low doped (LD) p-type semiconductor layer and an undoped semiconductor layer. It is formed by stacking (indicated by a plurality of thin lines in the drawing) (S120).

The superlattice layer 130 is grown to a thickness of 10 Å to 500 Å, and forms an amorphous form in forming the superlattice structure. That is, unlike the single crystal structure, the superlattice layer 130 has a form of amorphous (amorphous) in which the spatial arrangement of the component atoms (or molecules) is not regular according to the composition ratio.

The superlattice structure refers to a structure in which materials having different compositions and properties, such as a low doped p-type semiconductor layer and an undoped semiconductor layer, are alternately stacked with an extremely thin thickness.

When the period of the superlattice becomes less than the intrinsic electromagnetic wave of the material, it exhibits electrical / optical characteristics different from the hybrid crystal semiconductor (semiconductor formed by mixing the constituent materials of the crystal structure) by the quantum size effect.

By stacking two or more materials in different cycles, you can combine superlattice characteristics in various ways and create new artificial materials.The types of superlattices are largely chap superlattices (structures that change the cycles of superlattices in small increments) and irregularities. There are superlattices (structures with irregular compositions and cycles), doped superlattices (structures with different doping amounts), and these exhibit completely different characteristics from conventional materials and devices.

Looking at the specific growth conditions of the superlattice layer, the undoped semiconductor layer may be provided as an Un-GaN layer to form a superlattice structure by giving a temperature change in the range of 500 ℃ to 1000 ℃.

When the undoped semiconductor layer is temperature-controlled to form a superlattice structure, an interfacial layer (surface recovery (dislocation, pinhole, thermal pit reducing effect)) is naturally formed between the layers, thereby forming a high quality thin film.

The LD p-type semiconductor layer may be provided as an LD p-GaN layer and is doped to a value of about 30% to 70% of the doping level of the p-type semiconductor layer 140.

The LD p-type semiconductor layer and the undoped semiconductor layer may form a superlattice layer 130 by forming a superlattice structure of 3 to 100 cycles.

In addition, the superlattice layer 130 is formed on the active layer 125 to prevent back diffusion of Mg, which is a dopant, from the p-type semiconductor layer 140.

In this manner, when the superlattice layer 130 is formed, the p-type semiconductor layer 140 is formed thereon (S125).

The p-type semiconductor layer 140 is made of hydrogen as a carrier gas to raise the ambient temperature to 1000 ° C., TMGa (7 × 10 ⁻⁶ mol / min), trimethylaluminum (TMAl) (2.6 × 10 ⁻⁵ mol / min), Bicetyl cyclopentadienyl magnesium (EtCp2Mg) {Mg (C ₂ H ₅ C ₅ H ₄ ) ₂ } (5.2 x 10 ^-7 mol / min), and NH ₃ (2.2 x 10 ^-1 mol / min) was fed To a thickness of 0.02 to 0.1 μm.

Subsequently, annealing treatment is performed at a temperature of 950 ° C. for 5 minutes, for example, to adjust the maximum hole concentration of the p-type semiconductor layer 140.

When the basic stacked structure from the substrate 105 to the p-type semiconductor layer 140 is implemented as described above, wet etching, for example, anisotropic wet etching, is performed on the surface to expose a portion of the n-type semiconductor layer 120. (S130).

After the etching process, the n-side electrode 160 made of titanium (Ti) or the like is deposited on the n-type semiconductor layer 120.

The p-side electrode 150 may be implemented as a transparent electrode made of one of ITO, ZnO, RuOx, TiOx, and IrOx (S135).

Although the present invention has been described above with reference to the embodiments, these are only examples and are not intended to limit the present invention, and those skilled in the art to which the present invention pertains may have an abnormality within the scope not departing from the essential characteristics of the present invention. It will be appreciated that various modifications and applications are not illustrated. For example, each component specifically shown in the embodiment of the present invention can be modified. And differences relating to such modifications and applications will have to be construed as being included in the scope of the invention defined in the appended claims.

According to the present invention has the following effects.

First, the present invention can minimize the influence of lattice defects and crystal defects to form a high quality semiconductor layer, and has the effect of facilitating the combination of holes and electrons and the control of conductivity.

Second, the dopant of the p-type semiconductor layer can be prevented from being diffused back into the active layer, and the effects of strain and stress phenomena transferred from the lower layer are minimized, and potential defects, pinholes and thermal fits are reduced. As a result, the electrical and optical characteristics of the semiconductor device may be improved.

Third, according to the present invention, it is possible to increase the electron density on the active layer and to protect the active layer when static electricity is generated as the current is uniformly spread, and to minimize the effects of lattice defects and crystal defects to strengthen the interlayer physical structure and light emitting device There is an effect that can lower the driving voltage.

Claims (13)

Board; An n-type semiconductor layer formed on the substrate; An active layer formed on the n-type semiconductor layer; A superlattice layer in which a low doped p-type semiconductor layer and an undoped semiconductor layer are alternately stacked and formed on the active layer; And A nitride semiconductor light emitting device comprising a p-type semiconductor layer formed on the superlattice layer. The method of claim 1, wherein the undoped semiconductor layer of the superlattice layer A nitride semiconductor light emitting device characterized in that the alternating lamination in a superlattice structure given a temperature change in the range of 500 ℃ to 1000 ℃. The method of claim 1, wherein the superlattice layer A nitride semiconductor light emitting device, characterized in that the amorphous form. The method of claim 1, wherein the undoped semiconductor layer of the superlattice layer A nitride semiconductor light emitting device, characterized in that the Un-GaN layer. The method of claim 1, wherein the LD p-type semiconductor layer of the superlattice layer A nitride semiconductor light emitting device, characterized in that the LD p-GaN layer. The method of claim 1, wherein the superlattice layer A nitride semiconductor light emitting device comprising a superlattice structure having 3 to 100 cycles. The method of claim 1, wherein the superlattice layer A nitride semiconductor light emitting device, characterized in that formed in a thickness of 10Å to 500Å. The method of claim 1, wherein the LD p-type semiconductor layer of the superlattice layer A nitride semiconductor light emitting device, wherein the p-type semiconductor layer is doped to a value of 30% to 70% of the doping level. Forming an n-type semiconductor layer on the substrate; Forming an active layer on the n-type semiconductor layer; Forming a superlattice layer by alternately stacking an LD p-type semiconductor layer and an undoped semiconductor layer on the active layer; And A p-type semiconductor layer is formed on the superlattice layer. The method of claim 9, wherein the superlattice layer is formed The undoped semiconductor layer of the superlattice layer is a method of manufacturing a nitride semiconductor light emitting device comprising the step of alternately stacked in a superlattice structure given a temperature change in the range of 500 ℃ to 1000 ℃. The method of claim 9, wherein the superlattice layer is formed And the LD p-type semiconductor layer and the undoped semiconductor layer are alternately stacked in 3 to 100 cycles to form a superlattice structure. The method of claim 9, wherein the superlattice layer is formed The superlattice layer is a method of manufacturing a nitride semiconductor light emitting device, characterized in that forming the superlattice structure to a thickness of 10 ~ 500Å. The method of claim 9, wherein the superlattice layer is formed. And the LD p-type semiconductor layer of the superlattice layer is doped to a value of 30% to 70% of the doping level of the p-type semiconductor layer.

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