KR20100060098A - Nitride semiconductor light emitting device - Google Patents

Abstract

PURPOSE: A nitride semiconductor light emitting device is provided to simplify a process by radiating a white light through an active layer including layer having band gap of three different colors. CONSTITUTION: An n-type clad layer(120) is formed on a substrate. An electronic emitting layer is formed by laminating a first nitride semiconductor layer and a second nitride semiconductor layer which are formed on the n-type clad layer at least twice. An active layer is formed on the electronic emitting layer in two multiple quantum well structures. A p-type cladding layer is formed on the active layer. A P-contact is formed on the p-type cladding layer. N type electrode(160) is formed on the n-type clad layer.

Description

Nitride Semiconductor Light Emitting Device {NITRIDE SEMICONDUCTOR LIGHT EMITTING DEVICE}

The present invention relates to a nitride semiconductor light emitting device, and more particularly, to simplify the process by emitting white light through an active layer comprising a layer having three different band gaps capable of emitting red light, green light, and blue light. The present invention relates to a nitride semiconductor light emitting device capable of reducing manufacturing costs.

Nitride semiconductor light emitting devices have attracted much attention as environmentally friendly, high-life light sources as well as excellent physical and chemical properties. The nitride semiconductor is a material capable of generating red light, green light, and blue light, and is rapidly expanding its application range to various light sources such as a color display board, a traffic light, an image scanner, and a light source for illumination.

In addition, nitride semiconductor technology has been continuously developed as an application technology not only in the optical device industry but also in the electronic device industry, and is now being established as a key material in the electronic material field. In particular, as the light emitting device using the nitride semiconductor is adopted as a part of various electronic products, the importance of the light emitting device as well as reliability is gradually increasing.

BACKGROUND ART In general, nitride semiconductor light emitting devices are used in light emitting diodes (LEDs) or laser diodes (LDs), and are used as light sources. The nitride semiconductor includes an active layer of a quantum well structure (a single quantum well structure, a multi-quantum well structure) disposed between n-type and p-type nitride semiconductor layers, and generates light based on the principle of recombining electrons and holes in the active layer. Release it.

Light emission in the nitride semiconductor device is determined by recombination of electrons and holes in the multilayer quantum well, and red light, green light, and blue light are determined by the size of the energy band gap when the electrons and holes are recombined.

On the other hand, a white light emitting device is widely used as a backlight of an illumination device or a display device, a method of using a phosphor and a simple combination of blue, red and green LEDs made of individual LEDs are known.

First, as a method of manufacturing a white light emitting element using a phosphor, there is a method of using a blue light emitting element. In the case of using a blue light emitting device, by combining a yellow phosphor to the blue light emitting device, or by combining red and green phosphors, the blue light emitted from the blue light emitting device excites the phosphor, and finally emits white light. However, the light emitting device that generates white light by using a phosphor has an advantage that the configuration is simple. However, when the color reproducibility is lowered and used for a long time, the color of the white light is changed due to deterioration of the phosphor.

In order to solve the problem of the light emitting device that obtains white light by using the phosphor as described above, instead of using the phosphor, the light emitting device that emits red, green, and blue colors is combined to have better color reproduction and at the same time use color for a long time. White light emitting devices that do not deteriorate are known.

1 is an example of the prior art for a white light emitting device that emits white light by combining LEDs emitting red, green, and blue light.

The white light emitting device 50 according to FIG. 1 includes first and second light emitting parts 20 and 30 formed on one conductive substrate 41 side by side in a horizontal direction.

The first light emitting unit 20 includes an active layer 23 that is a GaN / InGaN-based multiwell structure for emitting blue light and an active layer 27 that is a GaN / InGaN-based multiwell structure for emitting green light. The light having two different wavelength bands is emitted. In addition, the second light emitting unit 30 formed in another region where the first light emitting unit 20 is not formed on the same surface on which the first light emitting unit 20 is formed is the n-type AlGaInP cladding layer 31 and the red light emitting unit. It comprises an active layer 33 and a p-type AlGaInP-based cladding layer 35 which is an AlGaInP-based multi-well structure.

Accordingly, in the conventional white light emitting device 50 of FIG. 1, the blue light and green light emitted from the first light emitting part 20 and the red light emitted from the second light emitting part 30 are synthesized. White light will be emitted.

However, in the conventional white light emitting device 50 as described above, since the first and second light emitting parts 20 and 30 having different components are formed on one conductive substrate 41, the manufacturing process is complicated. Since the first and second light emitting units 20 and 30 are made of active layers having different components, the driving voltages thereof are different, and thus the configuration of a circuit for controlling each light emitting unit is also complicated.

SUMMARY OF THE INVENTION The present invention has been proposed to solve the above problems, and an object thereof is to emit white light through an active layer comprising three different bandgap layers capable of emitting red light, green light, and blue light. To provide a nitride semiconductor light emitting device that can simplify and reduce the manufacturing cost.

The present invention is a substrate; An n-type cladding layer formed on the substrate; An electron emission layer on which the first nitride semiconductor layer and the second nitride semiconductor layer having different compositions formed on the n-type cladding are repeatedly formed at least twice; An active layer formed on the electron emission layer and formed of two or more multilayer quantum well structures; A p-type cladding layer formed on the active layer; A p-type electrode formed on the p-type cladding layer; And an n-type electrode formed on the n-type cladding layer.

In addition, the active layer is preferably formed by alternately laminating a GaN layer and an In _x Ga _1-x N layer (where 0 <x ≦ 1).

In addition, the uppermost layer and the lowermost layer of the laminated active layer is preferably formed of the GaN layer.

The In _x Ga _1-x N layer may include a first In _x Ga _1-x N layer, a second In _x Ga _1-x N layer, and a third In _x Ga _1-x layer having different energy band gaps. It is preferable to include an N layer.

The energy band gap of the first In _x Ga _1-x N layer is the highest among the first In _x Ga _1-x N layer to the third In _x Ga _1-x N layer, and the third In It is preferable that the energy band gap of the _x Ga _1-x N layer is the lowest.

In addition, the In _x Ga stacking sequence of the _1-x N layer, wherein ₁ In _x Ga _1-x N layer, wherein the 2 In _x Ga _1-x N layer and the second 3 In _x Ga _1-x N layer It is preferable that it is in order.

In addition, the In _x Ga stacking sequence of the _1-x N layer, wherein the 3 In _x Ga _1-x N layer, wherein the 2 In _x Ga _1-x N layer and the first ₁ In _x Ga _1-x N layer It is preferable that it is in order.

In addition, the In _x Ga stacking sequence of the _1-x N layer, wherein ₁ In _x Ga _1-x N layer, wherein the 2 In _x Ga _1-x N layer, wherein the 3 In _x Ga _1-x N layer , In order of the second In _x Ga _1-x N layer, and the first In _x Ga _1-x N layer.

The nitride semiconductor light emitting device according to the present invention emits white light through an active layer including three different bandgap layers capable of emitting red light, green light, and blue light, thereby simplifying the process and reducing manufacturing costs. To provide effective effects. In addition, the present invention also provides an effect of implementing a nitride semiconductor light emitting device capable of easily emitting white light as well as light having a different color through slight design changes.

Matters concerning the operational effects including the technical configuration of the above-mentioned object of the nitride semiconductor light emitting device according to the present invention will be clearly understood by the detailed description with reference to the following drawings in which preferred embodiments of the present invention are shown.

In the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity.

2 is a cross-sectional view illustrating a structure of a nitride semiconductor light emitting device according to an embodiment of the present invention. A nitride semiconductor light emitting device having a horizontal structure is illustrated.

First, as shown in FIG. 2, the nitride semiconductor light emitting device according to the exemplary embodiment of the present invention includes a substrate 110, an n-type cladding layer 120 and electron emission sequentially formed on the substrate 110. Layer 130, active layer 200, and p-type cladding layer 140.

The substrate 110 is preferably formed using a transparent material including sapphire, and in addition to sapphire, zinc oxide (ZnO), gallium nitride (GaN), silicon carbide (SiC) and Aluminum nitride (AlN) or the like.

A buffer layer (not shown) may be further formed between the substrate 110 and the n-type cladding layer 120 to improve lattice matching therebetween. Here, the buffer layer may be formed of GaN or AlN / GaN.

The n-type cladding layer 120 and the p-type cladding layer 140 may have an Al _x In _y Ga _(1-xy) N composition formula, where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, and 0 ≦ x + y ≦ 1. It may be made of a semiconductor material having a). More specifically, the n-type cladding layer 120 may be formed of a GaN layer or a GaN / AlGaN layer doped with n-type conductive impurities. For example, the n-type cladding layer 120 may be Si, Ge, Sn, or the like. Is used, and preferably Si is mainly used. In addition, the p-type cladding layer 140 may be formed of a GaN layer or a GaN / AlGaN layer doped with p-type conductive impurities. For example, Mg, Zn, and Be may be used as the p-type conductive impurities. Preferably, Mg is mainly used.

The electron emission layer 130 may be formed between the active layer 130 and the n-type cladding layer 120 and may be formed by repeatedly stacking InGaN / GaN layers at least twice. The InGaN layer and the GaN layer generally act as an electron emission layer to increase the carrier capture probability in the active layer 200 by increasing the effective amount of electrons lower than the effective amount of holes using the tunneling effect.

In addition, the electron emission layer 130 increases the lattice period through the InGaN / GaN layers of various thin layers, thereby lowering the driving voltage and increasing the luminous efficiency, and also affecting the ESD characteristics.

A portion of the p-type cladding layer 140, the active layer 200, and the electron-emitting layer 130 are removed by mesa etching to expose a portion of the n-type cladding layer 120 on the bottom surface. That is, the electron emission layer 130, the active layer 200, and the p-type cladding layer 140 are formed on a portion of the n-type cladding layer 120.

The p-type electrode 150 is formed on the p-type cladding layer 140 to serve as a reflective metal and a bonding metal.

Meanwhile, an n-type electrode 160 made of Ti / Al or the like is formed on the n-type cladding layer 120 exposed by mesa etching.

On the other hand, the active layer 200 is formed on the upper surface of the electron emission layer 130.

3 to 6 will be described in more detail with respect to the active layer 200 according to an embodiment of the present invention.

The active layer 240 may be a material having an Al x In y Ga (1-xy) N composition formula (where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, and 0 ≦ x + y ≦ 1), and preferably GaN / It may be formed of a multiple quantum well structure composed of an In _x Ga _1-x N layer (where 0 <x ≦ 1).

In particular, according to an embodiment of the present invention, the active layer 200 may be formed by alternately repeating the GaN layer 210 and the In _x Ga _1-x N layer 220 alternately. Since the GaN layer 210 has a high bandgap energy and acts as a barrier, the In _x Ga _1-x N layer 220 has a lower bandgap energy than the GaN layer 210 and thus serves as a quantum well. do. Therefore, as shown in FIG. 3, since it is preferable to be stacked in the order of “barrier / well / barrier ~ (omitted) to well / barrier”, the uppermost layer and the lowermost layer of the stacked active layer 200 are formed of GaN layer 210. It is preferable to form.

According to an embodiment of the present invention, in order to emit white light, the In _x Ga _1-x N layer 220 has a first In _x Ga _1-x N having a different energy band gap as shown in FIG. 4. Layer 221, a second In _x Ga _1-x N layer 222, and a third In _x Ga _1-x N layer 223. Among the first In _x Ga _1-x N layers to the third In _x Ga _1-x N layers 221, 222, and 223, an energy band gap of the first In _x Ga _1-x N layer 221 is The highest energy band gap of the third In _x Ga _1-x N layer 223 is the lowest. In other words, the first In _x Ga _1-x N layer 221 has the highest energy band gap and is expected to have short wavelength blue light, and the third In _x Ga _1-x N layer 223 has the lowest energy band gap and has a long wavelength. Red light is expected, the second In _x Ga _1-x N layer 222 has a lower energy band gap than the first In _x Ga _1-x N layer 221, and the third In _x Ga _1-x Since the energy band gap is higher than that of the N layer 223, green light, which is a wavelength between the blue light and the red light, is expected.

In fact, determining the red, green, and blue light in the process of the nitride semiconductor light emitting device doeneunya how the composition of the In in the thickness and In _x Ga _1-x N layer of In _x Ga _1-x N layer, that is, the value of x Seems to make a difference. In general, in order to increase the composition of In during the growth of In _x Ga _1-x N layer, there is a method of increasing the actual In source and lowering the growth temperature. Therefore, as the thickness of the In _x Ga _1-x N layer increases, the divergence characteristic changes from the short wavelength to the long wavelength, and when the composition of In increases or the growth temperature of the In _x Ga _1-x N layer decreases, The divergence characteristics change with a long wavelength.

Accordingly, in order for the first In _x Ga _1-x N layers to the third In _x Ga _1-x N layers 221, 222, and 223 to emit blue light, green light, and red light, the composition of x and the growth of each layer. Temperature and thickness can be adjusted. Preferably, the first In _x Ga _1-x N layer 221 emitting blue light emits visible light in the 430-480 nm region, and the second In _x Ga _1-x N layer 222 emits green light. Emits visible light in the region of 500 to 550 nm, and the third In _x Ga _1-x N layer 223 emitting red light controls the amount of indium to emit visible light in the region of 570 to 650 nm. For example, the x value of the first In _x Ga _1-x N layer 221 may be approximately 0.18 to 0.25, and the x value of the second In _x Ga _1-x N layer 222 may be approximately. Preferably, the thickness is 0.25 to 0.35, and the x value of the third In _x Ga _1-x N layer 223 is preferably about 0.45 to 0.60. In addition, in order to emit red light, green light, and blue light, the first In _x Ga _1-x N layer 221 to the third In _x Ga _1-x N layer 223 should constitute a small well. For this purpose the x value of each layer is increased or decreased within the range given above.

On the other hand, the ₁ In _x Ga _1-x N layer (221, In _x Ga _1-x N layer 220 in order to dissipate all of the blue light, green light, red light to realize a nitride semiconductor light-emitting device finally emit white light ) 3 to 3 In _x Ga _1-x N layer 221 may be a combination of the three variations as shown in Figs.

[Modification 1]

First, FIG. 4, the stacking order of the In _x Ga _1-x N layer 220 comprises a ₁ In _x Ga _1-x N layer 221, a 2 In _x Ga _1-x N layer, as shown in ( 222 and the third In _x Ga _1-x N layer 223. Accordingly, the active layer 200 is repeatedly stacked with a GaN layer 210 and an In _x Ga _1-x N layer 220, and the In _x Ga _1-x N layer 220 also has a first In _x Ga _{1-. The x} N layer 221 may be formed by being stacked in the order of the second In _x Ga _1-x N layer 222 → the third In _x Ga _1-x N layer 223. When the stacking order is briefly indicated by reference numerals, it may be referred to as 210/221/222/223/210/221/222/223 / ~ (omitted) to / 221/222/223/210.

[Modification 2]

In addition, the, In _x Ga stacking sequence of the _1-x N layer 220 is the 3 In _x Ga _1-x N layer 223, a 2 In _x Ga _1-x N layer as shown in Figure 5 ( 222 and the first In _x Ga _1-x N layer 221 may be in order. Accordingly, the active layer 200 may be repeatedly stacked with a GaN layer 210 and an In _x Ga _1-x N layer 220, and the In _x Ga _1-x N layer 220 may also have a third In _x Ga _1- layer. _{The x} N layer 223 may be formed by being stacked in the order of the second In _x Ga _1-x N layer 222 → the first In _x Ga _1-x N layer 221. When the stacking order is briefly represented by reference numerals, it may be referred to as 210/223/222/221/210/223/222/221 / ~ (omitted) to / 223/222/221/210.

[Modification 3]

On the other hand, the, In _x Ga stacking sequence of the _1-x N layer 220 comprises a ₁ In _x Ga _1-x N layer 221, a 2 In _x Ga _1-x N layer, as shown in Figure 6 ( 222, the third In _x Ga _1-x N layer 223, the second In _x Ga _1-x N layer 222, and the first In _x Ga _1-x N layer 221 may be in order. . Accordingly, the active layer 200 is repeatedly stacked with a GaN layer 210 and an In _x Ga _1-x N layer 220, and the In _x Ga _1-x N layer 220 also has a first In _x Ga _{1-. x} N layer 221 → 2nd In _x Ga _1-x N layer 222 → 3rd In _x Ga _1-x N layer 223 → 2nd In _x Ga _1-x N layer 222 → The 1 In _x Ga _1-x N layer 221 may be stacked and formed in the order. When the stacking order is shown only by reference numerals, 210/221/222/223/222/221/210/221/222/223/222/221 / ~ (omitted) to / 221/222/223/222/221/210 It can be said.

7 is a view briefly showing the bandgap energy of the active layer 200 according to an embodiment of the present invention. The energy bandgap of the active layer 200 is repeated between the GaN layer 210 having a large band gap and the In _x Ga _1-x N layer 220 having a relatively small band gap. In addition, when the In _x Ga _1-x N layer 220 having a small band gap is enlarged, the band gaps are represented by different values Eg1, Eg2, and Eg3 within the In _x Ga _1-x N layer 220. Shown in Figure 7 thereby, to adjust the value of x in In _x Ga _1-x N layer 220, or increasing the thickness of the In _x Ga _1-x N layer 220, or decreasing the growth temperature as described above, As described above, the band gap value may be adjusted in various ways (eg, Eg1, Eg2, Eg3).

In addition, since the subunit wells must be configured to emit red light, green light, and blue light, the first In _x Ga _1-x N layer 221 to the third In _x Ga _1-x N layer 223. Each does not have a fixed bandgap value, but increases or decreases within a range to reach a constant energy band value (eg, Eg1, Eg2, Eg3) as shown in FIG.

Therefore, as described above, the nitride semiconductor light emitting device according to the present invention simplifies the process by emitting white light through an active layer including a layer having three different band gaps capable of emitting red light, green light, and blue light. It is possible to reduce the manufacturing cost, and also to implement a nitride semiconductor light emitting device that can easily emit light having a white light as well as other colors through a slight design change.

Preferred embodiments of the present invention described above are disclosed for the purpose of illustration, and various substitutions, modifications and changes within the scope of the technical spirit of the present invention for those skilled in the art to which the present invention pertains. Changes may be made, but such substitutions, changes and the like should be regarded as belonging to the following claims.

1 is a cross-sectional view showing a white light emitting device for emitting white light according to the prior art.

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

3 is an enlarged cross-sectional view showing an active layer of a nitride semiconductor light emitting device according to an embodiment of the present invention;

4 to 6 are enlarged cross-sectional views showing the stacking order of active layers according to the first or third embodiment of the present invention.

7 is a cross-sectional view showing a band gap of the active layer of the nitride semiconductor light emitting device according to the present invention.

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

110: substrate 120 n-type cladding layer

130: electron emission layer 200: active layer

210: GaN layer 220: In _x Ga _1-x N layer

221: first In _x Ga _1-x N layer 222: second In _x Ga _1-x N layer

223: third In _x Ga _1-x N layer 140: p-type clad layer

150: p-type electrode 160: n-type electrode

Claims (8)

Board; An n-type cladding layer formed on the substrate; An electron emission layer on which the first nitride semiconductor layer and the second nitride semiconductor layer having different compositions formed on the n-type cladding are repeatedly formed at least twice; An active layer formed on the electron emission layer and formed of two or more multilayer quantum well structures; A p-type cladding layer formed on the active layer; A p-type electrode formed on the p-type cladding layer; And An n-type electrode formed on the n-type cladding layer; A nitride semiconductor device comprising a. The method of claim 1, The active layer is a nitride semiconductor device, characterized in that the GaN layer and In _x Ga _1-x N layer (where 0 <x _{≤ 1} ) is formed by alternately repeatedly stacked. The method of claim 2, The uppermost layer and the lowermost layer of the laminated active layer is formed of the GaN layer. The method of claim 3, The In _x Ga _1-x N layer may include a first In _x Ga _1-x N layer, a second In _x Ga _1-x N layer, and a third In _x Ga _1-x N layer having different energy bandgaps. A nitride semiconductor device comprising a. The method of claim 4, wherein The energy band gap of the first In _x Ga _1-x N layer is the highest among the first In _x Ga _1-x N layer to the third In _x Ga _1-x N layer, and the third In _x Ga A nitride semiconductor device characterized in that the energy bandgap of the _1-x N layer is the lowest. The method of claim 4, wherein The stacking order of the In _x Ga _1-x N layer is the order of the first In _x Ga _1-x N layer, the second In _x Ga _1-x N layer, and the third In _x Ga _{1 - x} N layer. A nitride semiconductor element, characterized in that. The method of claim 4, wherein The stacking order of the In _x Ga _1-x N layer is the order of the third In _x Ga _1-x N layer, the second In _x Ga _1-x N layer, and the first In _x Ga _{1 - x} N layer. A nitride semiconductor element, characterized in that. The method of claim 4, wherein The stacking order of the In _x Ga _1-x N layer is the first In _x Ga _1-x N layer, the second In _x Ga _1-x N layer, the third In _x Ga _1-x N layer, and The nitride semiconductor device of claim 2, wherein the second In _x Ga _1-x N layer and the first In _x Ga _1-x N layer are in order.

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