KR101311440B1 - Light emitting diode and manufacturing method thereof - Google Patents

Abstract

According to an embodiment of the present invention, an n-type nitride semiconductor layer formed on a substrate; An active layer formed on the n-type nitride semiconductor layer; And a p-type nitride semiconductor layer formed on the active layer and formed of a carbon (C) doped Al _x Ga _{1 - x} N layer (0.06 ≦ _x ≦ 0.55).

Description

LIGHT EMITTING DIODE AND MANUFACTURING METHOD THEREOF

The present invention relates to a light emitting device and a method of manufacturing the same.

Generally, bulbs or fluorescent lamps are widely used as indoor or outdoor illumination lamps, and such bulbs or fluorescent lamps have a short life span and therefore frequently have to be replaced. In addition, the conventional fluorescent lamp has a problem that the illuminance gradually decreases due to deterioration over time of its use.

In order to solve this problem, a light emitting diode (LED) has been developed that can realize excellent controllability, fast response speed, high electro-optical conversion efficiency, long life, low power consumption, high brightness, and sensitive lighting. .

Among the light emitting diodes, in particular, nitride semiconductor light emitting devices have a wide application field, and are widely used for light output such as blue / green.

Conventional nitride semiconductor light emitting devices include an n-type nitride semiconductor layer, an active layer, and a p-type nitride semiconductor layer. The n-type nitride semiconductor layer and the p-type nitride semiconductor layer form a pn junction, and light is emitted by combining electrons of the n-type nitride semiconductor layer and holes of the p-type nitride semiconductor layer in the active layer. The active layer generally consists of a multi-quantum well (MQW) structure.

Korean Patent Registration No. 0580752 (Registration Date: 2006.05.09.)

An object of the present invention is to provide a nitride-based light emitting device exhibiting a high Hall effect and having improved electrical properties.

According to an embodiment of the present invention, an n-type nitride semiconductor layer formed on a substrate; An active layer formed on the n-type nitride semiconductor layer; And a p-type nitride semiconductor layer formed on the active layer and formed of a carbon (C) doped Al _x Ga _{1 - x} N layer (0.06 ≦ _x ≦ 0.55).

The carbon source for carbon (C) doping of the p-type nitride semiconductor layer is preferably CBr ₄ .

The p-type nitride semiconductor layer may further include a magnesium (Mg) doped GaN layer.

The n-type nitride semiconductor layer may include at least one of a GaN layer, an AlGaN layer, or a silicon (Si) doped AlGaN layer.

The active layer may include at least one layer of a magnesium (Mg) doped GaN layer or an undoped GaN layer.

The p-type nitride semiconductor layer may have a thickness of 0.1 ~ 1.5㎛.

On the other hand, according to another embodiment of the present invention, growing an n-type nitride semiconductor layer on a substrate; Growing an active layer on the n-type nitride semiconductor layer; And growing a p-type nitride semiconductor layer formed of a carbon (C) doped Al _x Ga _{1 - x} N layer (0.06 ≦ _x ≦ 0.55) on the active layer. .

In the growing of the p-type nitride semiconductor layer, TMAl, TMGa, and NH ₃ may be used as source sources of Al, Ga, and N, and CBr ₄ may be used as a carbon source for the carbon (C) doping.

The growing of the n-type nitride semiconductor layer may include growing at least one of a GaN layer, an AlGaN layer, or a silicon (Si) doped AlGaN layer.

The growing of the active layer may include growing at least one layer of a magnesium (Mg) doped GaN layer or an undoped GaN layer.

The p-type nitride semiconductor layer may be grown to a thickness of 0.1 ~ 1.5㎛.

The growth of at least one of the n-type nitride semiconductor layer, the active layer, or the second type nitride semiconductor layer may be performed under a pressure of 40 mbar and a temperature condition of 1180 ° C.

At least one of the n-type nitride semiconductor layer, the active layer, or the n-type nitride semiconductor layer may be grown by a low pressure metal organic vapor phase epitaxy (LP-MOVPE) process.

The nitride-based light emitting device according to the present invention shows a high Hall effect, and shows an improved electrical efficiency.

1 is a view showing the structure of a light emitting device according to an embodiment of the present invention.
2A to 2D are views for explaining a method of manufacturing a light emitting device according to an embodiment of the present invention.
3 is a graph showing the Hall effect of the nitride semiconductor layer according to an embodiment of the present invention.
4 is a graph showing a CV measurement result for identifying characteristics of a light emitting device structure according to an exemplary embodiment of the present invention.
5A and 5B are graphs showing characteristics of the nitride semiconductor layer according to the embodiment of the present invention.
6 is a graph illustrating a result of SIMS analysis for identifying characteristics of a light emitting device structure according to an exemplary embodiment of the present invention.
7 is a graph illustrating an IV curve for identifying characteristics of a light emitting device structure according to an exemplary embodiment of the present invention.
8A and 8B are graphs showing an optical luminescence spectrum for explaining the characteristics of a nitride semiconductor layer according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION The following detailed description of the invention refers to the accompanying drawings that show, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. It should be understood that the various embodiments of the present invention are different, but need not be mutually exclusive. For example, certain features, structures, and characteristics described herein may be implemented in other embodiments without departing from the spirit and scope of the invention in connection with an embodiment. It is also to be understood that the position or arrangement of the individual components within each disclosed embodiment may be varied without departing from the spirit and scope of the invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is to be limited only by the appended claims, along with the full scope of equivalents to which such claims are entitled, if properly explained. In the drawings, like reference numerals refer to the same or similar functions throughout the several views.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings, so that those skilled in the art can easily carry out the present invention.

<Preferred embodiment of the present invention>

The light emitting element in the present specification preferably means a light emitting diode (LED) or a laser diode and the like, but it emits light and has the same or similar structure as the structure of the present invention shown in the following description. Other devices can also be used as the light emitting device of the present invention.

Hereinafter, a light emitting device and a manufacturing method thereof according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

[Overall Structure of Light-Emitting Element]

1 is a cross-sectional view showing the configuration of a light emitting device according to an embodiment of the present invention.

Referring to FIG. 1, in the light emitting device of the present invention, the buffer layer 120, the nitride layer 130, the first type nitride semiconductor layer 140, the active layer 150, and the second type nitride are formed on the substrate 110. The semiconductor layer 160 may be included.

The substrate 110 may be, for example, a sapphire substrate, but is not limited thereto. The buffer layer 120 is grown on a substrate 110 under normal growth conditions (eg, a growth temperature of 500 ° C. to 600 ° C.). The layer formed on the upper layer of the buffer layer 120 and the substrate 110 may have a different lattice structure, and thus cracks may occur, and the buffer layer 120 may be formed to prevent such a phenomenon. . The buffer layer 120 may be an undoped AlGaN / GaN multi buffer layer.

The nitride layer 130 may be formed on the buffer layer 120 to have a predetermined thickness (for example, several nm). The nitride layer 130 may be an undoped AlN layer or the like.

At least one of the buffer layer 120 and the nitride layer 130 may be omitted in the light emitting device structure of the present invention.

The first type nitride semiconductor layer 140 may be grown on the nitride layer 130 at normal growth conditions (eg, a temperature of about 1180 ° C. and a pressure of about 40 mbar). The first type nitride semiconductor layer 140 may be an n-type nitride semiconductor layer, for example, a GaN or AlGaN layer. The first type nitride semiconductor layer 140 may be in an undoped state, but may be doped with silicon (Si), for example. The first type nitride semiconductor layer 140 may be formed to a thickness of about 2 ~ 4㎛.

The active layer 150 may be grown as a single quantum well layer or multiple quantum well layers. The active layer 150 may be an undoped GaN layer. An ohmic contact layer (not shown) may be further included in addition to the active layer 150. The ohmic contact layer (not shown) may be, for example, a GaN layer doped with magnesium (Mg). The ohmic contact layer (not shown) may replace the active layer 150. That is, at least one layer of the active layer 150 or the ohmic contact layer (not shown) may be included in the light emitting device structure of the present invention.

The second type nitride semiconductor layer 160 according to an embodiment of the present invention may be grown on the active layer 150 under growth conditions of, for example, a temperature of about 1180 ° C. and a pressure of about 40 mbar. The second type nitride semiconductor layer 160 may be a p-type nitride semiconductor layer. The second type nitride semiconductor layer 160 may include an Al _x Ga _{1 - x} N layer doped with carbon (C), where 0.06 ≦ _x ≦ 0.55. If x is less than 0.06, the carbon doping effect is lowered. If x is more than 0.55, the resistance is high and the crystal growth characteristics are distorted, resulting in poor efficiency. Therefore, the value of x for the maximum efficiency of the carbon (C) doped Al _x Ga _{1 - x} N layer is preferably in the range of 0.06 ≦ x ≦ 0.55.

In addition, the second type nitride semiconductor layer 160 may further include a magnesium (Mg) doped GaN layer together with the Al _x Ga _{1 - x} N layer doped with carbon (C). At this time, the light emitting device according to the embodiment has a double hetero structure. On the other hand, the second type nitride semiconductor layer 160 may be formed to a thickness of about 0.1 ~ 1.5㎛.

Hereinafter, a method of manufacturing the light emitting device described with reference to FIG. 1 will be described.

[Method for Manufacturing Light-Emitting Element]

2A to 2D are views for explaining a method of manufacturing a light emitting device according to an embodiment of the present invention.

First, referring to FIG. 2A, the buffer layer 120 is grown on the sapphire substrate 110, and the nitride layer 130 is grown thereon at a high temperature. The buffer layer 120 is typically grown at a low temperature (eg, 500 to 600 ° C.). As the nitride layer 130 is grown in a high temperature environment, the buffer layer 120 may be crystallized under a high temperature environment. As described above, the buffer layer 120 may be an undoped AlGaN / GaN layer. A trimethylaluminium (TMAl) source, a trimethylgallium (TMGa) source, or an NH ₃ source gas may be used for the growth of the AlGaN layer. In addition, for the growth of the GaN layer, a TMGa source source and an NH ₃ source gas may be used. On the other hand, as described above, the nitride layer 130 may be an undoped AlN layer, a TMAl source source, NH ₃ source gas may be used for the growth of the AlN layer.

Referring to FIG. 2B, the first type nitride semiconductor layer 140 is grown on the nitride layer 130. As described above, the first type nitride semiconductor layer 140 may be an undoped GaN layer or an AlGaN layer. However, it may be doped with silicon (Si) or the like. The growth conditions may be an environment at a temperature of about 1180 ° C. and a pressure of about 40 mbar. In addition, a low pressure metal organic vapor phase epitaxy (LP-MOVPE) process can be used as the growth method. A TMAl source source, TMGa source source, NH ₃ source gas may be used for the growth of the AlGaN layer.

Referring to FIG. 2C, the active layer 150 is formed on the first type nitride semiconductor layer 140. As described above, the active layer 150 may be an undoped GaN layer, but may be formed together with the GaN layer doped with magnesium (Mg), and may be replaced by the same.

Referring to FIG. 2D, the second type nitride semiconductor layer 160 is grown on the active layer 150. As described above, the second type nitride semiconductor layer 160 may include a carbon (C) doped AlGaN layer. The growth conditions may be an environment at a temperature of about 1180 ° C. and a pressure of about 40 mbar. In addition, a low pressure metal organic vapor phase epitaxy (LP-MOVPE) process can be used as the growth method. That is, the growth conditions and the growth method may be the same as the growth conditions and the growth method of the first type nitride semiconductor layer 140. TMAl source source, TMGa source source, NH ₃ source gas may be used for the growth of the Al _x Ga _1-x N layer. Here, 0.06 ≦ x ≦ 0.55. In addition, CBr ₄ gas may be used as the carbon source for the carbon (C) doping. A magnesium (Mg) doped GaN layer may be further formed along with the carbon (C) doped AlGaN layer to form a double heterostructure.

[Experimental Example]

In the light emitting device structure according to the embodiment of the present invention, the second nitride semiconductor layer is formed of a carbon (C) doped p-type Al _x Ga _{1 - x} N layer, where 0.06 ≦ _x ≦ 0.55.

Hall effect

Figure 3 is a graph showing the Hall effect of the carbon (C) doped p-type Al _x Ga _{1 - x} N, it shows a change in characteristics according to the flow rate ratio of CB ₄ . As an example, x = 0.1 was set. CBr ₄ gas was used as the carbon source. The Hall effect was measured in an environment of room temperature, and in FIG. 3, black and white dots represent p-type and n-type semiconductor layers, respectively.

내지

로 나타난다. Referring to Figure 3, when the flow rate of a small value, CBr ₄ (0.06 ~ 0.3μ㏖ / min) Carbon (C) is doped Al _{0 .1} Ga _{0 .9} N is n-type, the electron concentration is

To

Appears.

로 떨어진다.When the flow ratio of the CBr ₄ 0.07μ㏖ / min of carbon (C) doped n-type Al _{0 .1} Ga electron concentration of _{0 .9} N is the lowest value,

Falls into.

에서

로 급격히 증가한다. Than when the continuously increasing the flow rate of CBr _4, about 3μ㏖ / min or more in CBr ₄ flow ratio of carbon (C) doped Al _{0 .1} Ga _{0 .9} N is changed from n-type to p-type. In addition, the hole concentration depends _on the flow rate of CBr ₄ .

in

Increases sharply.

일 때, 실온에서 약 0.9~20cm²/Vs가 된다.On the other hand, carbon (C) hole mobility of the doped p-type Al _{0 .1} Ga _{0 .9} N also has a hole concentration

, It is about 0.9-20 cm ² / Vs at room temperature.

As described above, in the light emitting device according to the present invention, a high hole concentration can be obtained by adjusting the flow rate ratio of CBr ₄ for the doping of the second type nitride semiconductor layer, thereby improving the hole effect.

C-V ( Capacitance - Voltage ) Measure

FIG. 4 is a graph showing a depth profile of an effective ionized acceptor density (EIAD) determined by CV measurement to identify characteristics of a light emitting device structure according to an exemplary embodiment of the present invention. Measurement conditions were set to room temperature. EIAD = N _A -N _D , where N _A and N _D are ionization acceptor and donor densities, respectively.

For this measurement, a magnesium (Mg) doped GaN layer (0.18 μm thick) / carbon (C) doped Al _x Ga _{1 - x} N layer (x = 0.55, about 1.0 μm thick) / silicon (Si) The structure of the doped Al _x Ga _{1 - x} N layer (x = 0.55, thickness of about 2-4 μm) was used.

Referring to FIG. 4, when the carbon (C) doped Al _x Ga _{1 − x} N (x = 0.55) is p-type, the EIAD is in the range of 0.18 to 1.2 μm (ie, the carbon (C) doped Al _x Ga _{1 −} It can be seen that it is fixed at about (6-7) x 10 ¹⁸ cm ^-3 in a section substantially equal to the thickness of the layer _x N (x = 0.55). On the other hand, the EIAD of the magnesium (Mg) doped GaN (thickness of 0.18 μm) layer was about 5 × 10 ¹⁸ cm ⁻³ .

5A and 5B are graphs showing characteristics when x = 0.1 and x = 0.55 in the Al _x Ga _{1 - x} N layer, respectively.

5A and 5B show a case where x = 0.1 and x = 0.55 in a nitride semiconductor layer made of carbon (C) doped Al _x Ga _{1 - x} N, respectively. In the graphs of FIGS. 5A and 5B, the x-axis is the flow rate ratio of CBr ₄ for carbon (C) doping, and the y-axis is the EIAD value.

5A and 5B, since the flow rate ratio of CBr ₄ is about 3 μmol / min or more, the carbon (C) doped Al _x Ga _{1 - x} N layer for the same reason as described with reference to FIG. Will have characteristics.

As shown in FIGS. 5A and 5B, it can be seen that the EIAD value can be easily changed from about 3 × 10 ¹⁶ cm ⁻³ to about 3 × 10 ¹⁸ cm ⁻³ by adjusting the flow rate ratio of CBr ₄ . It can be seen that the maximum EIAD value when the aluminum content is 55% is (6-7) x 10 ¹⁸ cm ^-3 .

SIMS ( Secondary Ion Mass Spectrometer ) analysis

6 is a graph illustrating a result of SIMS analysis for identifying characteristics of a light emitting device structure according to an exemplary embodiment of the present invention.

For SIMS analysis, a magnesium (Mg) doped GaN layer (about 0.08 μm thick) / carbon (C) doped Al _x Ga _{1 - x} N layer (x = 0.27, about 0.11 μm thick) / undoped GaN layer (thickness of about 15nm) / silicon (Si) doped Al _x Ga _{1 -} a double heterostructure consisting of a _x N layer (x = 0.1, about 3㎛ thickness) were constructed.

In FIG. 6, secondary ionic strength of aluminum and gallium is a value used as a reference for measurement.

Referring to FIG. 6, the carbon concentration of the carbon (C) doped AlGaN layer measured by SIMS analysis is about 7.3 × 10 ¹⁸ cm ⁻³ . On the other hand, in the p-type Al _x Ga _{1 - x} N (x = 0.27), the EIAD of the carbon acceptor is 5 x 10 ¹⁸ cm ^-3 . Therefore, the electrical efficiency of the carbon acceptor in the carbon (C) doped p-type AlGaN layer is measured as (5 / 7.3) x 100 = 68%, which is a very large value.

On the other hand, the EIAD of magnesium in the p-type GaN layer is (4-5) × 10 ¹⁸ cm ^-3 , and the concentration of magnesium in the magnesium-doped p-type GaN is 5 × 10 ¹⁹ cm ^{− by} SIMS analysis. Measured as ^three . Taken together, the electrical efficiency of the magnesium acceptor in the magnesium (Mg) doped p-type GaN layer is measured as (4-5 / 50) × 100 = 8-10%.

Therefore, when the carbon (C) doped p-type Al _x Ga _{1- x} N (x = 0.06 to 0.55) layer is used as the second nitride semiconductor layer according to the embodiment of the present invention, electrical efficiency may be maximized. .

pn  I-V characteristics of the junction

7 is a graph showing an I-V curve for identifying characteristics of a light emitting device structure according to an embodiment of the present invention.

For the data measurement of FIG. 7, a magnesium (Mg) doped p-type GaN layer / carbon (C) doped p-type Al _x Ga _{1 - x} N (x = 0.27) layer / undoped grown on a sapphire substrate A light emitting diode chip having a double heterostructure of a GaN layer / silicon (Si) doped n-type AlGaN layer was used. That is, the n-type AlGaN layer doped with silicon (Si) as the first type nitride semiconductor layer in FIG. 1, the undoped GaN layer as the active layer, and the p-type Al _x Ga doped with carbon (C) as the second type nitride semiconductor layer. _{A 1 - x} N (x = 0.27) layer was used, and further a magnesium (Mg) doped p-type GaN layer was formed on the carbon (C) doped p-type Al _x Ga _{1 -x} N (x = 0.27) layer. Form. The sample was formed in a size of 0.5 × 0.5 mm ² .

Referring to FIG. 7, it can be seen that a forward bias voltage of about 9 V is applied when the injection current is about 20 mA. That is, it can be seen that it exhibits sufficient characteristics to be used as an LED.

Optical luminescence ( PL : Photo Luminescence )

8A and 8B are diagrams showing an optical luminescence spectrum for explaining the characteristics of the nitride semiconductor layer according to the embodiment of the present invention. First, FIG. 8A shows an optical luminescence spectrum of an undoped AlGaN layer, and FIG. 8B shows an optical luminescence spectrum of a carbon (C) doped AlGaN layer. Photoluminescence spectral measurements were taken at low temperature (about 19K).

8A and 8B, it can be seen that the band edge emission (free exciton emission) energy is shown as 3.685 eV in the undoped AlGaN layer and 3.739 eV in the carbon (C) doped AlGaN layer. have. In addition, for carbon (C) doped p-type AlGaN, another emission (boundary exciton emission) occurred near the band-end emission at 3.710 eV. At this time, carbon (C) concentration of the hole-doped AlGaN layer is 1 ~ 3 × 1018cm ^- was ^three.

On the other hand, the energy gap between free exciton emission and boundary exciton emission for carbon (C) doped AlGaN was ΔE = 3.739 meV-3.710 meV = 29 meV. This is much smaller than ΔE = 230 meV, the energy gap between free exciton emission and boundary exciton emission for GaN.

According to an embodiment of the present invention, as the nitride (P) doped p-type Al _x Ga _{1 - x} N (x = 0.06 to 0.55) is used as the nitride semiconductor layer, the maximum EIAD is very high. Therefore, the electrical efficiency is improved.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, Those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Therefore, the spirit of the present invention should not be construed as being limited to the above-described embodiments, and all of the equivalents or equivalents of the claims, as well as the following claims, I will say.

110: substrate
120: buffer layer
130: nitride layer
140: nitride semiconductor layer 1
150: active layer
160: type 2 nitride semiconductor layer

Claims (13)

delete delete delete delete delete delete Growing an n-type nitride semiconductor layer on the substrate;
Growing an active layer on the n-type nitride semiconductor layer; And
Growing a p-type nitride semiconductor layer formed of a carbon (C) doped Al _x Ga _1-x N layer (0.06 ≦ _x ≦ 0.55) on the active layer,
In the growing of the p-type nitride semiconductor layer, TMAl, TMGa, and NH ₃ are used as source sources of Al, Ga, and N, respectively, and CBr ₄ is used as a carbon source for the carbon (C) doping.
By controlling the flow rate ratio of the CBr ₄ in the range of 3μmol / min or more to grow a p-type nitride semiconductor layer formed of the carbon (C) doped Al _x Ga _1-x N layer (0.06≤x≤0.55), Method of manufacturing a light emitting device. delete The method of claim 7, wherein
The growing the n-type nitride semiconductor layer includes growing at least one of a GaN layer, an AlGaN layer, or a silicon (Si) doped AlGaN layer. The method of claim 7, wherein
Growing the active layer comprises growing at least one of a magnesium (Mg) doped GaN layer or an undoped GaN layer. The method of claim 7, wherein
The p-type nitride semiconductor layer is grown to a thickness of 0.1 ~ 1.5㎛ manufacturing method of the light emitting device. The method of claim 7, wherein
The growth of at least one of the n-type nitride semiconductor layer, the active layer or the p-type nitride semiconductor layer is made under a pressure of 40 mbar, temperature conditions of 1180 ℃. The method of claim 7, wherein
The growth of at least one of the n-type nitride semiconductor layer, the active layer or the p-type nitride semiconductor layer is made by a Low Pressure Metal Organic Vapor Phase Epitaxy (LP-MOVPE) process.

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