KR100803246B1 - Nitride semiconductor device - Google Patents

Abstract

A nitride semiconductor device is provided to improve a current diffusion effect by depositing InGaN layer doped with different conductive impurities to form a current diffusion layer. An n-type nitride semiconductor layer(120) is formed on a substrate(100). A GaN layer(130a) and an InGaN layer(130b) are deposited on a portion of the n-type nitride semiconductor layer to form a current diffusion layer(130). An active layer(140) is formed on the current diffusion layer, and a p-type nitride semiconductor layer(150) is formed on the active layer. A p-type electrode(170) is formed on the p-type nitride semiconductor layer, and an n-type electrode(180) is formed on the n-type nitride semiconductor layer with no the current diffusion layer.

Description

Nitride Semiconductor Devices {NITRIDE SEMICONDUCTOR DEVICE}

1 is a cross-sectional view showing the structure of a nitride semiconductor device (LED) according to the prior art.

Figure 2 is a partial cross-sectional view showing a current spreading layer according to the prior art.

3 is a graph schematically showing an energy band gap profile of the current spreading layer illustrated in FIG. 2.

4 is a cross-sectional view illustrating a structure of a nitride semiconductor device (LED) according to an embodiment of the present invention.

5 is a partial cross-sectional view showing an InGaN layer of a current spreading layer according to a first embodiment of the present invention.

FIG. 6 is a graph schematically showing an example of a doping modulation profile of the InGaN layer shown in FIG. 5.

7 is a partial cross-sectional view showing an InGaN layer of a current spreading layer according to a second embodiment of the present invention.

FIG. 8 is a graph schematically showing an example of a doping modulation profile of the InGaN layer shown in FIG. 7.

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

100 substrate 110 buffer layer

120: n-type nitride semiconductor layer 130: current diffusion layer

130a: GaN layer 130b: InGaN layer

140: active layer 150: p-type nitride semiconductor layer

160: transparent conductor layer 170: p-type electrode

180: n-type electrode

200a: InGaN layer doped with p-type impurity

200b: InGaN layer doped with n-type conductivity

200c undoped InGaN layer

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting device such as a light emitting diode (LED), a laser diode (LD), a light emitting device such as a solar cell, an optical sensor, or a nitride semiconductor device used for electronic devices such as transistors and power devices.

Recently, III-V nitride semiconductors such as GaN have been spotlighted as core materials of light emitting devices such as light emitting diodes (LEDs) or laser diodes (LDs) due to their excellent physical and chemical properties. LEDs or LDs using III-V nitride semiconductor materials are widely used in light emitting devices for obtaining light in the blue or green wavelength band, and these light emitting devices are used as light sources of various products such as electronic displays and lighting devices. The III-V nitride semiconductor is generally made of a GaN-based material having a composition formula of In _X Al _Y Ga _{1 -X- Y} N (0≤X, 0≤Y, X + Y≤1).

Next, a conventional nitride semiconductor device (LED) using a III-V nitride semiconductor as described above will be described in detail with reference to FIGS. 1 to 3.

1 is a cross-sectional view schematically showing a structure of a nitride semiconductor device (LED) according to the prior art, FIG. 2 is a partial cross-sectional view showing a current diffusion layer according to the prior art, and FIG. 3 is an energy band of the current diffusion layer shown in FIG. It is a graph schematically showing a gap profile.

As shown, the LED using the nitride semiconductor according to the prior art, the buffer layer 110, n-type nitride semiconductor layer 120, active layer 140 and p of GaN on the sapphire substrate 100 which is a light transmissive substrate The type nitride semiconductor layer 150 has a basic structure sequentially stacked.

On the other hand, the conventional LED, the current diffusion layer 130 is inserted in the interface between the n-type nitride semiconductor layer 120 and the active layer 140, which lowers the operating voltage (V _f ) of the LED and increases the light output Do it.

In particular, the current spreading layer 130 according to the related art is formed of a plurality of GaN layers 130a, and has a single quantum well or multiple quantum well structure containing an InGaN layer 130b having a low energy band therebetween. (See Figure 3).

 The p-type nitride semiconductor layer 150, the active layer 140, and the current diffusion layer 130 are partially removed by a mesa etching process, and thus a part of the n-type nitride semiconductor layer 120 is formed. The upper surface is exposed.

In addition, an n-type electrode 180 is formed on the exposed n-type nitride semiconductor layer 120, and on the p-type nitride semiconductor layer 150, a transparent conductor layer 160 made of ITO or the like and a p-type electrode ( 170 is formed in a stacked structure. In this case, the p-type electrode 170 may be formed of a transparent electrode or a metal electrode. When the p-type electrode 170 is formed of a transparent electrode, the transparent conductor layer 160 disposed below may be omitted. As such, when the transparent conductor layer 160 is omitted, the p-type electrode 170 may be formed on the entire surface of the p-type nitride semiconductor layer 150.

As described above, the nitride semiconductor device (LED) is a double hetero having a current quantum well having a single quantum well or multiple quantum well structure having an InGaN layer (130b) to lower the operating voltage and increase the light output of the LED chip. The structure is adopted.

In particular, in the nitride semiconductor device (LED), since the multi-quantum well structure has a plurality of mini bands and has good efficiency, the device characteristics such as higher output and lower operating voltage than the single quantum well structure are improved. It is expected.

However, since the thickness of the InGaN layer 130b constituting the current spreading layer 130 is thick, current may be concentrated in a place where In composition is large due to nonuniformity of InGaN composition, and thus, electrostatic discharge of the LED device. (ESD) There is a problem of weak internal pressure.

Therefore, since the LED using the current diffusion layer 130 into which the InGaN layer 130b is inserted is generally weak in ESD, it is necessary to improve the electrostatic discharge characteristics. In particular, in the process of handling or using the LED, there is a problem that can be damaged by the static electricity easily generated in people or things.

Accordingly, in order to suppress damage of LEDs due to ESD, various studies have recently been conducted. For example, U.S. Patent No. 6,593,597 discloses a technique for integrating an LED and a Schottky diode on the same substrate to connect the LED and the Schottky diode in parallel to protect the LED from ESD. In addition, in order to improve ESD resistance, a method of connecting an LED device in parallel with a Zener diode has been proposed.

However, these methods have the problem of purchasing and assembling a separate zener diode or forming a Schottky junction, thereby increasing the overall manufacturing cost of the device.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a nitride semiconductor device that ensures high output characteristics by lowering the operating voltage (V _f ) and improving the electron retention effect and the current dispersion effect.

In addition, an object of the present invention is to provide a nitride semiconductor device that can implement a high ESD resistance without having to provide a separate device for improving the ESD resistance.

In order to achieve the above object, the present invention is formed by sequentially stacking a GaN layer and an InGaN layer on a substrate, an n-type nitride semiconductor layer formed on the substrate, and a portion of the n-type nitride semiconductor layer. The InGaN layer includes a current diffusion layer formed by repeatedly stacking InGaN layers doped with different types of conductive impurities one or more times, an active layer formed on the current diffusion layer, and formed on the active layer. A p-type nitride semiconductor layer, a p-type electrode formed on said p-type nitride semiconductor layer, and an n-type electrode formed on an n-type nitride semiconductor layer in which said current spreading layer is not formed. Provided is a nitride semiconductor device.

Further, in the nitride semiconductor device of the present invention, the InGaN layer doped with different types of conductive impurities constituting the current diffusion layer may be doped with an InGaN layer doped with n-type conductive impurities and a p-type conductive impurity. It is preferable that it consists of an InGaN layer.

In addition, in the nitride semiconductor device of the present invention, the InGaN layer doped with the n-type conductive impurity is composed of one or more InGaN layers in which the doping concentration of the n-type conductive impurity is sequentially increased, or the p The InGaN layer doped with the type conductive impurity is preferably composed of one or more InGaN layers in which the doping concentration of the p-type conductive impurity is sequentially increased.

Further, in the nitride semiconductor device of the present invention, the InGaN layer doped with different types of conductive impurities constituting the current diffusion layer includes an InGaN layer doped with n-type conductive impurities and InGaN doped with conductive impurities. It is preferable that the layer and the InGaN layer doped with the p-type conductive impurity.

Further, in the nitride semiconductor device of the present invention, it is preferable to further include a transparent conductor layer formed between the p-type nitride semiconductor layer and the p-type electrode. The transparent conductor layer may further increase the current diffusion effect by increasing the injection area of the current injected through the p-type electrode.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention.

In the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity. Like reference numerals designate like parts throughout the specification.

A nitride semiconductor device according to an embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

First, a nitride semiconductor device according to an embodiment of the present invention will be described in detail with reference to FIG. 4.

4 is a cross-sectional view illustrating a structure of a nitride semiconductor device (LED) according to an embodiment of the present invention.

As shown in FIG. 4, the substrate 100 which is light transmissive, the buffer layer 110, the n-type nitride semiconductor layer 120, the current diffusion layer (EEL) 130 on the substrate 100, The active layer 140 and the p-type nitride semiconductor layer 150 include a light emitting structure formed by sequentially stacking.

The substrate 100 is a substrate suitable for growing a nitride semiconductor single crystal, and may be a heterogeneous substrate such as a sapphire substrate and a silicon carbonate (SiC) substrate or a homogeneous substrate such as a nitride substrate.

The buffer layer 110 is a layer for improving lattice matching with the sapphire substrate 100 before the n-type nitride semiconductor layer 120 is grown, and is generally formed of AlN / GaN.

The n-type and p-type nitride semiconductor layers 120 and 150 and the active layer 140 have an In _X Al _Y Ga _{1 -X - Y} N composition formula (where 0 ≦ X, 0 ≦ Y, and X + Y ≦ 1). It may be made of a semiconductor material having. More specifically, the n-type nitride semiconductor layer 120 may be formed of a GaN layer or a GaN / AlGaN layer doped with n-type conductive impurities, for example, Si, Ge, Sn Etc. are used, and preferably Si is mainly used. In addition, the p-type nitride semiconductor layer 150 may be formed of a GaN layer or a GaN / AlGaN layer doped with a p-type conductive impurities, for example, Mg, Zn, Be, etc. It is used, Preferably Mg is mainly used. The active layer 140 may be formed of an InGaN / GaN layer having a multi-quantum well structure.

The current spreading layer 130 is formed of a plurality of GaN layers 130a, and has a single quantum well or multiple quantum well structure in which an InGaN layer 130b having a low energy band is inserted therebetween. The current spreading layer 130 serves to lower the operating voltage of the LED and increase the light output.

On the other hand, since the InGaN layer 130b having a low energy band of the current diffusion layer 130 is thicker than the GaN layer 130a, the current can be concentrated in a place having a large In composition due to nonuniformity of the InGaN composition. This has a problem of weakening the electrostatic discharge (ESD) breakdown voltage of the LED device.

Therefore, the InGaN layer 130b of the current spreading layer 130 according to the present invention has a structure in which InGaN layers doped with different types of conductive impurities are alternately stacked one or more times. This is because the InGaN layer 130b is composed of a plurality of InGaN layers modulated and doped with different conductivity-type impurities, thereby enabling electron mobility modulation of the InGaN layer 130b so that the InGaN layer 130b is inserted. Enhance the ESD immunity of the LED using the current spreading layer 130.

In addition, the nitride semiconductor device according to the present invention is formed by etching the p-type nitride semiconductor layer 150, the active layer 140 and the current diffusion layer 130 to expose a portion of the upper surface of the n-type nitride semiconductor layer 120. A plurality of mesas, an n-type electrode 180 formed on the exposed n-type nitride semiconductor layer 120 on the plurality of mesas, and a transparent formed on the p-type nitride semiconductor layer 150 to diffuse current The p-type electrode 170 that functions as a reflective metal and a bonding metal on the conductor layer 160 and the transparent conductor layer 160 is included.

In the light emitting structure of the present embodiment, the transparent conductor layer 150 is a layer for improving the current diffusion effect by increasing the current injection area, Indium Tin Oxide (ITO), Tin Oxide (TO), Indium Zinc (IZO) Oxide) and ITZO (Indium Tin Zinc Oxide) is preferably made of any one film selected from the group consisting of.

Then, the specific types of the InGaN layer 130b having the multilayer structure in which InGaN layers doped with different types of conductive impurities are alternately stacked one or more times, are described with reference to FIGS. This will be described with reference to.

Example  One

The InGaN layer of the current spreading layer according to the first embodiment of the present invention will be described in detail with reference to FIGS. 5 and 6.

FIG. 5 is a partial cross-sectional view showing an InGaN layer of the current diffusion layer according to the first embodiment of the present invention, and FIG. 6 is a graph schematically showing an example of a doping modulation profile of the InGaN layer shown in FIG.

Referring to FIG. 5, an InGaN layer 130b in which InGaN layers doped with different types of conductive impurities are alternately stacked one or more times among a plurality of GaN layers 130a constituting the current spreading layer 130. For example, an InGaN layer 130b formed by alternately stacking an InGaN layer 200a doped with p-type impurity and an InGaN layer 200b doped with n-type impurity is alternately formed. . In this case, for example, Mg, Zn, Be, and the like are used as the p-type conductivity impurities, and for example, Si, Ge, Sn, and the like are used as the n-type conductivity impurities.

On the other hand, the InGaN layer 200a doped with the p-type conductive impurity is composed of one or more InGaN layers in which the doping concentration of the p-type conductive impurity is sequentially increased, or the n-type conductive impurity is doped. The InGaN layer 210b may be formed of one or more InGaN layers in which one side the doping concentration of the n-type conductive impurity is sequentially increased. The InGaN layer 130b formed by alternately stacking the InGaN layer 200a doped with the p-type impurity and the InGaN layer 210b doped with the n-type impurity is alternately stacked three times.

Accordingly, the InGaN layer 130b according to the first embodiment of the present invention is different from the InGaN layer 200a doped with the p-type impurity and the InGaN layer 200b doped with the n-type impurity. 6, at the interface between the InGaN layer 200a doped with the p-type impurity and the InGaN layer 200b doped with the n-type impurity, as shown in FIG. The discontinuity of the doping band in which the mobility changes rapidly causes a two-dimensional electron gas layer (not shown) to be formed at the interface.

Therefore, when voltage is applied, a tunneling phenomenon occurs at the n ⁺ -p ⁺ junction through the two-dimensional electron gas layer, thereby securing a high electron mobility without increasing the operating voltage, thereby improving the current diffusion effect. As such, when the current spreading effect is improved in the INGaN layer 130b, the operating voltage V _f is lowered, and a nitride semiconductor device which secures light output can be implemented.

In addition, the InGaN layer 200a doped with the p-type conductivity impurity may be formed between the GaN layer 130a doped with the n-type conductivity and the InGaN layer 200b doped with the n-type conductivity or the n-type conductivity. Since the impurity is interposed between the InGaN layer 200b doped with a relatively high dielectric constant, the current spreading layer 130 may serve as a kind of capacitor. Accordingly, the current spreading layer 130 can protect the nitride semiconductor device from sudden surge voltage or electrostatic phenomena, thereby improving the ESD resistance of the device.

Example  2

7 and 8, a second embodiment of the present invention will be described. However, the description of the same parts as those of the first embodiment of the configuration of the second embodiment will be omitted, and only the configuration that is different from the second embodiment will be described in detail.

FIG. 7 is a partial cross-sectional view illustrating an InGaN layer of a current diffusion layer according to a second embodiment of the present invention, and FIG. 8 is a graph schematically showing an example of a doping modulation profile of the InGaN layer shown in FIG. 7.

As shown in FIG. 7 and FIG. 8, the InGaN layer 130b of the current diffusion layer 130 according to the second embodiment has the same configuration as that of the InGaN layer 130b according to the first embodiment. An undoped InGaN layer that is not doped with p-type and n-type conductivity impurities between the InGaN layer 200a doped with the p-type conductivity impurity and the InGaN layer 200b doped with the n-type conductivity impurity It differs from the first embodiment only in that it further includes 200c. In this case, the undoped InGaN layer 200c controls the difference in the doping band gap between the InGaN layer 200a doped with the p-type impurity and the InGaN layer 200b doped with the n-type impurity. It plays a role.

Therefore, the second embodiment not only obtains the same functions and effects as in the first embodiment, but also InGaN layer 200a doped with p-type impurity and InGaN layer 200b doped with n-type impurity. Doping bandgap that rapidly changes at the interface between the InGaN layer 200a doped with p-type impurity and the InGaN layer 200b doped with n-type impurity through an undoped InGaN layer 200c formed between By buffering this, there is an advantage that the characteristics can be more stably maintained in the device.

Although the preferred embodiments of the present invention have been described in detail above, those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. Accordingly, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concept of the present invention as defined in the following claims also fall within the scope of the present invention.

As described above, the present invention improves the current diffusion effect by forming a current diffusion layer by including an InGaN layer having a multi-layer structure formed by cross-laminating one or more InGaN layers having different doping bands between n-type GaN layers. You can.

As described above, the present invention reduces the operating voltage (V _f ) due to the improvement of the current diffusion effect to improve the luminous efficiency, thereby realizing a nitride semiconductor device that can obtain a high light output.

In addition, in the present invention, the structure in which InGaN layers having different doping bands of the current spreading layer are cross-laminated one or more times serves as a kind of capacitor, thereby eliminating the need for a separate device for improving ESD resistance. The nitride semiconductor device having high reliability can be realized by improving the efficiency.

Claims (8)

Board; An n-type nitride semiconductor layer formed on the substrate; A portion of the n-type nitride semiconductor layer is formed by sequentially stacking a GaN layer and an InGaN layer, and the InGaN layer is formed by alternately stacking one or more InGaN layers doped with different types of conductive impurities. A current spreading layer; An active layer formed on the current spreading layer; A p-type nitride semiconductor layer formed on the active layer; A p-type electrode formed on the p-type nitride semiconductor layer; And And an n-type electrode formed on the n-type nitride semiconductor layer on which the current spreading layer is not formed. The method of claim 1, A nitride semiconductor device comprising an InGaN layer doped with different types of conductive impurities constituting the current diffusion layer, an InGaN layer doped with n-type conductive impurities and an InGaN layer doped with p-type conductive impurities. . The method of claim 2, And the InGaN layer doped with the n-type conductive impurity comprises one or more InGaN layers in which the doping concentration of the n-type conductive impurity is sequentially increased. The method of claim 2, The InGaN layer doped with the p-type conductive impurity comprises at least one InGaN layer in which the doping concentration of the p-type conductive impurity is sequentially increased. The method of claim 1, The InGaN layer doped with different types of conductive impurities constituting the current spreading layer includes an InGaN layer doped with n-type conductive impurities, an InGaN layer doped with conductive impurities and an InGaN doped with p-type conductive impurities. A nitride semiconductor device comprising a layer. The method of claim 5, The InGaN layer doped with the n-type conductive impurity is a nitride semiconductor device comprising an InGaN layer in which the doping concentration of the n-type conductive impurity is sequentially increased. The method of claim 5, The InGaN layer doped with the p-type conductive impurity is a nitride semiconductor device comprising an InGaN layer in which the doping concentration of the p-type conductive impurity is sequentially increased. The method of claim 1, The nitride semiconductor device further comprises a transparent conductor layer formed between the p-type nitride semiconductor layer and the p-type electrode.

Images