KR100674709B1 - Nitride semiconductor device - Google Patents

Abstract

A nitride semiconductor device is provided to improve a cladding effect of an N type clad layer structure and to enhance a current spread effect by using an additional N type clad layer with a delta doping layer between an N type clad layer and an active layer. A first N type clad layer(120) is formed on a substrate(100). A second N type clad layer(200) with a predetermined delta doping layer is formed on the first N type clad layer. An active layer(130) is formed on the second N type clad layer. A first P type clad layer(140) is formed on the active layer. A P type electrode(160) is formed on the first P type clad layer. An N type electrode(170) is formed on the first N type clad 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.

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

3 is a partial cross-sectional view showing a second n-type cladding layer of the nitride semiconductor element shown in FIG.

FIG. 4 is a flow diagram of source gas shown to explain a method of manufacturing the second n-type clad layer shown in FIG. 3. FIG.

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

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

100 substrate 110 buffer layer

120: first n-type cladding layer 130: active layer

140: first p-type cladding layer 150: transparent conductor layer

160: p-type electrode 170: n-type electrode

200: second n-type cladding layer 300: second p-type cladding layer

210: delta doped 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 applied to 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 FIG. 1.

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

As shown in FIG. 1, an LED device using a nitride semiconductor according to the related art includes a buffer layer 110 made of GaN, an n-type cladding layer 120, and a single quantum well on a sapphire substrate 100 that is a light transmissive substrate. An active layer 130 and a p-type cladding layer 140 of a multi-quantum well (MQW) structure containing InGaN or InGaN having an (SQW) structure are sequentially stacked.

In addition, since some regions of the p-type cladding layer 140 and the active layer 130 are removed by some mesa etching process, some top surfaces of the n-type cladding layer 120 are exposed. In addition, an n-type electrode 170 is formed on the exposed n-type cladding layer 120, and on the p-type cladding layer 160, the transparent conductor layer 150 and the p-type electrode 160 made of ITO or the like. It is formed in this stacked structure.

As described above, the nitride semiconductor device (LED) may adopt a double heterostructure having an active layer 130 having a single quantum well structure or a multi quantum well structure having a well layer made of InGaN.

In particular, in the nitride semiconductor device (LED), the multi-quantum well structure has a large number of mini bands, has high efficiency, and can emit light even at a small current, so that the light emission output is higher than that of the single quantum well structure. Improvement is expected. This discloses an active layer having a multi-quantum well structure consisting of a barrier layer of undoped GaN and a well layer of undoped InGaN in order to improve luminous efficiency and luminous intensity in Japanese Patent Laid-Open No. 10-135514. In addition, a nitride semiconductor device including a cladding layer having a band gap larger than that of the barrier layer of the active layer is disclosed.

However, when the active layer has a multi-quantum well structure, high luminous efficiency and luminous intensity can be obtained, but there is a limit in luminous efficiency and luminous intensity, i.e., light output, for using a nitride semiconductor element as a light source for illumination or an outdoor display. have. In addition, when the active layer has a multi-quantum well structure, the thickness of the entire active layer is higher than that of the single quantum well structure, so that the series resistance in the longitudinal direction is high, and in particular, the operating voltage (V _f ) in the case of an LED element. There is a problem of getting higher.

In addition, since the light emitting device using the nitride semiconductor is generally poor in resistance to electrostatic discharge (ESD), it is necessary to improve the electrostatic discharge characteristics. In particular, the nitride semiconductor LED device or LD device has a problem that can be damaged by the static electricity easily generated in people or things in the process of handling or using the same.

Accordingly, in order to suppress damage of the nitride semiconductor device due to ESD, various studies have recently been conducted. For example, US Pat. No. 6,593,597 discloses a technique for protecting an LED device from ESD by integrating the LED device and the Schottky diode on the same substrate and connecting the LED device and the Schottky diode in parallel. 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 provides a substrate, a first n-type cladding layer formed on the substrate, and a portion of the first n-type cladding layer, the delta doping layer consisting of Group 3 or Group 5 elements A second n-type cladding layer having a structure inserted into at least one layer, an active layer formed on the second n-type cladding layer, a first p-type cladding layer formed on the active layer, and the first p-type Provided is a nitride semiconductor device including a p-type electrode formed on a clad layer and an n-type electrode formed on an n-type clad layer in which the second n-type clad layer is not formed.

In the nitride semiconductor device of the present invention, the second n-type cladding layer is preferably made of an In _X Al _Y Ga _1-XY N (0 ≦ X, 0 ≦ Y, X + Y ≦ 1) composition. Do.

In addition, the nitride semiconductor device of the present invention further includes a second p-type cladding layer formed of a structure in which at least one delta doping layer made of Group 3 or Group 5 elements is inserted between the active layer and the first p-type cladding layer. It is desirable to.

In the nitride semiconductor device of the present invention, the second p-type cladding layer is preferably composed of an In _X Al _Y Ga _1-XY N (0≤X, 0≤Y, X + Y≤1) composition. Do.

Further, in the nitride semiconductor device of the present invention, it is preferable to further include a transparent conductor layer formed between the first p-type cladding 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.

Example  One

First, the nitride semiconductor device according to the first embodiment of the present invention will be described in detail with reference to FIGS. 2 to 3.

2 is a cross-sectional view illustrating a structure of a nitride semiconductor device (LED) according to a first embodiment of the present invention, and FIG. 3 is a partial cross-sectional view illustrating a second n-type clad layer of the nitride semiconductor device shown in FIG. 2.

As shown in FIG. 2, the light transmissive substrate 100, the buffer layer 110, the first n-type cladding layer 120, the second n-type cladding layer 200, and the active layer on the substrate 100 are provided. The light emitting structure 130 and the first p-type cladding layer 140 are sequentially stacked.

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 110 before the n-type cladding layer 120 is grown, and is generally formed of AlN / GaN.

The first and second n-type cladding layers 120 and 200, the active layer 130, and the first p-type cladding layer 140 may have an In _X Al _Y Ga _{1 -X - Y} N composition formula (where 0 ≦ _X , 0 ≦ Y, X + Y ≦ 1).

More specifically, the first and second n-type cladding layers 120 and 200 may be formed of a GaN layer or a GaN / AlGaN layer doped with n-type conductive impurities. , Si, Ge, Sn, etc. are used, Preferably Si is mainly used. In addition, the first p-type cladding layer 140 may be formed of a GaN layer or a GaN / AlGaN layer doped with a p-type conductive impurity. For example, Mg, Zn, Be, etc. Is used, and preferably Mg is mainly used. The active layer 130 may be formed of an InGaN / GaN layer having a multi-quantum well structure.

In particular, as shown in FIG. 3, the second n-type cladding layer 200 according to the present invention has a group 3 or 5 element at an interface between the first n-type cladding layer 120 and the active layer 130. The delta doped layer 210 is formed of a structure in which one or more layers are inserted. This is to enhance the cladding effect and the current diffusion effect of the n-type cladding layer 120 and to enhance the resistance of the electrostatic discharge (ESD) characteristics.

In addition, the nitride semiconductor device according to the present invention may include a plurality of mesas formed by etching the first p-type cladding layer 140 and the active layer 130 to expose a portion of the upper surface of the first n-type cladding layer 120. And an n-type electrode 170 formed on the exposed first n-type cladding layer 120 on the plurality of mesas, and a transparent conductor layer formed on the first p-type cladding layer 140 to diffuse current. P-type electrode 160, which serves as a reflective metal and a bonding metal, is formed on the 150 and the transparent conductor layer 150.

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

Next, a method of manufacturing the second n-type cladding layer according to the present embodiment will be described in detail with reference to FIG. 4 and FIG. 3 described above.

FIG. 4 is a flow diagram of source gas shown to explain a method of manufacturing the second n-type cladding layer 200 shown in FIG. 3.

First, part of the second clad layer 200 is formed by supplying Si and Ga source gas (or ammonia source gas) into the reactor.

Then, the supply of Si and Ga source gas (or ammonia source gas) for growing the second clad layer 200 is stopped for several seconds, and then the reaction source gas inside the reactor is discharged to the outside of the reactor. Afterwards, a group 3 or 5 element, in this embodiment, is supplied with Al source gas for about several seconds into the reactor about 1nmol to about 100nmol to form a delta doped layer 210. At this time, the delta doped layer 210 is formed on the second cladding layer 200 which is growing in a two-dimensional limited surface in the form of surfaces, lines, and dots of atomic unit thickness.

Then, the supply of Al source gas for forming the delta doping layer 210 is stopped, and then the reaction raw material gas in the reactor is discharged to the outside of the reactor, and then the second clad layer 200 is grown again. Si and Ga source gas (or ammonia source gas) are supplied into the reactor to form the second clad layer 200.

Then, the delta doped layer 210 made of Al is formed to be inserted into the second clad layer 200 (see FIG. 3).

Meanwhile, in the present exemplary embodiment, the delta doped layer 210 is illustrated in the form of a two-dimensional surface having a group III or group 5 element having a thickness of an atomic unit, which is the crystallinity of the second n-type cladding layer 200. Within the range of not lowering the surface roughness, the Group 3 or Group 5 element may be formed in the form of a line or a dot having an atomic thickness in the second n-type cladding layer 200.

In addition, the thickness of the atomic unit of the delta doped layer 210 made of Al or the degree of covering the surface in two dimensions can be controlled according to the device characteristics by adjusting the delta doping time or the amount of Al source gas.

In addition, since the second n-type cladding layer 200 according to the embodiment of the present invention has different energy bands of the nitride semiconductor layer constituting the second cladding layer 200 and the delta doping layer 210, The discontinuity of the energy band in which the energy band changes rapidly at the interface between the nitride semiconductor layer and the delta doped layer forms a two-dimensional electron gas layer (not shown) at the interface.

Accordingly, in the present invention, when the voltage is applied, a tunneling phenomenon occurs through the second cladding layer 200 through the n ⁺ -p ⁺ junction, thereby improving the cladding effect of the n-type cladding layer and high carrier movement. It is possible to improve the current diffusion effect by securing the degree. As such, when the current diffusion effect is improved through the second n-type cladding layer 200, the operating voltage V _f is lowered, and the luminous efficiency is also improved due to the increase in the emission area, thereby ensuring the light output. A semiconductor device can be implemented.

In addition, the delta doped layer 210 is interposed in the second n-type cladding layer 200 to have a relatively high dielectric constant, and thus may serve as a kind of capacitor. Accordingly, the second n-type cladding layer 200 may protect the nitride semiconductor device from sudden surge voltage or electrostatic phenomenon, thereby improving the ESD resistance of the device.

Example  2

Next, the nitride semiconductor device according to the second embodiment of the present invention will be described with reference to FIG. 5. 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.

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

As shown in FIG. 5, the nitride semiconductor device according to the second embodiment has the same structure as that of the nitride semiconductor device according to the first embodiment, except that the active layer 130 and the first p-type cladding layer ( The second embodiment differs from the first embodiment only in that it further includes a second p-type cladding layer 300 including a delta doping layer composed of Group 3 or Group 5 elements at the interface between them.

That is, the first embodiment illustrates that a second n-type cladding layer in which a delta doping layer is inserted is formed between the first cladding layer and the active layer, and the second embodiment shows the active layer and the first p-type cladding. The example further includes a second p-type cladding layer formed between the layers.

Therefore, this second embodiment can not only obtain the same functions and effects as in the first embodiment, but also, through the second p-type cladding layer located between the active layer and the first p-type cladding layer, the p-type cladding layer. The cladding effect and the current diffusion effect of can also be improved.

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 includes another n-type cladding layer in which a delta doping layer is inserted between the n-type cladding layer and the active layer, thereby improving the cladding effect and the current diffusion effect of the n-type cladding layer. .

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, the present invention provides a highly reliable nitride semiconductor device by improving the ESD resistance without having to provide a separate capacitor for improving the ESD resistance by the delta doped layer inserted between the cladding layer serves as a kind of capacitor Done.

Claims (5)

Board; A first n-type clad layer formed on the substrate; A second n-type cladding layer formed on a portion of the first n-type cladding layer in a structure in which one or more delta doping layers made of group 3 or 5 elements are inserted; An active layer formed on the second n-type cladding layer; A first p-type cladding layer formed on the active layer; A p-type electrode formed on the first p-type cladding layer; And A nitride semiconductor device comprising an n-type electrode formed on the n-type cladding layer in which the second n-type cladding layer is not formed. The method of claim 1, The second n-type cladding layer is a nitride semiconductor device, characterized in that composed of In _X Al _Y Ga _{1 -X- Y} N (0≤X, 0≤Y, X + Y≤1) composition. The method of claim 1, And a second p-type cladding layer formed of a structure in which at least one delta doping layer made of a group 3 or group 5 element is inserted between the active layer and the first p-type cladding layer. The method of claim 3, The second p-type cladding layer is a nitride semiconductor device, characterized in that composed of In _X Al _Y Ga _{1 -X- Y} N (0≤X, 0≤Y, X + Y≤1) composition. The method of claim 1, The nitride semiconductor device further comprises a transparent conductor layer formed between the first p-type cladding layer and the p-type electrode.

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