KR20090104453A - Nitride Semiconductor Light Emitting Device - Google Patents

Abstract

PURPOSE: A nitride semiconductor light emitting device is provided to form an N type electrode having excellent electrical characteristic and high light-transmissive. CONSTITUTION: The nitride semiconductor light emitting device(20) includes the light emitting structure, an n-type and P-contacts(26a,26b), and the n-type ohmic contact layer(25). The light emitting structure includes an n-type, p-type nitride semiconductor layers(21,23) and the active layer(22). The N and P-contact are electrically connected to the n-type and p-type nitride semiconductor layer. The N ohmic contact layer includes the first layer, and the second layer. The first layer is formed between the n-type nitride semiconductor layer and N type electrode. The second level is formed on the first floors. The second layer is made of the transparent conducting oxide.

Description

Nitride Semiconductor Light Emitting Device

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nitride semiconductor light emitting device, and more particularly, to a nitride semiconductor light emitting device having an n-type electrode having high light transmittance and excellent electrical characteristics.

A light emitting diode (LED), which is one of semiconductor light emitting devices, is a semiconductor device capable of generating light of various colors based on recombination of electrons and holes at a junction portion of a p and n type semiconductor when current is applied thereto. These LEDs have a number of advantages over filament based light emitting devices, such as long life, low power, excellent initial driving characteristics, high vibration resistance, and high tolerance for repetitive power interruptions. In recent years, group III nitride semiconductors capable of emitting light in a blue short wavelength region have been in the spotlight.

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

The semiconductor light emitting device 10 includes a p-type semiconductor layer 13, an active layer 12, an n-type semiconductor layer 11, and an ohmic contact layer 15 sequentially formed on the conductive substrate 14. In addition, n-type and p-type electrodes 16a and 16b are formed on an upper surface of the ohmic contact layer 15 and a lower surface of the conductive substrate 14, respectively.

The semiconductor light emitting device 10 shown in FIG. 1 has a structure in which a light emitting structure is formed between n-type and p-type electrodes 16a and 16b, that is, a light emitting device having a vertical structure. It is emitted to the outside through 15).

In this case, the ohmic contact layer 15 uses Ti, Al, etc. having a relatively low work function to form an ohmic contact with the n-type semiconductor layer 11, and a stacked structure thereof may also be generally used. .

However, Ti, Al, and the like are metals having low light transmittance, and a substantial portion of the light emitted from the active layer 12 is absorbed by the ohmic contact layer 15, which leads to a decrease in luminous efficiency.

Therefore, there is a need in the art for a method for maintaining an n-type semiconductor layer and ohmic contact while having excellent optical characteristics.

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 light emitting device having an n-type electrode having high light transmittance and excellent electrical characteristics.

In order to achieve the above object, one embodiment of the present invention,

a light emitting structure having an n-type and p-type nitride semiconductor layer and an active layer formed therebetween, n-type and p-type electrodes electrically connected to the n-type and p-type nitride semiconductor layers, and the n-type nitride semiconductor layer and the A nitride semiconductor comprising an n-type ohmic contact layer formed between an n-type electrode and having a first layer made of a material containing Ru or Ir and a second layer formed on the first layer and made of a transparent conductive oxide. Provided is a light emitting device.

Preferably, the first layer may be made of Ru or Ir alloy, more specifically, the elements included in the Ru or Ir alloy are Ti, Al, Cr, Ni, Pd, Pt, Mo, Co and Mg It may be at least one element selected from the group consisting of.

In addition, the second layer may include at least one material selected from the group consisting of In, Sn, Al, Zn, and Ga. Specifically, the second layer may include ITO, CIO, and AZO (Al-doped ZnO). ), ZnO, NiO and In ₂ O ₃ It may be made of a material selected from the group consisting of.

On the other hand, it is preferable that the thickness of a said 1st layer is 10-300 GPa, and it is preferable that the thickness of a said 2nd layer is 100-1000 GPa.

In a preferred embodiment of the present invention, at least some of the first layer may be made of an oxide.

According to the present invention, it is possible to provide a nitride semiconductor light emitting device having an n-type electrode having high light transmittance and excellent electrical characteristics.

Hereinafter, with reference to the accompanying drawings will be described a preferred embodiment of the present invention.

However, embodiments of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below. In addition, the embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art. Accordingly, the shape and size of elements in the drawings may be exaggerated for clarity, and the elements denoted by the same reference numerals in the drawings are the same elements.

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

Referring to FIG. 2, the semiconductor light emitting device 20 according to the present embodiment may include a p-type nitride semiconductor layer 23, an active layer 22, and n formed sequentially on the conductive substrate 24 and the conductive substrate 24. The nitride semiconductor layer 21 and the n-type ohmic contact layer 25 are provided. In addition, an n-type electrode 26a is formed on an upper surface of the n-type ohmic contact layer 25, and a p-type electrode 26b is formed on a lower surface of the conductive substrate 26b.

In the case of this embodiment, it corresponds to a vertical structure nitride semiconductor light emitting device, and the manufacturing method thereof is a well-known process, and includes an n-type nitride semiconductor layer 21, an active layer 22, and a nitride single crystal growth substrate such as sapphire. After the p-type nitride semiconductor layer 23 is sequentially grown, the conductive substrate 24 corresponding to the support substrate may be formed by a plating or bonding process, and may be formed by a process of removing the sapphire substrate.

Hereinafter, the components constituting the semiconductor light emitting device 20 will be described in more detail.

The n-type and p-type semiconductor layers 22 and 24 and the active layer 23 constituting the light emitting structure will be described. First, the n-type and p-type semiconductor layers 22 and 24 are preferably made of nitride semiconductors. . In the present specification, the term "nitride semiconductor" means a binary component or a three component system represented by Al x In y Ga (1-xy) N (0≤x≤1, 0≤y≤1, 0≤x + y≤1). It means a ternary or quaternary compound semiconductor. That is, the n-type and p-type semiconductor layers 22 and 24 have an Al x In y Ga (1-xy) N composition formula, where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, and 0 ≦ x + y ≦ 1. The n-type impurity and the p-type impurity may be made of a semiconductor material, and typically, GaN, AlGaN, InGaN. In addition, Si, Ge, Se, Te or C may be used as the n-type impurity, and the p-type impurity may be representative of Mg, Zn or Be.

The active layer 23 is composed of an undoped nitride semiconductor layer having a single or multiple quantum well structure, and emits light having a predetermined energy by recombination of electrons and holes. The n-type and p-type semiconductor layers 22 and 24 and the active layer 23 are formed of a semiconductor single crystal growth process, in particular, an organometallic vapor deposition method (MOCVD), a molecular beam growth method (MBE), and the like known as a nitride single crystal growth process. It can be grown by a method such as hybrid vapor deposition (HVPE).

The conductive substrate 24 is included in the final component of the vertical light emitting device, and is used to support a light emitting structure having a relatively thin thickness in performing a process of removing a single crystal growth substrate. The conductive substrate 24 may be formed by combining with the light emitting structure by plating or wafer bonding, and is made of a material made of Si, Cu, Ni, Au, W, Ti, or the like.

The n-type and p-type electrodes 26a and 26b function as electrodes for electrical connection of the device. In this case, the n-type electrode and the p-type electrode 26a, 26b are generally made of Au or an alloy containing Au. Such n-type electrodes and p-type electrodes 26a and 26b may be formed by a deposition method or a sputtering process, which is a conventional metal layer growth method.

The n-type ohmic contact layer 25 may improve the luminous efficiency of the light emitting device by forming an ohmic contact between the n-type nitride semiconductor layer 21 and the n-type electrode 26a and having a high light transmittance. have.

To this end, the n-type ohmic contact layer 25 is configured to include two layers. Specifically, the first layer 25a is made of a material including Ru or Ir, and a second layer formed thereon. 25a is made of a transparent conductive oxide.

In the case of the first layer 25a, a material containing Ru or Ir may be sufficient. In particular, the first layer 25a may be made of only Ru or Ir or may be employed in an alloy form.

Ru and Ir are metals with a relatively large work function, and may not be suitable as metals for n-type ohmic contacts. However, the inventors of the present invention find that Ru and Ir are oxides. I could see that.

Accordingly, in the embodiment slightly modified in the present embodiment, as shown in FIG. 3, the n-type ohmic contact layer 35 is formed of a first layer 35a made of a material containing Ru or Ir and a material made of a transparent conductive oxide. The second layer 35b may be provided, and at least a portion of the first layer 35a may be present as a region A made of an oxide.

On the other hand, when the first layer 25a is a Ru or Ir alloy, elements included therein include Ti, Al, Cr, Ni, Pd, Pt, Mo, Co, Mg, and the like. It may be appropriately selected in consideration of light transmittance.

Referring again to FIG. 2, the second layer 25b may employ any material having high light transmittance and suitable electrical properties enough to be used as an electrode, and the most suitable material is a transparent conductive oxide. to be.

By forming the second layer 25b with a transparent conductive oxide, high light transmittance can be ensured, particularly in a vertical nitride semiconductor light emitting device.

In this case, the transparent conductive oxide forming the second layer 25b is a material containing elements such as In, Sn, Al, Zn, Ga, and the like, for example, ITO, CIO, AZO, ZnO, NiO, In ₂ O ₃ Equivalent to

Meanwhile, each of the thicknesses t1 and t2 of the first layer 25a and the second layer 25b included in the n-type ohmic contact layer 25 may be properly adjusted in terms of control of electrical resistance and light transmittance. have.

Although not limited thereto, the thickness t1 of the first layer 25a has a range of 10 to 300 kPa to form an ohmic contact, and the thickness t2 of the second layer 25b is 100 to 1000 kPa. It is desirable to have a range.

As described above, in the present embodiment, the ohmic contact is possible by employing Ru or Ir as a material forming the layer adjacent to the n-type nitride semiconductor layer while ensuring a high light transmittance by including a transparent conductive oxide in the n-type ohmic contact layer. I did it.

As a specific experimental example, in the nitride semiconductor light emitting device 20, the n-type ohmic contact layer 25 is made of Ru having a thickness of 1 nm and the first layer 25a is made of ITO having a thickness of 200 nm. In the case of (In-doped SnO), the IV curve measured at CTLM 28㎛ spacing showed linear function, that is, linear characteristic.

In a similar manner, in the nitride semiconductor light emitting device 20, the n-type ohmic contact layer 25 is Ir having a thickness of 1 nm of the first layer 25a, and the second layer 25b has a thickness of 200 nm. Even in the case of AZO (Al-doped ZnO), it can be seen that the IV curve shows a linear function. That is, the n-type ohmic contact layer employed in the present embodiment has high light transmittance and can form an ohmic contact with the n-type nitride semiconductor layer.

4 is a cross-sectional view illustrating a nitride semiconductor light emitting device according to an embodiment modified from the embodiment of FIG. 2.

In the nitride semiconductor light emitting device 40 of FIG. 4, the p-type nitride semiconductor layer 43, the active layer 42, and n are sequentially formed on the conductive substrate 44 and the conductive substrate 44 as in the case of FIG. 2. The n-type ohmic contact layer 45 having the type nitride semiconductor layer 41 and the first and second layers 45a and 45b is formed on the upper surface of the n-type ohmic contact layer 45. A p-type electrode 46b is formed on the lower surface of the conductive substrate 44.

In addition, a GaN substrate 47 is formed between the n-type nitride semiconductor layer 41 and the n-type ohmic contact layer 45.

The GaN substrate 47 is provided as a substrate for nitride single crystal growth, and exhibits electrical conductivity, so that the GaN substrate 47 may remain in the final light emitting device 40 without being removed after growth of the light emitting structure. However, instead of the GaN substrate 47, other substrates made of a material having electrical conductivity as a substrate for nitride single crystal growth, for example, a SiC substrate, may be employed as long as those skilled in the art can easily adopt them. .

In addition to these differences, other components represented by the same term may be understood to be the same as in the case of FIG. 2, and thus description thereof will be omitted.

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

The nitride semiconductor light emitting device 50 according to the present embodiment includes the n-type nitride semiconductor layer 51, the active layer 52, and the p-type nitride semiconductor sequentially grown on the sapphire substrate 54 and the sapphire substrate 54. The n-type ohmic contact layer 55 formed in the etched partial region of the layer, the p-type ohmic contact layer 58 and the n-type nitride semiconductor layer 51 and including the first and second layers 55a and 55b. And n-type and p-type electrodes 56a and 56b.

In this embodiment, the arrangement of the n-type and p-type electrodes 56a and 56b corresponds to a horizontal structure, and the function of securing light transmittance by the n-type ohmic contact layer 55 may be slightly inferior to that of the vertical structure. The electrode arrangement structure of the light emitting device that can be employed in the present invention can be extended not only in the vertical structure but also in the horizontal structure.

As described above, the n-type ohmic contact layer 55 may be applied not only to the vertical structure but also to the horizontal structure, in which the n-type ohmic contact layer is formed on the n-type nitride semiconductor layer. Alternatively, it can be understood that ohmic contacts can be formed on both P-polar surfaces.

In the case of the p-type ohmic contact layer 58, although not an essential component, a Ni / Au structure or the like may be generally used for ohmic contact with the p-type nitride semiconductor layer 53.

In addition to these differences, other components represented by the same term may be understood to be the same as in the case of FIG. 2, and thus description thereof will be omitted.

The present invention is not limited by the above-described embodiment and the accompanying drawings, but is intended to be limited by the appended claims. Accordingly, various forms of substitution, modification, and alteration may be made by those skilled in the art without departing from the technical spirit of the present invention described in the claims, which are also within the scope of the present invention. something to do.

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

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

3 is a cross-sectional view illustrating an ohmic contact layer that may be employed in the embodiment modified from the embodiment of FIG. 2.

4 is a cross-sectional view illustrating a nitride semiconductor light emitting device according to an embodiment modified from the embodiment of FIG. 2.

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

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

21: n-type nitride semiconductor layer 22: active layer

23: p-type nitride semiconductor layer 24: conductive substrate

25: n-type ohmic contact layer 26a, 26b: n-type and p-type electrodes

47: GaN substrate 54: Sapphire substrate

Claims (8)

a light emitting structure having n-type and p-type nitride semiconductor layers and an active layer formed therebetween; N-type and p-type electrodes electrically connected to the n-type and p-type nitride semiconductor layers, respectively; And An n-type formed between the n-type nitride semiconductor layer and the n-type electrode and having a first layer made of a material containing Ru or Ir and a second layer formed on the first layer and made of a transparent conductive oxide Ohmic contact layer; Nitride semiconductor light emitting device comprising a. The method of claim 1, The first layer is a nitride semiconductor light emitting device, characterized in that made of Ru or Ir alloy. The method of claim 2, The element included in the Ru or Ir alloy is at least one element selected from the group consisting of Ti, Al, Cr, Ni, Pd, Pt, Mo, Co and Mg. The method of claim 1, And the second layer comprises at least one material selected from the group consisting of In, Sn, Al, Zn and Ga. The method of claim 1, The second layer is nitride semiconductor light emitting device, characterized in that made of a material selected from the group consisting of ITO, CIO, AZO, ZnO, NiO and In ₂ O ₃ . The method of claim 1, The thickness of the first layer is a nitride semiconductor light emitting device, characterized in that 10 ~ 300Å. The method of claim 1, The thickness of the second layer is a nitride semiconductor light emitting device, characterized in that 100 ~ 1000Å. The method of claim 1, At least a part of the first layer is a nitride semiconductor light emitting device, characterized in that made of oxide.

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