KR100589645B1 - Zno based light emitting device and method of manufacturing the same - Google Patents

Abstract

The present invention relates to a zinc oxide light emitting device and a manufacturing method thereof, wherein the zinc oxide light emitting device includes an n-type first ohmic contact layer formed of zinc on an exposed portion of an n-type cladding layer, and an n-type first ohmic contact layer. And an n-type second ohmic contact layer formed on at least one of gold, platinum, silver, copper, and palladium. According to the zinc oxide light emitting device and its manufacturing method, the ohmic contact property with the n-type cladding layer is improved, thereby providing low specific contact resistance, excellent current-voltage characteristics, and thermal stability, thereby improving luminous efficiency and device life of the device. .

Description

Zinc oxide light emitting device and its manufacturing method {ZnO based light emitting device and method of manufacturing the same}

1 is a cross-sectional view showing an n-type electrode structure according to the present invention,

2 is a graph showing the results of measuring the current-voltage characteristics according to the heat treatment temperature of the n-type electrode structure according to an embodiment of the present invention,

3A and 3B are photographs showing the results of photographing the surface state of the n-type electrode structure of FIG. 2 before and after heat treatment.

4 is a cross-sectional view illustrating a light emitting device to which the n-type electrode structure of FIG. 1 is applied;

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

<Description of Symbols for Main Parts of Drawings>

10: substrate 20: n-type cladding layer

30: active layer 40: p-type cladding layer

50: n-type first ohmic contact layer 60: n-type second ohmic contact layer

70: p-type ohmic contact layer

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zinc oxide light emitting device and a method of manufacturing the same, and more particularly, to a zinc oxide light emitting device having an n-type electrode structure having improved ohmic characteristics and a method of manufacturing the same.

Zinc oxide semiconductors have been widely used in the field of optical devices such as transparent electrodes, window materials of solar cells, varistors and the like.

Recently, the zinc oxide semiconductor has been attracting attention as a material for a light emitting device to replace a gallium nitride (GaN) compound semiconductor by utilizing a characteristic of having a wide band gap (3.4 eV).

Unlike conventional gallium nitride semiconductors, zinc oxide semiconductors have an advantage of being capable of wet etching by chemical treatment. At present, gallium nitride compound semiconductor, which is widely used as a light emitting device material, is a very stable material, and wet etching by chemicals is extremely difficult. Physical etching of a coupled plasma (ICP), an ion reaction etcher (RIE), or the like is performed. There is a problem in that a thin film is damaged by the plasma during the etching process.

In order to implement a light emitting device such as a light emitting diode or a laser diode using a zinc oxide compound semiconductor, an ohmic contact structure between the light emitting chip and the electrode is very important.

In the case of n-type zinc oxide (n-ZnO), ohmic contact with low specific resistance of about 2 × 10 ^-4 Ω㎠ using a multilayer metal thin film of titanium (Ti) / gold (Au) applied by Kim Han-ki and two others in 2000 Has been reported in Applied Physics Letters 2000, vol. 77, p1647.

However, such a conventional n-type electrode structure has a low specific contact resistance, but there is a problem inferior in thermal stability. That is, in the case of the n-type electrode structure formed of titanium / gold, it is known that the bonding metal is separated from the zinc oxide during heat treatment at a temperature of 300 ° C. or higher. This phenomenon is closely related to the phenomenon in which the titanium is oxidized out-diffusion toward the surface of the bonding metal during the heat treatment process. Titanium oxide formed through this process has a large resistance and thus degrades electrical characteristics. Surface degradation of the electrode structure due to such deterioration causes a problem that the wire bonding in the packaging process is not good.

The present invention has been made to solve the above problems, and an object thereof is to provide a zinc oxide light emitting device having an n-type electrode structure having excellent low contact resistance and thermal stability and a method of manufacturing the same.

In order to achieve the above object, a zinc oxide light emitting device according to the present invention

A zinc oxide light emitting device that emits light by a current injected between an n-type cladding layer and a p-type cladding layer, the n-type first ohmic contact layer formed of zinc (Zn) on an exposed portion of the n-type cladding layer; ; And an n-type second ohmic contact layer formed on at least one of gold (Au), platinum (Pt), silver (Ag), copper (Cu), and palladium (Pd) on the n-type first ohmic contact layer.

Preferably, the n-type first ohmic contact layer is formed to a thickness of 0.1nm to 500nm.

In addition, the n-type second ohmic contact layer is formed to a thickness of 10nm to 1000nm.

In addition, the method for manufacturing a zinc oxide light emitting device according to the present invention in order to achieve the above object in the method for manufacturing a zinc oxide light emitting device that emits light by a current injected between the n-type cladding layer and the p-type cladding layer. , A. Forming an n-type first ohmic contact layer of zinc (Zn) on an exposed portion of the n-type cladding layer of the light emitting chip in which the n-type cladding layer and the p-type cladding layer are opposed to each other; I. Forming an n-type second ohmic contact layer on at least one of gold (Au), platinum (Pt), silver (Ag), copper (Cu), and palladium (Pd) on the n-type first ohmic contact layer. do.

Preferably. Heat treating the n-type electrode structure formed on the n-type cladding layer at 200 ° C. to 800 ° C. through step b.

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

1 is a cross-sectional view showing an n-type electrode structure according to an embodiment of the present invention.

Referring to the drawings, the n-type electrode structure includes an n-type first ohmic contact layer 50 and an n-type second ohmic contact layer 60 sequentially formed on the n-type cladding layer 20.

In the illustrated example, n-type first and second ohmics applied as n-type electrode structures formed in contact with the n-type cladding layer 20 requiring improvement of ohmic characteristics in a zinc oxide light emitting device implemented mainly using zinc oxide. In order to test the characteristics of the contact layers 50 and 60, a zinc oxide-based n-type cladding layer 20 is formed on the substrate 10, and the n-type first and second ohmic contacts on the n-type cladding layer 20. A structure in which layers 50 and 60 are laminated is shown.

The substrate 10 is made of sapphire.

As the n-type cladding layer 20, pure zinc oxide or n-type dopant to which zinc dopant is not added is applied.

Here, the n-type dopant may be a known material, for example, aluminum (Al) and gallium (Ga).

The n-type electrode structure includes an n-type first ohmic contact layer 50 and an n-type second ohmic contact layer 60.

The n-type first ohmic contact layer 50 is formed of zinc (Zn).

When the n-type first ohmic contact layer 50 is formed on the n-type cladding layer 20 using zinc, oxygen and n-type first ohmic in the zinc oxide (ZnO) forming the n-type cladding layer 20 after heat treatment are all formed. Oxygen vacancies are generated on the surface of the zinc oxide due to the reaction of the contact layer 50 with zinc or n under the n-type first ohmic contact layer 50 due to zinc atoms occupying the invasive sites of the n-type cladding layer 20. A layer having a high type carrier concentration is formed, which causes a carrier conduction phenomenon due to a field-emission phenomenon between the n-type first ohmic contact layer 50 and the n-type cladding layer 20. To form an excellent ohmic contact.

Preferably, the n-type first ohmic contact layer 50 is formed to a thickness of 0.1 nm to 500 nm.

The n-type second ohmic contact layer 60 protects the n-type first ohmic contact layer 50 from the outside atmosphere and is formed of a material having good wire bonding property.

Preferably, the n-type second ohmic contact layer 60 is formed of one of gold (Au), platinum (Pt), silver (Ag), copper (Cu), and palladium (Pd) or an alloy thereof.

In addition, the n-type second ohmic contact layer 60 is formed to a thickness of 10nm to 1000nm.

The n-type first ohmic contact layer 50 and the n-type second ohmic contact layer 60 of the n-type electrode structure have various known deposition methods, for example, an electron beam evaporator, a sputtering method, and physical vapor deposition (PVD). It may be formed by deposition, chemical vapor deposition (CVD), plasma laser deposition (PLD), thermal evaporator, dual-type thermal evaporator and the like.

The deposition temperature is performed in the range of 20 ° C to 1500 ° C, and the pressure in the reactor is performed at atmospheric pressure to about 10 ^-12 torr.

In addition, the n-type first ohmic contact layer 50 and the n-type second ohmic contact layer 60 of the n-type electrode structure are sequentially subjected to heat treatment after deposition.

Annealing is performed at 200 ° C to 800 ° C for 10 seconds to 10 hours in a vacuum or gas atmosphere.

When the heat treatment is performed in a gas atmosphere, at least one gas of nitrogen, argon, helium, oxygen, hydrogen, or air may be applied to the gas introduced into the reactor.

For the n-type electrode structure, the n-type first ohmic contact layer 50 is formed of zinc, and the n-type second ohmic contact layer 60 is formed of gold (Au), and then the current-voltage according to the heat treatment temperature. The results of measuring the properties are shown in FIG.

As can be seen from Figure 2 it can be seen that the ohmic characteristics are improved when the heat treatment at a temperature above 300 ℃.

On the other hand, photographs taken of the surface before and after the heat treatment of the n-type electrode structure applied to Figure 2 is shown in Figures 3a and 3b.

3A is a surface photograph before heat treatment, and FIG. 3B is a surface photograph after heat treatment.

As can be seen from the comparison of the photographs of FIGS. 3A and 3B, it can be confirmed that the surface roughness after the heat treatment is much reduced. This result is in contrast to the increase in surface roughness after heat treatment in the metal contact structure of the conventional n-type zinc oxide, it can be seen that the wire bonding properties can be improved.

4 is a view showing an example of a light emitting device to which the n-type electrode structure is applied. Elements having the same function as in the above-described drawings are denoted by the same reference numerals.

Referring to the drawings, the light emitting device has a structure in which a substrate 10, an n-type cladding layer 20, a p-type cladding layer 40, and a p-type electrode pad 70 are sequentially stacked. An n-type first ohmic contact layer 50 and an n-type second ohmic contact layer 60, which are n-type electrode structures, are formed on the exposed portion of the n-type cladding layer 20.

The light emitting chip for generating light includes an n-type cladding layer 20 and a p-type cladding layer 40.

When the n-type cladding layer 20 is applied to the substrate 10, the substrate 10 may be omitted.

The n-type cladding layer 20 is formed by adding an n-type dopant to pure zinc oxide or zinc oxide.

Al, Ga, or the like may be applied to the n-type dopant.

The n-type electrode structure includes an n-type first ohmic contact layer 50 and an n-type second ohmic contact layer 60 formed on an exposed portion of the n-type cladding layer 20.

The n-type electrode structures 50 and 60 may be formed of the material described above, and then heat treated.

As the p-type cladding layer 40, a p-type dopant is added to zinc oxide (ZnO).

Here, the p-type dopant may be applied to a single or two or more N, P, As and the like.

The p-type electrode pad 70 may be formed in a multilayer of a single layer or a heterogeneous material using various known materials.

In addition, as shown in FIG. 5, the n-type cladding layer 20 and the p-type cladding layer 40 may be implemented as a light emitting device having a light emitting chip further comprising an active layer 30.

The active layer 30 is formed by including any one or both of Cd and Mg as an additive element to zinc oxide in an appropriate ratio.

When either one of Cd and Mg is added to the zinc oxide which is the main component of the active layer 30 alone, or when Cd and Mg are added together, the band gap is reduced and the amount of Mg is increased. What is necessary is just to apply the addition amount corresponding to a desired band gap in consideration of the characteristic that a band gap becomes large.

The active layer 30 can be configured in a variety of known ways, such as a monolayer or an MQW layer.

The method of forming each layer may be a deposition method described above, for example, an electron beam evaporator, a physical vapor deposition (PVD), a chemical vapor deposition (CVD), a plasma laser deposition, a thermal evaporator, or a dual type thermal evaporator ( It can be formed by a dual-type thermal evaporator.

That is, the light emitting chip in which the substrate 10, the n-type cladding layer 20, the active layer 30, and the p-type cladding layer 4 are sequentially stacked is formed in a mesa structure, and then on the n-type cladding layer 20. The n-type first and second ohmic contact layers 50 and 60 may be formed, the p-type electrode pads 70 may be deposited on the p-type cladding layer 40, and then heat-treated.

This light emitting device may be applied to a variety of known structures in addition to the illustrated structure.

As described above, according to the zinc oxide light emitting device and the method of manufacturing the same, the ohmic contact property with the n-type cladding layer is improved, thereby providing a low specific contact resistance, excellent current-voltage characteristics, and thermal stability. Improves luminous efficiency and device life.

Claims (5)

In a zinc oxide light emitting device which emits light by a current injected between an n-type cladding layer and a p-type cladding layer, An n-type first ohmic contact layer formed of zinc (Zn) on an exposed portion of the n-type cladding layer; And an n-type second ohmic contact layer formed on at least one of gold (Au), platinum (Pt), silver (Ag), copper (Cu), and palladium (Pd) on the n-type first ohmic contact layer. Zinc oxide type light emitting element which is used. The zinc oxide light emitting device of claim 1, wherein the n-type first ohmic contact layer is formed to a thickness of 0.1 nm to 500 nm. The zinc oxide light emitting device of claim 1, wherein the n-type second ohmic contact layer has a thickness of 10 nm to 1000 nm. In the method of manufacturing a zinc oxide light emitting device which emits light by electric current injected between an n-type cladding layer and a p-type cladding layer, end. Forming an n-type first ohmic contact layer of zinc (Zn) on an exposed portion of the n-type cladding layer of the light emitting chip in which the n-type cladding layer and the p-type cladding layer are opposed to each other; I. Forming an n-type second ohmic contact layer on at least one of gold (Au), platinum (Pt), silver (Ag), copper (Cu), and palladium (Pd) on the n-type first ohmic contact layer. A method of manufacturing a zinc oxide light emitting device, characterized in that. The method of claim 4, wherein All. And heat-treating the n-type electrode structure formed on the n-type cladding layer at 200 ° C. to 800 ° C. through step b.

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