KR20060062636A - Transparent electrode and compound semiconductor light emitting device including the same - Google Patents

Abstract

A transparent electrode and a compound semiconductor light emitting device having the same are disclosed. According to the present invention, in an electrode formed on a p-type compound semiconductor layer of a compound semiconductor light emitting device, the electrode is formed on the first electrode layer and the first electrode layer formed of a transparent conductive oxide on the p-type compound semiconductor layer Provided is a transparent electrode of a compound semiconductor light emitting device having a second electrode layer having a plurality of nanorods. According to the present invention, there is provided a compound semiconductor light emitting device comprising the transparent electrode.

Description

Transparent electrode and compound semiconductor light emitting device including the same

1 is a cross-sectional view showing a transparent electrode according to a first embodiment of the present invention.

2 is a cross-sectional view illustrating a transparent electrode according to a second exemplary embodiment of the present invention.

3 is a cross-sectional view illustrating a compound semiconductor light emitting device including the transparent electrode of FIG. 1.

4 is a cross-sectional view illustrating a compound semiconductor light emitting device including the transparent electrode of FIG. 2.

<Description of Symbols for Major Parts of Drawings>

20: p-type compound semiconductor layer 21: ohmic contact layer

22, 23: transparent electrode 22a: first electrode layer

22b: second electrode layer 100: substrate

102: n-type cladding layer 104: active layer

106: p-type cladding layer 108, 109: p-type electrode

120: n-type electrode

The present invention relates to a transparent electrode and a compound semiconductor light emitting device having the same, and more particularly to a transparent electrode having a low contact resistance, improved electrical conductivity and particularly high light transmittance and a compound semiconductor light emitting device having the same.

Compound semiconductor light emitting devices that convert an electrical signal into light by using the characteristics of the compound semiconductor, for example, laser light of a semiconductor laser diode such as a light emitting diode (LED) or a laser diode (LD) are used in optical communication, multiple communication, and space communication. It is currently being put to practical use in such applications. The semiconductor laser is a light source of a means for transferring data or recording and reading data in a communication field such as optical communication or a device such as a compact disk player (CDP) or a digital versatile disk player (DVDP). It is widely used.

Such compound semiconductor light emitting devices are classified into top-emitting light emitting diodes (TLEDs) and flip-chip light emitting diodes (FCLEDs) according to light emission directions.

The flip chip light emitting diode has a structure in which light generated in an active layer is reflected by a reflective electrode formed on a p-type compound semiconductor layer, and the reflected light is emitted through a substrate.

The top emit light emitting diode has a structure in which light is emitted through a p-type electrode forming an ohmic contact with a p-type compound semiconductor layer. Here, the p-type electrode mainly has a structure in which a nickel (Ni) layer and a gold (Au) layer are sequentially stacked on the p-type compound semiconductor layer. However, the p-type electrode formed of the nickel layer / gold layer has translucency, and the top-emitting type light emitting diode to which the p-type electrode is applied has low light utilization efficiency and low luminance characteristics.

In order to solve this problem, researches on electrode materials and electrode structures having low contact resistance and high light transmittance have been conducted.

SUMMARY OF THE INVENTION The present invention provides a transparent electrode having a low contact resistance, an improved electrical conductivity, and particularly a high light transmittance, and a compound semiconductor light emitting device including the same.

According to the present invention, in an electrode formed on a p-type compound semiconductor layer of a compound semiconductor light emitting device,

The electrode,

A first electrode layer formed of a transparent conductive oxide on the p-type compound semiconductor layer; And

Provided on the first electrode layer is a transparent electrode of a compound semiconductor light emitting device comprising; a second electrode layer having a plurality of nanorods.

Further, according to the present invention, in a compound semiconductor light emitting device comprising n-type and p-type electrodes and at least an n-type cladding layer, an active layer and a p-type cladding layer therebetween,

The p-type electrode,

A first electrode layer formed of a transparent conductive oxide on the p-type cladding layer; And                     

Provided is a compound semiconductor light emitting device having a second electrode layer having a plurality of nanorods formed on the first electrode layer.

The transparent conductive oxide is at least selected from the group consisting of In, Sn, Zn, Ga, Cd, Mg, Be, Ag, Mo, V, Cu, Ir, Rh, Ru, W, Co, Ni, Mn, Al, and La. It is an oxide of either element. The nanorods are formed of any one selected from the group consisting of Zn _x Mg _1-x O (0 ≦ _x ≦ ₁ ) and Al _x Ga _1-x N (0 ≦ _x ≦ 1). In addition, the p-type cladding layer is formed of any one selected from the group consisting of Zn _x Mg _1-x O (0 ≦ _x ≦ ₁ ) and Al _x Ga _1-x N (0 ≦ _x ≦ 1).

Preferably, between the p-type compound semiconductor layer and the first electrode layer,

Formed of any one selected from the group consisting of Ag, Ag-based alloys, Zn-based alloys, Ni-based alloys, La-based alloys, Mg-based alloys, indium oxides containing additional elements, and SnO ₂ containing additional elements Ohmic contact layer; may be further provided. Here, the additive elements are Mg, Ag, Zn, Sc, Hf, Zr, Te, Se, Ta, W, Nb, Cu, Si, Ni, Co, Mo, Cr, Mn, Hg, Pr, Sb and La At least one selected from the group consisting of. The content ratio of the added element to the indium oxide and SnO ₂ is 0.001 to 49 at%, respectively, and the thickness of the ohmic contact layer is in the range of 0.1 nm to 500 nm.

1 is a cross-sectional view showing a transparent electrode according to a first embodiment of the present invention.

Referring to FIG. 1, a transparent electrode 22 is formed on an upper surface of the p-type compound semiconductor layer 20. The transparent electrode 22 according to the first embodiment of the present invention includes a first electrode layer 22a and a second electrode layer 22b that are sequentially stacked on the upper surface of the p-type compound semiconductor layer 20.

The first electrode layer 22a is a transparent conductive oxide, for example, In, Sn, Zn, Ga, Cd, Mg, Be, Ag, Mo, V, Cu, Ir, Rh, Ru, W, Co, Ni, Mn , Oxides of at least one element selected from the group consisting of Al and La.

The second electrode layer 22b is crystal-grown to have a plurality of nanorods, and the nanorods are Zn _x Mg _1-x O (0≤x≤1) and Al _x Ga _1-x N ( 0? X? 1). For example, when the second electrode layer 22b is formed of ZnO, when the ZnO is formed in an atmosphere having more oxygen (O) than zinc (Zn), the ZnO may be crystal-grown into nanorods. . The same principle also applies to other materials forming the second electrode layer 22b.

The first electrode layer 22a may be formed by a physical vapor deposition (PVD) method such as a sputter. The second electrode layer 22b may be formed by a chemical vapor deposition (CVD) method. At this time, the deposition temperature of each of the first electrode layer 22a and the second electrode layer 22b is 20 ° C to 1500 ° C, and the pressure in the reactor is from atmospheric pressure to 10 ^-12 torr.

After the second electrode layer 22b is formed, an annealing process on the resultant is performed. Specifically, the resultant formed second electrode layer 22b is annealed in a gas atmosphere containing at least one of nitrogen, argon, helium, oxygen, hydrogen, air. The annealing is performed for 10 seconds to 2 hours in the temperature range of 200 ℃ to 700 ℃.

The transparent electrode according to the present invention has a low contact resistance and improved electrical conductivity, in particular, the light extraction efficiency is improved through the nanorod has a high light transmittance.

2 is a cross-sectional view illustrating a transparent electrode according to a second exemplary embodiment of the present invention.

In the second embodiment of the present invention, only parts different from the above-described first embodiment will be described. In addition, the same reference number is used as it is about the same member.

Referring to FIG. 2, the transparent electrode 23 according to the second embodiment of the present invention may include the ohmic contact layer 21, the first electrode layer 22a, and the stacked upper layers of the p-type compound semiconductor layer 20 in order. The second electrode layer 22b is provided. The transparent electrode 23 according to the second embodiment of the present invention differs from the above-described first embodiment in the ohmic contact layer 21 between the p-type compound semiconductor layer 20 and the first electrode layer 22a. Is further provided.

The ohmic contact layer 21 forms an ohmic contact with the p-type compound semiconductor layer 20 and has a low contact resistance. The ohmic contact layer 21 includes Ag, Ag-based alloys, Zn-based alloys, Ni-based alloys, La-based alloys, Mg-based alloys, indium oxide containing additional elements, and SnO ₂ containing additional elements. It is formed of any one selected from the group consisting of. Here, the additive elements are Mg, Ag, Zn, Sc, Hf, Zr, Te, Se, Ta, W, Nb, Cu, Si, Ni, Co, Mo, Cr, Mn, Hg, Pr, Sb and La At least one selected from the group consisting of. The ohmic contact layer 21 is formed to a thickness of 0.1nm to 500nm.

The additive element improves the ohmic contact characteristics of the ohmic contact layer 21 by adjusting a band gap, electron affinity, and work function of the indium oxide and SnO ₂ . Specifically, the additive element increases the effective carrier concentration of the p-type compound semiconductor layer 20, and is reactive with components other than nitrogen among the compounds forming the p-type compound semiconductor layer 20.

For example, when the p-type compound semiconductor layer 20 is a GaN compound, the additive element preferentially reacts with gallium (Ga) rather than nitrogen. In this case, gallium vacancy is formed on the surface of the p-type compound semiconductor layer 20 by the reaction of gallium (Ga) of the p-type compound semiconductor layer 20 and the additive element. Gallium vacancy formed in the p-type compound semiconductor layer 20 acts as a p-type dopant and increases the effective carrier concentration on the surface of the p-type compound semiconductor layer 20.

In addition, the indium oxide to which the additive element is added remains on the surface of the p-type compound semiconductor layer 20 and serves as an obstacle to carrier flow at the interface between the p-type compound semiconductor layer 20 and the ohmic contact layer 21. Reacts with gallium oxide (Ga ₂ O ₃ ), a natural oxide layer. By the reaction, a transparent conductive oxide is formed at an interface between the p-type compound semiconductor layer 20 and the ohmic contact layer 21, and the ohmic contact layer 21 and the p-type compound semiconductor layer 20 are formed by the transparent conductive oxide. Tunneling conduction phenomenon occurs at the interface. Therefore, the ohmic contact characteristic of the ohmic contact layer 21 is improved. Therefore, the transparent electrode 23 having the ohmic contact layer 21 has a low contact resistance and improved electrical conductivity.

The content ratio of the additive element to the indium oxide and the SnO ₂ is 0.001 to 49 atomic percentages, respectively.

The ohmic contact layer 21 is an electron beam and thermal evaporator (e-beam & thermal evaporator), PVD (physical vapor deposition), CVD (chemical vapor deposition), PLD (plasma laser deposition) or dual-type thermal evaporator (dual-) type thermal evaporator). At this time, the deposition temperature is 20 ℃ to 1500 ℃, the pressure in the reactor (reactor) is from atmospheric pressure to 10 ^-12 torr.

3 is a cross-sectional view illustrating a compound semiconductor light emitting device including the transparent electrode of FIG. 1. The description of the components described in FIG. 1 will be omitted. In addition, the same reference number is used as it is about the same member.

Referring to FIG. 3, the compound semiconductor light emitting device including the transparent electrode according to the first exemplary embodiment of the present invention includes n-type and p-type electrodes 120 and 108 and at least n-type compound semiconductor layer 102 therebetween. And an active layer 104 and a p-type compound semiconductor layer 106. As the p-type electrode 108, the transparent electrode 22 shown in FIG. 1 was adopted as it is. That is, the p-type electrode 108 is formed on the first electrode layer 22a formed of a transparent conductive oxide and the second electrode layer 22b having a plurality of nanorods formed on the first electrode layer 22a.

The n-type compound semiconductor layer 102 includes a first compound semiconductor layer as a lower contact layer stacked on an upper surface of the substrate 100 and a lower clad layer stacked on an upper surface of the first compound semiconductor layer. The n-type lower electrode 120 is positioned at a portion where the stepped portion of the first compound semiconductor layer is formed.

The substrate 100 is mainly used as a sapphire substrate or a freestanding GaN substrate, and the first compound semiconductor layer is formed of an n-GaN-based group III-V nitride compound semiconductor layer, in particular an n-GaN layer. desirable. However, the present invention is not limited thereto, and may be another compound semiconductor layer of group III-V capable of laser oscillation (raising). The lower clad layer is preferably an n-GaN / AlGaN layer having a predetermined refractive index, but may be another compound semiconductor layer capable of lasing.

The active layer 104 may use any material layer as long as it is a material layer capable of lasing. Preferably, the active layer 104 uses a material layer capable of generating a laser light having a low threshold current value and stable lateral mode characteristics. GaN-based group III-V nitride compound semiconductor having In _x Al _y Ga _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1 and x + y ≦ 1) containing Al in a predetermined ratio in the active layer 104 Preference is given to using layers. Here, the active layer may have a structure of any one of a multi-quantum well or a single quantum well, and the structure of the active layer does not limit the technical scope of the present invention.

Upper and lower waveguide layers may be further formed on upper and lower surfaces of the active layer 104. The upper and lower waveguide layers are formed of a material having a smaller refractive index than the active layer 104, and preferably formed of a GaN-based group III-V compound semiconductor layer. The lower waveguide layer is formed of an n-GaN layer and the upper waveguide layer is formed of a p-GaN layer.

The p-type compound semiconductor layer 106 is stacked on the upper surface of the active layer 104, the upper cladding layer having a lower refractive index than the active layer 104, and the second cladding on the upper surface of the upper clad layer as an ohmic contact layer It includes a compound semiconductor layer. The second compound semiconductor layer is formed of a p-GaN-based group III-V nitride compound semiconductor layer, but preferably a p-GaN layer. However, the present invention is not limited thereto, and may be another compound semiconductor layer of group III-V capable of laser oscillation (raising). The upper clad layer is preferably formed of any one selected from the group consisting of Al _x Ga _1-x N (0≤x≤1) and Zn _x Mg _1-x O (0≤x≤1) having a predetermined refractive index. It may be formed of another compound semiconductor capable of lasing.

An n-type electrode 120 is formed in the stepped portion of the first compound semiconductor layer as the lower ohmic contact layer. However, the substrate 100 may be formed on the bottom surface of the substrate 100 to face the p-type electrode 108. In this case, the substrate 100 may be formed of silicon carbide (SiC) or gallium nitride (GaN).

The compound semiconductor light emitting device including the transparent electrode 108 of the present invention has excellent current-voltage characteristics, and the light transmittance of the electrode is improved, thereby improving light output and luminous efficiency.

4 is a cross-sectional view illustrating a compound semiconductor light emitting device including the transparent electrode of FIG. 2. Descriptions of the components described with reference to FIGS. 2 and 3 will be omitted. In addition, the same reference number is used as it is about the same member.

The p-type electrode 109 of the compound semiconductor light emitting device illustrated in FIG. 4 further includes an ohmic contact layer 21 as compared to the p-type electrode 108 illustrated in FIG. 3, and the ohmic contact layer 21. Has already been described in detail with reference to FIG. 2.

By providing the ohmic contact layer 21, the ohmic contact characteristic of the p-type electrode 109 is improved. Accordingly, the p-type electrode 109 including the ohmic contact layer 21 has low contact resistance and improved electrical conductivity, and the light output and luminous efficiency of the compound semiconductor light emitting device including the p-type electrode 109 is improved. Can be improved.

The transparent electrode according to the present invention has a low contact resistance and improved electrical conductivity, in particular, the light extraction efficiency is improved through the nanorod has a high light transmittance.

In addition, the compound semiconductor light emitting device including the transparent electrode of the present invention has excellent current-voltage characteristics, and improves light output and luminous efficiency by improving light transmittance at the electrode.

The transparent electrode according to the present invention may be applied to a light emitting device such as a light emitting diode (LED) or a laser diode (LD).

While some exemplary embodiments have been described and illustrated in the accompanying drawings in order to facilitate understanding of the present invention, it should be understood that these embodiments merely illustrate the broad invention and do not limit it, and the invention is illustrated and described. It is to be understood that the invention is not limited to structured arrangements and arrangements, as various other modifications may occur to those skilled in the art.

Claims (15)

In the electrode formed on the p-type compound semiconductor layer of the compound semiconductor light emitting device, The electrode, A first electrode layer formed of a transparent conductive oxide on the p-type compound semiconductor layer; And And a second electrode layer having a plurality of nanorods formed on the first electrode layer, wherein the transparent electrode of the compound semiconductor light emitting device is provided. The method of claim 1, The transparent conductive oxide is at least selected from the group consisting of In, Sn, Zn, Ga, Cd, Mg, Be, Ag, Mo, V, Cu, Ir, Rh, Ru, W, Co, Ni, Mn, Al, and La. A transparent electrode of a compound semiconductor light emitting device, characterized in that the oxide of any one element. The method of claim 1, The nanorod is formed of any one selected from the group consisting of Zn _x Mg _1-x O (0≤x≤1) and Al _x Ga _1-x N (0≤x≤1). Transparent electrode. The method of claim 1, Between the p-type compound semiconductor layer and the first electrode layer, Formed of any one selected from the group consisting of Ag, Ag-based alloys, Zn-based alloys, Ni-based alloys, La-based alloys, Mg-based alloys, indium oxides containing additional elements, and SnO ₂ containing additional elements Ohmic contact layer; Transparent electrode of a compound semiconductor light emitting device characterized in that it is further provided. The method of claim 4, wherein The additive element is a group consisting of Mg, Ag, Zn, Sc, Hf, Zr, Te, Se, Ta, W, Nb, Cu, Si, Ni, Co, Mo, Cr, Mn, Hg, Pr, Sb and La At least one selected from the transparent electrode of the compound semiconductor light emitting device. The method of claim 5, A content ratio of the additive element to the indium oxide and SnO ₂ is 0.001 to 49 at%, respectively. The method of claim 4, wherein The thickness of the ohmic contact layer is a transparent electrode of the compound semiconductor light emitting device, characterized in that in the range of 0.1nm to 500nm. A compound semiconductor light emitting device comprising n-type and p-type electrodes and at least an n-type cladding layer, an active layer, and a p-type cladding layer therebetween, The p-type electrode, A first electrode layer formed of a transparent conductive oxide on the p-type compound semiconductor layer; And And a second electrode layer having a plurality of nanorods formed on the first electrode layer. The method of claim 8, The transparent conductive oxide is at least selected from the group consisting of In, Sn, Zn, Ga, Cd, Mg, Be, Ag, Mo, V, Cu, Ir, Rh, Ru, W, Co, Ni, Mn, Al, and La. Compound semiconductor light emitting device, characterized in that the oxide of any one element. The method of claim 8, The nanorod is formed of any one selected from the group consisting of Zn _x Mg _1-x O (0≤x≤1) and Al _x Ga _1-x N (0≤x≤1). The method of claim 8, The p-type cladding layer is formed of any one selected from the group consisting of Zn _x Mg _1-x O (0≤x≤1) and Al _x Ga _1-x N (0≤x≤1) device. The method of claim 8, Between the p-type cladding layer and the first electrode layer, Formed of any one selected from the group consisting of Ag, Ag-based alloys, Zn-based alloys, Ni-based alloys, La-based alloys, Mg-based alloys, indium oxides containing additional elements, and SnO ₂ containing additional elements Ohmic contact layer; Compound semiconductor light emitting device characterized in that it is further provided. The method of claim 12, The additive element is a group consisting of Mg, Ag, Zn, Sc, Hf, Zr, Te, Se, Ta, W, Nb, Cu, Si, Ni, Co, Mo, Cr, Mn, Hg, Pr, Sb and La Compound semiconductor light emitting device, characterized in that at least one selected from. The method of claim 13, The compound semiconductor light emitting device, characterized in that the content ratio of the additional element to the indium oxide and SnO ₂ are 0.001 to 49 at%, respectively. The method of claim 8, The thickness of the ohmic contact layer is a compound semiconductor light emitting device, characterized in that in the range of 0.1nm to 500nm.

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