KR20050121313A - Ⅲ-Nitride compound semiconductor light emitting device with low contact resistance - Google Patents

Abstract

In the III-nitride semiconductor light emitting device according to the present invention, an active layer made of III-nitride semiconductor is provided between the lower contact layer 12 made of n-type III-nitride semiconductor and the upper contact layer 14 made of p-type III-nitride semiconductor. A III-nitride semiconductor light emitting device comprising an electrode layer 15 interposed therebetween and in contact with the upper contact layer 14 on the upper contact layer 14, between the upper contact layer 14 and the electrode layer 15. An n-type or p-type carbon-containing compound layer is interposed. In general, in the case of forming a transparent electrode layer directly on a p-type nitride semiconductor due to the large energy bandgap and low doping efficiency (<5x10 ¹⁷ atoms / cm ³ ) of the p-type nitride semiconductor light emitting device in III-nitride semiconductor light emitting device There is a large contact resistance between them, which reduces the efficiency of the device. However, this problem can be solved by interposing a carbon-containing compound layer capable of high concentration doping between the p-type nitride semiconductor and the transparent electrode layer as in the present invention.

Description

Ⅲ-Nitride compound semiconductor light emitting device with low contact resistance}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a III-nitride semiconductor light emitting device, and more particularly, to a III-nitride semiconductor light emitting device which can effectively supply holes to the active layer by lowering contact resistance between an upper contact layer made of a p-type nitride semiconductor and an electrode layer in contact therewith It is about.

1 is a cross-sectional view illustrating a conventional III-nitride semiconductor light emitting device. Referring to FIG. 1, the conventional III-nitride semiconductor light emitting device includes a buffer layer 11 made of GaN without dopant doping, a lower contact layer 12 made of n-GaN, and InGaN on a sapphire substrate 10. After sequentially stacking the active layer 13 having a multi-quantum well structure of / GaN, and the upper contact layer 14 made of p-GaN, mesa-etched to expose the lower contact layer 12 and the upper contact layer 14 Is formed by forming the n-type electrode 16 and the p-type electrode 17 on the transparent electrode layer 15.

In the III-nitride semiconductor light emitting device, the efficiency of the device may be defined as the intensity of light generated relative to external applied power. However, p-GaN constituting the upper contact layer 14 has a large energy band gap (˜3.3 eV) and the doping efficiency is less than 5 × 10 ¹⁷ atoms / cm ^{3, which} is not good. The contact resistance between the two is so large that the efficiency of the device is not good and the higher voltage is needed to produce the same light intensity.

To reduce the contact resistance between the upper contact layer 14 and the transparent electrode layer 15, a heavily doped p-GaN should be formed, but the large bandgap and low doping efficiency (<5x10 ¹⁷ atoms / cm of p-GaN) ³ ), it is very difficult to form highly doped p-GaN.

Various methods have been introduced to reduce contact resistance between p-GaN and the transparent electrode layer 15 used as the upper contact layer 14. As one example, the upper contact layer 14 is not made of a single layer of p-GaN, but is made of a superlattice structure such as p-GaN / p-InGaN or p-GaN / p-AlGaN, thereby making the piezoelectric structure within the superlattice structure. A method of obtaining a hole concentration much higher than that obtained in a single p-GaN layer by a piezoelectric field may be mentioned. However, in such a configuration, the potential barrier is felt in the vertical direction in the superlattice structure before holes are injected into the active layer, which is undesirable.

In another example, there is a method of growing a GaAs layer or an AlGaAs layer capable of high concentration doping (> 10 ²⁰ atoms / cm ³ ) between the upper contact layer 14 and the transparent electrode layer 15 (US patent). 6,410,944). However, in this case, since the bandgap of the GaAs layer or AlGaAs layer is smaller than the visible light region, the light generated in the active layer 13 is mostly absorbed in the GaAs layer or AlGaAs layer, thereby limiting the application field.

As described above, the conventional III-nitride semiconductor light emitting device has a disadvantage in that the efficiency of the device is not good because the contact resistance between the upper contact layer 14 and the transparent electrode layer 15 is large. It is not yet presented.

Accordingly, an object of the present invention is to provide a III-nitride semiconductor light emitting device having good efficiency by reducing contact resistance between the upper contact layer 14 and the electrode layer formed in contact with the upper contact layer 14.

In order to achieve the above technical problem, a III-nitride semiconductor light emitting device includes a III-nitride semiconductor between a bottom contact layer made of an n-type III-nitride semiconductor and an upper contact layer made of a p-type III-nitride semiconductor. An III-nitride semiconductor light emitting device including an electrode layer interposed between an active layer and an upper contact layer on the upper contact layer, wherein an n-type or p-type carbon-containing compound layer is interposed between the upper contact layer and the electrode layer. It features.

The carbon-containing compound layer may include SiC, SiCN, or CN.

Si, N, As, or P may be used as the n-type dopant of the carbon-containing compound layer.

B or Al may be used as the p-type dopant of the carbon-containing compound layer.

The doping concentration of the n-type or p-type dopant of the carbon-containing compound layer is preferably 1 × 10 ¹⁸ ~ 1 × 10 ²² atoms / cm ³ .

 The carbon-containing compound layer preferably has a thickness of 5 to 500 kPa.

The carbon-containing compound layer is preferably formed in a temperature range of 600 ~ 1200 ℃.

The electrode layer is selected from the group consisting of nickel, gold, silver, chromium, titanium, platinum, palladium, rhodium, iridium, aluminum, tin, ITO, indium, tantalum, copper, cobalt, iron, ruthenium, zirconium, tungsten, and molybdenum It may include at least one.

It may further include an n-type electrode layer in ohmic contact with the lower contact layer, wherein the n-type electrode layer is nickel, gold, silver, chromium, titanium, platinum, palladium, rhodium, iridium, aluminum, tin, ITO, At least one selected from the group consisting of indium, tantalum, copper, cobalt, iron, ruthenium, zirconium, tungsten, and molybdenum.

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention will be described in detail. In the drawings, the same reference numerals as in FIG. 1 denote components that perform the same function, and a repetitive description thereof will be omitted. The following examples are only presented to understand the content of the present invention, and those skilled in the art will be capable of many modifications within the technical spirit of the present invention. Accordingly, the scope of the present invention should not be construed as being limited to these embodiments.

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

Referring to FIG. 2, the present invention is characterized in that, unlike the prior art, an n-type or p-type carbon-containing compound layer 21 is interposed between the upper contact layer 14 and the transparent electrode layer 15.

The carbon-containing compound layer 21 may include silicon carbide (SiC), silicon carbon nitride (SiCN), or carbon nitride (CN). The carbon-containing compound 21 may be Si, N, N-type dopants such as As or P or p-type dopants such as B or Al can be easily doped at a high concentration of about 1 × 10 ¹⁸ to 1 × 10 ²² atoms / cm ^3, thereby reducing the thickness of the potential barrier to reduce holes. The carbon-containing compound layer 21 can be made to be easily tunneled.

The silicon carbide layer can be obtained by reacting silicon and carbon in a vapor deposition machine. SiH ₃ , Si ₂ H ₆ , DTBSi and the like can be used as the silicon raw material, and CBr ₄ or CxHy can be used as the carbon raw material.

Generally, the growth temperature of silicon carbide is higher than 1300 ℃, but if silicon carbide is grown on GaN at too high temperature, it will damage GaN-based devices during silicon carbide growth, so the growth temperature of silicon carbide is 600 ~ 1200 ℃ Is preferably.

Further, if the thickness of the silicon carbide layer is too thick, the tunneling barrier becomes thick, which is not preferable, so the thickness of the silicon carbide layer is preferably about 5 to 500 kPa. The doping concentration, the thickness, and the growth temperature of the silicon carbide layer are not limited to the silicon carbide layer but are similarly applied to the formation of a silicon carbon nitride (SiCN) layer or a carbon nitride (CN) layer.

The transparent electrode layer 15 and the n-type electrode layer 16 include lanthanum (La), nickel, gold, silver, chromium, titanium, platinum, palladium, rhodium, iridium, aluminum, tin, ITO, indium, tantalum, copper, cobalt, It may comprise at least one selected from the group consisting of iron, ruthenium, zirconium, tungsten, and molybdenum.

3 is an XRD analysis result of silicon carbide grown on a cyer substrate. At this time, the growth temperature was 1000 ° C., and the growth rate was 2 μs / sec. The thickness of the grown silicon carbide was set to 5000Å to enable XRD analysis, and NH ₃ was used as the N source for high concentration n doping, and the doping concentration was 4.63 × 10 ¹⁹ atoms to be sufficient for tunneling to occur. / cm ³ . Referring to FIG. 3, it can be seen that silicon carbide is properly grown.

Table 1 shows the electrical characteristics of a device made by growing about 20 microseconds of heavily doped silicon carbide in a typical GaN-based LED. The electrode used at this time was an ITO electrode, and it can be seen that the silicon carbide layer has a lower contact resistance value than when the electrode was formed directly on p-GaN without silicon carbide.

Contact layer Vf @ 20mA [V] Vf @ 10㎂ [V] Vr @ -10㎂ [V] case 1 p-GaN 5.25 2.37 24.1 case 2 SiC / p-GaN 3.65 2.35 25.1

4 is a schematic energy band diagram when an n-type silicon carbide layer is present between the upper contact layer 14 and the transparent electrode layer 15. Referring to FIG. 4, it can be seen that holes can flow more efficiently into the upper contact layer 14 due to the presence of the heavily doped n-type silicon carbide layer.

FIG. 5 illustrates a case in which the transparent electrode layer 15 is present directly on the upper contact layer 14 (a) and a p-type silicon carbide layer doped with a high concentration between the upper contact layer 14 and the transparent electrode layer 15. This is a schematic energy band diagram of case (b). Referring to FIG. 5, when the heavily doped p-type silicon carbide layer is present, it may be confirmed that holes may flow into the upper contact layer 14 more efficiently.

In general, in the III-nitride semiconductor light emitting device, when the transparent electrode layer is formed directly on the p-type nitride semiconductor due to the large energy band gap and the low doping efficiency of the p-type nitride semiconductor, a large contact resistance is generated between them. This makes the device less efficient. However, this problem can be solved by interposing a carbon-containing compound layer capable of high concentration doping between the p-type nitride semiconductor and the transparent electrode layer as in the present invention.

1 is a cross-sectional view illustrating a conventional III-nitride semiconductor light emitting device;

2 is a cross-sectional view illustrating a III-nitride semiconductor light emitting device according to an embodiment of the present invention;

3 is an XRD analysis graph of silicon carbide grown on a sapphire substrate;

4 is an energy band diagram of a metal / n-SiC / p-GaN structure;

5 is an energy band diagram for explaining the operation principle of the metal / p-SiC / p-GaN structure.

Claims (1)

Lanthanide is formed between the lower contact layer made of n-type III-nitride semiconductor and the upper contact layer made of p-type III-nitride semiconductor, and the active layer made of III-nitride semiconductor is in contact with the upper contact layer on the upper contact layer. La) A III-nitride semiconductor light emitting device comprising an electrode layer, A III-nitride semiconductor light emitting device comprising an n-type or p-type carbon-containing compound layer interposed between the upper contact layer and the electrode layer.