KR101393914B1 - Semiconductor light-emitting device and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a nitride semiconductor light emitting device and a manufacturing method thereof.

A nitride semiconductor light emitting device according to an embodiment of the present invention includes a substrate; An n-type contact layer formed on the substrate; An InGaN relief layer formed on the n-type contact layer; An active layer formed on the InGaN relief layer; And a p-type contact layer formed on the active layer.

Nitride, semiconductor, light emitting device, strain

Description

TECHNICAL FIELD The present invention relates to a nitride semiconductor light emitting device,

1 is a view showing a conventional nitride semiconductor light emitting device.

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

3 (a) and 3 (b) are photographs comparing the surface of the active layer of two samples measured by AFM according to the indium component ratio in the present invention.

Fig. 4 is a graph showing the PL intensity according to the wavelength of the samples of Fig. 3; Fig.

Description of the Related Art

200: nitride semiconductor light emitting device 201: substrate

210: buffer layer 211: undoped GaN layer

220: n-type contact layer 225: n-type electrode

230: InGaN relief layer 240: InGaN relief layer 240:

250: p-type cladding layer 260: p-type contact layer

265: p-type electrode

The present invention relates to a nitride semiconductor light emitting device and a manufacturing method thereof.

In general, the nitride semiconductor light emitting device has a light emitting region covering ultraviolet, blue, and green regions. In particular, the GaN-based nitride semiconductor light emitting device is applied to blue / green LED optical devices, high-speed switching devices such as MESFET (Metal Semiconductor Field Effect Transistor) and HEMT (Hetero Junction Field Effect Transistors) have.

The nitride semiconductor light emitting device has a structure in which an active layer of a single quantum well (SQW) structure or a multiple quantum well structure (MQW) having a well layer made of InGaN is formed of an n-type nitride semiconductor and a p- And a hetero structure located between the nitride semiconductors. Blue and green wavelengths are determined by increasing or decreasing the In composition ratio of the InGaN well layer.

1 is a cross-sectional view of a conventional nitride semiconductor light emitting device.

1, the nitride semiconductor light emitting device 100 includes a buffer layer 112 formed on a sapphire substrate 110 or a SiC substrate, an n-type contact layer 114 doped with Si is formed on the buffer layer 112, do.

An active layer 116 having a single or multiple quantum well structure is formed on the n-type contact layer 114 with a periodicity of an InGaN well layer / GaN barrier layer. The active layer 116 is formed with a Mg-doped p-type contact layer 118 Is formed.

After the n-type contact layer 114 is partially etched from the p-type contact layer 118 to the n-type contact layer 114, the p-type electrode 120 is formed on the p- And an n-type electrode 122 is formed on the n-type contact layer 114 so that a current can be applied from the outside.

In the nitride semiconductor light emitting device 100, electrons and holes injected into the n-type and p-type contact layers 114 and 118 must be confined in the active layer 116. The GaN n-type contact layer 114 and the p- ) And the InGaN-based active layer 116 have a heterojunction structure, which limits the brightness of the nitride semiconductor light emitting device.

A large strain is formed between the InGaN well layer and the GaN barrier layer due to the difference in thermal expansion coefficient between the InGaN and the GaN in the active layer 116, which is a large lattice constant. As a result, a large piezoelectic field is generated in the active layer, resulting in a decrease in luminous efficiency due to the distance between the holes and the electrons.

In addition, the strain between the InGaN well layer and the GaN barrier layer causes V-pits to be generated in the active layer. When the active layer is stacked, the interface between the well layer and the barrier layer becomes rough, And there is a problem in manufacturing a high efficiency LED.

The present invention provides a nitride semiconductor light emitting device and a method of manufacturing the same.

The InGaN relief layer having a high indium content is formed between the n-type semiconductor layer and the active layer so as to suppress the generation of strain and V-pits between the well layer and the barrier layer in the active layer, A nitride semiconductor light emitting device and a method of manufacturing the same are provided.

A nitride semiconductor light emitting device according to an embodiment of the present invention includes a substrate; An n-type contact layer formed on the substrate; An InGaN relief layer formed on the n-type contact layer; An active layer formed on the InGaN relief layer; And a p-type contact layer formed on the active layer.

A method of manufacturing a nitride semiconductor light emitting device according to an embodiment of the present invention includes: forming an n-type contact layer on a substrate; Forming an InGaN relief layer containing indium on the n-type contact layer; Forming an active layer on the InGaN relief layer; And forming a p-type contact layer on the active layer.

Hereinafter, the present invention will be described with reference to the accompanying drawings.

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

2, the nitride semiconductor light emitting device 200 includes a substrate 201, a buffer layer 210, an undoped GaN layer 211, an n-type contact layer 220, an InGaN relief layer 230, an active layer 240 a p-type cladding layer 250, a p-type contact layer 260, and p-type and n-type electrodes 265 and 225.

The substrate 201 may be a sapphire substrate, a substrate made of GaN, SiC, ZnC, GaAs, or Si. A buffer layer 210 may be formed on the substrate 201. The buffer layer 210 may be formed by selectively using GaN, AlN, AlGaN, InGaN, AlGaNn, or the like to improve lattice matching with the substrate. , More than one layer can be formed.

An undoped GaN layer 211 is formed on the buffer layer 210. An n-type contact layer 220 is formed on the undoped GaN layer 211.

The n-type contact layer 220 may be formed of an AlGaInN system including GaN or indium, and doped with silicon (Si) as a dopant. Here, the n-type GaN layer may be doped with Se, Ge, Te or the like as a dopant.

On the n-type contact layer 220, an InGaN relief layer 230 is formed. The InGaN relaxed layer 230 is formed between the n-type contact layer 220 and the active layer 240. The InGaN relaxed layer 230 is grown in an N ₂ atmosphere at a composition ratio of In of 10 to 30% give. At this time, the growth thickness of the InGaN relief layer 230 is 30 to 100 nm. Also, the InGaN relief layer 230 may be selectively doped with Si and Mg.

An active layer 240 is formed on the InGaN relief layer 230. For example, in the case of blue light emission having a wavelength of 460 to 470 nm, the InGaN well layer / GaN barrier layers 241a and 242a may be formed of a material having a band cap energy depending on the wavelength of light to be emitted. May be formed as a single or multiple quantum well structure. Here, the well layer In _x Ga _1-x N can be adjusted to 0 _{? X? 1} .

A p-type cladding layer 250 made of AlGaN-based material may be formed on the active layer 240. A p-type contact layer 260 is formed on the p-type cladding layer 250. The p-type region is made of p-type InAlGaN doped with a p-type dopant. As the p-type dopant, for example, Mg, Zn, Be and the like can be used. A transparent electrode may be formed on the p-type contact layer 260.

A part of the p-type contact layer 260 is partially etched to a part of the n-type contact layer 220 and then an n-type electrode 225 is formed on the n-type contact layer 220 and a p-type contact layer 260 The p-type electrode 265 is formed.

3 (a) and 3 (b), the pit density at the surface of the active layer grown on the InGaN relief layer is reduced. 3 (a) and 3 (b) are photographs showing the surface of the active layer grown on the InGaN relief layer according to the present invention by AFM (Atomic Force Microscopy). The AFM is a device for directly observing a nanoscale object. The AFM measures the surface shape of the active layer using the static dynamic deformation and the frequency characteristic of the cantilever appearing by approaching the micro-micro cantilever tip to the sample surface.

3 (a) shows a sample (sample A) with the In composition ratio of less than 10% in the InGaN relief layer and FIG. 3 (b) shows the In composition ratio of the InGaN relief layer between 10% (Sample B). As shown in FIGS. 3A and 3B, it can be seen that the pit density on the surface of the active layer is decreased as the In composition ratio is increased.

FIG. 4 is a graph showing photoluminescence intensity characteristics at 430 to 480 nm wavelengths for the samples (a) and (b) of FIG. 3. Here, the solid line (sample A) is the light emission characteristic for the sample (a) in Fig. 3, and the dotted line is the light emission characteristic for the sample (b) in Fig. As shown in FIG. 3 (b), the emission intensity for the sample (sample B) is high. It can be seen that the luminescence intensity increases in proportion to the indium component ratio in the InGaN relief layer.

The InGaN relief layer 230 is formed between the n-type contact layer 220 and the active layer 240 and is formed below the active layer before the growth of the active layer, thereby relaxing the strain in the active layer and improving the crystal quality , And the luminous efficiency can be increased. That is, by using the InGaN relief layer 230, strain relaxation and V-pits generation between the well layer and the barrier layer are suppressed in the active layer, thereby increasing the crystallinity of the active layer. As a result, the quantum-confine stark effect (QCSE) is reduced due to the reduction of the piezoelectric field, thereby improving the recombination efficiency of holes and electrons in the active layer, thereby improving the luminous efficiency and LED characteristics of the active layer.

Although the present invention has been described with respect to the pn junction structure in the nitride semiconductor light emitting device, the present invention can also be applied to a pnp (npn) junction structure or the like.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, It will be understood that various modifications and applications not illustrated in the drawings are possible.

For example, each component specifically shown in the embodiments of the present invention can be modified and implemented. It is to be understood that all changes and modifications that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

According to the nitride semiconductor light emitting device and the method for fabricating the same according to the embodiment of the present invention, since the InGaN relief layer is grown before the active layer is grown, the strain relaxation and the crystal quality in the active layer can be improved and the luminous efficiency can be improved .

Claims (10)

Board; An n-type contact layer formed on the substrate; An InGaN relief layer formed on the n-type contact layer; An active layer formed on the InGaN relief layer; A p-type contact layer formed on the active layer; And a p-type cladding layer formed between the active layer and the p-type contact layer, The composition ratio of In in the InGaN relief layer ranges from 10% to 30% The InGaN relief layer is doped with Si, The InGaN relief layer is formed to a thickness of 30 to 100 nm, And the p-type cladding layer is formed of an AlGaN-based material. Board; An n-type contact layer formed on the substrate; An InGaN relief layer formed on the n-type contact layer; An active layer formed on the InGaN relief layer; A p-type contact layer formed on the active layer; And a p-type cladding layer formed between the active layer and the p-type contact layer, The composition ratio of In in the InGaN relief layer ranges from 10% to 30% The InGaN relief layer is doped with Mg, The InGaN relief layer is formed to a thickness of 30 to 100 nm, Wherein the p-type cladding layer is formed of an AlGaN-based semiconductor. 3. The method according to claim 1 or 2, And a buffer layer formed between the substrate and the n-type contact layer. The method of claim 3, And an undoped GaN layer on the buffer layer. 3. The method according to claim 1 or 2, Wherein the n-type contact layer comprises an AlGaInN system including GaN or indium, and is doped with silicon (Si). The nitride semiconductor light emitting device according to claim 1 or 2, comprising a first electrode formed on the n-type contact layer and a second electrode formed on the p-type contact layer. Forming an n-type contact layer on the substrate; Forming an InGaN relief layer containing indium on the n-type contact layer; Forming an active layer on the InGaN relief layer; Forming a p-type contact layer on the active layer; And forming a p-type cladding layer between the active layer and the p-type contact layer, The InGaN relief layer has a composition ratio of In ranging from 10% to 30% The InGaN relief layer is formed to a thickness of 30 to 100 nm, The InGaN relief layer is doped with Si or Mg, And the p-type cladding layer is formed of an AlGaN-based material. delete delete delete

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