KR100974924B1 - A nitride based light emitting device - Google Patents

Abstract

The present invention relates to a nitride based light emitting device comprising a substrate, a buffer layer, an n-type nitride semiconductor layer, an active layer, and a p-type nitride semiconductor layer. The present invention relates to an Al _{1 - x} Si _x N intermediate layer between n-type nitride-based semiconductor layers. It is characterized by inserting (interlayer).

As a result, it is possible to reduce the threading dislocation which starts to occur from the initial stage of growth on the substrate and to alleviate the tensile strain, thereby realizing a nitride-based light emitting device having high reliability. have.

Interlayer, potential defect, nitride system, light emitting element, superlattice

Description

Nitride-based light emitting device {A NITRIDE BASED LIGHT EMITTING DEVICE}

The present invention relates to a nitride-based light emitting device, by inserting an interlayer between the n-type nitride semiconductor layer, the potential generated from the beginning of the growth due to the lattice mismatch generated between the substrate and the n-type nitride-based semiconductor layer The present invention relates to a high-quality nitride-based light emitting device that reduces threading dislocation and at the same time reduces tensile strain generated during growth to improve constant voltage resistance.

In general, nitride-based semiconductors are widely used in blue / green light emitting diodes or laser diodes as light sources for full-color displays, traffic lights, general lighting, and optical communication devices. The nitride-based light emitting device includes an InGaN-based multi-quantum well structured active layer disposed between n-type and p-type nitride semiconductor layers, and generates and emits light on the principle of recombination of electrons and holes in the active layer.

There is a lattice mismatch of about 14% between the sapphire (Al2O3) substrate and GaN.

Several buffer layers are used to reduce the lattice mismatch, but still include dislocation defect densities of 10 ⁸ to 10 ¹⁰ cm ^{-2 at} the sapphire substrate and GaN interface. In addition, cracks are formed on the wafer surface due to tensile strain during growth. These phenomena lead not only to the deterioration of the constant voltage but also to the reduction of the internal quantum efficiency.

The present invention is to solve the problems of the prior art described above, by inserting an intermediate layer between the n-type nitride semiconductor layer to reduce the potential defects occurring at the sapphire substrate and GaN boundary to improve characteristics such as improvement of the constant voltage, The purpose is.

The present invention for achieving the above object, in the nitride-based light emitting device consisting of a buffer layer, an n-type nitride semiconductor layer, an active layer and a p-type nitride semiconductor layer on a substrate, Al _{1 - x} Si _{x in} the n-type nitride semiconductor layer It is characterized by having an intermediate layer consisting of N.

It is preferable that Si composition ratio x of the said intermediate | middle layer has a range of 0.02-0.2, More preferably, it has a range of 0.02-0.12.

In addition, the intermediate layer preferably has a thickness of 10 ~ 500nm, for example, it can be grown at 800 ~ 1000 ℃.

The intermediate layer may be formed at a point at which a lower surface corresponds to 1/3 to 2/3 of the total thickness of the n-type semiconductor layer with respect to the lower surface of the n-type nitride semiconductor layer, and the intermediate layer and the n-type nitride semiconductor layer It may be formed of a super lattice structure repeatedly stacked. In this case, the thickness ratio of the intermediate layer and the n-type nitride semiconductor layer is preferably 1:10 to 3: 7, for example, the superlattice of the intermediate layer and the n-type nitride semiconductor layer is the intermediate layer and the n-type nitride semiconductor The layer may be formed by repeating 2 to 10 times.

As described above, according to the present invention, the intermediate layer is formed while growing while reducing the threading dislocation occurring from the beginning of growth caused by the lattice mismatch generated between the substrate and the n-type nitride-based semiconductor layer. It is possible to greatly improve the voltage resistance characteristics by reducing the tensile strain problem.

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

1 is a cross-sectional view of a nitride light emitting device according to a general embodiment, and FIG. 2 is a cross-sectional view of a nitride light emitting device according to an embodiment of the present invention.

First, referring to FIG. 2, in the nitride-based semiconductor device, an n-type nitride semiconductor layer 2-3 and an active layer 2 are sequentially formed after forming a buffer layer 2-2 on the substrate 2-1. -4) and p-type nitride semiconductor layers 2-5. An n-layer electrode 2-6 is disposed on the exposed upper surface of the n-type nitride semiconductor layer 2-3, and a p-layer electrode 2-7 is disposed on the exposed upper surface of the p-type nitride semiconductor layer 2-5. Each is provided.

The Al _{1 - x} Si _x N intermediate layer (2-a) used in the present embodiment is located between the n-type nitride semiconductor layers and has an appropriate thickness and composition to reduce the potential defects occurring at the sapphire substrate and the GaN interface. It can be configured to have.

A first embodiment of the nitride based light emitting device according to the present invention is as follows.

Growth methods of nitride-based light emitting devices include metal organic chemical vapor deposition (MOCVD), molecular beam growth (MBE; Molecular Beam Epitaxy) and hydride vapor phase growth (HVPE). Various methods can be used, and the present embodiment uses organometallic chemical vapor deposition (MOCVD).

Referring to FIG. 2, an Al _{1 - x} Si _x N intermediate layer 2 disposed between the buffer layer 2-2, the n-type nitride semiconductor layer 2-3, and the n-type nitride semiconductor layer on the substrate 2-1. -a), the active layer 2-4 and the p-type nitride semiconductor layer 2-5 are sequentially formed.

The substrate refers to a wafer for fabricating a nitride-based light emitting device, and uses a heterogeneous substrate such as sapphire (Al 2 O 3), silicon carbide (SiC), silicon (Si), gallium arsenide (GaAs), or the like. At least one of the substrates is used. In this embodiment, a crystal growth substrate made of sapphire is used.

The buffer layer 2-2 is to reduce lattice mismatch between the substrate and subsequent layers during crystal growth on the substrate, and may include InAlGaN series, SiC, or ZnO. In this embodiment, a buffer layer composed of InAlGaN series is used.

The n-type nitride semiconductor layer 2-3 is a layer in which electrons are produced, and an n-type nitride semiconductor layer doped with Si is used. In this embodiment, an impurity concentration of 1 × 10 ¹⁷ / cm 3 to 5 × 10 ¹⁹ / cm 3 is used as an n-type nitride semiconductor layer using an inert gas such as SiH 4, Si 2 H 4, or an MO source such as DTBSi. It is possible to form an n-type nitride semiconductor layer having a thickness of 1.0 ~ 5.0㎛.

The intermediate layer 2-a positioned between the n-type nitride semiconductor layers uses Al _{1 - x} Si _x N as a layer to improve the constant voltage. In this embodiment, in an NH 3 atmosphere of 800 to 1000 ° C., an MO source of TMAl (trimethylaluminum) for obtaining Al, an inert gas such as SiH 4 or Si 2 H 4 for obtaining Si, or an MO source such as DTBSi (source) ), An Al _{1 - x} Si _x N intermediate layer having an impurity concentration of 3 × 10 ¹⁸ / cm 3 to 5 × 10 ²⁰ / cm 3 can be formed to a thickness of 10-500 nm.

In addition, the mixing ratio of the Al _{1 - x} Si _x N layer may be formed in a composition of 0.02 <x <0.2, more preferably 0.02 <x <0.12.

In addition, the lower surface of the intermediate layer is formed at a point corresponding to 1/3 to 2/3 of the total thickness of the n-type semiconductor layer based on the lower surface of the n-type nitride semiconductor layer.

In addition, the Al _{1 - x} Si _x N intermediate layer is formed once between the n-type nitride semiconductor layer, and is formed in a superlattice form between the Al _{1 - x} Si _x N intermediate layer and the n-type nitride semiconductor layer. can do.

In this case, the thickness ratio between the Al _{1 - x} Si _x N intermediate layer and the n-type nitride semiconductor layer may have a thickness ratio between 1:10 and 3: 7.

Next, the active layer 2-4 was formed. The active layer 2-4 includes an In _x Ga _{1 -} xN (0.1 <x <1) quantum well layer 3-1 and an In _y Ga _{1- y} N (0 <y <0.5) quantum barrier layer (3- 2) formed a multi-quantum well structure consisting of at least two or more and ten or fewer repetitions. More preferably, each quantum well layer 3-1 is formed with a thickness of 1-4 nm and In (0.1 <x <0.4), and each quantum barrier layer 3-2 has a thickness of 5-20 nm and an In content ( 0 <y <0.2).

Next, a p-type nitride semiconductor layer 2-5 doped with Mg is formed on the active layer 2-4. Here, trimethylgallium (TMGa) or triethylgallium (TEGa) may be used as a source gas for Ga, and ammonia (NH 3), dimethylhydrazine (DMHy) may be used as a source gas for N, and a source for Mg. The gas may be CP2Mg or DMZn. By using this, a p-type nitride semiconductor layer 2-5 having a thickness of Mg 1 to 3 µm of 3 to 8 x 10 ¹⁷ / cm 3 is formed. Thereafter, after appropriately mesa etching, the n-layer electrode 2-6 is exposed on the exposed top surface of the n-type nitride semiconductor layer 2-3, and the p-layer is exposed on the upper surface of the p-type nitride semiconductor layer 2-5. The electrodes 2-7 are formed, respectively.

(Comparative Example)

A nitride light emitting device was manufactured under the same condition as the above-described embodiment, except for the Al _{1 - x} Si _x N intermediate layer employed in the present invention. This follows the form in Figure 1.

* ESD results of applying the constant voltage of the nitride light emitting device obtained in the above-described Examples and Comparative Examples from -100V to -1kV in steps are shown in the table of FIG.

As shown in FIG. 3, when the constant voltage is increased from -100V to -1kV, it can be confirmed that the comparative example is -500V ESD level. On the other hand, in the case of using the Al _{1 - x} Si _x N intermediate layer, it can be seen that the constant voltage is improved to -900V ESD level.

As such, by inserting an Al _{1 - x} Si _x N interlayer between n-type nitride semiconductor layers, dislocation defects arise from the beginning of growth caused by lattice mismatch occurring between the substrate and the n-type nitride semiconductor layer. In addition to reducing threading dislocations, it is possible to improve the constant voltage characteristics by reducing the tension strain generated during growth.

In the above embodiment, a nitride-based light emitting device has been described as an example, but it is apparent to those skilled in the art that the present invention can be advantageously employed in other nitride-based optical devices having a similar structure, such as semiconductor laser devices.

As described above, the present invention has been described in detail through preferred embodiments, but the scope of the present invention is not limited to the specific embodiments and should be interpreted by the appended claims. In addition, those skilled in the art should understand that many modifications and variations are possible without departing from the scope of the present invention.

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

2 is a cross-sectional view of a nitride-based light emitting device according to the present invention.

3 is a table showing the ESD yield (yield) with respect to the constant voltage of the nitride-based light emitting device and the conventional nitride-based light emitting device according to the present invention.

<Code Description of Main Parts of Drawing>

2-1: substrate, 2-2: buffer layer

2-3: n-type nitride semiconductor layer

2-a: Al _{1 - x} Si _x N intermediate layer, 2-4: active layer

2-5: p-type nitride semiconductor layer

2-6: n-layer electrode, 2-7: p-layer electrode

Claims (6)

In a nitride based light emitting device comprising a buffer layer, an n-type nitride semiconductor layer, an active layer and a p-type nitride semiconductor layer on a substrate, At least one intermediate layer made of Al _1-x Si _x N is inserted into an n-type nitride semiconductor layer having a thickness of 1.0 to 5.0 μm, The intermediate layer is formed of a nitride-based light emitting, characterized in that formed in a thickness of 10-500nm from the point corresponding to 1/3 to 2/3 of the total thickness of the n-type nitride semiconductor layer with respect to the start point of the n-type nitride semiconductor layer device. The nitride-based light emitting device of claim 1, wherein the number of intermediate layers repeatedly inserted into the n-type nitride semiconductor layer is 2 to 10. The nitride-based light emitting device of claim 1, wherein the intermediate layer is grown at 800 to 1000 ° C. The method of claim 1, wherein the substrate is a sapphire substrate, the n-layer electrode is formed on the exposed upper surface of the n-type nitride semiconductor layer into which the intermediate layer is inserted, wherein the intermediate layer is located below the n-layer electrode Nitride-based light emitting device. delete The nitride-based light emitting device of claim 1, wherein the n-type nitride semiconductor layer into which the intermediate layer is inserted is directly in contact with the active layer, and directly in contact with the buffer layer.

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