KR100573489B1 - Method for growing active layer of light emitting device - Google Patents

Abstract

The present invention relates to a method of growing an active layer of a light emitting device, wherein an active layer is formed on an N semiconductor layer, a P semiconductor layer is formed on the active layer, and the active layer is formed by an electric current applied to the N semiconductor layer and the P semiconductor layer. In the method of growing an active layer of a light emitting device having a light emitting structure, the active layer is a first anneal (annealing) after sequentially growing a quantum barrier layer, a quantum well layer, a quantum barrier layer on the N-type semiconductor layer A first step of carrying out the process; After performing the first annealing process, the quantum well layer and the quantum barrier layer are sequentially grown on the uppermost quantum barrier layer grown in the first step, and then, the second step of performing the second annealing process is performed. To grow.

Therefore, in the present invention, the quantum well layer and the quantum barrier layer are grown at a constant temperature, the quantum well layer is protected by the quantum barrier layer, and then an annealing process is performed to grow the active layer, thereby decomposing and evaporating the quantum well layer. By suppressing the interfacial properties, the optical properties and the uniformity of the thickness can be improved, and the deterioration of the quality of the quantum well layer can be minimized, thereby improving the light efficiency.

Luminescence, device, active layer, annealing,

Description

{Method for growing active layer of light emitting device}

1 is a graph representing a growth temperature and a growth time of an active layer growth method of a light emitting device according to the prior art;

FIG. 2 is a TEM photograph of an active layer grown by the method of FIG. 1. FIG.

3 is a graph representing a growth temperature and a growth time of another active layer growth method of a light emitting device according to the prior art;

4 is a conceptual diagram illustrating a method of growing an active layer of a light emitting device according to a first embodiment of the present invention;

5 is a graph showing a growth temperature and a growth time of an active layer growth method according to a first embodiment of the present invention;

6 is a conceptual diagram illustrating a method of growing an active layer of a light emitting device according to a second embodiment of the present invention;

Figure 7 is a graph showing the growth temperature and growth time of the active layer growth method according to a second embodiment of the present invention

8 is a TEM (transmission electron microscope) photograph of an active layer of a light emitting device grown by the method according to the present invention.

9 is a graph measuring the photoluminescence of a light emitting device having an active layer grown by the method according to the present invention and the prior art method

<Description of the symbols for the main parts of the drawings>

100 light emitting element 110 N semiconductor layer

120: active layer 130: P semiconductor layer

The present invention relates to a method of growing an active layer of a light emitting device, and more particularly, to grow a quantum well layer and a quantum barrier layer at a constant temperature, protect the quantum well layer with a quantum barrier layer, and then perform an annealing process. By growing the active layer, the decomposition and evaporation of the quantum well layer can be suppressed to improve the interfacial properties, the optical properties and the uniformity of the thickness, and the deterioration of the quality of the quantum well layer can be minimized, thereby improving the light efficiency. It relates to a method of growing an active layer of a device.

Recently, with the growth technology of nitride semiconductors, development of light emitting diodes and blue-violet laser diodes covering a red wavelength band in ultraviolet rays has been completed, and they have already been widely used in traffic lights, electronic signs, mobile phones, and the like.

Despite these remarkable achievements, light-emitting diodes are not a replacement for incandescent or fluorescent lamps for lighting applications, and blue-violet laser diodes have low light output and cannot be used for recorders with double speed.

In order to dominate the larger market and open new markets, the development of high output light emitting devices is required.

In order to increase the output of the light emitting device, it is necessary to improve several parts, but the most important of them is the improvement of the quality of the active layer that actually emits light.

Currently, the most widely used active layer structure is a multi-quantum well (MQW) layer formed by repeatedly overlapping a quantum well (QW) layer and a quantum barrier (QB) layer several times.

The material component of the quantum well layer is mainly In _x Ga _1-x N (0 <x ≤ 1), and the quantum barrier layer component is In _y Ga _1-y N (0 ≤ y <1, which has a lower In composition than the quantum well layer. , x> y).

The main difference between the quantum well layer and the quantum barrier layer is the In composition, and the controlling factor is the temperature at the time of thin film growth and the flow rate of In.

That is, the higher the growth temperature, the lower the In composition, and even if the In flow rate is lowered, the In composition decreases.

In the implementation of the multi-quantum well structure, there are various growth methods, but two of the most representative methods are shown in FIGS. 1 and 2.

1 is a graph showing a growth temperature and a growth time of an active layer growth method of a light emitting device according to the prior art, wherein an N-type semiconductor layer made of GaN or AlGaN is grown at a high temperature T1, and then In _y Ga _1-y N ( 0 ≤ y <1) Lower to T2 temperature to grow quantum barrier layer, T3 temperature to grow higher In _x Ga _1-x N (0 <x ≤ 1, x> y) quantum well layer Lower it further.

As a result, in the prior art, the quantum barrier layer and the quantum well layer are repeatedly grown by controlling temperature, and finally, the quantum barrier layer is grown to complete the active layer with a multi-quantum well structure.

In this way, care must be taken when growing each InGaN layer, because the In composition is temperature-sensitive, stabilization time is required to stabilize the temperature when the temperature is changed from T2 to T3 or from T3 to T2. Should give.

Therefore, the active layer grown in this way is excellent in light efficiency characteristics, but the interface characteristics of the multiple quantum well layer and the thickness control of each thin film layer are poor.

That is, as shown in the TEM (transmission electron microscope) image shown in FIG. 2, the quantum well layer 10 includes the thicknesses d1, d2, d3, d4 of the left, right, middle, and neighboring well layers, and the quantum barrier layer ( 11) the thickness of each is not constant.

This is because the quantum barrier layer growth temperature (T2) is higher than the quantum well layer temperature (T3) and the quantum well layer InGaN layer is partially decomposed in the process of raising and stabilizing the temperature, thereby uniformly distributing Ga and In atoms. This is because the thickness and composition uniformity are broken by moving or evaporating at.

3 is a graph showing a growth temperature and a growth time of another active layer growth method of a light emitting device according to the prior art, in which the temperature is fixed at 'T3' and only the In flow rate is adjusted to control the quantum barrier layer and the quantum well Grow the layer.

Therefore, since the method has no change in temperature, the quantum barrier layer can be grown immediately as soon as quantum well layer growth is completed, thereby minimizing the problem of decomposition and evaporation of the quantum well layer.

Therefore, each interface and thickness uniformity in the multiple quantum well layer is improved.

However, a disadvantage of this method is that there is no annealing effect at high temperatures since there is no temperature change.

On the other hand, annealing induces the formation of quantum dots (QDs) in the InGaN quantum well layer, which causes optical characteristics to be improved.

Table 1 compares the field emission (Electro-luminescence, EL) characteristics of the light emitting diodes manufactured by the above two methods, the brightness of the light emitting diodes grown by the method of Figure 1 is 10 times higher than the light emitting diodes grown by the method of Figure 2 .

Growing way Peak wavelength EL brightness Method of FIG. 400 nm 200 2 method 400 nm 20

In order to solve the above problems, the present invention is to grow a quantum well layer and a quantum barrier layer by keeping the temperature constant, protect the quantum well layer with a quantum barrier layer, and then grow an active layer by performing an annealing process. Growth of the active layer of the light emitting device to improve the efficiency of light by improving the interfacial properties, optical properties and uniformity of thickness by inhibiting decomposition and evaporation of the quantum well layer. The purpose is to provide a method.

According to a preferred aspect of the present invention, an active layer is formed on an N semiconductor layer, and a P semiconductor layer is formed on the active layer, and applied to the N semiconductor layer and the P semiconductor layer. In the active layer growth method of a light emitting device having a structure in which light is emitted from the active layer by the current,

The active layer,

A first step of sequentially growing a quantum barrier layer, a quantum well layer, and a quantum barrier layer on the N-type semiconductor layer, and then performing a first annealing process;

After performing the first annealing process, the quantum well layer and the quantum barrier layer are sequentially grown on the uppermost quantum barrier layer grown in the first step, and then, the second step of performing the second annealing process is performed. There is provided a method of growing an active layer of a light emitting device, characterized in that the growth is carried out.

Another preferred aspect for achieving the above objects of the present invention, the active layer is formed on the N semiconductor layer, the P semiconductor layer is formed on the active layer, applied to the N semiconductor layer and P semiconductor layer In the active layer growth method of a light emitting device having a structure in which light is emitted from the active layer by the supplied current,

The active layer,

A first step of sequentially growing a quantum barrier layer, a quantum well layer, a quantum barrier layer, a quantum well layer, and a quantum barrier layer on the N-type semiconductor layer;

After the first step, there is provided a method of growing an active layer of a light emitting device, characterized in that the growth by performing a second step of performing an annealing (Annealing) process.

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

4 is a conceptual diagram illustrating a method of growing an active layer of a light emitting device according to a first embodiment of the present invention. Basically, the light emitting device 100 includes an active layer 120 formed on an N semiconductor layer 110. The P semiconductor layer 130 is formed on the active layer 120.

In this case, when a current is injected into the N semiconductor layer 110 and the P semiconductor layer 130 from a power source, light is emitted from the active layer 120.

In the first embodiment of the present invention, the active layer 120 is formed by growing a quantum well layer and a quantum barrier layer at the same temperature, and protecting and annealing the quantum well layer that is temperature sensitive with the quantum barrier layer.

The quantum well layer and the quantum barrier layer may be formed by changing the In composition of the InGaN layer by adjusting the In flow rate.

That is, the method of growing the active layer of the first embodiment according to the present invention will be described with reference to FIG. 4. First, first, the quantum barrier layer, the quantum well layer, and the quantum barrier layer are sequentially grown on the N-type semiconductor layer. Annealing process is performed.

After performing the first annealing process, the quantum well layer and the quantum barrier layer are sequentially grown on the uppermost quantum barrier layer grown in the first step, and then, the second step of performing the second annealing process is performed. As a result, the active layer 120 of the light emitting device is grown.

Here, in the first embodiment of the present invention, the growth process and annealing process of the quantum well layer and the quantum barrier layer, which are performed after the first annealing process, are performed at least one or more times, thereby making the active layer 120 formed of a multi-quantum well layer. ) Can be formed.

5 is a graph showing a growth temperature and a growth time of the active layer growth method according to the first embodiment of the present invention. As described above, in the first embodiment of the present invention, the quantum well layer and the quantum well layer are controlled by adjusting the In flow rate. The barrier layer is grown at the same temperature T3.

Here, since there is no change in temperature, it is possible to quickly deposit a quantum barrier layer on the grown quantum well layer.

In this case, in the situation where the quantum well layer is covered, the annealing process (A, B) is performed by raising the temperature to 'T2 (T2> T3)' to improve the optical characteristics.

That is, since the annealing temperature T2 is higher than the temperature T3 for growing the quantum well layer and the quantum barrier layer, the annealing process is performed at a high temperature T2 after the quantum barrier layer is grown.

Therefore, in the first embodiment of the present invention, since the decomposition and evaporation can be suppressed by protecting the quantum well layer from the external environment, the interface property, the optical property and the uniformity of the thickness can be improved.

FIG. 6 is a conceptual view illustrating a method of growing an active layer of a light emitting device according to a second embodiment of the present invention. In the second embodiment of the present invention, the quantum well layer and the quantum barrier may be formed at the same temperature. After growing the layer, the last step is to perform the annealing process.

Similarly, each of the quantum well layer and the quantum barrier layer is formed by changing the In composition of the InGaN layer by adjusting the In flow rate.

That is, the method of growing the active layer of the second embodiment according to the present invention will be described with reference to FIG. 6, in which the quantum barrier layer, the quantum well layer, the quantum barrier layer, the quantum well layer, and the quantum barrier layer are sequentially formed on the N-type semiconductor layer. After growing, the annealing process is performed.

At this time, before performing the annealing process, the process of growing a quantum well layer and a quantum barrier layer on the final quantum barrier layer is performed at least one or more times to form an active layer 120 formed of a multi-quantum well layer. can do.

7 is a graph showing an active layer growth method according to a second embodiment of the present invention with a growth temperature and a growth time. The active layer growth method of the second embodiment adjusts the In flow rate to make the quantum well layer and the quantum barrier layer at the same temperature. After growing in (T3), before the P-type semiconductor layer is grown, the temperature is raised to 'T2 (T2 &gt; T3)' to perform one annealing step (C).

Therefore, the number of annealing experienced by all the quantum well layers is the same, thereby minimizing the quality degradation of each quantum well layer, and improving the consistency and uniformity.

On the other hand, the annealing process for improving the light efficiency proceeds at a temperature higher than the growth temperature of the quantum well layer, so that even if the quantum well layer is protected by the quantum barrier layer, multiple annealing may deteriorate the quality of the quantum well layer. Even when the quantum well layer is grown, the characteristics of the quantum well layer are changed according to the number of times of the annealing process. In the second embodiment of the present invention, this problem can be solved.

8 is a TEM (transmission electron microscope) photograph of an active layer of a light emitting device grown by the method according to the present invention. As shown in this TEM photograph, the quantum well layer 10 has a uniform thickness. Able to know.

9 is a graph measuring photoluminescence of a light emitting device having an active layer grown by the method according to the present invention and the prior art, 'K' of FIG. 7 is the light of the light emitting device according to the prior art 'L' is the photoluminescence of the light emitting device according to the present invention.

Therefore, it can be seen that the photoluminescence L of the light emitting device according to the present invention is increased two to three times higher than that of the light emitting device according to the prior art.

As described above, in the present invention, the quantum well layer and the quantum barrier layer are grown at a constant temperature, the quantum well layer is protected by the quantum barrier layer, and then an annealing process is performed to grow the active layer, thereby providing a quantum well layer. By suppressing the decomposition and evaporation of the interfacial properties, the optical properties and the uniformity of the thickness can be improved, the quality deterioration of the quantum well layer can be minimized, thereby improving the light efficiency.

Although the invention has been described in detail only with respect to specific examples, it will be apparent to those skilled in the art that various modifications and variations are possible within the spirit of the invention, and such modifications and variations belong to the appended claims.

Claims (8)

A method of growing an active layer of a light emitting device having a structure in which an active layer is formed on an N semiconductor layer, and a P semiconductor layer is formed on the active layer, and light is emitted from the active layer by a current applied to the N semiconductor layer and the P semiconductor layer. To The active layer, A first step of sequentially growing a quantum barrier layer, a quantum well layer, and a quantum barrier layer on the N-type semiconductor layer, and then performing a first annealing process; After performing the first annealing process, the quantum well layer and the quantum barrier layer are sequentially grown on the uppermost quantum barrier layer grown in the first step, and then, the second step of performing the second annealing process is performed. To grow, After the active layer growth process, the active layer growth method of the light emitting device, characterized in that to grow a P semiconductor layer on the grown active layer. The method of claim 1, The quantum well layer and the quantum barrier layer each grow to an InGaN layer, And forming each of the quantum well layer and the quantum barrier layer by changing the In composition of the InGaN layer at the same temperature. The method of claim 1, The first and second annealing, The method of growing an active layer of a light emitting device, characterized in that performed at a temperature higher than the temperature for growing the quantum well layer and the quantum barrier layer. The method according to any one of claims 1 to 3, And after performing the second step, performing the second step at least once more. A method of growing an active layer of a light emitting device having a structure in which an active layer is formed on an N semiconductor layer, and a P semiconductor layer is formed on the active layer, and light is emitted from the active layer by a current applied to the N semiconductor layer and the P semiconductor layer. To The active layer, A first step of sequentially growing a quantum barrier layer, a quantum well layer, a quantum barrier layer, a quantum well layer, and a quantum barrier layer on the N-type semiconductor layer; After the first step, to grow by performing a second step of performing an annealing (Annealing) process, After the active layer growth process, the active layer growth method of the light emitting device, characterized in that to grow a P semiconductor layer on the grown active layer. The method of claim 5, wherein The quantum well layer and the quantum barrier layer each grow to an InGaN layer, And forming each of the quantum well layers and the quantum barrier layers by changing the In composition of the InGaN layer at the same temperature. The method of claim 5, wherein The annealing is The method of growing an active layer of a light emitting device, characterized in that performed at a temperature higher than the temperature for growing the quantum well layer and the quantum barrier layer. The method according to any one of claims 5 to 7, Between the first and second steps, And growing the quantum well layer and the quantum barrier layer sequentially on the uppermost quantum barrier layer grown in the first step at least one or more times.

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