KR101189164B1 - Nitride light emitting device and method of nitride semiconductor - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nitride-based light emitting device and a method of manufacturing the nitride semiconductor thereof, and more particularly, to a manufacturing method of a light emitting device and a nitride-based light emitting device and a method of manufacturing the nitride semiconductor capable of improving the characteristics thereof. The present invention is characterized in that it comprises a step of growing a first conductive nitride semiconductor layer at a temperature of 800 to 1100 ℃ directly on the substrate in the manufacturing method of the nitride semiconductor.

LED, nitride, HVPE, light emitting device, semiconductor.

Description

Nitride light emitting device and method of manufacturing nitride semiconductor thereof

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nitride-based light emitting device and a method of manufacturing the nitride semiconductor thereof, and more particularly, to a manufacturing method of a light emitting device and a nitride-based light emitting device and a method of manufacturing the nitride semiconductor capable of improving the characteristics thereof.

Light Emitting Diodes (LEDs) are well-known semiconductor light emitting devices that convert current into light.In 1962, red LEDs using GaAsP compound semiconductors were commercialized, along with GaP: N series green LEDs. It has been used as a light source for display images of electronic devices, including.

The wavelength of light emitted by such LEDs depends on the semiconductor material used to make the LEDs. This is because the wavelength of the emitted light depends on the band-gap of the semiconductor material, which represents the energy difference between the valence band electrons and the conduction band electrons.

Gallium nitride compound semiconductors (Gallium Nitride (GaN)) have high thermal stability and wide bandgap (0.8 to 6.2 eV), which has attracted much attention in the development of high-power electronic components including LEDs.

One reason for this is that GaN can be combined with other elements (indium (In), aluminum (Al), etc.) to produce semiconductor layers that emit green, blue and white light.

In this way, the emission wavelength can be adjusted to match the material's characteristics to specific device characteristics. For example, GaN can be used to create a white LED that can replace the blue LEDs and incandescent lamps that are beneficial for optical recording.

Due to the advantages of these GaN-based materials, the GaN-based LED market is growing rapidly. Therefore, since commercial introduction in 1994, GaN-based optoelectronic device technology has rapidly developed.

The brightness or output of the LED using the GaN-based material as described above is large, the structure of the active layer, the light extraction efficiency to extract light to the outside, the size of the LED chip, the type and angle of the mold (mold) when assembling the lamp package , Fluorescent material and the like.

On the other hand, one of the reasons why the growth of GaN-based semiconductors is more difficult than other III-V compound semiconductors is that there are no high-quality substrates, that is, wafers made of materials such as GaN, InN, and AlN.

Therefore, the LED structure is grown on a heterogeneous substrate such as sapphire, and many defects are generated, and these defects have a great influence on the LED performance.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide a nitride based light emitting device including a high quality nitride semiconductor grown at a high temperature without a buffer layer on a substrate, and a method of manufacturing the nitride semiconductor.

As a first aspect for achieving the above technical problem, the present invention, in the method for manufacturing a nitride semiconductor, comprising the step of growing a first conductive nitride semiconductor layer directly on the substrate at a temperature of 800 to 1100 ℃ It features.

As a second aspect for achieving the above technical problem, the present invention relates to a nitride semiconductor having a flat stepped structure having a width of 0.1 μm or more using a Group 3/5 element in a method of manufacturing a nitride semiconductor. It characterized in that it comprises a step of growing directly on the substrate.

As a third aspect for achieving the above technical problem, the present invention is characterized by comprising a nitride-based light emitting device comprising a nitride semiconductor manufactured by the above-described method.

The present invention can grow a high quality thin film directly at a high temperature without forming a stress absorbing layer or a buffer layer at a low temperature, thereby eliminating the process of manufacturing a low temperature buffer layer, thereby simplifying the thin film growth process, and eventually There is an effect that can greatly save the time and cost of producing a thin film.

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

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. Rather, the intention is not to limit the invention to the particular forms disclosed, but rather, the invention includes all modifications, equivalents and substitutions that are consistent with the spirit of the invention as defined by the claims.

Like reference numerals denote like elements throughout the description of the drawings. In the drawings the dimensions of layers and regions are exaggerated for clarity. In addition, each embodiment described herein includes an embodiment of a complementary conductivity type.

It will be appreciated that when an element such as a layer, region or substrate is referred to as being present on another element "on," it may be directly on the other element or there may be an intermediate element in between . If a part of a component, such as a surface, is expressed as 'inner', it will be understood that this means that it is farther from the outside of the device than other parts of the element.

Furthermore, relative terms such as "beneath" or "overlies" refer to the relationship of one layer or region to one layer or region and another layer or region with respect to the substrate or reference layer, as shown in the figures. Can be used to describe.

It will be understood that these terms are intended to include other directions of the device in addition to the direction depicted in the figures. Finally, the term 'directly' means that there is no element in between. As used herein, the term 'and / or' includes any and all combinations of one or more of the recorded related items.

Although the terms first, second, etc. may be used to describe various elements, components, regions, layers, and / or regions, such elements, components, regions, layers, and / or regions It will be understood that it should not be limited by these terms.

These terms are only used to distinguish one element, component, region, layer or region from another region, layer or region. Thus, the first region, layer or region discussed below may be referred to as the second region, layer or region.

Embodiments of the present invention will be described with reference to a gallium nitride (GaN) based light emitting device formed on a nonconductive substrate such as, for example, a sapphire (Al ₂ O ₃ ) based substrate. However, the present invention is not limited to this structure.

Embodiments of the invention may use other substrates, including conductive substrates. Thus, combinations of AlGaInP diodes on GaP substrates, GaN diodes on SiC substrates, SiC diodes on SiC substrates, SiC diodes on sapphire substrates, and / or nitride based diodes on GaN, SiC, AlN, ZnO and / or other substrates may be included. have. Moreover, the present invention is not limited to the use of the diode region. Other forms of active area may also be used in accordance with some embodiments of the present invention.

A method of forming a nitride semiconductor using a hydride vapor phase epitaxy (HVPE) system uses a system in which a semiconductor is formed on a substrate using a gas containing a group V element through a metal III group element and another tube as a source.

One of the biggest challenges in the growth of nitride semiconductors (Al _x In _y Ga _{1 -x- y} N) is the growth of flat nitride semiconductor thin films due to the large differences in lattice constants and thermal expansion coefficients between sapphire and nitride semiconductors used as substrates. There is a big difficulty.

Therefore, the growth of the low temperature buffer layer was a necessary process for stress accommodation. Nitriding of the sapphire substrate with the growth of the low temperature buffer layer may improve crystallinity and surface shape.

These two processes were considered to be able to efficiently provide nucleation sites for heterogeneous growth of nitride semiconductors including GaN and to be essential for growing high quality nitride semiconductor thin films. Hereinafter, gallium nitride (GaN) will be described as an example of a nitride semiconductor.

In the GaN thin film grown on the buffer layer, nucleated islands grow in size and are partially aligned by the generation of edge-type treading dislocations in the process of combining these islands with each other.

Since no domain tilting is involved in the process of merging these islands, the flat top of each island is expected to be unobstructed and immediate surface smoothing is usually not well observed.

As described above, the direct growth of the GaN thin film without the low temperature nucleation layer is not practical, but recently it has been reported to grow a high quality GaN thin film without the buffer layer.

Surface morphology evolution and stress relaxation of the GaN thin film grown on the buffer layer are important and well understood, but the growth of the thin film without the low temperature nucleation layer has been overlooked with respect to the surface shape development and stress relaxation described above. There has been not enough research yet.

The present invention includes the results of surface shape development and stress relaxation when the GaN thin film is grown in the absence of a low temperature nucleation layer (buffer layer).

Surface shape development is observed to be significantly different than when grown on a low temperature buffer layer. In determining the surface shape development, it has been found that the shape of the penetrating dislocation occurring in the process of combining islands plays a very important role. Very interestingly, it was observed that the stress had already been sufficiently relaxed before the nucleated islands merged.

<Examples>

In the exemplary embodiment of the present invention, as shown in FIG. 1, a hydride vapor phase epitaxy (HVPE) system is used, a Ga group is used as the Group III element, and NH ₃ is used as the Group V element. ) And a nitride semiconductor (Al _x In _y Ga _{1- x- y} N) is grown. Inert gas may be used as the carrier gas of Ga metal, and gallium nitride may be manufactured using N ₂ , H ₂ , Argon gas, or the like.

0) 방향으로 0.3°어긋나게 잘린 기판을 이용하였고, 캐리어(carrier) 가스로는 N₂ 가스가 이용되었다. At this time, a horizontal crystal reactor 10 is heated by five crucibles. The c-plane sapphire substrate 100 has an M-plane (10

Substrate cut by 0.3 ° in the direction of 0) was used, and N ₂ gas was used as a carrier gas.

The reactor 10 includes a first connecting pipe 30 which is a moving path of a carrier gas of Ga connected to the vessel 20 including Ga and a second connecting pipe 40 which is a moving path of an NH ₃ gas. ) Is connected. An exhaust port 50 is provided at the other side of the reactor 10 to which the connection pipes 30 and 40 are connected.

The sapphire substrate 100 and the two gallium (Ga) vessels 20 were heated to 1050 ° C. (or 1100 ° C.) and 850 ° C., respectively, and the flow rates of NH ₃ and HCl were 3 standard liter per minute (SLM) and 40 SCCM (standard cubic centimeter per minute at STM).

Each region of the crucible was maintained at a uniform temperature, and the substrate 100 was charged to the growth section by a quartz rod arm. The temperature of the sample can be accurately measured by a thermo-couple located under the sample holder.

Since the substrate 100 has a low heat capacity, the temperature quickly rises to the growth temperature within 4 minutes as soon as it is charged. The mixed source gas may be controlled at variable time intervals by a gas valve. However, in this embodiment the valves were controlled to open at the same time.

In practice, the valves were controlled so that NH ₃ gas was supplied 23 seconds (or 30 seconds) before Ga, because the time taken for each reaction gas to enter the reactor after the valve was different.

In this embodiment, the source gas is supplied at a high temperature so the low temperature nucleation layer may not be present in any form.

It may be important to simultaneously control the valves of HCl and NH ₃ gas to obtain the results of this example. If the valves are not controlled simultaneously, the surface shape can vary. After growth, the sample is taken out using a quartz loading arm.

X-ray diffraction measurements were performed on the 3C2 beamline of the light source in the Pohang Accelerator Laboratory.

2 to 13 are secondary electron images (SEIs) images of the GaN surface with the growth time. 2 is an image with a growth time of 5 seconds, FIG. 3 is 10 seconds, FIG. 4 is 15 seconds, FIG. 5 is 30 seconds, FIG. 6 is 45 seconds, FIG. 7 is 1 minute, and FIG. 8 is 1 minute 30 seconds. 9 shows an image in which the growth time is adjusted to 2 minutes, 10 minutes to 3 minutes, FIG. 11 to 4 minutes, FIG. 12 to 5 minutes, and FIG. 13 to 10 minutes.

Looking at the surface of the GaN thin film with growth time, it can be seen that a smooth surface can be obtained after a certain time. In the early stages, a large number of nucleated grains (islands) occur, but they can be merged over time and form a smooth surface on their own after 5 to 10 minutes.

From this series of images there are some notable things:

First, nucleated islands with initially flat tops are fused, but the surface is not immediately smoothed. Several steps of different surface morphologies result in a race-and-step structure. On the other hand, fused islands in thin films grown on the buffer layer almost immediately become flat surfaces.

As can be seen from the atomic force microscopy image shown in FIG. 14, in the case of a sample having a flat surface grown for 10 minutes or more, it is usually 0.1 μm although there is a slight difference depending on the degree of miscutting of the substrate. It can be seen that a flat stepped terrace having the above width is formed.

Second, pyramidal islands are formed and the surface roughness is greatly increased during the intermediate process from FIG. 4 to FIG. 8. Referring to Figure 2 and the shape of the islands observed in Figures 4 to 8 can be seen the following differences. That is, in FIG. 2, the islands are hexagonal columns (which can be clearly seen through a plan view not attached here) or pyramids in FIGS. 4 to 8.

The change in island shape can be understood to be due to the changing V / III ratio due to the gas mixing process of the reaction gases.

15 shows the actual supply cycle of NH ₃ and GaCl. As mentioned above, NH ₃ reaches the reactor 23 seconds faster than GaCl. In FIG. 15, the gas supply is shown in a stepped function form, but there is residual gas in the reactor for some time even after the NH ₃ gas valve is closed.

As a result, in the first three samples, NH ₃ and GaCl are partially mixed rather than completely mixed. Considering the constant disappearance time of NH ₃ in the reactor, the V / III ratio of the sample grown for 5 seconds in FIG. 2 is smaller than that for the sample grown for 15 seconds in FIG.

It has been reported that high growth temperatures and low V / III ratios increase the lateral growth rate in HVPE. And the change in island shape depends on the lateral growth dependence on the V / III ratio.

At this time, even if NH ₃ gas is first injected for about 30 seconds, or GaCl and NH ₃ simultaneously reach the substrate, there is no significant difference in the surface shape of the GaN thin film.

The various developments of the surface shape observed when growing a GaN thin film on the buffer layer may be characterized by the fact that the surface does not suddenly become smooth for the fusion of the nucleated islands in the steps of FIGS. 3 and 4.

As shown in FIG. 16, the full width at half maximum (FWHM) of the (002) sample is the maximum in the sample grown for 10 seconds and gradually decreases. However, in the case of 102 it simply decreases.

As can be seen from FIGS. 2, 3, and 16, the half width of the Bragg peak of the (002) sample is sensitive to screw or mixed type penetration potential, and (102) Since the half width of the Bragg peak of the sample is sensitive to the screw or edge type penetration potential, the density of the screw or mixed penetration potential increases greatly when the nucleated islands are fused, but the edge type penetration potential does not increase. .

Therefore, the inability to sharply surface in island fusion may contribute to domain tilting by a sharp increase in screw-type or mixed penetration potential since the surface may be affected when domain tilting occurs.

On the other hand, for GaN thin films grown on the buffer layer, edge-type through dislocations are mainly formed by twisting when islands are fused. In this case the flat upper surface of the initial nucleated islands is not significantly affected and the fusion leads to a sharply flat surface.

On the other hand, let's take a look at how stress is relaxed and how much is relaxed without additional buffer layer.

The stress of initially nucleated islands from X-ray diffraction measurements is fully relaxed before the islands are fused (the height of the nucleated islands grown for 5 seconds is approximately 20 nm).

It can be seen from FIG. 17 that a highly disordered layer is formed near the interface, and thus stress is effectively alleviated even if no intentional buffer layer is inserted.

Unlike a thin film grown on a low temperature buffer layer, no sharp softening of the surface is observed when the islands fuse, whereas the three-dimensional islands become a terrace-and-step structure in surface shape development. It develops through several intermediate stages.

The large number of screw or mixed penetration potentials occurring during island fusion appears to play an important role in the regional development of surface features.

With disordered layers formed simultaneously, the stress is fully relaxed before the nucleated islands are fused.

The GaN semiconductor layer formed as described above may be formed of the n-type semiconductor layer 110 including an n-type dopant to be manufactured as a light emitting device, as shown in FIG. 18.

The n-type semiconductor layer 110 formed directly on the substrate 100 may have a thickness of 0.1 to 5 μm, and the active layer 120 and the p-type semiconductor layer are formed on the n-type semiconductor layer 110. 130 may be included.

On the other hand, such a light emitting device structure may have a different position. That is, the p-type semiconductor layer 130 may be formed first, and then the active layer 120 and the n-type semiconductor layer 110 may be formed.

The light emitting device structure formed as described above may be used as a light emitting device by forming an electrode through an appropriate process later. Such a light emitting device structure may have a side, vertical, or flip chip bonded structure.

The above embodiment is an example for explaining the technical idea of the present invention in detail, and the present invention is not limited to the above embodiment, various modifications are possible, and various embodiments of the technical idea are all protected by the present invention. It belongs to the scope.

1 is a schematic diagram illustrating an HVPE system.

2 to 13 are images showing the surface of the GaN thin film grown with different growth times, respectively.

14 is a photograph showing the surface of a GaN thin film grown for 10 minutes.

15 is a graph showing the supply period of the source gas in the HVPE system.

16 is a graph showing the full width at half maximum of a thin film with growth time.

17 is an image showing the interface of the GaN thin film.

18 is a cross-sectional view showing an example of a light emitting element structure.

Claims (9)

In the method of manufacturing a nitride semiconductor, On the sapphire substrate cut off against any one of the crystal planes, using a Group 3/5 element at a temperature of 800 to 1100 ° C., it has a surface characteristic having a flat step structure having a width of 0.1 μm or more and stress relief. A method of manufacturing a nitride semiconductor, comprising the step of growing a first conductive nitride semiconductor layer. The method of manufacturing a nitride semiconductor according to claim 1, wherein the nitride semiconductor layer is grown by HVPE. The method of manufacturing a nitride semiconductor according to claim 1, wherein the nitride semiconductor layer is an n-type semiconductor layer. The method of manufacturing a nitride semiconductor according to claim 1, wherein the nitride semiconductor layer has a thickness of 0.1 to 5 m. The method of claim 1, wherein the growing of the nitride semiconductor layer, Forming nucleation grains on the substrate; And And nucleating the granules in a state in which stress is completely relaxed to planarize. The method of manufacturing a nitride semiconductor according to claim 1, wherein the sapphire substrate is a C-plane sapphire substrate which is cut 0.3 degrees apart in the M-plane direction. The method of claim 1, wherein the source of growing the nitride semiconductor is NH ₃ and GaCl. The method of manufacturing a nitride semiconductor according to claim 1, wherein the sapphire substrate which is misaligned has a stepped surface. A nitride based light emitting device comprising a nitride semiconductor grown by the method of claim 1.

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