CN100389503C - Preparation method of LED chip with discrete grain vertical structure - Google Patents

Abstract

The invention provides a method for preparing an LED with high light power, which is characterized in that a tube core shape design with high light emitting efficiency is provided, an LED chip with discrete crystal grains is grown through the epitaxial growth of an LED in an island region, and the discrete LED chip is packaged into a vertical structure with upper and lower electrodes after laser stripping. In the epitaxial growth process of the island-shaped region of the epitaxial layer of the discrete crystal grain LED, the dislocation density in the epitaxial layer is reduced and the crystal quality is improved due to the improvement of stress distribution, so that the quantum efficiency in the LED is improved. The shape of the island-shaped area is designed, so that the geometric shape of the grown crystal grains is polygonal and circular which are suitable for light guide, and the light power of the LED is improved. The island-shaped region growth is beneficial to releasing stress, the stress generated by laser irradiation at the interface of the GaN substrate and the sapphire substrate is reduced in the laser stripping process, the damage in the stripping process is reduced, the movement of the luminous spectrum of the LED before and after stripping due to stress change is reduced, and the high-performance LED is obtained by stripping the substrate.

Description

Preparation method of LED chip with discrete grain vertical structure

technical field

The invention belongs to the field of optoelectronic technology, and specifically relates to a method for preparing a power-type semiconductor light-emitting diode (LED) chip in combination with metal organic chemical vapor deposition (MOCVD) epitaxial growth technology, laser lift-off and reverse packaging technology. The invention proposes a method for directly obtaining discrete grain LED chips through growth, provides a new way for the geometric design of the LED chip not to be limited by the post-process of the LED chip, and is suitable for the preparation of new-type and high-power LEDs.

Background technique

Usually, LED is obtained by epitaxial growth on the substrate, thus, the preparation of LED is restricted by the crystal lattice structure of the substrate. The differences in lattice mismatch and thermal expansion coefficient cause a large number of dislocations due to the accumulation and release of stress in the chip epitaxial layer during the epitaxial growth stage, especially for the GaN-based LED epitaxial layer on the sapphire substrate, the dislocation density is as high as 10 ¹¹ /cm ² fundamentally restricts the further improvement of LED power. In terms of light extraction, due to the difference between the refractive index of the semiconductor and the refractive index of air, the efficiency of light output from the semiconductor is suppressed, and the absorption of the semiconductor material on the light output surface and the absorption of the metal electrode layer cannot be ignored. In addition, the heat dissipation of the substrate also greatly affects the characteristics of power LEDs. The above three aspects have become the main factors affecting the optical power of power semiconductor LED chips.

The post-process of chip preparation - the LED shape and yield obtained by slicing and splitting are also generally affected by the crystal structure on the substrate. For GaN-based devices on sapphire substrates, the shape of the chip is limited because the cleavage plane of sapphire is different from that of the GaN epitaxial layer, which restricts the geometrical design of the die that is conducive to light extraction. In addition, the use of difficult-to-process substrates increases the cost of chip fabrication.

At present, there are many reports on the research results of reducing the dislocation density in the epitaxial layer and improving the crystal quality, mainly for the selective lateral epitaxial growth technology (LEO) and the transition layer growth technology. Japan's Nakamura Shuji and others used lateral epitaxy technology to reduce the threading dislocation density originating from the substrate by two orders of magnitude. Japan's KazuyukiTadatomo et al. prepared LED research reports from LED epitaxial layers grown on patterned substrates, and the dislocation density decreased. It is one-third of the conventionally grown epitaxial wafer, while the LED optical power is increased by nearly five times, and the external quantum efficiency reaches 24%. M.Iwaya et al. from the research group of Isamu Akasaki, Meijo University, Japan reported that the low-temperature AIN insertion layer can release the tensile stress , obtained a good result that the density of dark spots corresponding to dislocations on the epitaxial wafer was reduced to 2×10 ⁷ cm ^-2 ; various buffer layer structures reported by T.Wang et al. and CCYang et al. The results for etch pit densities on the order of 10 ⁶ cm ^-2 indicate a significant increase in crystal quality, and good results were obtained for a substantial increase in the power of ultraviolet light-emitting diodes (UVLEDs).

For the heterogeneous growth of GaN-based materials, although the mechanism of lateral epitaxy (LEO) and transition layer growth technology can improve the crystal quality is still unclear, but it cannot be ruled out that the stress change during the growth process is a Key factor.

Using laser lift-off technology to lift off the sapphire substrate to prepare GaN-based LEDs with vertical electrode structures has become a development direction worthy of attention. Japan's Nichia and Germany's Osram have already introduced equipment related to this technology. At the same time, since the LED with the inverted package structure avoids the absorption of the P electrode and P-GaN, and uses the sapphire surface with a lower refractive index than GaN to emit light, it has been proved that the optical power can be significantly increased, even without peeling off the sapphire substrate. Increase the optical power by more than 1.5 times. The results reported by J.J.Wierer et al. of Lumileds Lighting in the United States and the patent US6573537 B1 proposed by Daniel Steigerwald et al. indicate that the light extraction efficiency of the flip chip is increased by 1.6 times.

JTShu in Taiwan, China, carried out the method of HVPE island-like selective growth of LEDs, and observed that the etch pit density (EPD) in the island-like growth region was 1-5×10 ⁷ cm ^-2 , indicating that the island-like epitaxial growth has obtained a good Crystal quality, and at the same time the shape of the LED is made into a hexagon, so that the light power of the LED is twice that of the conventional non-island-shaped square LED.

Therefore, the use of growth methods to improve crystal quality, combined with flip-packaging, and the preparation of vertically structured LEDs is the main direction for improving the optical power of LEDs.

On the basis of the above research, this invention proposes a different way to change the stress distribution in the epitaxial growth process to reduce the dislocation density and improve the crystal quality, that is, MOCVD island growth, combined with high light efficiency tube core shape design and laser lift-off technology, obtained Simple, effective new approach to high-power LED chips.

Contents of the invention

The purpose of the present invention is to propose a tube core shape design combined with high light extraction efficiency, through the epitaxial growth of LEDs in island-shaped regions, to grow discrete grain LED chips, and to package the discrete LED chips into a vertical structure with upper and lower electrodes after laser stripping. Process for the preparation of LEDs with higher optical power.

During the epitaxial growth process of the discrete grain LED epitaxial layer, due to the improvement of the stress distribution, the dislocation density in the epitaxial layer is reduced, and the crystal quality is improved, thereby improving the internal quantum efficiency of the LED.

The shape of the island-like region is designed so that the geometric shape of the crystal grains obtained by growth is a polygon or a circle suitable for light export, so as to increase the optical power of the LED.

Since the growth of the island-shaped region is conducive to the release of stress, the stress at the interface between GaN and sapphire substrate due to laser irradiation is reduced during the laser lift-off process, the damage during the lift-off process is reduced, and the light-emitting spectrum of the LED before and after lift-off is reduced due to stress. The movement occurs to ensure that the substrate is peeled off to obtain a high-performance LED.

Traditional LED preparation methods are MOCVD epitaxial growth, electrode preparation, epitaxial wafer thinning, and splitting to obtain chips. In the present invention, discrete LED crystal grains are obtained during epitaxial growth, and LED chips can be obtained only by removing the substrate and electrode preparation by laser stripping. Compared with the advanced technology, the post-process is reduced and the cost is reduced.

The method for obtaining vertical structure LEDs with discrete grains by epitaxial growth in island-like regions proposed by the invention has simple process and is easy to implement, and is an effective way to improve the efficiency of light-emitting diodes.

Since this method combines laser lift-off technology to peel off the sapphire substrate and prepare a vertical LED chip, and the shape of the chip is designed to be circular and polygonal, it has a significant difference with the LED chip method obtained by island growth reported by J.T.Shu et al. different.

The preparation method of the discrete grain vertical structure light-emitting diode of the present invention has the following key points:

1. Epitaxial growth of discrete grain LED epitaxial layers in the island-like region is different from conventional whole-chip growth and lateral epitaxial growth, and the growth is limited to a certain area on the chip scale.

2. The stress distribution is improved during the growth process, a thicker epitaxial layer can be grown, the dislocation density in the epitaxial layer is reduced, and the crystal quality is improved.

3. During the laser lift-off process, the growth of the island-like region can reduce the stress at the interface between GaN and sapphire substrate due to laser irradiation, reduce the damage during the lift-off process, and reduce the shift of the LED light emission spectrum due to stress changes before and after lift-off , to ensure high performance LEDs are obtained by peeling off the substrate.

4. The geometry of the island-like area is a polygon and a circle suitable for the light to be derived from the tube core, thereby realizing the control of the shape and size of the tube core through growth, and overcoming the difficulty of obtaining polygonal and circular tube cores in post-processing. Core preparation offers a new avenue.

5. Discrete LED grains are obtained during epitaxial growth, and LED chips can be obtained only by laser stripping to remove the substrate and electrode preparation. LED chips can be obtained without thinning and dividing sapphire or GaN. Compared with the conventional LED process, the cost of the post-process is reduced and the cost is reduced.

According to the preparation method of the discrete grain vertical structure light emitting diode of the present invention, there are two specific technical solutions, and the specific steps of each technical solution are described in detail below:

The first preparation method of a light-emitting diode chip light-emitting diode with a vertical structure of discrete grains, the specific steps are as follows:

1. Deposit SiO ₂ on the sapphire substrate and etch the SiO ₂ to define the island growth area and geometry. The geometry of the growth zone is designed to favor light export polygons and circles.

2. On the substrate with SiO ₂ patterns, grow n-type GaN, LED active layer, and p-type GaN in sequence; the epitaxial wafer also needs to undergo conventional P-type activation annealing.

3. Prepare the electrode and reflective layer on p-GaN. The electrode metal must be able to obtain good ohmic contact. At the same time, it must also take into account that it has good adhesion to the reflective layer metal that acts as a reflective mirror. After deposition, it must pass through the alloy. The ohmic contact between p-GaN and p-GaN is obtained; the metal of the reflective layer is selected to be a metal with high reflectivity, good stability, good adhesion to the metal of the ohmic contact layer, and no adverse effect on the ohmic contact.

4. Bond the above-mentioned LED epitaxial wafer with P electrode on the Si or Cu support substrate with a metal layer, place it in a vacuum chamber to remove the air bubbles in the metal layer, and ensure that the island-shaped growth layer and the surface of the support substrate are uniform and free of voids The close contact of the support substrate is processed into a figure with the function of inducing lobes.

5. Laser lift-off removes difficult-to-process sapphire substrates. Since there is less bonding between GaN and the sapphire substrate, a lower energy laser beam can be used in laser lift-off, which reduces the damage to the crystal at the interface during the lift-off process. After the stripping is completed, the metal Ga on the surface of the epitaxial layer needs to be removed.

6. Complete the n-electrode preparation on the n-GaN surface; due to the requirements of the light-emitting surface, the n-electrode should occupy a smaller area as much as possible, and the electrode size is usually designed on the minimum required scale to ensure the bonding wire.

7. Separate the island-shaped growth region into an LED chip with a vertical electrode structure.

The second method of manufacturing a light-emitting diode chip light-emitting diode with a vertical structure of discrete grains, the specific steps are as follows:

1. Deposit SiO ₂ on the sapphire substrate and etch the SiO ₂ to define the island growth area and geometry. The geometry of the growth zone is designed to favor light export polygons and circles.

2. Using hydride vapor phase epitaxy (HVPE) technology to grow thick n-GaN epitaxial layer on the sapphire substrate.

3. On the substrate with thick n-GaN island growth layer, use MOCVD technology to secondary grow Si-doped GaN, LED active layer, and p-type GaN. The epitaxial wafer also needs to undergo conventional P-type activation annealing.

4. Prepare the electrode and reflective layer on p-GaN. The electrode metal must be able to obtain good ohmic contact. At the same time, it must also take into account that it has good adhesion to the reflective layer metal that acts as a reflective mirror. After deposition, it must pass through the alloy. The ohmic contact between p-GaN and p-GaN is obtained; the metal of the reflective layer is selected to be a metal with high reflectivity, good stability, good adhesion to the metal of the ohmic contact layer, and no adverse effect on the ohmic contact.

5. Bond the above-mentioned LED epitaxial wafer with P electrodes on the Si or Cu support substrate with a metal layer, place it in a vacuum chamber to remove the air bubbles in the metal layer, and ensure that the island-shaped growth layer and the surface of the support substrate are uniform and free of voids The close contact of the support substrate is processed into a figure with the function of inducing lobes.

6. Laser lift-off removes difficult-to-process sapphire substrates. Since there is less bonding between GaN and the sapphire substrate, a lower energy laser beam can be used in laser lift-off, which reduces the damage to the crystal at the interface during the lift-off process. After the stripping is completed, the metal Ga on the surface of the epitaxial layer needs to be removed.

7. Complete the n-electrode preparation on the n-GaN surface. Due to the requirements of the light-emitting surface, the n-electrode should occupy a smaller area as much as possible. Usually, the electrode size is designed on the minimum required scale to ensure the bonding wire.

8. Separate the island-shaped growth region into an LED chip with a vertical electrode structure.

The above two methods are also applicable to the preparation of the LED with the AlGaN electron blocking layer in the epitaxial layer.

Description of drawings

Below in conjunction with accompanying drawing, the present invention is described in further detail:

Figure 1 Plane geometry structure of island growth;

Figure 2 n-type electrode plan view;

Figure 3(a)-(g) are the fabrication process of LED chips with vertical structure of discrete grains;

Figure 4(a) and (b) respectively show the relationship between the reflectivity of Al and Ag and the film thickness.

DETAILED DESCRIPTION OF THE BEST EMBODIMENTS

The preferred embodiment of the present invention is described in more detail below with reference to the accompanying drawings of the present invention.

Figure 3 (a) to (f) shows the process of manufacturing discrete grain vertical structure light-emitting diode chips. In the figure 1 represents a sapphire substrate or a substrate with a GaN growth layer, 2 represents SiO ₂ , and 3 represents LED Epitaxial wafer, 4 is a transparent electrode (Ni/Au), 5 is a reflective layer, 6 is a supporting substrate (Si or Cu), and 7 is a bonding metal (Au-Sn alloy). Below in conjunction with accompanying drawing, describe preferred embodiment one concrete steps in detail:

(a) Deposit SiO ₂ 2 on the sapphire substrate 1 and etch the SiO ₂ 2 to define the island growth area and geometry. The size of the growth area is the size of the LED device, and the geometry of the growth area is polygonal and circular, which are conducive to light export. Figure 1 illustrates rectangles, hexagons and circles;

(b) On the substrate obtained in step (a), use MOCVD technology to grow the LED epitaxial layer, and perform P-type activation annealing.

)/Au()，然后在氧气氛中500℃下合金5分钟。(c) Evaporate a transparent electrode 4 on the surface of the GaN-based LED epitaxial wafer 3p, with a structure of Ni(

)/Au( ), and then alloyed at 500°C for 5 minutes in an oxygen atmosphere.

)/Ni(

)/Au(

)反射层5。反射层5中高反射率金属可以为Al或Ag，对应波长，可根据厚度与反射率关系进行调整。图4所示为对应于不同波长，Al层厚度和Ag层厚度与反射率的关系曲线图。(d) Evaporate Ni on the transparent electrode ( )/Al(

)/Ni(

)/Au(

) reflective layer 5. The metal with high reflectivity in the reflective layer 5 can be Al or Ag, and the corresponding wavelength can be adjusted according to the relationship between thickness and reflectivity. FIG. 4 is a graph showing the relationship between Al layer thickness and Ag layer thickness and reflectivity corresponding to different wavelengths.

(e) SiO ₂ insulating layer is prepared on Si or Cu supporting substrate, Au-Sn alloy or other metal layer 7 that can be used for bonding is evaporated, and placed in a vacuum chamber to remove the bubbles in the metal layer 7 to ensure the island shape The growth layer is in uniform and close contact with the surface of the support substrate without voids, and the support substrate is processed into a pattern and structure that can induce lobes.

(f) The LED epitaxial wafer is bonded to the Si substrate or the copper substrate 6 at a temperature of about 300°C or lower.

(g) Use a KrF excimer laser to irradiate from the side of the sapphire substrate and peel off the sapphire substrate. The laser wavelength is 248nm, the irradiation energy density is 400-600mJ/cm ² , and the scanning frequency is 1Hz; after the peeling is completed, the metal on the surface of the epitaxial layer needs to be removed Ga.

/Al 

/Ti 100～

/Au 

(h) Evaporate the n-electrode metal on the n-GaN surface, and obtain the n-electrode after pattern stripping; Figure 3 shows the plan view of the n-type electrode, and the electrode structure in the figure is Ti

/Al

/Ti 100～

/Au

(i) separating the island-shaped growth region, and obtaining a high-power LED chip with a vertical electrode structure. The technical scheme of the best embodiment two is as follows, and the concrete steps of the present embodiment are illustrated with reference to Fig. 3:

(a) Deposit SiO ₂ 2 on the sapphire substrate 1 and etch the SiO ₂ 2 to define the island growth area and geometry. The size of the growth area is the size of the LED device, and the geometric shape of the growth area is polygonal and circular, which are favorable for light export. Figure 1 illustrates rectangle, hexagonal and circular.

(b) On the substrate obtained in step (a), a thick n-GaN epitaxial layer is grown on the sapphire substrate by using hydride vapor phase epitaxy (HVPE) technology to obtain an island-shaped n-type GaN substrate.

(c) On the island-shaped GaN substrate obtained in step (b), use MOCVD technology to re-grow Si-doped GaN, LED active layer, and p-type GaN, and the epitaxial wafer is also subjected to conventional P-type activation annealing.

)/Au(

)，然后在氧气下500℃下合金5分钟。(d) Evaporate a transparent electrode 4 on the p-side of the GaN-based LED epitaxial wafer, with a structure of Ni(

)/Au(

), and then alloyed at 500°C for 5 minutes under oxygen.

)/Al(

)/Ni()/Au(

)反射层5。反射层5中高反射率金属可以为Al或Ag，对应波长，可根据厚度与反射率关系进行调整。图4所示为对应于不同波长，Al层厚度和Ag层厚度与反射率的关系曲线图。(e) Evaporate Ni on the transparent electrode (

)/Al(

)/Ni( )/Au(

) reflective layer 5. The metal with high reflectivity in the reflective layer 5 can be Al or Ag, and the corresponding wavelength can be adjusted according to the relationship between thickness and reflectivity. FIG. 4 is a graph showing the relationship between Al layer thickness and Ag layer thickness and reflectivity corresponding to different wavelengths.

(f) Prepare SiO ₂ insulating layer on Si or Cu supporting substrate 1, vapor-deposit Au-Sn alloy or other metal layer 7 that can be used for bonding, and place it in a vacuum chamber to remove the bubbles in the metal layer 7 to ensure that the island The uniform growth layer is in close contact with the surface of the support substrate without voids, and the support substrate is processed into patterns and structures that can induce lobes 6 .

(g) The LED epitaxial wafer is bonded to the Si substrate or the copper substrate 6 at a temperature of about 300°C or lower.

(h) Use a KrF excimer laser to irradiate from the side of the sapphire substrate and peel off the sapphire substrate. The laser wavelength is 248nm, the irradiation energy density is 400-600mJ/cm ² , and the scanning frequency is 1Hz; after the peeling is completed, the metal on the surface of the epitaxial layer needs to be removed Ga.

/Al /Ti 100～

/Au  (i) Evaporate the n-electrode metal on the surface of n-GaN, and obtain the n-electrode after pattern stripping; Figure 3 shows the plan view of the n-type electrode, and the electrode structure in the figure is Ti

/Al /Ti 100～

/Au

(j) separating the island-shaped growth region, and obtaining a LED chip with a high-power vertical electrode structure.

In the above two preferred embodiments of the preparation method of the light-emitting diode chip corresponding to the two kinds of discrete grain vertical structures, adding an AlGaN electron blocking layer or performing other growths in the epitaxial growth step will obtain an AlGaN electron blocking layer or Light-emitting diode chips with a vertical discrete grain structure of other epitaxial structures can implement the technical solutions described above for the preparation method of a light-emitting diode chip with a vertical discrete grain structure.

The advantage of this invention:

(1) Epitaxial growth of discrete grain LED epitaxial layers in island-shaped regions, which is different from conventional whole-chip growth and lateral epitaxial growth, limits the growth area to the chip scale, and obtains high-quality island-shaped LED epitaxial layers of chip size.

(2) Stress distribution is improved during the growth process, a relatively thick epitaxial layer can be grown, the dislocation density in the epitaxial layer is reduced, the crystal quality is improved, and the LED luminous efficiency is improved.

(3) Directly implement a process close to that of ordinary GaN-based LED growth on the island-shaped pattern substrate, which is easy to achieve mass production;

(4) During the laser lift-off process, the growth of island-like regions can reduce the stress at the interface of GaN and sapphire substrate due to laser irradiation, reduce the damage during the lift-off process, and reduce the occurrence of LED luminescence spectra due to stress changes before and after lift-off. Move to ensure high performance LEDs from the substrate peeled off.

(5) The geometry of the island-like area is a polygon and a circle suitable for the light to be derived from the die, so that the shape and size of the die can be controlled through growth, and the difficulty of obtaining a polygonal and circular die through post-processing is overcome. Die preparation offers a new avenue.

(6) Discrete LED grains are obtained during epitaxial growth, and LED chips can be obtained only by laser stripping to remove the substrate and electrode preparation, and LED chips can be obtained without thinning and dividing sapphire or GaN. Compared with the conventional LED process, the cost of post-process is reduced, and the cost is reduced.

(7) The p-type reflective layer adopts a high-reflectivity Al composite layer structure to improve the light extraction efficiency of the chip.

The invention provides a new method for GaN-based high-power light-emitting devices, and is especially significant for short-wavelength light-emitting diodes. The LED prepared by this method has a vertical electrode structure with the potential to become the mainstream, so the optical power and thermal characteristics are good, and the optical power will be further improved due to the use of a tube core shape (circular, polygonal) that is conducive to light emission. Compared with the currently reported method for improving the light extraction efficiency, the LED chip preparation process involved in the present invention is simple, which is conducive to the realization of industrialization.

Although the preferred embodiment and drawings of the present invention have been disclosed for illustrative purposes, those skilled in the art will understand that various alternatives, changes and modifications can be made without departing from the spirit and scope of the present invention and the appended claims. It's all possible. Therefore, the present invention should not be limited to what is disclosed in the preferred embodiments and drawings.

Claims (10)

1. the LED preparation method of a separate crystal grain vertical structure specifically may further comprise the steps:

1) deposit SiO on Sapphire Substrate ₂, and etching SiO ₂To limit island growth zone and geometry;

2) at etching SiO ₂The back forms on the substrate of figure growing n-type GaN, LED active layer, p type GaN successively, and epitaxial wafer also will carry out conventional P type and activate annealing;

3) preparation electrode and reflector on p-GaN;

4) utilize metal level to be bonded on Si or the Cu support substrates the above-mentioned P of having electrode LED epitaxial wafer,

Be placed on and take bubble in the metal level in the vacuum chamber away;

5) laser lift-off is removed Sapphire Substrate;

6) on the n-GaN face, finish the n electrode preparation;

7) separating the island growth district is the led chip of vertical electrode structure.

2. the LED preparation method of separate crystal grain vertical structure according to claim 1, it is characterized in that: support substrates is processed into and helps figure and the structure that chip is cut apart.

3. the LED preparation method of separate crystal grain vertical structure according to claim 1 is characterized in that: at island areas utilization metal organic-matter chemical vapor deposition techniques growth separate crystal grain LED epitaxial loayer.

4. the LED preparation method of separate crystal grain vertical structure according to claim 1 and 2 is characterized in that: etching SiO ₂Island growth zone and geometry are defined as circle or polygon.

5. the LED preparation method of separate crystal grain vertical structure according to claim 1 is characterized in that: the laser lift-off Sapphire Substrate, and to adopt the energy density of laser beam in stripping process be 400-600mJ/cm ²Between.

6. the LED preparation method of separate crystal grain vertical structure according to claim 1 is characterized in that: after laser lift-off removal Sapphire Substrate is finished, remove the metal Ga of epi-layer surface.

7. the LED preparation method of separate crystal grain vertical structure according to claim 1 is characterized in that: with growth technology growth AlGaN electronic barrier layer.

8. the LED preparation method of a separate crystal grain vertical structure specifically may further comprise the steps:

1) deposit SiO on Sapphire Substrate ₂, and etching SiO ₂To limit island growth zone and geometry;

2) grow thick n-GaN epitaxial loayer on Sapphire Substrate;

3) diauxic growth Si Doped GaN, LED active layer, p type GaN on the substrate that has thick n-GaN island growth layer, epitaxial wafer also will carry out conventional P type and activate annealing;

4) preparation electrode and reflector on p-GaN;

5) utilize metal level to be bonded on Si or the Cu support substrates the above-mentioned P of having electrode LED epitaxial wafer,

Be placed on and take bubble in the metal level in the vacuum chamber away;

6) laser lift-off is removed Sapphire Substrate;

7) on the n-GaN face, finish the n electrode preparation;

8) separating the island growth district is the led chip of vertical electrode structure.

9. the LED preparation method of separate crystal grain vertical structure according to claim 8 is characterized in that: at first adopt the thick n-GaN epitaxial loayer of hydride gas-phase epitaxy technology growth in the island growth zone.

10. the LED preparation method of separate crystal grain vertical structure according to claim 8 is characterized in that: on the substrate that has thick n-GaN island growth layer, use the metal organic chemical vapor deposition growth technology, diauxic growth LED epitaxial structure.

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