CN104347775B - LED chip with graphical N electrode - Google Patents

Abstract

This patent invention relates to an LED chip with a patterned N electrode. Since a barrier layer with extremely weak light reflection is formed at the edge area between the LED chips, the N electrode is extended to the top of the barrier layer. On the one hand, due to the expansion of the N electrode On the barrier layer with extremely weak light, it does not affect the reflection efficiency of the mirror; on the other hand, the expanded N electrode can make the current distribution more uniform, and improve the uniformity of the light emission and heat dissipation of the LED chip.

Description

LED chips with patterned N electrodes

technical field

The invention relates to the field of LED manufacturing, in particular to an LED chip with patterned N electrodes.

Background technique

With the gradual application of LEDs in the field of lighting, the market has higher and higher requirements for the light efficiency of white LEDs. GaN-based vertical structure LEDs have good heat dissipation capabilities and can withstand large current injections. Such a vertical structure LED chip can be equivalent to several The conversion cost is only a fraction of the formal structure chip. Therefore, GaN-based vertical structure LEDs are the direction of the market and an inevitable trend in the development of semiconductor lighting. Compared with the traditional planar structure LED, the vertical structure LED has many advantages: the two electrodes of the vertical structure LED are on both sides of the LED, the current almost all flows vertically through the epitaxial layer, there is no lateral flow of current, the current distribution is uniform, and the resulting The heat is reduced; the sapphire substrate with poor thermal conductivity is removed by bonding and stripping, and replaced with a substrate with good electrical conductivity and high thermal conductivity, which can effectively dissipate heat; the n-GaN layer is the light-emitting surface, which has A certain thickness is convenient for making surface microstructures to improve light extraction efficiency. In short, compared with the traditional planar structure, the vertical structure has obvious advantages in light extraction and heat dissipation.

With the rapid development of semiconductor technology, the internal quantum efficiency of LED can reach more than 90%, while the improvement of external quantum efficiency is not significant, which is affected by many factors, such as LED structure, electrode shape, electrode material, current spreading layer thickness, etc. , has become the dominant factor restricting the improvement of LED luminous efficiency. Compared with other methods to improve LED brightness (such as high reflective film, substrate peeling, surface roughening, etc.), the easiest to operate is to optimize the electrode shape of the chip, which has a great influence on the light output. If the current Insufficient and uneven diffusion will lead to a decrease in light output, and the luminous efficiency of the LED can be improved by rationally designing the shape of the electrode.

In theory, the farther away from the electrode, the smaller the current and the lower the brightness. For the existing vertical electrode structure technology, it is traditionally believed that the I-V performance of LED chips with electrode shapes in the shape of "ten" or "m" is the best. However, the "ten" or "m"-shaped electrodes are in the center of the chip. Since the electrodes are relatively concentrated, the current is also relatively concentrated, which leads to uneven distribution of LED current, especially to the edge of the table. The current distribution is extremely uneven, making The brightness of the edge part is very small. Around the central circular electrode and near the fingers, the current is crowded, and at the edge of the chip, the current is small. The current trend is getting smaller and smaller from the middle to the edge, and the brightness is getting weaker and weaker.

Generally, when making vertical structure LEDs, metal silver is usually used as the reflector, but due to the easy diffusion of Ag, a barrier layer (barrier) will be made to wrap the reflector, and there will be about 5 μm to 10 μm around each chip without reflection layer (as shown in Figure 1), in Figure 1, reflector 20 is surrounded by barrier layer 10, because reflector 20 is used for reflecting light, and barrier layer 10 is due to material limitation, and reflected light is extremely weak, causes this region to reflect light A large part of the loss, and after the general "ten" or "m" shaped N electrode is evaporated, the current distribution in this area is not uniform, and the contribution to light emission is also greatly reduced.

Contents of the invention

The purpose of the present invention is to provide an LED chip with a patterned N electrode, which can utilize the defect of weak light reflection of the edge barrier layer to form an N electrode on it, so as to make the current distribution more uniform and improve the luminous efficiency.

In order to achieve the above object, the present invention proposes a LED chip with a patterned N electrode, including: a reflector, a barrier layer, an epitaxial layer and an N electrode, the reflector is formed in the barrier layer and exposes the reflector The epitaxial layer is formed on the surface of the mirror and the barrier layer, the N electrode is formed on the surface of the epitaxial layer, the N electrode includes a central region and fingers, and a part of the fingers are formed on On the surface of the epitaxial layer directly above the barrier layer, the insert fingers completely or partially cover directly above the barrier layer, and the insert fingers are connected to the central region.

Further, the epitaxial layer includes P-GaN, quantum wells and N-GaN formed in sequence, the P-GaN is formed on the surface of the mirror and the barrier layer, and the N electrode is formed on the N- GaN surface.

Further, the insert fingers are elongated and arranged point-symmetrically along the central area.

Further, the insertion fingers form a square or an octagon.

Further, the width range of the insert fingers is 3 μm˜10 μm.

Further, the central area is circular or polygonal.

Further, when the central region is circular, the diameter of the central region ranges from 50 μm to 120 μm; when the central region is polygonal, the side length of the central region ranges from 30 μm to 100 μm.

Further, the material of the N electrode is one or more of Cr, Al, Ti, Pt, Au.

Compared with the prior art, the beneficial effects of the present invention are mainly reflected in: since the barrier layer with extremely weak light reflection is formed at the edge area between the LED chips, the N electrode is extended to the top of the barrier layer, on the one hand, because the N electrode The expansion on the barrier layer with extremely weak reflection does not affect the reflection efficiency of the mirror; on the other hand, the expanded N electrode can make the current distribution more uniform and improve the uniformity of the LED chip's light emission and heat dissipation.

Description of drawings

FIG. 1 is a schematic structural view of a barrier layer surrounding a reflector in the prior art;

2 is a top view of the N electrode of the LED chip in the first embodiment of the present invention;

Fig. 3 is a schematic sectional view along A-A' in Fig. 2;

Fig. 4 is a top view of the N electrode of the LED chip in the second embodiment of the present invention.

detailed description

The LED chip with patterned N electrodes of the present invention will be described in more detail below in conjunction with schematic diagrams, wherein a preferred embodiment of the present invention is represented, and it should be understood that those skilled in the art can modify the present invention described here and still implement the present invention. Beneficial effects of the invention. Therefore, the following description should be understood as the broad knowledge of those skilled in the art, but not as a limitation of the present invention.

In the interest of clarity, not all features of an actual implementation are described. In the following description, well-known functions and constructions are not described in detail since they would obscure the invention with unnecessary detail. It should be appreciated that in the development of any actual embodiment, numerous implementation details must be worked out to achieve the developer's specific goals, such as changing from one embodiment to another in accordance with system-related or business-related constraints. Additionally, it should be recognized that such a development effort might be complex and time consuming, but would nevertheless be merely a routine undertaking for those skilled in the art.

In the following paragraphs the invention is described more specifically by way of example with reference to the accompanying drawings. Advantages and features of the present invention will be apparent from the following description and claims. It should be noted that all the drawings are in a very simplified form and use imprecise scales, and are only used to facilitate and clearly assist the purpose of illustrating the embodiments of the present invention.

Embodiment one

Please refer to FIG. 2 and FIG. 3. In this embodiment, a LED chip with a patterned N electrode is proposed, including: a reflector 110, a barrier layer 100, an epitaxial layer, and an N electrode 300. The reflector 110 forms In the barrier layer 100 and exposing a surface of the mirror 110, the epitaxial layer is formed on the surface of the mirror 110 and the barrier layer 100, and the N electrode 300 is formed on the surface of the epitaxial layer, The N-electrode 300 includes a central region 310 and an insertion finger 320 , a part of the insertion finger 320 is formed on the surface of the epitaxial layer directly above the barrier layer 100 , and the insertion finger 320 completely or partially covers the epitaxial layer directly above the barrier layer 100 layer, the fingers 320 are connected to the central region 310 .

Specifically, please refer to FIG. 3, the epitaxial layer includes P-GaN210, quantum well 220 and N-GaN230 formed in sequence, the P-GaN210 is formed on the surface of the mirror 110 and the barrier layer 100, the The N electrode 300 is formed on the surface of the N-GaN 230 , wherein the specific epitaxial layer is not shown in FIG. 2 .

In this embodiment, the insert fingers 320 are strip-shaped and arranged point-symmetrically along the central area 310, that is, the insert fingers 320 form a square shape with a certain right angle, and the width range of the insert fingers 320 is 3 μm to 10 μm, for example 5 μm, since the barrier layer 100 usually has a width of 5 μm to 10 μm, the interposer 320 can completely or partially cover the barrier layer 100 , which can be determined according to the requirements of the process.

In this embodiment, the central region 310 is circular, and the diameter of the central region 310 ranges from 50 μm to 120 μm, such as 100 μm; the material of the N electrode is Cr, Al, Ti, Pt, Au or similar metals one or more.

In this embodiment, because the N electrode includes the fingers 320, the current can be distributed more uniformly on the N-GaN surface, the light emission and heat generation can be improved, and the luminous efficiency of the LED chip can be increased. Directly above the barrier layer 100 , the reflective efficiency of the mirror 110 will not be blocked more.

Embodiment two

In this embodiment, the proposed LED chip with a patterned N electrode is an improvement on Embodiment 1, the difference lies in that the shape of the finger 320 of the N electrode 300 is octagonal, and another difference is that it is different from the The central area 310 is polygonal, and the side length of the central area is in the range of 30 μm-100 μm, for example, 60 μm. The rest are the same as those in Embodiment 1, and will not be repeated here. For details, please refer to Embodiment 1.

Since the insertion finger 320 in the first embodiment is in the shape of a square with a corner of 90°, the current distribution at this location is relatively dense, making the current distribution near this area uneven, which affects the luminous efficiency to a certain extent. Therefore, please refer to FIG. 4 (the specific epitaxial layer is also not shown in FIG. 4 ), in this embodiment, the insertion finger 320 is modified from the square shape in Embodiment 1 to an octagon, which can solve the current density at the corner. phenomenon, and reduce the blocked light-emitting area, so that the current distribution on the N-GaN surface is more uniform, and the luminous efficiency is further improved. In addition, a part of the fingers 320 are still formed on the blocking layer 100 that does not reflect light, and do not occupy much of the reflection area of the mirror 100 .

To sum up, in the LED chips with patterned N electrodes provided by the embodiments of the present invention, since a barrier layer with extremely weak light reflection is formed at the edge region between LED chips, the N electrodes are extended to directly above the barrier layer. On the one hand, because the N electrode is extended on the barrier layer with extremely weak light reflection, it does not affect the reflection efficiency of the mirror; on the other hand, the extended N electrode can make the current distribution more uniform, and improve the uniformity of the LED chip's light emission and heat dissipation.

The foregoing are only preferred embodiments of the present invention, and do not limit the present invention in any way. Any person skilled in the technical field, without departing from the scope of the technical solution of the present invention, makes any form of equivalent replacement or modification to the technical solution and technical content disclosed in the present invention, which does not depart from the technical solution of the present invention. The content still belongs to the protection scope of the present invention.

Claims (6)

1. a kind of LED chip with graphical N electrode, it is characterised in that including：Speculum, barrier layer, epitaxial layer and N electricity Pole, the speculum is formed in the barrier layer and exposes a surface of speculum, and the epitaxial layer is formed at described anti- On the surface for penetrating mirror and barrier layer, the N electrode is formed at the surface of the epitaxial layer, the N electrode include central area and Insert and refer to, the slotting finger-type of a part is into the epi-layer surface directly over the barrier layer, and the slotting finger is covered in whole or in part The surface of epitaxial layer directly over the barrier layer, the slotting finger is connected with the central area, and the slotting finger-type is into octagon.

2. there is the LED chip of graphical N electrode as claimed in claim 1, it is characterised in that the epitaxial layer is included successively P-GaN, SQW and the N-GaN of formation, the P-GaN formation is on the surface on the speculum and barrier layer, the N electrode It is formed at the surface of the N-GaN.

3. there is the LED chip of graphical N electrode as claimed in claim 1, it is characterised in that the width range of the slotting finger It is 3 μm~10 μm.

4. there is the LED chip of graphical N electrode as claimed in claim 1, it is characterised in that the central area is circle Or polygon.

5. there is the LED chip of graphical N electrode as claimed in claim 4, it is characterised in that the central area is circle When, the diameter range of the central area is 50 μm -120 μm；When the central area is polygon, the side of the central area Long scope is 30 μm -100 μm.

6. there is the LED chip of graphical N electrode as claimed in claim 1, it is characterised in that the material of the N electrode is Cr, Al, Ti, Pt, Au one or more.