CN111261762A - Gallium nitride-based vertical structure light-emitting diode with current blocking layer and manufacturing method thereof - Google Patents

Abstract

The invention discloses a gallium nitride-based vertical structure light-emitting diode with a current blocking layer, comprising: a conductive substrate on the bottom layer; a second soldering layer on the surface of the conductive substrate; and a first soldering layer on the surface of the second soldering layer The diffusion barrier layer on the surface of the first welding layer; the nickel-silver reflective layer on the surface of the diffusion barrier layer; the Al layer on the surface of the diffusion barrier layer; the gallium nitride-based light-emitting epitaxial layer on the surface of the nickel-silver reflective layer and the Al layer; The n electrode is located on the surface of the light-emitting epitaxial layer, and the Al metal layer is located in the projection area under the n electrode. The Al metal layer acts as a current blocking layer to change the current injection and improve the luminous efficiency.

Description

A gallium nitride-based vertical structure light-emitting diode with a current blocking layer and its manufacture method

technical field

The invention belongs to the field of semiconductors, and in particular relates to a gallium nitride-based vertical structure light-emitting diode with a current blocking layer and a manufacturing method thereof.

Background technique

In recent years, vertical structure LEDs have won a place in the market because of their good performance under high current injection. Vertical structure LEDs remove the growth substrate and transfer the GaN-based light-emitting layer to a secondary substrate with better thermal conductivity. , which improves its heat dissipation performance under high current conditions. In addition, because its electrodes are upper and lower structures, there is no current crowding effect. Compared with traditional front-mounted structure LEDs, vertical structure LEDs have obvious advantages under high current conditions. High-power fields, such as high-brightness torches, are widely used.

Because the n-electrode of the vertical structure LED is on the upper part, most of the light emitted by the injected current below the n-electrode is blocked by the electrode and cannot be emitted, so the designer proposes the design idea of the current blocking layer. CN200810237845 patent proposes a scheme of using local diffusion barrier layer and Ag to degrade through high temperature annealing. When this scheme is implemented, it must be ensured that Au will diffuse to the surface of the current blocking region, and the reflectivity of Au is lower than that of Ag, resulting in current blocking The regional reflectivity decreases, reducing the light extraction efficiency. The solution with the published application number 201811636723.5 is similar to the present invention, but the structure is slightly more complicated. It uses one or more layers of transparent dielectric materials as the current blocking layer. When the dielectric material is used as the current blocking layer, because semiconductors are commonly used The difference in thermal expansion coefficient between the dielectric material and the metal material is large, and its adhesion to the metal is not good. When bonding, the bonding is difficult, and the bonding failure is prone to occur, resulting in the luminescent layer falling off.

SUMMARY OF THE INVENTION

The gallium nitride-based vertical structure light-emitting diode with a current blocking layer and its manufacturing method proposed by the present invention overcome the above-mentioned shortcomings, and the use of Al metal as the current blocking layer not only realizes the adjustment of the current distribution of the light-emitting layer, It also achieves good light reflection, and at the same time, the method is relatively simple and easy to implement.

The present invention is achieved through the following technical solutions:

A vertical structure gallium nitride-based light-emitting diode, the structure of which includes:

providing a conductive substrate;

A second soldering layer is covered on the upper surface of the conductive substrate;

The surface of the second welding layer is covered with a first welding layer;

A diffusion barrier layer is covered on the surface of the first welding layer;

Covering part of the surface of the diffusion barrier layer with a nickel-silver metal layer as a p-type ohmic contact reflective metal film;

Covering part of the surface area of the diffusion barrier layer with an Al layer as a current blocking layer to change the current injection;

The surface of the Al layer and the current blocking layer is covered with a gallium nitride-based light-emitting epitaxial layer;

A partial area of the upper surface of the gallium nitride-based light-emitting epitaxial layer covers the n-electrode.

In the above vertical light emitting diode structure, the innovation of the present invention is that the n metal electrode is directly facing the lower surface area of the gallium nitride-based epitaxy, and there is an Al metal film as a current blocking layer instead of an insulating medium.

In order to achieve the above purpose, the present invention also provides a manufacturing method of a gallium nitride-based vertical structure light-emitting diode, including:

1), grow a gallium nitride-based epitaxial layer, and sequentially grow an n-GaN layer, an MQW layer and a p-GaN layer on a sapphire substrate;

2), deposit Ni/Ag layer on p-GaN layer;

3), photolithography on the Ni/Ag layer;

4), wet etching the Ni/Ag layer, and retain the photoresist;

5), deposit Al layer on the wafer surface with glue;

6), wet stripping off the photoresist and the surface Al layer;

7), forming a diffusion barrier layer on the surface of the Ni/Ag layer and the Al layer;

8), forming the first welding layer containing Au on the surface of the diffusion barrier layer;

9), a conductive substrate is provided, and the substrate surface forms the second welding layer containing Au;

10), pressing and heating the first welding layer and the second welding layer, so that the epitaxial layer and the conductive substrate are connected together;

11), remove the sapphire substrate to expose the n-GaN layer;

12), roughening the exposed n-GaN layer;

13), forming an n-electrode in a local area on the roughened n-GaN layer.

In the above steps of the present invention, the patterns of the Al layer and the Ni/Ag layer are defined by a process similar to self-alignment, and only one step of photolithography is used to complete the pattern definition of the two thin films, which can ensure that the two thin films do not overlap. stack, and reduce the cost even lower.

Description of drawings

FIG. 1 is a cross-sectional view of a vertical structure GaN-based light emitting diode according to an embodiment of the present invention.

2-10 are cross-sectional schematic diagrams of the fabrication process of the vertical structure gallium nitride-based light emitting diode according to the embodiment.

Description of parts symbols in the figure:

101: Sapphire substrate

102: n-GaN layer

103: MQW light-emitting layer

104: p-GaN layer

120: Diffusion Barrier

121: The first welding layer

130: Ni/Ag layer

140: Al layer

150: n electrode

220: Second welding layer

Detailed ways

The present invention will be further described in detail below in conjunction with specific embodiments, which are to explain rather than limit the present invention.

The main purpose of the present invention is to provide a vertical gallium nitride based light emitting diode, the specific structure is shown in FIG. 1 , the present invention uses Al metal as the current blocking layer of the vertical structure gallium nitride based light emitting diode. The use of Al metal as the current blocking layer is mainly based on the following reasons: 1. When the heat treatment temperature is lower than 320 °C, the Al metal forms a non-ohmic contact with the p-GaN surface, so the Al metal can block the current; 2. , During the bonding process, pressure heating is required. When the two are combined, the thermal expansion coefficients of Ag and Al are 19.5E-6/K and 23.2E-6/K, respectively, which are close in size. In addition, Al has good adhesion to p-GaN. , so it is easy to achieve high-reliability bonding; 3. Al has a high reflectivity in the light-emitting band of GaN-based devices. To sum up, this solution not only achieves the current blocking effect, but also achieves the maximum reflected light. When Ni is in contact with highly doped p-GaN, a good ohmic contact can be formed without annealing, so the Ni/Ag layer can form a reflective electrode with good contact and high reflectivity.

To make a gallium nitride-based epitaxial wafer, grow a 102n-GaN layer, a 103MQW light-emitting layer and a 104p-GaN layer on a 101 sapphire substrate in sequence; as shown in Figure 2.

A 110Ni/Ag thin film was evaporated on the 104p-GaN layer as a reflective layer with a thickness of 1nm/200nm, and photolithography was performed with a negative photoresist to expose the area to be etched, and the Ni that was not covered by the photoresist was etched away by wet method. /Ag layer; Figure 3.

Al metal was evaporated on the surface of the epitaxial wafer formed in the previous step, and then soaked in organic solvent, the photoresist and the Al metal on the surface were peeled off, and a current blocking layer 140Al layer was formed in the current blocking area with a thickness of 201 nm; as shown in Figure 4.

On the surface of the epitaxial wafer formed in the previous step, the diffusion barrier layer 120Ti/Au and the first welding layer 121Ti/Au are sequentially evaporated, the thickness of 120 is 100nm/100nm, and the thickness of 121 is 250nm/500nm; as shown in Figure 5.

A second soldering layer 220Ti/Au/AuSn was evaporated on a 210 tungsten copper substrate with a thickness of 100nm/200nm/2500nm, wherein the Au:Sn ratio of AuSn was 80:20, as shown in Figure 6.

The second metal connection layer 220 on the surface of the 210 tungsten copper substrate and the 121 on the surface of the epitaxial wafer are bonded together, heated to 295° C., pressurized 3000N, and bonded as a whole; as shown in FIG. 7 .

The sapphire surface of the epitaxial wafer is irradiated with a laser with a wavelength of 248 nm, and the laser penetrates the sapphire substrate, causing the gallium nitride at the interface between the sapphire and the gallium nitride to be decomposed into Ga metal and N ₂ , and the sapphire substrate 101 is removed; as shown in FIG. 8 .

The wafer with n-type gallium nitride exposed after peeling was immersed in a 20% KOH solution heated to 75° C. to make the surface of n-type gallium nitride rough; as shown in Figure 9.

Through photolithography and evaporation process, the n-electrode 150Al/Ti/Au is formed on the 102n-GaN layer in the area opposite to 140, and the thickness is 250nm/150nm/2000nm respectively; as shown in Figure 10.

The basic principles and main features of the present invention and the advantages of the present invention have been shown and described above. Those skilled in the art should understand that the present invention is not limited by the above-mentioned embodiments, and the descriptions in the above-mentioned embodiments and the description are only to illustrate the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have Various changes and modifications fall within the scope of the claimed invention. The claimed scope of the present invention is defined by the appended claims and their equivalents.

Claims (10)

1. A gallium nitride-based vertical structure light emitting diode with a current blocking layer, the structure comprising:

providing a conductive substrate;

covering a second welding layer on the upper surface of the conductive substrate;

a first welding layer covers the surface of the second welding layer;

covering a diffusion barrier layer on the surface of the first welding layer;

covering a nickel-silver metal layer on the partial surface area of the diffusion barrier layer to serve as a p-type ohmic contact reflection metal film;

covering an aluminum layer on the partial surface area of the diffusion barrier layer to serve as a current barrier layer for changing current injection;

covering the surfaces of the aluminum layer and the current barrier layer with a gallium nitride-based epitaxial layer;

and covering the upper surface part of the gallium nitride-based epitaxial layer with an n electrode.

2. The light-emitting diode with the gallium nitride-based vertical structure and the current blocking layer according to claim 1, wherein: the gallium nitride-based epitaxial layer sequentially comprises an n-GaN layer, an MQW light-emitting layer and a p-GaN layer from top to bottom.

3. The light-emitting diode with the gallium nitride-based vertical structure and the current blocking layer according to claim 1, wherein: the aluminum layer is positioned in a projection area right below the n metal electrode and is not overlapped with the nickel silver layer, and the area of the aluminum layer is the same as or close to that of the n metal electrode.

4. The light-emitting diode with the gallium nitride-based vertical structure and the current blocking layer according to claim 1, wherein: the nickel-silver layer is composed of a nickel layer and a silver layer, the nickel layer covers the lower surface of the gallium nitride-based epitaxial layer, the silver layer covers the lower surface of the nickel layer, and the thickness of the nickel layer is 0.2-20 nm.

5. The light-emitting diode with the gallium nitride-based vertical structure and the current blocking layer according to claim 1, wherein: the thickness of the aluminum layer is the same as or close to that of the nickel silver layer.

6. The light-emitting diode with the gallium nitride-based vertical structure and the current blocking layer according to claim 2, wherein: the doping concentration of the p-GaN layer is more than or equal to 10¹⁹/cm³。

7. A method for manufacturing a gallium nitride-based vertical structure light-emitting diode with a current blocking layer comprises the following steps:

1) growing a gallium nitride-based epitaxial layer, and sequentially growing an n-GaN layer, an MQW layer and a p-GaN layer on the sapphire substrate;

2) depositing a Ni/Ag layer on the p-GaN layer;

3) photoetching on the Ni/Ag layer;

4) carrying out wet etching on the Ni/Ag layer, and reserving the photoresist;

5) depositing an Al layer on the surface of the wafer with the adhesive;

6) stripping off the photoresist and the surface Al layer by a wet method;

7) forming a diffusion barrier layer on the surface of the Ni/Ag layer and the surface of the Al layer;

8) forming a first welding layer containing Au on the surface of the diffusion impervious layer;

9) providing a conductive substrate, and forming a second welding layer containing Au on the surface of the substrate;

10) pressurizing and heating the first welding layer and the second welding layer to enable the epitaxial layer and the conductive substrate to be connected together;

11) removing the sapphire substrate to expose the n-GaN layer;

12) coarsening the exposed n-GaN layer;

13) and forming an n electrode in a local area on the coarsened n-GaN layer.

8. The method for manufacturing a light-emitting diode with a gallium nitride-based vertical structure according to claim 7, wherein: the highest temperature of the preparation process does not exceed 320 ℃.

9. The method for manufacturing a light-emitting diode with a gallium nitride-based vertical structure according to claim 7, wherein: the metal deposition method of steps 2) to 6) may be one or more of evaporation, sputtering, or electroplating.

10. The method for manufacturing a light-emitting diode with a gallium nitride-based vertical structure according to claim 7, wherein: the coarsening of the n-type layer is realized by adopting a solution containing KOH for wet etching, the molar concentration of the KOH is 2-20mol/L, and the etching temperature is 60-90 ℃.

Images