Gallium nitride-based vertical light-emitting diode and manufacturing method thereof

Abstract

The present invention discloses a gallium nitride-based vertical light-emitting diode and a manufacturing method thereof, which sequentially include, from bottom to top: a support substrate, a bonding metal layer, a P-type electrode, a P-type semiconductor layer, a quantum well light-emitting layer, an N-type semiconductor layer, a buffer layer, and an N-type electrode. Among them, the buffer layer has a penetrating V-shaped hole structure; the N-type semiconductor completely fills the V-shaped holes of the buffer layer; the N-type electrode is in contact with the N-type semiconductor in the V-shaped holes to form an ohmic contact. A buffer layer with a penetrating V-shaped hole is grown on the Si substrate, and then a highly doped N-type semiconductor layer is grown, and the V-shaped holes of the buffer layer are completely filled with the N-type semiconductor. The combination of this structure ensures good N-type ohmic contact characteristics of the device while retaining a high-strength buffer layer, and enables the manufacture of a gallium nitride-based vertical light-emitting diode with an ultra-thin epitaxial layer.

Description

Technical Field

[0001] The present invention relates to the field of light-emitting diodes, and more particularly to a gallium nitride-based vertical structure light-emitting diode and a manufacturing method thereof. Background Art

[0002] With the booming development of emerging wearable and portable technologies, micro-scale LED chips (Micro LED) have received great attention and research due to their application prospects in fields such as display, visible light communication, and biomedicine. The size of the LED chip is reduced from the existing mm level to less than 10 μm, which is one percent of the original size, to be a Micro LED. By chip manufacturing and packaging processes, a miniaturized LED array is formed. Each Micro LED is a light-emitting source and can achieve addressing of each light-emitting pixel, driving it to emit light individually, and forming a self-emitting display. Micro LED display has excellent performance such as high-speed response performance at the nanosecond (ns) level, stable characteristics of inorganic materials, high luminous efficiency, high reliability, high color purity and contrast, and transparency. The combination of these characteristics cannot be achieved by liquid crystal display (LCD) and organic LED (OLED).

[0003] As the preferred solution for the next-generation display technology, in order to suppress the light loss caused by the lateral light emission of Micro LED and the light crosstalk phenomenon between adjacent pixels, and increase the proportion of front light emission, it is necessary to reduce the device thickness as much as possible. For the vertical structure thin-film chip, since there is no lateral light emission from the transparent substrate, more light is emitted in the normal direction of the chip, which is one of the preferred technical solutions for Micro LED. When the size of the InGaN chip is further reduced to the scale of 2 μm to 10 μm, based on the GaN epitaxial film thickness of usually 3 to 4 μm, the ratio of the lateral light emission to the normal light emission of the chip sidewall increases sharply, resulting in a decrease in the proportion of front light emission and large light crosstalk of the chip. To solve this problem, an obvious solution is to use dry ICP or wet etching methods to thin the LED epitaxial layer to achieve the manufacture of a thin epitaxial layer chip. However, this method has problems such as stress concentration during the thinning process, a decrease in chip strength, resulting in cracks in the chip, and a decrease in device performance and yield. Another obvious solution is to grow a thin epitaxial layer and not significantly thin the epitaxial layer during the chip manufacturing process to ensure the strength and device performance of the chip, but this method also has the problem of difficulty in preparing ohmic contact electrodes on the buffer layer.

[0004] To obtain a low-resistance ohmic contact, a low contact barrier height, a high doping concentration, or both are required. For GaN-based LED devices, an AlN buffer layer is a commonly used essential functional layer. AlN is a wide-bandgap material with a high contact barrier height; moreover, the ionization energy of AlN n-type dopants is also very high, making it difficult to achieve heavy doping. Even during epitaxial growth, n-type doping of the AlN layer will lead to an increase in defects in the subsequent grown epitaxial layer and a deterioration in crystal quality. So far, there are few reports on successfully fabricating ohmic contacts on AlN. Therefore, there is a necessary need for manufacturing light-emitting diodes without removing the AlN buffer layer in the epitaxial layer. Summary of the Invention

[0005] To solve the problem of difficult preparation of ohmic contact electrodes on the AlN buffer layer, the first object of the present invention is to provide a GaN-based vertical structure light-emitting diode, which realizes the manufacture of a GaN-based vertical structure light-emitting diode with an ultra-thin epitaxial layer while ensuring that the device has good N-type ohmic contact characteristics.

[0006] The second object of the present invention is to provide a manufacturing method for a GaN-based vertical structure light-emitting diode with an ultra-thin epitaxial layer.

[0007] The first object of the present invention is achieved as follows:

[0008] A GaN-based vertical structure light-emitting diode includes, from bottom to top in sequence: a support substrate, a bonding metal layer, a P-type electrode, a P-type semiconductor layer, a quantum well light-emitting layer, an N-type semiconductor layer, a buffer layer, and an N-type electrode; characterized in that: the buffer layer has a penetrating V-shaped hole structure; the N-type semiconductor completely fills the V-shaped holes of the buffer layer; the N-type electrode contacts the N-type semiconductor in the V-shaped holes to form an ohmic contact.

[0009] The buffer layer is an Al x Ga (1-x) N single layer or a multi-layer structure entirely composed of Al x Ga (1-x) N layers, where 0.3 ≤ x ≤ 1, the thickness is 500 Å to 5000 Å, and the density of the V-shaped holes is 1 × 10 7 ~1 × 10 10 / cm².

[0010] The material of the N-type semiconductor layer is an Al x Ga (1-x) N single layer or a multi-layer structure entirely composed of Al x Ga (1-x) N layers, where 0 ≤ x ≤ 0.6, the thickness is 0.1 μm to 2 μm, and the Si concentration is 1 × 10 18 / cm³ to 1×10 20 / cm³.

[0011] The support substrate is a Si substrate.

[0012] The second object of the present invention is achieved as follows:

[0013] A manufacturing method of a gallium nitride-based vertical structure light-emitting diode, characterized by comprising the following steps:

[0014] A. Sequentially grow a buffer layer with V-shaped holes, an N-type semiconductor layer, a quantum well light-emitting layer, and a P-type semiconductor layer on a substrate;

[0015] B. Form a P-type electrode and a bonding metal layer on the surface of the P-type semiconductor layer;

[0016] C. Bond the epitaxial wafer with the P-type electrode and the bonding metal layer to the support substrate;

[0017] D. Remove the substrate;

[0018] E. Etch a certain thickness of the buffer layer to expose the N-type semiconductor layer in the V-shaped holes of the buffer layer;

[0019] F. Evaporate ohmic contact metal on the surface of the buffer layer where the N-type semiconductor layer in the exposed V-shaped holes is located to form an N-type electrode.

[0020] In step E, the etched thickness of the buffer layer is 0% to 80% of the total thickness of the buffer layer.

[0021] A gallium nitride-based vertical structure light-emitting diode provided by the present invention is characterized in that: the buffer layer has a through V-shaped hole structure; the N-type semiconductor completely fills the V-shaped holes of the buffer layer; the N-type electrode contacts the N-type semiconductor in the V-shaped holes to form an ohmic contact. A buffer layer with V-shaped holes penetrating is grown on a Si substrate, and then a highly doped N-type semiconductor layer is grown, and the V-shaped holes of the buffer layer are completely filled with the N-type semiconductor. The combination of this structure ensures good N-type ohmic contact characteristics of the device while retaining a high-strength buffer layer, and can realize the manufacture of a gallium nitride-based vertical structure light-emitting diode with an ultra-thin epitaxial layer. Description of the Drawings

[0022] Figure 1 It is a schematic diagram of the epitaxial structure of a conventional gallium nitride-based vertical structure light-emitting diode. In the figure: 10 - substrate, 20 - buffer layer, 30 - N-type semiconductor layer, 40 - quantum well light-emitting layer, 50 - P-type semiconductor layer;

[0023] Figure 2Schematic diagram of the chip structure of a conventional gallium nitride-based vertical structure light-emitting diode. In the figure: 60 - support substrate, 70 - bonding metal layer, 80 - P-type electrode, 50 - P-type semiconductor layer, 40 - quantum well light-emitting layer, 30 - N-type semiconductor layer, 90 - N-type electrode;

[0024] Figure 3 Schematic diagram of the epitaxial structure of the gallium nitride-based vertical structure light-emitting diode of the present invention. In the figure: 101 - substrate, 102 - buffer layer, 103 - N-type semiconductor layer, 104 - quantum well light-emitting layer, 105 - P-type semiconductor layer;

[0025] Figure 4 Schematic diagram of the epitaxial structure of the gallium nitride-based vertical structure light-emitting diode of the present invention after growing the buffer layer. In the figure: 101 - substrate, 102 - buffer layer;

[0026] Figure 5 Schematic diagram of the epitaxial structure of the gallium nitride-based vertical structure light-emitting diode of the present invention after growing the N-type semiconductor layer. In the figure: 101 - substrate, 102 - buffer layer, 103 - N-type semiconductor layer;

[0027] Figure 6 Schematic diagram of the chip structure of the gallium nitride-based vertical structure light-emitting diode of the present invention after etching a certain thickness of the buffer layer in the chip manufacturing process. In the figure: 201 - support substrate, 301 - bonding metal layer, 401 - P-type electrode, 105 - P-type semiconductor layer, 104 - quantum well light-emitting layer, 103 - N-type semiconductor layer, 102 - buffer layer;

[0028] Figure 7 Schematic diagram of the chip structure of the gallium nitride-based vertical structure light-emitting diode of the present invention. In the figure: 201 - support substrate, 301 - bonding metal layer, 401 - P-type electrode, 105 - P-type semiconductor layer, 104 - quantum well light-emitting layer, 103 - N-type semiconductor layer, 102 - buffer layer, 501 - N-type electrode. Detailed implementation manners

[0029] The present invention will be further described in detail below in conjunction with the embodiments and with reference to the accompanying drawings.

[0030] As Figure 3 shown, the epitaxial structure of the gallium nitride-based vertical structure light-emitting diode provided by the embodiment of the present invention includes: 101 - substrate, 102 - buffer layer, 103 - N-type semiconductor layer, 104 - quantum well light-emitting layer, 105 - P-type semiconductor layer.

[0031] As Figure 7As shown, it is the chip structure of a gallium nitride-based vertical structure light-emitting diode provided by an embodiment of the present invention, which includes: 201 - support substrate, 301 - bonding metal layer, 401 - P-type electrode, 105 - P-type semiconductor layer, 104 - quantum well light-emitting layer, 103 - N-type semiconductor layer, 102 - buffer layer, 501 - N-type electrode.

[0032] The buffer layer 102 is a porous AlGaN structure with through V-shaped holes. The V-shaped holes are pits that are V-shaped when viewed from the cross-section and are formed by controlling the material growth conditions. As x Ga (1-x) shown, where 0.3 ≤ x ≤ 1, the thickness of the buffer layer 102 is 2000 Å, and the density of the V-shaped holes is 2×10 Figure 4 / cm². 8 / cm².

[0033] The material of the N-type semiconductor layer 103 is a single layer of AlGaN doped with Si element or a multi-layer structure entirely composed of AlGaN layers, where 0 ≤ x ≤ 0.6, the thickness is 1 μm, the Si concentration is 5×10 x Ga (1-x) N or a multi-layer structure entirely composed of AlGaN layers, where 0 ≤ x ≤ 0.6, the thickness is 1 μm, the Si concentration is 5×10 x Ga (1-x) / cm³, and it completely fills the V-shaped holes of the buffer layer 102, as 18 shown. Figure 5 shown.

[0034] The N-type electrode 501 contacts the N-type semiconductor layer 103 in the V-shaped holes of the buffer layer 102 to form an ohmic contact, as Figure 7 shown. The combination of this structure ensures good N-type ohmic contact characteristics of the device while retaining a high-strength buffer layer, enabling the manufacture of a gallium nitride-based vertical structure light-emitting diode with an ultra-thin epitaxial layer.

[0035] A manufacturing method of a gallium nitride-based vertical structure light-emitting diode includes the following steps:

[0036] (1) First, use the conventional MOCVD growth method to prepare the epitaxial material of the gallium nitride-based vertical structure light-emitting diode, provide the substrate 101, the material of the substrate 101 can be one of Si, SiC, and Al2O3, and sequentially grow an epitaxial buffer layer 102 with V-shaped holes, an N-type semiconductor layer 103, a quantum well light-emitting layer 104, and a P-type semiconductor layer 105 on the substrate 101, as Figure 3 shown;

[0037] (2) Evaporate an Ag metal reflective layer with a thickness of 1 nm - 1000 nm on the P-type semiconductor layer 105 to complete the preparation of the P-type electrode 401;

[0038] (3) Then, a bonding metal layer 301 is fabricated on the P-type electrode 401, and the epitaxial wafer with the P-type electrode 401 and the bonding metal layer 301 is bonded to the support substrate 201, and the material of the substrate 201 is Si;

[0039] (4) Then, the substrate 101 is removed, and the buffer layer 102 with a thickness of 50% is etched by dry ICP etching or wet etching to expose the N-type semiconductor layer 103 in the V-shaped hole of the buffer layer 102, as Figure 6 shown;

[0040] (5) The buffer layer 102 with a certain etched thickness is roughened, and the roughened area does not include the area of the N-type electrode 501 to be fabricated;

[0041] (6) An ohmic contact metal is deposited on the surface of the buffer layer 102 of the N-type semiconductor layer 103 in the exposed V-shaped hole by an electron beam evaporation platform to form the N-type electrode 501. The material of the N-type electrode 501 is one of AlTiAu and CrPtAu, and the thickness is 1000 - 3000 nm; as Figure 7 shown.

[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A gallium nitride-based vertical structure light-emitting diode, comprising, from bottom to top in sequence: A support substrate, a bonding metal layer, a P-type electrode, a P-type semiconductor layer, a quantum well light-emitting layer, an N-type semiconductor layer, a buffer layer, and an N-type electrode; characterized in that: the buffer layer has a penetrating V-shaped hole structure; the N-type semiconductor completely fills the V-shaped holes of the buffer layer; the N-type electrode contacts the N-type semiconductor in the V-shaped holes to form an ohmic contact.

2. The gallium nitride-based vertical structure light-emitting diode according to claim 1, characterized in that: The buffer layer is an Al x Ga (1-x) N single layer or a multi-layer structure composed entirely of Al x Ga (1-x) N layers, where 0.3 ≤ x ≤ 1, the thickness is 500 Å to 5000 Å, and the density of V-shaped holes is 1×10 7 ~1×10 10 / cm².

3. The gallium nitride-based vertical structure light-emitting diode according to claim 1, characterized in that: The material of the N-type semiconductor layer is Al doped with Si element x Ga (1-x) N monolayer or a multilayer structure composed entirely of Al x Ga (1-x) N layers, where 0 ≤ x ≤ 0.6, the thickness is 0.1 μm to 2 μm, and the Si concentration is 1×10 18 / cm³ to 1×10 20 / cm³.

4. The gallium nitride-based vertical light-emitting diode according to claim 1, characterized in that: The support substrate is a Si substrate.

5. A manufacturing method of a gallium nitride-based vertical structure light-emitting diode, characterized in that: It includes the following steps: A. Sequentially grow a buffer layer with V-shaped holes, an N-type semiconductor layer, a quantum well light-emitting layer, and a P-type semiconductor layer on a substrate; B. Form a P-type electrode and a bonding metal layer on the surface of the P-type semiconductor layer; C. Bond the epitaxial wafer with the P-type electrode and the bonding metal layer to the support substrate; D. Remove the substrate; E. Etch a certain thickness of the buffer layer to expose the N-type semiconductor layer in the V-shaped holes of the buffer layer; F. Evaporate an ohmic contact metal on the surface of the buffer layer where the N-type semiconductor layer in the exposed V-shaped holes is located to form an N-type electrode.

6. The manufacturing method of the gallium nitride-based vertical structure light-emitting diode according to claim 5, wherein: In step E, the thickness of the buffer layer etched is 0% to 80% of the total thickness of the buffer layer.

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