Electroluminescent Device

Abstract

To solve a problem in which, after an electroluminescent device is assembled onto a package substrate, the epitaxial and or dielectric layer of the electroluminescent device may be fractured by stress.SOLUTION: An electroluminescence divice includes an epitaxial layer, a first contact electrode, a bonding layer, a substrate, a first metal pad, a second contact electrode, and a second metal pad. The epitaxial layer has a vertical trench formed therein dividing the epitaxial layer into a first region and a second region spaced apart from each other. The first contact electrode is disposed on the epitaxial layer and has an opening. The bonding layer is disposed on the first contact electrode. The substrate is disposed on the bonding layer. The first metal pad is disposed below the first region and extends vertically to be electrically connected to the first contact electrode. The second contact electrode is disposed below the second region. The second metal pad is disposed below the second region via the second contact electrode.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to electroluminescent devices, and more particularly to electroluminescent devices that include an epitaxial layer having a trench. [Background technology]

[0002] Electroluminescence (EL) elements such as vertical cavity surface emitting lasers (VCSELs) and light-emitting diodes (LEDs) are widely used as light sources in electronic devices. The main structure of electroluminescence elements is epitaxial, and they are often flip-chip structured to improve heat dissipation. To ensure the yield of pick-and-place in the flip-chip surface mount technology (SMT), the P-pad and N-pad of the electroluminescence element are designed to be equal in height to the epitaxial layer.

[0003] However, after the electroluminescent element is assembled onto the package substrate, since the materials of the substrate of the electroluminescent element and the package substrate are different from each other and have different thermal expansion coefficients, the epitaxial layer or dielectric layer of the electroluminescent element may be destroyed by stress, which may damage the electroluminescent element.

[0004] In view of the above circumstances, the present invention proposes an electroluminescence device capable of solving the above-mentioned problems. Summary of the Invention

[0005] The object of the present invention is to provide an electroluminescence device that prevents the epitaxial layer and the dielectric layer from being broken by stress after the electroluminescence device is assembled on a package substrate by separating the epitaxial layers of the P-side pad and the N-side pad. Another object of the present invention is to prevent the electroluminescence device from operating as expected due to the breakdown of the epitaxial layer and the dielectric layer, which causes electrical conduction between the P-side metal electrode in contact with the P-type semiconductor and the N-side metal electrode in contact with the N-type semiconductor, preventing current from flowing through the multiple quantum well (MQW) layer.

[0006] In order to achieve the above-mentioned object, the electroluminescent element of the present invention includes an epitaxial layer in which a vertical trench is formed and which is divided by the trench into a first region and a second region spaced apart from each other, a first contact electrode disposed on the epitaxial layer and having an opening, a bonding layer disposed on the first contact electrode, a substrate disposed on the bonding layer, a first metal pad disposed below the first region of the epitaxial layer, extending vertically and electrically connected to the first contact electrode, a second contact electrode disposed below the second region of the epitaxial layer, and a second metal pad disposed below the second region of the epitaxial layer via the second contact electrode.

[0007] In an embodiment of the present invention, the electroluminescent device is a Vertical Cavity Surface Emitting Laser (VCSEL) flip chip.

[0008] In an embodiment of the present invention, the substrate is a transparent substrate, such as a sapphire substrate.

[0009] In an embodiment of the present invention, the epitaxial layer comprises an N-type epitaxial layer, a multiple quantum well layer disposed on the N-type epitaxial layer, a P-type epitaxial layer disposed on the multiple quantum well layer, and two current barrier layers disposed in the P-type epitaxial layer and spaced apart laterally from each other. The first metal pad is disposed below the N-type epitaxial layer in the first region, and the second contact electrode is disposed below the N-type epitaxial layer in the second region. The first contact electrode is disposed on the P-type epitaxial layer in the first region and the P-type epitaxial layer in the second region.

[0010] In an embodiment of the present invention, the epitaxial layer is formed by metalorganic chemical vapor deposition or molecular beam epitaxy using a III-V or II-VI semiconductor material.

[0011] In an embodiment of the present invention, the epitaxial layer has an energy gap of 1.3 to 2.5 eV.

[0012] In an embodiment of the present invention, the trench is formed by a wet etching process or a dry etching process.

[0013] In an embodiment of the present invention, a vertical through hole is formed in the first region of the epitaxial layer, and the first metal pad extends vertically through the vertical through hole and is electrically connected to the first contact electrode.

[0014] In an embodiment of the present invention, the first metal pad extends vertically along a sidewall of the first region and is electrically connected to the first contact electrode.

[0015] In an embodiment of the present invention, the electroluminescent element further includes a dielectric layer, the dielectric layer being disposed between the first contact electrode and an upper surface of the epitaxial layer, and having a first portion that does not overlap with the first region of the epitaxial layer and the opening, a second portion that is disposed on a sidewall of the first region of the epitaxial layer adjacent to the trench and on a sidewall of the second region of the epitaxial layer, and a third portion that is disposed on a lower surface of the epitaxial layer and does not overlap with the first metal pad and the second contact electrode.

[0016] Those skilled in the art can understand other objects of the present invention, as well as the technical means and embodiments of the present invention, by referring to the drawings and the embodiments described below. [Brief description of the drawings]

[0017] [Figure 1] 1 is a cross-sectional view showing an electroluminescent device according to an embodiment of the present invention; [Diagram 2] Cross-sectional view of the electroluminescent device of FIG. 1 with a dielectric layer added [Diagram 3] FIG. 2 is a cross-sectional view showing an electroluminescent device according to another embodiment of the present invention; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] The contents of the present invention will be described below through examples. The examples of the present invention are examples of embodiments, and are not intended to limit the present invention to the environments, applications, or specific aspects described in the examples. Therefore, the explanation of the examples is for explaining the present invention, but does not limit the present invention. In the embodiments and drawings, components that are not directly related to the present invention are omitted and not shown. The dimensional relationship between the components in the drawings is for ease of understanding, and does not limit the actual dimensions.

[0019] The present invention relates to an electroluminescent device such as a VCSEL device or an LED device. A trench is formed in the epitaxial layer of the electroluminescent device according to the present invention. The vertical trench divides the epitaxial layer into a first region corresponding to a P-side pad and a second region corresponding to an N-side pad, which are spaced apart from each other. The first region and the second region are spaced apart from each other. Therefore, the electroluminescent device of the present invention can prevent the epitaxial layer and the dielectric layer from being broken due to stress after the electroluminescent device is assembled on a package substrate. The present invention can prevent the electroluminescent device from operating as expected due to electrical conduction between the P-side metal electrode in contact with the P-type semiconductor and the N-side metal electrode in contact with the N-type semiconductor, preventing current from flowing through the multiple quantum well (MQW) layer.

[0020] In the following examples, the electroluminescent device is described as a VCSEL device. However, those skilled in the art will understand that the structural features of the present invention (e.g., an epitaxial layer having a trench, etc.) can also be applied to other electroluminescent devices having similar structures, such as LED devices. Therefore, these electroluminescent devices are also included in the scope of protection of the present invention.

[0021] 1 shows an electroluminescent device 1 configured as a flip chip structure according to a first embodiment of the present invention. That is, the electroluminescent device 1 is a vertical cavity surface emitting laser (VCSEL) flip chip. The electroluminescent device 1 includes an epitaxial layer 11, a first contact electrode 12, a bonding layer 13, a substrate 14, a first metal pad 15, a second contact electrode 16, and a second metal pad 17.

[0022] A trench 20 is formed in the epitaxial layer 11, dividing the epitaxial layer 11 into a first region R1 and a second region R2. The first region R1 and the second region R2 are spaced apart from each other. The trench 20 is formed by a wet or dry etching process. The trench 20 does not need to be filled with any material or elastic material, as long as the epitaxial layer or the dielectric layer does not break when subjected to stress.

[0023] The epitaxial layer 11 is formed by metal-organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE) using a III-V group semiconductor material or a II-VI group semiconductor material. For example, the epitaxial layer 11 may be formed by alternately stacking gallium arsenide (GaAs) and aluminum arsenide (AlAs). The energy gap of the epitaxial layer 11 is 1.3 to 2.5 eV.

[0024] In the VCSEL device, the epitaxial layer 11 includes an N-type epitaxial layer 11a, a multi-quantum well layer 11b, and a P-type epitaxial layer 11c. The N-type epitaxial layer 11a and the P-type epitaxial layer 11c are each a reflective laminated structure such as a distributed Bragg reflector (DBR). The multi-quantum well layer 11b is disposed on the N-type epitaxial layer 11a. The P-type epitaxial layer 11c is disposed on the multi-quantum well layer 11b. As shown in FIG. 1, the epitaxial layer 11 includes two current barrier layers 11d disposed in the P-type epitaxial layer 11c and spaced apart from each other in the lateral direction. The current barrier layer 11d is an insulating layer formed by moisture oxidation or ion implantation. The two current barrier layers 11d are used to regulate the current flow so that it is concentrated in the region between them.

[0025] The first contact electrode 12 is disposed on the epitaxial layer 11 and has an opening 12a. The opening 12a has an opening size that allows light to be emitted vertically. The first contact electrode 12 is made of a metal material such as gold (Au), titanium (Ti), or platinum (Pt). The bonding layer 13 is disposed on the first contact electrode 12 and bonds with a substrate 14 disposed thereon. Depending on the actual structure, the bonding layer 13 may be disposed on other layers such as the epitaxial layer 11 or a dielectric layer 18 described below. The bonding layer 13 is an adhesive, a dielectric, or a combination thereof. For example, the adhesive may be a benzo-cyclo-butene (BCB) adhesive. The dielectric layer may be silicon nitride (SiNx). The substrate 14 may be, but is not limited to, a sapphire (Al2O3) substrate. Depending on the application, any transparent substrate with a light transmittance of 90% or more may also be used.

[0026] The first metal pad 15 is a P-side pad (P-pad), which is disposed under the first region R1 of the epitaxial layer 11, extends vertically, and is electrically connected to the first contact electrode 12. As shown in FIG. 1, a vertical through hole 22 is formed in the first region R1 of the epitaxial layer 11. The first metal pad 15 extends vertically through the vertical through hole 22 and is electrically connected to the first contact electrode 12. The material of the first metal pad 15 may be the same as that of the first contact electrode 12, such as gold (Au), titanium (Ti), or platinum (Pt). The vertical through hole 22 is formed by a wet etching process or a dry etching process, and may be formed by the same process as the trench 20.

[0027] The second contact electrode 16 is disposed under the second region R2 of the epitaxial layer 11. The second contact electrode 16 is in ohmic contact with the epitaxial layer 11 and may be made of, but is not limited to, gold germanium (GeAu). The second metal pad 17 is an N-side pad (N-pad) and is disposed under the second region R2 of the epitaxial layer 11 via the second contact electrode 16. The material of the second metal pad 17 may be the same as that of the first metal pad 15, for example, gold (Au), titanium (Ti), or platinum (Pt).

[0028] As shown in FIG. 1, the first metal pad 15 is disposed under the N-type epitaxial layer 11a in the first region R1. The second contact electrode 16 and the second metal pad 17 are disposed under the N-type epitaxial layer in the second region R2. The first contact electrode 12 is disposed on the P-type epitaxial layer 11c in the first region R1 and the P-type epitaxial layer 11c in the second region R2. Since the first region R1 and the second region R2 of the epitaxial layer 11 are separated from each other by the trench 20, in such a structure, the present invention can avoid a situation in which the P-side metal electrode in contact with the P-type semiconductor (i.e., the first metal pad 15) and the N-side metal electrode in contact with the N-type semiconductor (i.e., the second metal pad 17) are electrically conducted, and a current does not flow in the multiple quantum well (MQW) layer, causing the electroluminescent device to not operate as expected.

[0029] The electroluminescent device 1 further includes a dielectric layer 18. The material of the dielectric layer 18 may be, but is not limited to, silicon dioxide (SiO2). As shown in FIG. 1, the dielectric layer 18 has a first portion disposed between the first contact electrode 12 and the upper surface of the epitaxial layer 11, a second portion disposed on the sidewall of the first region R1 of the epitaxial layer 11 adjacent to the trench 20 and the sidewall of the second region R2 of the epitaxial layer 11, and a third portion disposed on the lower surface of the epitaxial layer 11. The first portion does not overlap the first region R1 of the epitaxial layer 11 and the opening 12a. The third portion does not overlap the first metal pad 15 and the second contact electrode 16.

[0030] 2 is a diagram showing an electroluminescent element 2 according to a second embodiment of the present invention. In this embodiment, the dielectric layer 18 of the electroluminescent element 2 is formed not only in the region shown in FIG. 1 but also on the upper surface, lower surface, and two side walls of the first region R1 of the epitaxial layer 11 and the side wall of the vertical through hole 22.

[0031] It should be noted that the dielectric layer 18 of the electroluminescent device of the present invention can be disposed in any region as an electrical insulator to prevent current leakage or loss in any region according to the actual application, therefore, the electroluminescent device with any feasible dielectric layer falls within the protection scope of the present invention.

[0032] 3 is a diagram showing an electroluminescent element 3 according to a third embodiment of the present invention. The main difference from the electroluminescent element 1 of FIG. 1 is that the first metal pad 15 of the electroluminescent element 3 extends vertically along the sidewall of the first region R1 and is electrically connected to the first contact electrode 12. Therefore, in this embodiment, the first region R1 of the epitaxial layer 11 does not have a vertical through hole 22.

[0033] The electroluminescent elements 1, 2, and 3 according to the present invention can be assembled to a package substrate in a subsequent process. The package substrate can be an aluminum nitride (AIN) substrate or a silicon substrate depending on the application, but is not limited thereto. Note that a person skilled in the art can easily understand how to assemble the electroluminescent elements of the present invention to a package substrate, and therefore the description thereof will be omitted.

[0034] As described above, in the electroluminescent device according to the present invention, by separating the epitaxial layers of the P-side pad and the N-side pad, it is possible to prevent the epitaxial layer and the dielectric layer from being destroyed by stress after the electroluminescent device is assembled on the package substrate, and to avoid a situation in which the destruction prevents a current from flowing through the multiple quantum well (MQW) layer, causing the electroluminescent device to not function as expected.

[0035] The above examples are for explaining the embodiments of the present invention and for explaining the characteristic configuration of the present invention. The present invention is not limited to the above examples. Modifications or equivalent arrangements that can be easily made by those skilled in the art are also within the scope of the present invention. The scope of protection of the rights of the present invention is based on the claims. [Explanation of symbols]

[0036] 1. Electroluminescent device 2. Electroluminescent device 3. Electroluminescent Device 11 Epitaxial layer 11a N-type epitaxial layer 11b Multiple quantum well layer 11c P-type epitaxial layer 11d Current barrier layer 12 First contact electrode 12a opening 13 Bonding layer 14 Substrate 15 First metal pad 16 Second contact electrode 17 Second metal pad 18 Dielectric layer 20. Trench 22 Vertical through hole R1 1st area R2 2nd area

Claims

1. An electroluminescent device, A vertical trench (except that the trench is filled with any material. an epitaxial layer having a first region and a second region separated from each other by the trench; a first contact electrode disposed on the epitaxial layer and having an opening; a bonding layer disposed on the first contact electrode; A substrate disposed on the bonding layer; a first metal pad disposed under the first region of the epitaxial layer, extending vertically and electrically connected to the first contact electrode; a second contact electrode disposed under the second region of the epitaxial layer; a second metal pad disposed under the second region of the epitaxial layer via the second contact electrode.

2. The electroluminescent device of claim 1 , wherein the electroluminescent device is a vertical cavity surface emitting laser (VCSEL) flip chip.

3. 3. The electroluminescent device according to claim 2, wherein the substrate is a transparent substrate.

4. The epitaxial layer is an N-type epitaxial layer; a multiple quantum well layer disposed on the N-type epitaxial layer; a P-type epitaxial layer disposed on the multiple quantum well layer; two current barrier layers disposed within the P-type epitaxial layer and laterally spaced apart from one another; the first metal pad is disposed under the N-type epitaxial layer in the first region, and the second contact electrode is disposed under the N-type epitaxial layer in the second region; The electroluminescent device according to claim 2 , wherein the first contact electrode is disposed on the P-type epitaxial layer in the first region and on the P-type epitaxial layer in the second region.

5. 3. The electroluminescent device according to claim 2, wherein the epitaxial layer is formed by metal organic chemical vapor deposition or molecular beam epitaxy using a III-V group semiconductor material or a II-VI group semiconductor material.

6. 3. The electroluminescent device according to claim 2, wherein the energy gap of the epitaxial layer is 1.3 to 2.5 eV.

7. The electroluminescent device of claim 1 , wherein the trench is formed by a wet etching process or a dry etching process.

8. 2. The electroluminescent device of claim 1, wherein a vertical through hole is formed in the first region of the epitaxial layer, and the first metal pad extends vertically through the vertical through hole and is electrically connected to the first contact electrode.

9. The device of claim 1 , wherein the first metal pad extends vertically along a sidewall of the first region and is electrically connected to the first contact electrode.

10. The electroluminescent device further includes a dielectric layer, The dielectric layer is a first portion disposed between the first contact electrode and an upper surface of the epitaxial layer, the first portion not overlapping the first region of the epitaxial layer and the opening; a second portion disposed on a sidewall of the first region of the epitaxial layer adjacent the trench and on a sidewall of the second region of the epitaxial layer; The electroluminescent device according to claim 1 , further comprising a third portion disposed on a lower surface of the epitaxial layer, the third portion not overlapping the first metal pad and the second contact electrode.

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