Electroluminescent element

Abstract

An electroluminescent element 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 is provided with a groove which longitudinally divides the epitaxial layer into a first region and a second region, so that the first region and the second region are separated from each other. The first contact electrode is disposed on the epitaxial layer and includes 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 arranged below the first area and longitudinally extends to be electrically connected with the first contact electrode. The second contact electrode is arranged below the second area. The second metal pad is disposed under the second region across the second contact electrode.

Description

Technical Field

[0001] The present invention relates to an electroluminescent element, in particular to an electroluminescent element comprising an epitaxial layer with a groove. Background Art

[0002] Electroluminescence (EL) components, such as vertical cavity surface emitting laser (VCSEL) components and light-emitting diode (LED) components, are widely used as light sources in consumer electronics. The main structure of EL components is made of epitaxial wafers, and for better heat dissipation, they are often made into flip chip structures. In order to ensure the pick-and-place yield of the flip chip surface mount technology (SMT), the P-pad and N-pad of the EL component are designed to be equal and higher than the epitaxial layer.

[0003] However, after the EL device is subsequently bonded to the package substrate, the epitaxial layer or dielectric layer of the EL device may be stressed and fractured, resulting in damage to the EL device, because the EL device substrate and the package substrate are made of different materials and have different thermal expansion coefficients.

[0004] In view of this, the present invention provides an electroluminescent element to solve the above-mentioned problems. Summary of the invention

[0005] The present invention aims to provide an electroluminescent element, which separates the epitaxial layer between the P-side pad and the N-side pad, so as to prevent the epitaxial layer or the dielectric layer from being subjected to stress and breaking after the electroluminescent element is mounted on the packaging substrate. In addition, another object of the present invention is to prevent 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 from being electrically connected due to the break of the epitaxial layer or the dielectric layer, thereby causing leakage current, thereby causing the current not to flow through the multiple quantum well (MQW) layer, so that the electroluminescent element cannot operate as expected.

[0006] To achieve the above-mentioned purpose, the present invention discloses an electroluminescent element, which includes: an epitaxial layer having a groove, wherein the groove longitudinally divides the epitaxial layer into a first region and a second region, so that the first region and the second region are separated from each other; a first contact electrode, which is disposed on the epitaxial layer and includes an opening; a bonding layer, which is disposed on the first contact electrode; a substrate, which is disposed on the bonding layer; a first metal pad, which is disposed under the first region of the epitaxial layer and longitudinally extends to be electrically connected to the first contact electrode; a second contact electrode, which is disposed under the second region of the epitaxial layer; and a second metal pad, which is disposed under the second region of the epitaxial layer via the second contact electrode.

[0007] In one embodiment, the electroluminescent element is a vertical cavity surface emitting laser (VCSEL) flip chip.

[0008] In one embodiment, the substrate is a transparent substrate, such as a sapphire substrate.

[0009] In one embodiment, the epitaxial layer includes: an N-type epitaxial layer; a multi-quantum well layer disposed on the N-type epitaxial layer; a P-type epitaxial layer disposed on the multi-quantum well layer; and two current blocking layers disposed in the P-type epitaxial layer and laterally separated from each other by a distance. 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 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 one embodiment, the epitaxial layer is grown by using Group III-V semiconductor material or Group II-VI semiconductor material by an organic metal chemical vapor deposition method or a molecular beam epitaxy method.

[0011] In one embodiment, the bandgap of the epitaxial layer is between 1.3 and 2.5 eV.

[0012] In one embodiment, the trench is formed by a wet etching process or a dry etching process.

[0013] In one embodiment, the first region of the epitaxial layer has a longitudinal through hole, and the first metal pad extends longitudinally along the longitudinal through hole and is electrically connected to the first contact electrode.

[0014] In one embodiment, the first metal pad extends longitudinally along a side wall of the first region and is electrically connected to the first contact electrode.

[0015] In one embodiment, the electroluminescent element further includes a dielectric layer, wherein the dielectric layer includes: a first portion, disposed between the first contact electrode and an upper surface of the epitaxial layer, wherein the first portion does not overlap with the first region of the epitaxial layer and the opening; a second portion, disposed on a side wall of the first region of the epitaxial layer adjacent to the groove and on two side walls of the second region of the epitaxial layer; and a third portion, disposed on a lower surface of the epitaxial layer, wherein the third portion does not overlap with the first metal pad and does not overlap with the second contact electrode.

[0016] After referring to the accompanying drawings and the embodiments described below, a person skilled in the art will be able to understand other objects, technical means and embodiments of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a cross-sectional schematic diagram of an electroluminescent element according to an embodiment of the present invention;

[0018] Figure 2 for Figure 1 A schematic cross-sectional view of a dielectric layer of an electroluminescent element adding portion; and

[0019] Figure 3 FIG. 4 is a cross-sectional schematic diagram of an electroluminescent element according to another embodiment of the present invention.

[0020] Description of reference numerals:

[0021] 1: Electroluminescent element

[0022] 2: Electroluminescent element

[0023] 3: Electroluminescent element

[0024] 11: Epitaxial layer

[0025] 11a: N-type epitaxial layer

[0026] 11b: Multiple quantum well layer

[0027] 11c: P-type epitaxial layer

[0028] 11d: Current barrier layer

[0029] 12: First contact electrode

[0030] 12a: Opening

[0031] 13: Bonding layer

[0032] 14: Substrate

[0033] 15: First metal pad

[0034] 16: Second contact electrode

[0035] 17: Second metal pad

[0036] 18: Dielectric layer

[0037] 20: Groove

[0038] 22: Longitudinal through hole

[0039] R1: First Area

[0040] R2: The second area. DETAILED DESCRIPTION

[0041] The present invention will be explained below through embodiments. The embodiments of the present invention are not intended to limit the present invention to any specific environment, application or special method as described in the embodiments. Therefore, the description of the embodiments is only for the purpose of explaining the present invention, and is not intended to limit the present invention. It should be noted that in the following embodiments and drawings, elements that are not directly related to the present invention have been omitted and not drawn, and the dimensional relationship between the elements in the drawings is only for easy understanding, and is not intended to limit the actual proportion.

[0042] The present invention relates to an electroluminescent element, such as a VCSEL element and an LED element. The epitaxial layer of the electroluminescent element of the present invention has a groove. The groove longitudinally divides the epitaxial layer into a first area corresponding to the P-side pad and a second area corresponding to the N-side pad, so that the first area and the second area are separated from each other. Therefore, the electroluminescent element of the present invention can prevent the epitaxial layer or the dielectric layer from being subjected to stress and breaking after the electroluminescent element is mounted on a packaging substrate, and can prevent 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 from being electrically conductive to cause leakage current, causing the current not to flow through the multiple quantum well (MQW) layer, so that the electroluminescent element cannot operate as expected.

[0043] The following embodiments are described using VCSEL elements as electroluminescent elements. However, those skilled in the art will appreciate that the structural features of the present invention (e.g., the epitaxial layer has grooves, etc.) can also be applied to other electroluminescent elements with similar structures such as LED elements, and thus the electroluminescent elements also fall within the protection scope of the present invention.

[0044] Figure 1 The electroluminescent device 1 of the first embodiment of the present invention is shown. The electroluminescent device 1 is made of a flip chip structure, 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.

[0045] The epitaxial layer 11 has a groove 20, which divides the epitaxial layer 11 into a first region R1 and a second region R2 in the longitudinal direction. In this way, the first region R1 and the second region R2 can be separated from each other. The groove 20 can be formed by a wet etching process or a dry etching process in the process. The groove 20 can be filled with no material or filled with an elastic material, as long as it can withstand stress to prevent the epitaxial layer or the dielectric layer from breaking.

[0046] The epitaxial layer 11 can be formed by using a III-V semiconductor material or a II-VI semiconductor material by a metal-organic chemical vapor deposition (MOCVD) method or a molecular beam epitaxy (MBE) method. For example, the epitaxial layer 11 can be formed by alternately stacking gallium arsenide (GaAs) and aluminum arsenide (AlAs). The band gap of the epitaxial layer 11 can be between 1.3 and 2.5 eV.

[0047] In addition, in the VCSEL device, the epitaxial layer 11 may include 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 may each be a stack of reflectors, such as a distributed Bragg reflector (DBR). The multi-quantum well layer 11b is disposed on the N-type epitaxial layer 11a, and the P-type epitaxial layer 11c is disposed on the multi-quantum well layer 11b. Furthermore, if Figure 1 As shown, the epitaxial layer 11 further includes two current blocking layers 11d, which are disposed in the P-type epitaxial layer 11c and are laterally separated from each other by a distance. Each current blocking layer 11d is an insulating layer, which can be formed by wet oxidation or ion implantation. The two current blocking layers 11d are used to confine the current so that the current can be concentrated through the area between them.

[0048] The first contact electrode 12 is disposed on the epitaxial layer 11 and includes an opening 12a. The opening 12a has an aperture so that light can be radiated 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 to bond the substrate 14 disposed thereon. According to the actual structure, the bonding layer 13 will also be disposed on other layers, such as on the epitaxial layer 11 or on the dielectric layer 18 described later. The bonding layer 13 may include glue, dielectric or a combination thereof. For example, the glue may use benzocyclobutene (BCB) glue, and the dielectric may use silicon nitride (SiNx). The substrate 14 may be a sapphire (Al2O3) substrate, but is not limited thereto. According to different applications, any transparent substrate with a transmittance of more than 90% may be used.

[0049] The first metal pad 15 is a P-pad, which is disposed below the first region R1 of the epitaxial layer 11 and extends longitudinally to be electrically connected to the first contact electrode 12. Figure 1 As shown, the first region R1 of the epitaxial layer 11 has a longitudinal through hole 22, so the first metal pad 15 can extend longitudinally along the longitudinal through hole 22 and be electrically connected to the first contact electrode 12. The material of the first metal pad 15 can be the same as that of the first contact electrode 12, such as gold (Au), titanium (Ti) or platinum (Pt). The longitudinal through hole 22 can also be formed by a wet etching process or a dry etching process in the process, and can be formed in the same process stage as the trench 20.

[0050] The second contact electrode 16 is disposed under the second region R2 of the epitaxial layer 11. The second contact electrode 16 is to provide an ohmic contact with the epitaxial layer 11, and may be made of germanium gold (GeAu), but is not limited thereto. The second metal pad 17 is an N-pad, which is disposed under the second region R2 of the epitaxial layer 11 across 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, such as gold (Au), titanium (Ti) or platinum (Pt).

[0051] like Figure 1As shown, the first metal pad 15 is disposed under the N-type epitaxial layer 11a of the first region R1, and the second contact electrode 16 and the second metal pad 17 are disposed under the N-type epitaxial layer of the second region R2. The first contact electrode 12 is disposed on the P-type epitaxial layer 11c of the first region R1 and the P-type epitaxial layer 11c of 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 groove 20, under this structure, the present invention can avoid the P-side metal electrode (i.e., the first metal pad 15) in contact with the P-type semiconductor and the N-side metal electrode (i.e., the second metal pad 17) in contact with the N-type semiconductor being electrically connected to cause leakage current, causing the current not to flow through the multiple quantum well (MQW) layer, so that the electroluminescent element cannot operate as expected.

[0052] The electroluminescent element 1 further comprises a dielectric layer 18. The material of the dielectric layer 18 may be silicon dioxide (SiO2), but is not limited thereto. Figure 1 As shown, the dielectric layer 18 includes a first portion disposed between the first contact electrode 12 and an upper surface of the epitaxial layer 11, a second portion disposed on a side wall adjacent to the first region R1 of the epitaxial layer 11 and the groove 20 and on both side walls of the second region R2 of the epitaxial layer 11, and a third portion disposed on a lower surface of the epitaxial layer 11. The first portion does not overlap with the first region R1 and the opening 12a of the epitaxial layer 11. The third portion does not overlap with the first metal pad 15 and does not overlap with the second contact electrode 16.

[0053] Figure 2 FIG. 2 shows an electroluminescent device 2 according to a second embodiment of the present invention. In this embodiment, the dielectric layer 18 of the electroluminescent device 2 is formed on Figure 1 In addition to the illustrated region, the crystal is also formed on the upper and lower surfaces, the two side walls and the side walls of the longitudinal through hole 22 of the first region R1 of the epitaxial layer 11 .

[0054] It should be noted that the dielectric layer 18 of the electroluminescent device of the present invention can be disposed in any region for electrical insulation depending on the actual application to prevent current leakage and loss in any region. Therefore, the electroluminescent device with any feasible dielectric layer configuration is protected by the present invention.

[0055] Figure 3 The electroluminescent device 3 of the third embodiment of the present invention is shown. Figure 1 The main difference between the electroluminescent element 1 and the embodiment is that the first metal pad 15 extends longitudinally along a side wall of the first region R1 and is electrically connected to the first contact electrode 12. Therefore, in the present embodiment, there is no longitudinal through hole 22 in the first region R1 of the epitaxial layer 11.

[0056] The electroluminescent elements 1, 2, and 3 of the present invention may be subsequently bonded to a packaging substrate. Depending on the application, the packaging substrate may be an aluminum nitride (AIN) substrate or a silicon substrate, but is not limited thereto. Since a person skilled in the art can easily understand how to bond the electroluminescent elements of the present invention to a packaging substrate, no further details are given here.

[0057] In summary, the electroluminescent element of the present invention separates the epitaxial layer between the P-side pad and the N-side pad, thereby preventing the epitaxial layer or the dielectric layer from being subjected to stress and breaking after the electroluminescent element is mounted on the packaging substrate, and preventing the current from not flowing through the multiple quantum well (MQW) layer due to the break, so that the electroluminescent element cannot operate as expected.

[0058] The above embodiments are only used to illustrate the embodiments of the present invention and explain the technical features of the present invention, and are not used to limit the protection scope of the present invention. Any changes or equivalent arrangements that can be easily completed by those skilled in the art belong to the scope claimed by the present invention, and the scope of protection of the present invention shall be based on the claims.

Claims

1. An electroluminescent element, comprising: An epitaxial layer having a groove, wherein the groove vertically divides the epitaxial layer into a first region and a second region, so that the first region and the second region are separated from each other; a first contact electrode disposed on the epitaxial layer and comprising 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 and extending longitudinally to be 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 is disposed below the second region of the epitaxial layer via the second contact electrode.

2. The electroluminescent element according to claim 1, wherein The electroluminescent element is a vertical cavity surface emitting laser flip chip.

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

4. The electroluminescent element according to claim 2, wherein The epitaxial layer comprises: an N-type epitaxial layer; A multi-quantum well layer is disposed on the N-type epitaxial layer; A P-type epitaxial layer disposed on the multi-quantum well layer; and Two current blocking layers are disposed in the P-type epitaxial layer and are laterally separated from each other by a distance; Wherein, 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 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.

5. The electroluminescent element according to claim 2, wherein The epitaxial layer is grown by using III-V semiconductor material or II-VI semiconductor material in an organic metal chemical vapor deposition method or a molecular beam epitaxial method.

6. The electroluminescent element according to claim 2, wherein The band gap of the epitaxial layer is between 1.3 and 2.5 eV.

7. The electroluminescent element according to claim 1, wherein The trench is formed by a wet etching process or a dry etching process.

8. The electroluminescent element according to claim 1, wherein The first region of the epitaxial layer has a longitudinal through hole, and the first metal pad extends longitudinally along the longitudinal through hole and is electrically connected to the first contact electrode.

9. The electroluminescent element according to claim 1, wherein The first metal pad extends longitudinally along a side wall of the first region and is electrically connected to the first contact electrode.

10. The electroluminescent device as claimed in claim 1, further comprising a dielectric layer, wherein the dielectric layer comprises: A first portion is disposed between the first contact electrode and an upper surface of the epitaxial layer, wherein: The first portion does not overlap with the first region of the epitaxial layer and the opening; a second portion disposed on a side wall of the first region of the epitaxial layer adjacent to the trench and on two side walls of the second region of the epitaxial layer; as well as A third portion is disposed on a lower surface of the epitaxial layer, wherein the third portion does not overlap with the first metal pad and does not overlap with the second contact electrode.

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