Near infrared light emitting diode and manufacturing method thereof

Abstract

This invention provides a near-infrared light-emitting diode and its manufacturing method. The near-infrared light-emitting diode includes a substrate, an epitaxial composite layer, a top electrode, and a black photoresist. The epitaxial composite layer is disposed on the substrate and has a light-emitting layer with a light emission wavelength ranging from 750 nanometers (nm) to 1000 nanometers (nm). The top electrode is disposed on the upper surface of the epitaxial composite layer. The black photoresist covers the epitaxial composite layer, exposing only the top electrode, thereby absorbing visible light in the light emission wavelength range and allowing only infrared light to pass through the black photoresist and be emitted.

Description

Technical Field

[0001] This invention relates to a near-infrared light-emitting diode and its manufacturing method, and more particularly to a near-infrared light-emitting diode that can suppress red glow phenomenon and its manufacturing method. Prior Technology

[0002] The applications of near-infrared (NIR) light-emitting diodes (LEDs) are becoming increasingly widespread, covering fields such as communications, medical, industrial, and consumer electronics. For example, in optical communications, NIR LEDs provide stable and low-power light sources in the main wavelength ranges of 850 nm and 940 nm, suitable for high-frequency modulated signals and short-distance data transmission, such as fiber optic communications and high-speed local area networks. Alternatively, in medical applications, NIR LEDs have the characteristic of penetrating the skin, making them suitable for measuring blood oxygen saturation and heart rate. They are already used in wearable devices for blood oxygen and heart rate monitoring.

[0003] However, the common near-infrared light, primarily used in wavelengths such as 850 nm and 940 nm, has an emission spectrum that is very close to or even partially covers the visible light wavelength range of 700 nm or shorter. If the application module is poorly packaged, this can easily cause a "red glow phenomenon," making people see red light in the dark. Currently, commercially available near-infrared LED application modules typically use encapsulating adhesives or encapsulation modules to block visible light red glow. While this method blocks visible light, it also blocks near-infrared light, significantly reducing the brightness of the near-infrared LED. Furthermore, the external encapsulating adhesive of near-infrared LEDs often has concerns about light leakage due to external factors, leading to poor reliability of application module products. To overcome these problems, the industry urgently needs an innovative near-infrared LED architecture to improve the red glow phenomenon and overcome the light leakage problem caused by poor encapsulation of infrared light. Summary of the Invention

[0004] The main objective of this invention is to provide an innovative near-infrared light-emitting diode and its manufacturing method. Compared with traditional optoelectronic components, this invention utilizes black photoresist to coat the epitaxial layer of the near-infrared light-emitting diode. By leveraging the characteristic of black photoresist to effectively absorb visible light while allowing infrared light to pass through, the invention aims to suppress red glow phenomena and maintain high brightness.

[0005] To achieve the above objectives, the present invention provides a near-infrared light-emitting diode, comprising a substrate, an epitaxial composite layer, a top electrode, and a black photoresist. The epitaxial composite layer is disposed on the substrate and has a light-emitting layer with a light emission wavelength ranging from 750 nanometers (nm) to 1000 nanometers (nm). The top electrode is disposed on the upper surface of the epitaxial composite layer. The black photoresist covers the epitaxial composite layer, exposing only the top electrode, thereby absorbing visible light in the light emission wavelength range and allowing only infrared light to pass through the black photoresist and be emitted externally.

[0006] In one embodiment of the present invention, the infrared light emitted by the near-infrared light-emitting diode through the black photoresist is in the range of 850 nanometers (nm) to 940 nanometers (nm).

[0007] In one embodiment of the present invention, the thickness of the black photoresist in the near-infrared light-emitting diode is about 1 to 5 micrometers (µm).

[0008] In one embodiment of the near-infrared light-emitting diode of the present invention, the black photoresist material comprises 1-Methoxy-2-propanol acetate and cyclohexanone.

[0009] In one embodiment of the near-infrared light-emitting diode of the present invention, the epitaxial composite layer further comprises a P-type epitaxial layer and an N-type epitaxial layer sandwiching the light-emitting layer.

[0010] In one embodiment of the near-infrared light-emitting diode of the present invention, the materials of the P-type epitaxial layer and the N-type epitaxial layer include gallium arsenide (GaAs) or aluminum gallium arsenide (AlGaAs), and the material of the light-emitting layer includes indium gallium arsenide (InGaAs) or aluminum gallium arsenide (AlGaAs).

[0011] In one embodiment of the present invention, the near-infrared light-emitting diode has a substrate that is either a gallium arsenide (GaAs) substrate or a silicon (Si) substrate.

[0012] To achieve the above objectives, the present invention provides a method for manufacturing a near-infrared light-emitting diode, comprising the following steps: providing an epitaxial composite layer disposed on a substrate, the epitaxial composite layer having a light-emitting layer with a light emission wavelength of 750 nanometers (nm) to 1000 nanometers (nm); providing an upper electrode disposed on the upper surface of the epitaxial composite layer; and providing a black photoresist covering the epitaxial composite layer and exposing only the upper electrode, thereby absorbing visible light in the light emission wavelength and allowing only infrared light to penetrate the black photoresist and be emitted to the outside.

[0013] In one embodiment of the present invention, the method for manufacturing a near-infrared light-emitting diode includes a step of providing a black photoresist with a thickness of about 1 to 5 micrometers (µm). The material of the black photoresist includes 1-methoxy-2-propanol acetate and cyclohexanone.

[0014] In one embodiment of the present invention, the step of providing an epitaxial composite layer in the manufacturing method of a near-infrared light-emitting diode involves providing a P-type epitaxial layer and an N-type epitaxial layer sandwiching the light-emitting layer.

[0015] In one embodiment of the present invention, the manufacturing method of a near-infrared light-emitting diode includes a P-type epitaxial layer and an N-type epitaxial layer made of gallium arsenide (GaAs) or aluminum gallium arsenide (AlGaAs), and a light-emitting layer made of indium gallium arsenide (InGaAs) or aluminum gallium arsenide (AlGaAs).

[0016] In one embodiment of the present invention, the method for manufacturing a near-infrared light-emitting diode uses a gallium arsenide (GaAs) substrate or a silicon (Si) substrate as the substrate.

[0017] After referring to the drawings and the embodiments described below, those skilled in the art will understand other objects of the present invention, as well as the technical means and implementation of the present invention. Simple Explanation of the Diagram

[0018] Figures 1 and 2 show schematic diagrams of manufacturing a near-infrared light-emitting diode according to an embodiment of the present invention; Figure 3 shows a top view of a near-infrared light-emitting diode in one embodiment of the present invention; Figure 4 shows a cross-sectional view of line segment AA in Figure 3; and Figure 5 shows a schematic diagram of the manufacturing process steps of a near-infrared light-emitting diode in one embodiment of the present invention. Implementation

[0019] The present invention will be explained below through embodiments. These embodiments are not intended to limit the implementation of the invention to any specific environment, application, or special method as described in the embodiments. Therefore, the descriptions of the embodiments are for illustrative purposes only and are not intended to limit the invention. It should be noted that in the following embodiments and drawings, elements not directly related to the present invention have been omitted and are not shown, and the dimensional relationships between the elements in the drawings are for ease of understanding only and are not intended to limit the actual scale.

[0020] Please refer to Figure 1, which shows a schematic diagram of fabricating a near-infrared light-emitting diode 1 according to an embodiment of the present invention. In this embodiment, a substrate 10 is first provided, which is preferably an opaque substrate, such as a gallium arsenide (GaAs) substrate or a silicon (Si) substrate. Next, an epitaxial composite layer 100 is formed on the substrate 10. This epitaxial composite layer 100 includes an N-type epitaxial layer 110, a light-emitting layer 120, and a P-type epitaxial layer 130. Specifically, the light-emitting layer 120 is a multiple quantum well (MQW) structure formed of indium gallium arsenide (InGaAs) or aluminum gallium arsenide (AlGaAs) ternary compound semiconductor, sandwiched between the N-type epitaxial layer 110 and the P-type epitaxial layer 130. In this embodiment, the emission wavelength of the multiple quantum wells can be from 750 nanometers (nm) to 1000 nanometers (nm) to provide infrared light with the main wavelength at 850 nanometers (nm) or 940 nanometers (nm).

[0021] Furthermore, the N-type epitaxial layer 110 is an N-type gallium arsenide (GaAs) layer or an N-type aluminum gallium arsenide (AlGaAs) layer, and the P-type epitaxial layer 130 is a P-type gallium arsenide (GaAs) layer or a P-type aluminum gallium arsenide (AlGaAs) layer. It should be noted that the materials described in the above embodiments are merely one example, and the present invention is not limited thereto. In practical applications, the materials and their composition can be adjusted according to the emission wavelength; for example, the epitaxial layer can be gallium phosphide (GaP), indium phosphide (InP), indium gallium arsenide (InGaAs), etc. Next, an electrode metallization process is performed to form an upper electrode 140 on the epitaxial composite layer 100 and a lower electrode 150 on the back side of the substrate 10. The materials of the upper electrode 140 and the lower electrode 150 can be, for example, germanium gold (GeAu), germanium gold nickel (GeAuNi), or germanium titanium platinum (GeTiPtAu).

[0022] Referring to Figure 2, a protective layer (not shown) is then formed on the surface of the component, followed by a meta-electrode etching (MESA) process to etch a portion of the epitaxial composite layer 100. Specifically, the N-type epitaxial layer 110, the light-emitting layer 120, and the P-type epitaxial layer 130 are etched to form a meta-electrode structure on the substrate 10. Next, please refer to Figures 3 and 4 together. Figure 3 shows a top view of the near-infrared light-emitting diode 1 in an embodiment of the present invention, and Figure 4 is a cross-sectional view of line segment AA in Figure 3. As shown in these two figures, a black photoresist 160 coating process is then performed to completely cover the epitaxial composite layer 100, exposing only the upper electrode 140 to facilitate subsequent electrode wire bonding. In a specific embodiment, the black photoresist 160 is made of 1-methoxy-2-propanol acetate and cyclohexanone, which absorb visible light in the emission band of the light-emitting layer 120 while allowing only infrared light to pass through the black photoresist and be emitted. Specifically, the black photoresist 160 can absorb red light in the band of about 700 nanometers (nm) and only allow infrared light with the main band of 850 nanometers (nm) or 940 nanometers (nm) to pass through, thus ensuring that the near-infrared light-emitting diode 1 of the present invention can suppress the red glow phenomenon of conventional near-infrared light-emitting diodes. Specifically, the thickness of the black photoresist 160 is about 1 to 5 micrometers (µm), preferably, the thickness of the black photoresist 160 is 3 micrometers (µm).

[0023] It must be emphasized that the black photoresist coating on the epitaxial composite layer of the near-infrared light-emitting diode (NILED) of this invention is formed during the wafer stage. Based on the current number of chips on a single wafer, each wafer can simultaneously perform a one-time black photoresist coating process on 30,000 to 40,000 NILED chips, ensuring that the epitaxial layer of each chip is completely covered with black photoresist to absorb visible light while allowing near-infrared light outside the visible light band to be emitted. In contrast, the aforementioned traditional module light-shielding process using black encapsulant during the encapsulation stage is performed at the chip encapsulation stage. However, such a light-shielding process can only coat a single package at a time, and cannot simultaneously coat a large number of packages. Therefore, the innovative structure and manufacturing method disclosed in this invention not only achieves a tight, leak-free red glow suppression effect, but its corresponding production process and capacity efficiency are also far superior to the traditional black glue encapsulation process.

[0024] Please refer to Figure 5, which shows a schematic diagram of the fabrication process steps of the near-infrared light-emitting diode of the present invention. First, in step S01, an epitaxial composite layer is provided and disposed on a substrate. This epitaxial composite layer has a light-emitting layer with a light emission wavelength ranging from 750 nanometers (nm) to 1000 nanometers (nm). Second, in step S02, an upper electrode is provided and disposed on the upper surface of the epitaxial composite layer. Finally, in step S03, a black photoresist is provided, covering the epitaxial composite layer and exposing only the upper electrode, thereby absorbing visible light in the light emission wavelength range and allowing only infrared light to pass through the black photoresist and be emitted externally. The descriptions of the relevant components can be found in the foregoing content and will not be repeated here.

[0025] The above embodiments are merely illustrative of the implementation of the present invention and to explain its technical features, and are not intended to limit the scope of protection of the present invention. Any changes or equivalent arrangements that can be easily made by those skilled in the art are within the scope of the present invention, and the scope of protection of the present invention shall be determined by the scope of the patent application.

[0026] 1: Near-infrared light-emitting diode 10:Substrate 100: Epitaxial Composite Layer 110: N-type epitaxial layer 120: Emissive layer 130: P-type epitaxial layer 140: Upper electrode 150: Lower electrode 160: Black photoresist AA: Line segment

Claims

1. A near-infrared light-emitting diode, comprising: a substrate; an epitaxial composite layer having a platform structure disposed on the substrate, having a light-emitting layer having an emission wavelength of 750 nanometers (nm) to 1000 nanometers (nm); a top electrode disposed on the upper surface of the platform structure; and a black photoresist covering the platform structure and exposing only the top electrode, wherein the black photoresist has a thickness of 1 to 5 micrometers (µm), and the material of the black photoresist comprises 1-methoxy-2-propanol acetate and cyclohexanone, thereby absorbing visible light below 700 nanometers (nm) in the emission wavelength range and allowing only infrared light of 850 nanometers (nm) to 940 nanometers (nm) to pass through the black photoresist and be emitted to the outside.

2. The near-infrared light-emitting diode as described in claim 1, wherein the epitaxial composite layer further comprises a P-type epitaxial layer and an N-type epitaxial layer sandwiching the light-emitting layer.

3. The near-infrared light-emitting diode as described in claim 2, wherein the materials of the P-type epitaxial layer and the N-type epitaxial layer comprise gallium arsenide (GaAs) or aluminum gallium arsenide (AlGaAs), and the material of the light-emitting layer comprises indium gallium arsenide (InGaAs) or aluminum gallium arsenide (AlGaAs).

4. The near-infrared light-emitting diode as described in claim 1, wherein the substrate is a gallium arsenide (GaAs) substrate or a silicon (Si) substrate.

5. A method for manufacturing a near-infrared light-emitting diode, comprising: providing an epitaxial composite layer having a platform structure disposed on a substrate, the epitaxial composite layer having a light-emitting layer having an emission wavelength of 750 nanometers (nm) to 1000 nanometers (nm); providing an upper electrode disposed on the upper surface of the platform structure; and providing a black photoresist covering the platform structure and exposing only the upper electrode, wherein the black photoresist has a thickness of 1 to 5 micrometers (µm), and the material of the black photoresist comprises 1-methoxy-2-propanol acetate and cyclohexanone, thereby absorbing visible light below 700 nanometers (nm) in the emission wavelength range and allowing only infrared light of 850 nanometers (nm) to 940 nanometers (nm) to pass through the black photoresist and be emitted to the outside.

6. The method for manufacturing a near-infrared light-emitting diode as described in claim 5, wherein the step of providing the epitaxial composite layer involves providing a P-type epitaxial layer and an N-type epitaxial layer sandwiching the light-emitting layer.

7. The method for manufacturing a near-infrared light-emitting diode as described in claim 6, wherein the materials of the P-type epitaxial layer and the N-type epitaxial layer comprise gallium arsenide (GaAs) or aluminum gallium arsenide (AlGaAs), and the material of the light-emitting layer comprises indium gallium arsenide (InGaAs) or aluminum gallium arsenide (AlGaAs).

8. A method for manufacturing a near-infrared light-emitting diode as described in claim 5, wherein the substrate is a gallium arsenide (GaAs) substrate or a silicon (Si) substrate.

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