Photocoupled single-chip structure and method for manufacturing the same

Abstract

The present invention provides an optically coupled single chip structure and a method for manufacturing the same. [Solution] The optically coupled single-chip structure includes an epitaxial growth substrate, a light emitting unit, an electrical insulating layer, and a light receiving unit. The light emitting unit is disposed on the epitaxial growth substrate. The electrical insulating layer is disposed on the light emitting unit. The light receiving unit is disposed on the electrical insulating layer. The light emitting unit generates an optical signal in response to an input signal. The optical signal passes through the electrical insulating layer and is directly absorbed by the light receiving unit and converted into an output signal.

Description

Technical Field

[0001] The present invention relates to an optical coupling element and a method for manufacturing the same, and particularly to a structure of an optical coupling single chip having a light emitting unit and a light receiving unit simultaneously on a single chip and a method for manufacturing the same.

Background Art

[0002] An optical coupling element is an electronic element that transmits an electrical signal using light. Usually, two chips having different functions, namely a light emitting diode and a light detection unit (for example, a phototransistor, a photodiode, etc.) are arranged to realize electrical insulation and signal transmission. In this design, since there is no direct electrical connection between the input circuit and the output circuit, the effects of high voltage insulation and noise suppression can be obtained.

[0003] As shown in FIG. 1, the conventional optical coupling element 1 generally has a package structure with left - right arrangement and a package structure with up - down arrangement. In the optical coupling element 1 with the left - right arrangement package structure, the light emitting diode 10 and the light detection unit 20 are respectively arranged at positions facing each other on the left and right inside the optical coupling element 1. On the other hand, in the optical coupling element 1 with the up - down arrangement package structure, the light emitting diode 10 and the light detection unit 20 are respectively arranged at positions facing each other on the up and down inside the optical coupling element 1. However, in the optical coupling element 1 with the left - right arrangement or up - down arrangement package structure, the light emitting diode 10 and the light detection unit 20 are individual independent chips. In the optical signal transmission path, since the optical signal passes through the air or the package medium outside the light emitting diode 10 and is then received by the light detection unit 20, the external quantum efficiency of the light emitting diode is significantly reduced.

[0004] On the other hand, from a physical structural perspective, the two independent chips, the light-emitting diode 10 and the photodetector unit 20, each need to be mounted on a lead frame 30 and assembled as a final device. Therefore, conventional optical coupling devices require designing the lead frame space to accommodate the two independent chips. After assembly, these occupy a considerable volume. Furthermore, conventional optical coupling devices have problems such as complex manufacturing processes and high costs. The problems currently faced by conventional optical coupling devices, such as issues with the optical signal transmission path, excessive device volume, and high costs, urgently need to be addressed. [Overview of the Initiative]

[0005] The main objective of this invention is to provide an innovative optically coupled single-chip structure and a method for manufacturing the same. This not only improves the external quantum efficiency of the light-emitting diode, but also reduces the overall volume of the optically coupled element, enabling thinner package elements and further reducing manufacturing time and cost.

[0006] To achieve the above objective, the present invention provides an optically coupled single-chip structure. The optically coupled single-chip structure includes an epitaxial growth substrate, a light-emitting unit, an electrical insulating layer, and a light-receiving unit. The light-emitting unit is mounted on the epitaxial growth substrate. The electrical insulating layer is mounted on the light-emitting unit. The light-receiving unit is mounted on the electrical insulating layer. The light-emitting unit generates an optical signal in response to an input signal. The optical signal passes through the electrical insulating layer and is directly absorbed by the light-receiving unit, where it is converted into an output signal.

[0007] In an embodiment of the optically coupled single-chip structure of the present invention, the difference in lattice constants of the materials of the light-emitting unit, the light-receiving unit, and the electrical insulating layer is 0.4 angstroms (Å) or less.

[0008] In an embodiment of the optically coupled single-chip structure of the present invention, the band gap (Energy Band Gap, Eg) of the light-emitting unit is greater than or equal to the band gap of the light-receiving unit.

[0009] In an embodiment of the optically coupled single-chip structure of the present invention, the band gap of the electrical insulating layer is at least 0.1 eV larger than the band gap of the light-emitting unit.

[0010] In an embodiment of the photocoupled single-chip structure of the present invention, the epitaxial growth substrate is a gallium arsenide (GaAs) substrate.

[0011] In an embodiment of the photocoupled single-chip structure of the present invention, the electrical insulating layer includes an N-type / P-type indium gallium phosphide (InGaP) reverse bias interface layer, and the doping concentration of the N-type / P-type indium gallium phosphide reverse bias interface layer is 10 17 / cm 3 It is less than.

[0012] In an embodiment of the optically coupled single-chip structure of the present invention, the light-emitting unit has a pair of positive and negative electrodes, which are mounted on a light-receiving unit and electrically connected to the light-emitting unit by passing through the light-receiving unit.

[0013] To achieve the above objective, the present invention provides an optically coupled single-chip structure. The optically coupled single-chip structure includes an epitaxial growth substrate, a light-receiving unit, an electrical insulating layer, and a light-emitting unit. The light-receiving unit is mounted on the epitaxial growth substrate. The electrical insulating layer is mounted on the light-receiving unit. The light-emitting unit is mounted on the electrical insulating layer. The light-emitting unit generates an optical signal in response to an input signal. The optical signal passes through the electrical insulating layer and is directly absorbed by the light-receiving unit, where it is converted into an output signal.

[0014] In an embodiment of the optically coupled single-chip structure of the present invention, the light-receiving unit has a pair of positive and negative electrodes, which are mounted on a light-emitting unit and electrically connected to the light-receiving unit by passing through the light-emitting unit.

[0015] To achieve the above objective, the present invention provides a method for manufacturing an optically coupled single-chip structure. The manufacturing method includes the steps of: preparing an epitaxial growth substrate; forming a light-emitting unit on the epitaxial growth substrate; forming an electrical insulating layer on the light-emitting unit; and forming a light-receiving unit on the electrical insulating layer. The light-emitting unit generates an optical signal in response to an input signal. The optical signal passes through the electrical insulating layer and is directly absorbed by the light-receiving unit, where it is converted into an output signal.

[0016] In an embodiment of the method for manufacturing the photocoupled single-chip structure of the present invention, the steps for forming the light-emitting unit, forming the electrical insulating layer, and forming the light-receiving unit are all carried out by epitaxial growth on an epitaxial growth substrate using metal-organic chemical vapor deposition.

[0017] In an embodiment of the method for manufacturing the optically coupled single-chip structure of the present invention, the method further includes the step of forming a pair of positive and negative electrodes that are electrically connected to a light-emitting unit and a light-receiving unit, respectively, wherein the positive and negative electrodes of the light-emitting unit penetrate the light-receiving unit.

[0018] Those skilled in the art will be able to 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 later. [Brief explanation of the drawing]

[0019] [Figure 1] Cross-sectional diagrams showing two conventional types of optical coupling elements. [Figure 2] Cross-sectional view corresponding to the manufacturing process of the photocoupled single-chip structure of the present invention. [Figure 3] Cross-sectional view corresponding to the manufacturing process of the photocoupled single-chip structure of the present invention. [Figure 4] Cross-sectional view corresponding to the manufacturing process of the photocoupled single-chip structure of the present invention. [Figure 5] Plan view showing the electrode layout of the photocoupled single-chip structure of the present invention. [Figure 6] Flowchart of the manufacturing process for the photocoupled single-chip structure of the present invention

Best Mode for Carrying Out the Invention

[0020] Hereinafter, the content of the present invention will be described through examples. Note that the examples of the present invention are examples of embodiments, and are not intended to be limited to the environments, applications, or specific aspects as described in the examples. Therefore, the description of the examples is for explaining the present invention, but does not limit the present invention. In the embodiments and the drawings, components not directly related to the present invention are omitted and not shown. The dimensional relationships of the components in the drawings are for facilitating understanding and do not limit the actual dimensions.

[0021] The present invention discloses an optical coupling single-chip structure and a manufacturing method thereof. As shown in FIG. 2, first, an epitaxial growth substrate 100 is prepared. This epitaxial growth substrate is a gallium arsenide (GaAs) wafer, but is not limited thereto. Next, a light-emitting unit 200, an electrical insulation layer 300, and a light-receiving unit 400 are sequentially epitaxially grown on the epitaxial growth substrate 100 by metal-organic chemical vapor deposition (MOCVD). In addition, the vertical structure of another optical coupling single-chip of the present invention is a configuration in which the light-emitting unit is disposed below the light-receiving unit, that is, a light-receiving unit and an electrical insulation layer are sequentially formed on the epitaxial growth substrate, and finally the light-emitting unit is formed. This vertical structure is also included in the scope of the optical coupling single-chip structure of the present invention. However, for the sake of simplicity, the structure shown in FIG. 2 will be described as an example hereinafter.

[0022] In addition, in order to form three functional units including the light-emitting unit 200, the electrical insulation layer 300, and the light-receiving unit 400 by an epitaxial growth method on the same epitaxial growth substrate, when selecting the materials for each layer of these three functional units, it is necessary to select materials with substantially close lattice constants, and the difference in lattice constants should not be too large. Specifically, the difference in lattice constants of each layer material is set to be 0.4 angstroms (Å) or less, so that each layer material can grow epitaxially smoothly on the wafer. In the embodiment shown in FIG. 2, in this optically coupled single-chip structure, since the light-emitting unit 200 is in direct contact with the epitaxial growth substrate 100, during device operation, the waste heat generated by the light emission of the light-emitting unit 200 is directly released through the epitaxial growth substrate 100, thereby improving the performance of the device.

[0023] Also, as can be seen from FIG. 2, different from the conventional optically coupled device, one technical feature of the optically coupled device of the present invention is that this device has a single-chip structure. That is, as shown in FIG. 2, the light-emitting unit 200 and the light-receiving unit 400 are sequentially formed by an epitaxial growth method on a wafer. There is an electrical insulation layer 300 for electrical insulation between the light-emitting unit 200 and the light-receiving unit 400. Therefore, the present invention can overcome the problems of the prior art such as the device volume being too large, the manufacturing cost being high, and the optoelectronic efficiency of the device being insufficient.

[0024] Referring to Figure 3, the structure and composition of each layer of the light-emitting unit 200, the electrical insulating layer 300, and the light-receiving unit 400 in a specific embodiment of the optically coupled single-chip structure of the present invention will be described in detail. A gallium arsenide buffer layer that can adjust the lattice during subsequent epitaxial growth may be provided between the epitaxial growth substrate 100 and the light-emitting unit 200. The light-emitting unit 200 is a III-V epitaxial composite layer, but is not limited thereto. This epitaxial composite layer has, in order, an N-type doped epitaxial layer 210, a multiple quantum well (MQW) 220, and a P-type doped epitaxial layer 230. In this embodiment, the N-type doped epitaxial layer 210 is a ternary compound semiconductor layer, for example, a highly doped layer of N-type indium gallium phosphide (InGaP), and functions as an N-type contact layer. Similarly, the P-type doped epitaxial layer 230 is a ternary compound semiconductor layer, such as a highly doped P-type indium gallium phosphide (InGaP) layer, and functions as a P-type contact layer. The multiple quantum wells 220 use an aluminum gallium arsenide (AlGaAs) ternary material as a barrier layer and gallium arsenide (GaAs) as the quantum well layer. In addition, an intrinsic spacer layer may be provided outside the barrier layer and the quantum well layer. For example, by selecting undoped aluminum gallium arsenide (AlGaAs) as the spacer layer, doping impurities can be prevented from diffusing into the quantum well structure, thereby improving the electron and hole confinement efficiency within the quantum well.

[0025] Furthermore, preferably, a distributed Bragg reflector (DBR), such as an aluminum gallium arsenide / aluminum arsenide (AlGaAs / AlAs) layer, is selectively placed between the N-type doped epitaxial layer 210 and the multiple quantum well 220. This prevents photons from dissipating towards the substrate, increases the number of photons reflected upward, and improves the light extraction efficiency of the light-emitting diode. Alternatively, an additional N-type doped layer, such as an N-type aluminum gallium arsenide (AlGaAs) layer, may be provided between the N-type doped epitaxial layer 210 and the multiple quantum well 220. This provides a high free electron concentration and helps electrons to be effectively injected into the MQW structure. By providing a P-type doped layer, such as a P-type aluminum gallium arsenide (AlGaAs) layer, between the P-type doped epitaxial layer 230 and the multiple quantum well 220, a high free hole concentration can be provided, injecting holes into the MQW structure and forming a barrier corresponding to the N-type aluminum gallium arsenide (AlGaAs) layer, thereby promoting effective electron-hole recombination.

[0026] Referring to Figure 3, the structure and composition of the photodetector unit 400 in an embodiment of the optically coupled single-chip structure of the present invention will be described. As shown in Figure 3, the photodetector unit 400 of the present invention is a typical photodiode structure that converts an optical signal output from the light-emitting unit into an electrical signal. The structure of the photodetector unit mainly includes an N-type high-concentration doping layer 410, an intrinsic layer 420, and a P-type high-concentration doping layer 430. The N-type high-concentration doping layer 410 is an N-type indium gallium phosphide (InGaP) high-concentration doped epitaxial layer that functions as an N-type contact layer and can provide a high free electron concentration. Similarly, the P-type high-concentration doping layer 430 is a P-type indium gallium phosphide (InGaP) high-concentration doped epitaxial layer that functions as a P-type contact layer and provides a high free hole concentration, which helps holes to be injected into the intrinsic layer 420. Furthermore, in this embodiment, the intrinsic layer 420 is an undoped or lightly doped gallium arsenide (GaAs) layer, which functions as the active region of the photodiode, absorbing photons output from the light-emitting unit and generating electron-hole pairs. By adjusting the thickness of the intrinsic layer, the light absorption and quantum efficiency can be adjusted.

[0027] In a specific embodiment, a spacer layer can be provided between the intrinsic layer 420 and the N-type high-concentration doping layer 410 and the P-type high-concentration doping layer 430. For example, undoped aluminum gallium arsenide (AlGaAs) can be selected as the spacer layer. This prevents doping impurities on both sides of the intrinsic layer 420 from diffusing into the active region. Alternatively, an N-type doped layer, such as an N-type aluminum gallium arsenide (AlGaAs) layer, can be provided between the spacer layer and the intrinsic layer 420. A P-type doped layer, such as a P-type aluminum gallium arsenide (AlGaAs) layer, can be provided between the spacer layer and the intrinsic layer 420, thereby providing a high free hole concentration.

[0028] As shown in Figure 3, in order for the two different functional units, the light-emitting unit 200 and the light-receiving unit 400, to operate normally and not interfere with each other, it is necessary to first install an electrical insulating layer 300 on the light-emitting unit 200 on the epitaxial growth substrate 100 after the epitaxial growth of the light-emitting unit 200 is completed. In an embodiment of the present invention, this electrical insulating layer 300 is an N-type / P-type reverse bias interface layer. That is, the effect of electrical insulation is achieved by utilizing the principle of reverse bias of a PN diode. Specifically, a lightly doped P-type indium gallium phosphide (InGaP) layer is first epitaxially grown on the light-emitting unit 200, and then an N-type / P-type indium gallium phosphide (InGaP) reverse bias interface layer is formed on the lightly doped N-type indium gallium phosphide (InGaP) layer, thereby achieving the effect of electrical insulation. In a more preferred embodiment, the doping concentration of this N-type / P-type indium gallium phosphide reverse bias interface layer is 10 17 / cm 3 It is less than [value missing]. Low doping concentrations can increase the width of the depletion region and enhance the electrical insulation effect. Preferably, undoped aluminum gallium arsenide (AlGaAs) may be further epitaxially grown between the electrical insulation layer 300 and the light-emitting unit 200 and the light-receiving unit 400, respectively, to function as spacer layers.

[0029] Furthermore, the structure and composition of the light-emitting unit 200, the electrical insulating layer 300, and the light-receiving unit 400 described above are merely illustrative and do not limit the present invention. Those skilled in the art can make modifications after understanding the above, and these modifications are also included within the scope of the present invention. Incidentally, when selecting the materials for each unit, the band gap (Energy Band Gap, Eg) of each layer of the light-emitting unit must be greater than or equal to the band gap of each layer of the light-receiving unit. That is, the wavelength of the light generated by the light-emitting unit is smaller than the wavelength of the light absorbed by the light-receiving unit. After the light-emitting unit generates an optical signal, the optical signal is smoothly absorbed by the light-receiving unit, and then converted and output as an electrical signal. When selecting the material for the electrical insulating layer, it is preferable that the band gap of the electrical insulating layer be at least 0.1 eV larger than the band gap of the light-emitting unit in order to prevent the electrical insulating layer from absorbing the light output from the light-emitting unit, that is, to make the electrical insulating layer "transparent" to the light-emitting unit. As a result, most of the light output from the light-emitting unit is absorbed by the light-receiving unit.

[0030] Figure 4 is a schematic diagram of the electrode design of an optically coupled single-chip structure in an embodiment of the present invention. The pair of positive and negative electrodes (positive electrode 240, negative electrode 250) of the light-emitting unit 200 and the pair of positive and negative electrodes (positive electrode 440, negative electrode 450) of the light-receiving unit 400 are both arranged on one surface of the light-receiving unit 400. The pair of positive and negative electrodes of the light-emitting unit 200 penetrate the light-receiving unit 400 and the electrical insulation layer 300, and are electrically connected to the light-emitting unit 200. That is, the positive electrode 240 is electrically connected to the P-type doped epitaxial layer 230. The negative electrode 250 is electrically connected to the N-type doped epitaxial layer 210. The positive electrode 440 of the light-receiving unit 400 is electrically connected to the P-type high-concentration doping layer 430. The negative electrode 450 of the light-receiving unit 400 penetrates the P-type high-concentration doping layer 430 and the intrinsic layer 420 and is electrically connected to the N-type high-concentration doping layer 410. Furthermore, the portions of the electrodes that penetrate the epitaxial layer are insulated from the epitaxial layer by an insulating layer to prevent short circuits. On the other hand, according to the above description, if the optically coupled single-chip structure of the present invention consists of an epitaxial growth substrate, a light-receiving unit, an electrically insulating layer, and a light-emitting unit from bottom to top, the electrode design must be adjusted accordingly. That is, the pair of positive and negative electrodes of the light-receiving unit are installed on the light-emitting unit and adjusted to penetrate the light-emitting unit and be electrically connected to the light-receiving unit. A person skilled in the art can easily infer this based on the above description, so a detailed explanation is omitted.

[0031] Furthermore, this electrode layout can be designed as a wire-bonding electrode or a flip-chip electrode, depending on the requirements of the device, to achieve a thinner design. A more preferred embodiment will be described with reference to Figure 5. Figure 5 is a plan view showing the electrode layout of the optically coupled single-chip structure of the present invention. As shown in Figure 5, the present invention improves the efficiency of the device by increasing the covering area of ​​the positive electrode 440 of the light-receiving unit, thereby reflecting light emitted from the light-emitting unit to the outside but not absorbed by the light-receiving unit 400 back into the light-receiving unit 400. In the above embodiment, the epitaxial growth substrate is an intrinsic semi-insulating substrate. In other embodiments where the substrate is a conductive substrate, the layout in which the four electrodes are arranged on the same side is changed to a layout in which three electrodes are arranged on one surface and the remaining electrode is arranged on the conductive substrate.

[0032] In summary, in the optically coupled single-chip structure of the present invention, a light-emitting unit, an electrical insulating layer, and a light-receiving unit are formed on a wafer by an epitaxial growth method. Therefore, the light emitted from the epitaxial layer of the light-emitting diode passes through an internal material with a similar refractive index, then directly through the electrical insulating layer and is absorbed by the light-receiving unit. In this way, the external quantum efficiency of the light-emitting diode is greatly improved. That is, the light-emitting unit of the optically coupled single-chip structure of the present invention generates an optical signal in response to an external input signal. Subsequently, the optical signal passes through the electrical insulating layer and is directly absorbed by the light-receiving unit of the optically coupled single-chip element, and converted into an output signal. The present invention overcomes the problem in conventional optically coupled elements where light must pass outside the light-emitting unit in the transmission path before being received by the light-receiving unit, resulting in reduced optical efficiency. Furthermore, the volume of the single-chip structure in the present invention is also greatly reduced, thereby enabling the element to be made thinner and reducing manufacturing process time and cost.

[0033] FIG. 6 is a flowchart of the manufacturing process of the optical coupling single chip structure of the present invention. First, in step S01, an epitaxial growth substrate is prepared. Next, in step S02, a light emitting unit is formed. This light emitting unit is a light emitting diode. Next, in step S03, an electrically insulating layer is formed on the light emitting unit. In step S04, a light receiving unit is formed on the electrically insulating layer. Thereby, the optical coupling single chip structure of the present invention has a light emitting unit and a light receiving unit simultaneously in a single structure. For a detailed description of each unit, reference may be made to the foregoing content, which is omitted here.

[0034] The above embodiments are for explaining the embodiments of the present invention and for explaining the characteristic configurations of the present invention. The present invention is not limited to the above embodiments. 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 shall be based on the scope of the claims.

Description of Reference Numerals

[0035] 1 Optical coupling element 10 Light emitting diode 20 Photodetection unit 30 Lead frame [[ID=I18]] 100 Epitaxial growth substrate 200 Light emitting unit 210 N-type doped epitaxial layer 220 Multiple quantum well 230 P-type doped epitaxial layer 240 Positive electrode 250 Negative electrode 300 Electrically insulating layer 400 Light receiving unit 410 N-type high concentration doping layer 420 Intrinsic layer 430 P-type high concentration doping layer 440 Positive electrode 450 Negative electrode

Claims

1. It is an optically coupled single-chip structure, Epitaxial growth substrate and A light-emitting unit installed on the epitaxial growth substrate, An electrically insulating layer installed on the light-emitting unit, The light receiving unit is installed on the electrical insulating layer, The light-emitting unit generates an optical signal in response to an input signal. The aforementioned optical signal passes through the electrical insulating layer and is directly absorbed by the light receiving unit, where it is converted into an output signal. The epitaxial growth substrate is a gallium arsenide (GaAs) substrate. The aforementioned electrical insulating layer includes an N-type / P-type indium gallium phosphide (InGaP) reverse bias interface layer, and the doping concentration of the N-type / P-type indium gallium phosphide reverse bias interface layer is less than 10¹⁷ / cm³, in a photocoupled single-chip structure.

2. The optically coupled single-chip structure according to claim 1, characterized in that the difference in lattice constants of the materials of the light-emitting unit, the light-receiving unit, and the electrical insulating layer is 0.4 angstroms (Å) or less.

3. The optically coupled single-chip structure according to claim 1, characterized in that the band gap (Energy Band Gap, Eg) of the light-emitting unit is greater than or equal to the band gap of the light-receiving unit.

4. The optically coupled single-chip structure according to claim 1, characterized in that the band gap of the electrical insulating layer is at least 0.1 eV larger than the band gap of the light-emitting unit.

5. The light-emitting unit has a pair of positive and negative electrodes, The optically coupled single-chip structure according to claim 1, characterized in that the positive and negative electrodes are installed on the light-receiving unit and are electrically connected to the light-emitting unit through the light-receiving unit.

6. It is an optically coupled single-chip structure, Epitaxial growth substrate and A light-receiving unit installed on the epitaxial growth substrate, An electrical insulating layer installed on the light receiving unit, The electrical insulating layer includes a light-emitting unit installed on the aforementioned electrical insulating layer, The light-emitting unit generates an optical signal in response to an input signal. The aforementioned optical signal passes through the electrical insulating layer and is directly absorbed by the light receiving unit, where it is converted into an output signal. The epitaxial growth substrate is a gallium arsenide (GaAs) substrate. The aforementioned electrical insulating layer includes an N-type / P-type indium gallium phosphide (InGaP) reverse bias interface layer, and the doping concentration of the N-type / P-type indium gallium phosphide reverse bias interface layer is less than 10¹⁷ / cm³, in a photocoupled single-chip structure.

7. The optically coupled single-chip structure according to claim 6, characterized in that the difference in lattice constants of the materials of the light-emitting unit, the light-receiving unit, and the electrical insulating layer is 0.4 angstroms (Å) or less.

8. The light receiving unit has a pair of positive and negative electrodes, The optically coupled single-chip structure according to claim 6, characterized in that the positive and negative electrodes are installed on the light-emitting unit and electrically connected to the light-receiving unit through the light-emitting unit.

9. A method for manufacturing an optically coupled single-chip structure, The process of preparing an epitaxial growth substrate, The process of forming a light-emitting unit on the epitaxial growth substrate, The process of forming an electrically insulating layer on the light-emitting unit, The process includes forming a light-receiving unit on the electrical insulating layer, The light-emitting unit generates an optical signal in response to an input signal. The aforementioned optical signal passes through the electrical insulating layer and is directly absorbed by the light receiving unit, where it is converted into an output signal. The epitaxial growth substrate is a gallium arsenide (GaAs) substrate. A manufacturing method comprising the step of forming the electrical insulating layer, wherein the step includes an N-type / P-type indium gallium phosphide (InGaP) reverse bias interface layer, and the doping concentration of the N-type / P-type indium gallium phosphide reverse bias interface layer is less than 10¹⁷ / cm³.

10. The manufacturing method according to claim 9, characterized in that the steps for forming the light-emitting unit, forming the electrical insulating layer, and forming the light-receiving unit are all carried out by epitaxial growth on an epitaxial growth substrate using metal-organic chemical vapor deposition.

11. The process further includes the step of forming a pair of positive and negative electrodes that are electrically connected to the light-emitting unit and the light-receiving unit, respectively. The manufacturing method according to claim 9, characterized in that the positive and negative electrodes of the light-emitting unit penetrate the light-receiving unit.

Images