JPH06338628A - Optical coupler - Google Patents

Abstract

PURPOSE:To facilitate an alignment of a light-emitting element with a photodetector by a method wherein an insulating layer consisting of a transparent or semi-transparent material is formed on the semiconductor light-emitting element, the polycrystalline or amorphous semiconductor photodetector is formed on the insulating layer and light emitted when a current is injected in the light- emitting element reaches the photodetector. CONSTITUTION:An N-type GaP film 21 and a P-type GaP film 22 doped with Zn and O are grown on an N-type GaP substrate 20 by a liquid phase method. An N-type electrode 23 having an opening part 24 is formed on the rear of the substrate 20. An SiO2 film 25 is formed on the whole surface of the electrode 23 and a Cr film 26 provided with an opening part 27 is formed as an electrode of a photodiode. Si films 28 to 30, the electrode 26 and the film 25 are etched to form a step 31 for taking out the electrode 23 on the rear of the substrate 20 and the Si layers 28 to 30 are etched to form a step 32 for taking out the electrode 26 under the P-type Si layer 28. Lastly, an N-type electrode 33 and a P-type GaP electrode 34 of the photodiode are deposited and an optical coupler can be formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical coupler which can be used for separating electrical wiring and the like, and more particularly to an optical coupler which facilitates alignment between a light emitting element and a light receiving element.

[0002]

2. Description of the Related Art Conventionally, an optical coupler has been used to electrically separate a circuit in an electric circuit. This is a module in which a semiconductor light emitting element 51 and a light receiving element 52 are combined as shown in FIG. 10, and when a current flows through a first circuit (not shown) connected to the light emitting element 51, the element emits light and emits the light. The light receiving element 52 receives light and an electric signal is generated in a second circuit (not shown) connected to the light receiving element 52. Although the first circuit and the second circuit are connected by light, they are electrically independent, so that electrical noise generated in the first circuit, for example, is not transmitted to the second circuit.

[0003]

Both the light emitting element 51 and the light receiving element 52 shown in FIG. 10 are made of a single crystal material, and a semiconductor film is formed on the single crystal by epitaxial growth or the like and processed. , Chips that have been cut out have been used. Further, in the conventional optical coupler manufacturing process, it is said that the light emitting element 51 and the light receiving element 52 manufactured through such a complicated process are aligned at the position where the light emitted from the light emitting element 51 is coupled to the light receiving element 52. The process is included. Therefore, the manufacturing cost of the optical coupler is increased. Therefore, an object of the present invention is to provide an optical coupler that facilitates alignment between a light emitting element and a light receiving element.

[0004]

The above objects of the present invention can be achieved by the following constitutions. That is, a semiconductor light emitting element that injects a current into a pn junction or a pin junction formed on a semiconductor substrate to emit light, and a semiconductor light emitting element formed on the semiconductor light emitting element,
When a light composed of an insulating layer made of a material transparent or semitransparent to the emission wavelength of the light emitting element and a polycrystalline or amorphous semiconductor formed on the insulating layer enters, a pn junction or a pin junction is formed. An optical coupler which is composed of a light receiving element for generating carriers, and which emits light when a current is injected into the light emitting element reaches the light receiving element, or emits light by injecting a current into a pn junction or a pin junction formed on a semiconductor substrate. A semiconductor light emitting element, and an insulating layer formed on the back surface of a semiconductor substrate that is transparent or semitransparent to the emission wavelength of the light emitting element, and made of a material that is transparent or semitransparent to the emission wavelength of the light emitting element, When light composed of a polycrystalline or amorphous semiconductor formed on the insulating layer enters, carriers are generated in the pn junction or the pin junction. That it consists of a light receiving element, an optical coupler in which light is reaching the light receiving element when a current is injected into the light emitting element. Here, the light emitting elements and the light receiving elements are arranged in an array or two-dimensionally, and the light emitting elements and the light receiving elements are in one-to-one correspondence, or the light emitted from a single semiconductor light emitting element is two. It can be arranged so that it can be received by one or more light receiving elements, or it can be arranged so that a single light receiving element can receive the light emitted from two or more light emitting elements.

As the substrate, GaAs, AlGaAs,
Various materials such as InP, GaP, Si and ZnSe can be given. GaA is used as a material for forming the light emitting element.
s, AlGaAs, AlInP, GaInP, InGa
As, AlGaAsP, InGaAsP, ZnSe, I
nP, AlInAs, GaAsSb, AlAsSb, I
Any material including nGaAsP, GaP, ZnO, and any material that emits light by injecting a current into a pn junction or a pin junction can be used in the present invention. As the insulating film material for separating the light emitting element and the light receiving element, SiO ₂ , Al ₂ O ₃ ,
An insulating material such as Si ₃ N ₄ can be used,
It is preferable that the material has a small absorption coefficient with respect to the emission wavelength of the light emitting element. Further, as the light receiving element, Si, Ga
Any material such as As, AlGaAs, and ZnSe may be used, but it is necessary to have a band gap smaller than at least the energy corresponding to the emission wavelength of the light emitting element to be integrated and have a non-zero spectral sensitivity.

[0006]

【Example】

Example 1 FIG. 1 shows a process of manufacturing the element of this example, FIG. 2 (b) is a schematic perspective view of the manufactured element, and FIG. 3 is a sectional structure of the device. First, as shown in FIG.
An n-GaAs buffer layer 2, an n-AlGaAs layer 3 having an Al composition ratio of 0.4, a p-AlGaAs layer 4 having an Al composition ratio of 0.4, and a p-A formed on the -GaAs substrate 1 by MOCVD.
The lGaAs contact layer 5 was produced. Here, trimethylgallium and trimethylaluminum were used as the Group 3 raw material, arsine was used as the Group 5 raw material, and hydrogen was used as the carrier gas. Group 5 raw material / 3rd by growth of each layer
The group material ratio was 40. On this growth film, a SiO ₂ film 6 having a 50 μm square opening 7 was formed by the CVD method (FIG. 1B). This opening 7 is a p-AlGaAs layer 5
Will reach. Furthermore, 30μ on the SiO ₂ film 6
A Cr film 8 was formed as a p-type electrode for the p-AlGaAs layer 5 having an m-square opening 9 (FIG. 1C). Then, the SiO ₂ film 10 is formed again on the entire surface by the CVD method,
30 μm as the electrode of the photodiode formed on top
An electrode 11 having a corner opening 12 was prepared (FIG. 2).
(A)). Then, the p-Si layer 1 is formed by the plasma CVD method.
3, i-Si layer 14, and n-Si layer 15 were formed (FIG. 2).
(B)). Then, as shown in the cross-sectional view of FIG. 3, a step 16 for removing a part of the Si layers 13 to 15, the electrode 11 and the SiO ₂ film 10 to take out the AlGaAs electrode 8 and the Si layers 13 to 15 are formed. Etch Si
Each step 17 for taking out the electrode 11 of the layer was produced. Finally, the n-type electrode 18 and n of the photodiode
An n-GaAs electrode 19 was deposited on the back surface of the -GaAs substrate 1.

When a forward bias is applied between the electrodes 8 to 19, the n-AlGaAs layer 3 and the p-AlGaAs layer 4 are formed.
Light was emitted from the pn junction formed by. At that time, the emitted light of the light emitting diode reached the photodiode through the openings 7, 9, 12 and generated a voltage between the electrodes 11-18. The above shows that the light emitting diode and the photodiode are electrically separated but connected by light, and thus function as an optical coupler.

By using the element having the structure shown in the present embodiment, the light emitting diode and the photodiode can be separated into various configurations. In the example shown in FIG. 4, when the SiO ₂ film 42 is arranged between the light emitting diode 40 and the photodiode 41, and the light emitted from the light emitting diode 40 reaches the photodiode 41 through the opening 43, a pair is formed. It becomes the union of 1. Further, in the example of FIG. 5, the boundary portion 44 between two adjacent photodiodes 41 is arranged at a position corresponding to the opening 43 through which the light emitted from the light emitting diode 40 reaches. The light emitting diode 40 and the photodiode 41 are separated from each other. 1
It becomes a pair 2 bond. The example of FIG. 6 shows two light emitting diodes 4
The light emitted from 0 is arranged so as to reach the single photodiode 41 through the corresponding openings 43, and the light emitting diode 40 and the photodiode 41 form a two-to-one coupling. There is. Further, in the case of the structure shown in FIG. 7, a plurality of light emitting diodes 40a-4a arranged in parallel
The light emitted from the light source 0c is received by the photodiodes 41a to 41d, which are separated from each other by the boundary portions 44a to 44c of the plurality of photodiodes 41a to 41d arranged in parallel from the openings 43a to 43c. In this case, the light emitting diode 40 and the photodiode 41 correspond to one-to-two coupling, but for example, the light emission of the light emitting diodes 40a and 40b can be received by 41b. Although the light emitting diodes 40 and the photodiodes 41 are considered as a one-dimensional array in the above embodiment, they may be arranged in a two-dimensional (planar) shape. Further, there is no problem even if the light emitting diode 40 and the photodiode 41 are provided in the substrate by mixing the couplings such as one-to-one, one-to-many, and many-to-one.

Embodiment 2 As another embodiment of the present invention, an example in which a GaP light emitting diode and a photodiode are combined will be described with reference to FIGS. 8 and 9. As shown in FIG. 8, the n-GaP substrate 2
A substrate on which n-GaP21, p-GaP22 doped with Zn and O was grown by a liquid phase method was used. When current is injected into this element, it acts as a light emitting diode.
It emits light with a peak of 00 nm. Ga that is the substrate 20
Since the P layer has a band gap of 2.261 eV (about 550 nm) at room temperature, light emission of 700 nm reaches the back surface through the substrate 20. Therefore, an n-type electrode 23 having a 30 μm square opening 24 is formed on the back surface of the n-GaP substrate 20. Then, an SiO ₂ film 25 is formed on the entire surface of the n-type electrode 23, and a Cr film 26 having an opening 27 of 30 μm square is formed as an electrode of the photodiode. Then, a p-Si layer 28, an i-Si layer 29, and an n-S layer are formed by plasma CVD.
The i layer 30 is sequentially formed.

Subsequently, as shown in FIG. 9, Si layers 28 to 30, a part of the substrate 20, an electrode 26 and a SiO ₂ film 25 are formed.
Is formed by etching, and step 31 for taking out the electrode 23 of the GaP substrate 20 and step 32 for etching the Si layers 28 to 30 to take out the electrode 26 of the p-Si layer 28 are prepared. Finally n of the photodiode
The mold electrode 33 and the p-GaP electrode 34 are deposited. Electrode 23
When a forward bias is applied between the electrodes 34 to 34, light is emitted from the pn junction formed by the n-GaP layer 21 and the p-GaP layer 22, reaches the photodiode through the openings 24 and 27, and the electrodes 26 to 33 are electrically connected. Generated voltage. The above shows that the light emitting diode and the photodiode are electrically separated but connected by light, and thus function as an optical coupler.

[0011]

According to the present invention, a light emitting element and a light receiving element can be formed on a substrate by a simpler process than before, and alignment for coupling light can be realized by mask alignment during the process. Further, according to the present invention, a multi-channel optical coupler can be easily realized.

[Brief description of drawings]

FIG. 1 is a schematic view showing a manufacturing process of an optical coupler according to a first embodiment of the present invention.

FIG. 2 is a schematic view showing a manufacturing process of the optical coupler according to the first embodiment of the present invention.

FIG. 3 is a schematic sectional view of an optical coupler of Example 1 of the present invention.

FIG. 4 is a schematic cross-sectional view showing an element arrangement for making a one-to-one correspondence between the light emitting diode and the photodiode of the embodiment of the present invention.

FIG. 5 is a schematic cross-sectional view showing an element arrangement for making the light emitting diode and the photodiode of the embodiment of the present invention correspond one to two.

FIG. 6 is a schematic sectional view showing an element arrangement for making the light emitting diode and the photodiode of the embodiment of the present invention correspond to each other in a two-to-one relationship.

FIG. 7 is a schematic cross-sectional view showing an element arrangement for making the light emitting diode and the photodiode of the embodiment of the present invention correspond one to two.

FIG. 8 is a schematic view showing a manufacturing process of the optical coupler according to the second embodiment of the present invention.

FIG. 9 is a schematic sectional view of an optical coupler according to a second embodiment of the present invention.

FIG. 10 is a diagram showing a module in which a semiconductor light emitting element and a light receiving element of a conventional technique are combined.

[Explanation of symbols]

1 ... n-GaAs substrate, 2 ... n-GaAs buffer layer,
3 ... n-AlGaAs layer, 4 ... p-AlGaAs layer, 5
... p-AlGaAs contact layer, 6, 10, 25 ... S
iO ₂ film, 7, 9, 12, 24, 27, 43 ... Opening part,
8 ... p-type electrode (to AlGaAs), 11 ... p-type electrode (to Si), 13, 28 ... p-Si layer, 14, 29 ... i-S
i layer, 15, 30 ... n-Si layer, 16, 17, 31, 3
2 ... Step, 18 ... N-type electrode (to Si), 19 ... N-type electrode (to GaAs), 26, 33 ... N-type electrode (to S)
i), 34 ... P-type electrode (against GaP), 40 ... Light emitting diode, 41 ... Photodiode, 42 ... SiO ₂ film, 4
4 ... Border

Claims (5)

[Claims] 1. A semiconductor light-emitting device that emits light by injecting a current into a pn junction or a pin junction formed on a semiconductor substrate, and a semiconductor light-emitting device formed on the semiconductor light-emitting device and transparent or semi-transparent to the emission wavelength of the light-emitting device. An insulating layer made of a transparent material; and a light receiving element that is made of a polycrystalline or amorphous semiconductor formed on the insulating layer and generates carriers at a pn junction or a pin junction when light is incident on the insulating layer.
An optical coupler, wherein light emission when current is injected into the light emitting element reaches a light receiving element. 2. A semiconductor light emitting element for injecting a current into a pn junction or a pin junction formed on a semiconductor substrate to emit light, and a back surface of the semiconductor substrate transparent or semitransparent to an emission wavelength of the light emitting element. An insulating layer formed of a material that is transparent or semi-transparent to the emission wavelength of the light-emitting element and a light composed of a polycrystalline or amorphous semiconductor formed on the insulating layer are incident on the pn junction or It consists of a light receiving element in which carriers are generated in the pin junction,
An optical coupler, wherein light emission when current is injected into the light emitting element reaches a light receiving element. 3. The optical coupler according to claim 1, wherein the light emitting element and the light receiving element are arranged in a one-to-one corresponding array or two-dimensional form. 4. The optical coupler according to claim 1, wherein the optical coupler is arranged so that light emitted from a single light emitting element is received by two or more light receiving elements. 5. The optical coupler according to claim 1, wherein the optical coupler is arranged so that light emitted from two or more light emitting elements can be received by a single light receiving element.