JPS5858823B2 - Optical coupling semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optically coupled semiconductor device comprising a combination of a light emitting element and a light receiving element.

Recently, optically coupled semiconductor devices (hereinafter referred to as "photocouplers"), which combine a semiconductor light-emitting element and a semiconductor light-receiving element, have been attracting attention as a new solid-state device, and are widely used for solid-state relays, transmission line isolation, etc. There is.

1 and 2 are cross-sectional views of a known photocoupler.

In FIGS. 1 and 2, 10 is a light emitting diode commonly used as a semiconductor light emitting device, which is composed of an n-type crystal layer 11. p-type crystal layer 12, p- type crystal layer formed between both layers
It is removed from the n-junction 13, the cathode electrode 14, and the anode electrode 15.

If a voltage is applied between the electrodes 14 and 15 of the light emitting diode 10 and a current is caused to flow, light can be generated near the pn junction 13.

Reference numeral 20 denotes a photothyristor used in solid-state relays, etc., which consists of a p-type emitter layer 21, an n-type base layer 22, a p-type base layer 23, an n-type emitter layer 24, and a p- It is separated from the n-junction 25, the p-n junction 26, the p-n junction 27, the anode electrode 28, and the cathode electrode 29.

When a voltage of several volts is applied between the electrodes 28 and 29 of the photothyristor 20, the photothyristor 20 is normally in an off state, but when the light emitted from the light emitting diode 10 is irradiated onto it, the photothyristor 20 is turned off. Central joint [
A photocurrent is generated near the junction formed between the n-type base layer 22 and the p-type base layer 26, and the photocurrent switches the photothyristor 20 to the on state.

The cathode electrode 14 of the above-mentioned light emitting diode 10 is a metal conductor 5
The anode electrode 15 is electrically connected to the metal conductor 52 by a lead wire 61.

On the other hand, the anode electrode 28 of the photothyristor 20 is made of metal conductor 5.
The cathode electrode 29 is electrically connected to the metal conductor 54 by a lead wire 62.

Metal conductor 51. 52, 53, and 54 can be electrically connected to an external circuit, respectively.

The light emitting diode 10 and the photothyristor 20 after soldering and lead bonding are shown in FIG. The light-receiving surface) 30 is arranged to face the light-receiving surface.

Furthermore, although not shown in the figure, by placing a transparent material with a high refractive index between the light extraction surface 16 of the light emitting diode 10 and the light receiving surface 30 of the photothyristor 20, the luminous flux transmitted from the light emitting diode 10 to the photothyristor 20 can be reduced. Efforts are usually made to increase the

When a voltage is applied between the metal conductor 51 and the metal conductor 52 to cause a current to flow through the light emitting diode 10, light is generated near the p-n junction 13, and a portion of this light passes through the light extraction surface 16. and is radiated to the outside.

These lights are irradiated onto the light receiving surface 30 of the photothyristor 20, which faces the light extraction surface 16 of the light emitting diode 10.

A part of the irradiated light enters the inside of the photothyristor 20 and reaches the vicinity of the p-n junction 26, where a photocurrent is generated.

These photocurrents switch the photothyristor 20 from an off state to an on state.

However, the structure shown in FIG. 1 has the following drawbacks.

Typically, silicon (Si) is used as the material for the light receiving element, and a Si-doped GaAs light emitting diode is generally used as the light emitting diode.

In that case, the peak wavelength of the light emitting diode is 9400'A
It is.

The absorption coefficient of Si crystal for this 9400'A light is 5
It is about 00 cm-1.

That is, most of the light that has entered the interior of the crystal through the main surface 30 of the photothyristor 20 is absorbed at a depth of approximately 20 μm.

Therefore, when the p-n junction 26 at the center of the photothyristor 20 is located at a depth of 20 μm or more from the main surface 30, the light flux reaching the vicinity of the p-n junction 26 from the light emitting diode is small and is generated in the photothyristor 20. The photocurrent becomes very small.

That is, the light transmission effect of the photocoupler is poor.

A photocoupler having the structure shown in FIG. 2 was devised to eliminate the above drawbacks.

In this photocoupler, one main surface of the light emitting diode 10 (
Light extraction surface) 16 is the side surface 31 of the photocilis 1 and 20
is placed opposite.

Since the p-n junction 26 is exposed on the side surface 31 (or covered with a transparent and stable material such as glass),
The light emitted from the light emitting diode 10 directly reaches the vicinity of the p-n junction 26 of the photothyristor 20 (without being absorbed on the way as in the case of FIG. 1).

These lights generate a photocurrent and the photothyristor 20
is switched from the off state to the on state.

However, this photocoupler also has the following drawbacks.

Generally, the part of a photothyristor that responds well to light is p-n
The depletion layer extending to the junction 26 and its vicinity [Figures 1 and 2]
This is the part indicated by 32 in the figure.

Now, if we assume that the carrier concentration in the p-type base layer 23 is sufficiently higher than the carrier concentration in the n-type base layer 22, the depression in the depletion layer 32 is ≠! It is given by eV/eNp.

ε is the dielectric constant of Si, e is the electron charge, and ■ is the applied voltage, which is usually several volts.

Now, the carrier concentration ND of the n-type base layer 22 is I x 1
If the width of the depletion layer 32 is calculated as 0''/7, it will be about 10 μm.

That is, in FIG. 2, the region 32 on the side surface 31 of the photothyristor 20 having a width of about 10 μm near the p-n junction 26 responds well to light.

On the other hand, the main surface 16 of the light emitting diode 10 is usually 4.00μ
It has a shape of m x 400 μm.

Therefore, when viewed from the light emitting diode 10 side, of the light emitted from the light extraction surface 16, only the light emitted from a width of approximately 10 μm reaches the light receiving portion of the photothyristor 20.

That is, in the configuration shown in FIG. 2, most of the light emitted from the light extraction surface 16 of the light emitting diode 10 is wasted, and the light transmission efficiency is also poor.

In order to eliminate this wasted light, the shape of the light extraction surface 16 of the light emitting diode may be elongated, for example, by making one side 400 μm while the other side is approximately several tens of μm.

However, a light emitting diode with a width of about several tens of micrometers is difficult to handle, and various problems arise in device manufacturing and assembly.

Furthermore, in the conventional structure shown in FIGS. 1 and 2,
Assembling the light emitting diode 10 (soldering, lead bonding) and the photothyristor 20 are performed separately, and then the light emitting diode 10 and the photothyristor 20 are aligned, so the process is complicated and the alignment is not accurate. It had the disadvantage that it could not be performed well.

In addition, in general, the light transmission efficiency increases as the distance between the light emitting element and the light receiving element becomes shorter, so it is desirable to have them as close as possible. However, in the conventional structure shown in FIGS. Since there is a lead wire 61 above, the two cannot be brought very close together.

The present invention has been made in view of the above-mentioned drawbacks, and has a high light transmission efficiency, is easy to assemble, and can accurately align the light emitting element and the light receiving element, and can be arranged sufficiently close to each other. The object is to provide an optically coupled semiconductor device.

The gist of the present invention is that p-n is approximately parallel to the main surface.
a semiconductor light emitting element having at least one junction surface and generating light in the vicinity of the p-n junction surface; In an optically coupled semiconductor device comprising a semiconductor light-receiving element that responds to light in the vicinity, at least one side surface of two substantially parallel opposing side surfaces of the semiconductor light-emitting element and a side surface of the semiconductor light-receiving element A transparent insulating material having a refractive index at least higher than air is filled only between the opposing side surfaces, and the light emitted from the side surface of the semiconductor light emitting device is transmitted to the side surface of the semiconductor light receiving device. This is a photocoupler that is characterized by efficient irradiation.

The present invention will be explained below with reference to Examples.

FIG. 3 is a sectional view of an embodiment of a photocoupler according to the present invention.

In the photocoupler shown in FIG. 3, a light emitting diode 10 and a photothyristor 20 are assembled on an insulating substrate 71.

The cathode electrode 14 of the light emitting diode 10 is soldered onto a metal film (or metal plate) 51 electrically connected to the insulating substrate T1, and the anode electrode 28 of the photothyristor 20 is electrically connected to the insulating substrate T1. It is soldered onto another connected metal film (metal plate) 53.

The anode electrode 15 of the light emitting diode 10 and the cathode electrode 29 of the photothyristor 20 are connected to other metal films 52 and 5 of the insulating substrate 71 by lead wires 61 and 62, respectively.
4.

The space between the side surface 17 of the light emitting diode 10 and the side surface 31 of the photothyristor 20 is filled with a transparent insulator having a high refractive index, such as an epoxy resin 72.

When a voltage is applied between the metal film (metal plate) 51 and the metal film (metal plate) 52, a current flows through the light emitting diode 10, and p
Light is generated near the -n junction 13, passes through the side surface 17 of the light emitting diode 10, passes through the transparent insulator 72, and reaches the (llIJi 31) of the photothyristor 20.

The light reaching the p-n junction 26 on the side surface of the photothyristor 20 and its vicinity 32 generates a photocurrent that switches the photothyristor 20 from an off state to an on state.

The light generated inside the light emitting diode 10 is also radiated to the outside from the main surface 16 and side surfaces 17';
Since the outside of 7' is air (or a substance with a low refractive index), the effect of total internal reflection is large and the proportion of light radiated to the outside through these surfaces is small.

On the other hand, since there is a material 72 with a high refractive index outside the side surface 17, the effect of total reflection is small, and the main surface 16 and the side surface 17'
Even the light reflected by can be taken out from the side surface 17.

Therefore, light generated inside the light emitting diode 10 can be effectively guided to the photothyristor 20.

Furthermore, in the photocoupler shown in FIG.
Since it can be assembled on the top, the tying process is easy.
It is also easy to align the light emitting diode 10 and the photothyristor 20.

Furthermore, the side surface 17 of the light emitting diode 10 and the photothyristor 2
The light emitting diode 10 and the photothyristor 2
0 can be made sufficiently close to each other, and the light transmission efficiency can be increased.

FIG. 4 is a sectional view of another embodiment of the photocoupler according to the present invention.

In the photocoupler shown in FIG. 4, a side surface 31a of the photothyristor 20a is arranged opposite to the side surface 17a of the light emitting diode 10, and a side surface 31b of the other photothyristor 20b is arranged opposite to the other side surface 17b of the light emitting diode 10. There is.

Although not shown in the figure, the cathode electrode 29a of the photothyristor 20a is electrically connected to the anode electrode 28b of the photothyristor 20b. are connected to the same metal film (metal plate) by a lead wire 62b],
The anode electrode 28a of the photothyristor 20a is electrically connected to the cathode electrode 29b of the photothyristor 20b.
A metal film (metal plate) 53a and a metal film (
(metal plate) 53b is electrically connected].

Similar to the photocoupler shown in FIG.
0. Since the photothyristor 20a and the photothyristor 20b are all arranged on the same insulating substrate 71, assembly is easy. The alignment can be performed with high precision and sufficiently close to each other.

Light generated inside the light emitting diode 10 passes from the side surface 17a through the transparent insulator 72a with a high refractive index to the side surface 31b of the photothyristor 20a, and from the side surface 17b through the transparent insulator 72b with a high refractive index to the photothyristor. 2
It is effectively guided to the side surface 31b of 0b.

In this case, Tsukuda 1 side 17a, 17b of issuing diode 10
Since the outside of the side surface and the main surface 16 that are substantially perpendicular to the surface is air, the effect of total internal reflection is large, and the proportion of light radiated to the outside through these surfaces is small.

To briefly explain the operating principle of the photocoupler shown in FIG. 4, the cathode electrode 29a of the photothyristor 20a and the anode electrode 2Bb side of the photothyristor 20b are negative, the anode electrode 28a of the photothyristor 20a and the photothyristor 20b are negative.
If a voltage is applied so that the cathode electrode 29b side of b is positive and a current flows through the light emitting diode 10, the photothyristor
0a switches from off state to on state.

When a voltage with the polarity reversed is applied to cause a current to flow through the light emitting diode 10, the photothyristor 20b is switched from an off state to an on state.

That is, it is equivalent to a photocoupler including a phototriac that switches from an off state to an on state in response to an optical signal from a light emitting diode.

In the above-described embodiment of the photocoupler according to the present invention, a photothyristor is used as a light receiving element. If so, it can be considered as an embodiment of the photocoupler according to the present invention in which the light receiving element is a phototransistor.

In the case of other general light-receiving elements, the side surface of the light-emitting element and the side surface of the light-receiving element are placed facing each other in the same manner as described above, and a transparent and refracting element is placed between these opposing sides. Providing an insulator with a high ratio provides an embodiment of the photocoupler according to the present invention.

Further, the photocoupler according to the present invention can be obtained by using not only a light emitting diode but also a general semiconductor light emitting device, a semiconductor laser, etc. as the semiconductor light emitting device.

As detailed above, in the optically coupled semiconductor device according to the present invention, the side surface of the semiconductor light emitting element where the edge of the pn junction that generates light is exposed in the vicinity thereof, and the semiconductor light receiving element responsive to light in the vicinity thereof. The semiconductor light-emitting element and the semiconductor light-receiving element are disposed so that the side surfaces on which the edges of the p-n junction are exposed face each other, and an insulator that is transparent and has a refractive index at least higher than air is provided only between the two side surfaces. Since it is filled with a substance, it has a high light transmission efficiency and can be assembled easily and accurately.

[Brief explanation of the drawing]

1 and 2 are respectively sectional views of an example of a conventional photocoupler, FIG. 3 is a sectional view of an embodiment of a photocoupler according to the present invention, and FIG. 4 is a sectional view of another embodiment of a photocoupler according to the present invention. It is. In the figure, 10 is a light emitting diode (semiconductor light emitting device)
, 13 are p-n junctions 17, 17' that generate light in the vicinity of the light emitting diode 10. 17a and 17b are the sides of the light emitting diode, 20° 20a
, 20b is a photothyristor (semiconductor light receiving element), 3L
31a and 31b are side surfaces of the photothyristor; 26.
26a and 26b are p-n junctions that respond to light in the vicinity of the photothyristor 20, and γ2° 72a and γ2b are transparent insulating materials. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1. At least of two substantially parallel and opposite side surfaces in which the edge of the p-n junction of a semiconductor light-emitting device having a p-n junction that generates light in the vicinity thereof is exposed. The semiconductor light-emitting device and at least one light-emitting device are arranged so that one side surface in which an edge of the p-n junction of the semiconductor light-receiving device having a p-n junction that responds to light faces the one side surface. the semiconductor light-receiving element, and a transparent insulating material having a refractive index at least higher than air is filled only between the side surface of the semiconductor light-emitting element and the side surface of the semiconductor light-receiving element opposing thereto. Features of optically coupled semiconductor devices. 2. Claim 1, characterized in that a semiconductor light-emitting device and a semiconductor light-receiving device are disposed on the same insulating substrate.
The optically coupled semiconductor device described in . 3. Claim 1, characterized in that one semiconductor light-receiving element is disposed on each of two substantially parallel opposing side surfaces of one semiconductor light-emitting element, or 2. The optically coupled semiconductor device according to item 2. 4. The optically coupled semiconductor device according to any one of claims 1 to 3, wherein the semiconductor light receiving element is a photothyristor. 5. One photothyristor is arranged on each of the two substantially parallel and opposite side surfaces of one semiconductor light emitting device, and the two photothyristors are electrically connected so that they are antiparallel. 5. The optically coupled semiconductor device according to claim 4, wherein the optically coupled semiconductor device is connected to.