JPH07122729A - Photothyristor - Google Patents

Abstract

PURPOSE:To improve the light receiving sensitivity of a photothyristor without increasing the self-ignition by a leak current at high-temperature time and chip area of the thyristor. CONSTITUTION:Phototransistor sections are provided in two of the three N<->-type layers 13, 15, and 18 divided by a dielectric body 19 and a two-way thyristor section is provided in the remaining one of the three layers. The emitter terminals of the phototransistors are respectively connected to the gate terminals of thyristors and collector terminals of the phototransistors are connected to the anodes of the thyristors.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical semiconductor device, and more particularly to a photothyristor.

[0002]

2. Description of the Related Art FIG. 3 shows a conventional horizontal photothyristor chip.
Figure 4 shows a cross-sectional view of the
It As shown in FIG. 4, the PNP transistor 21, NP
N-transistor 22 and resistor R for sensitivity adjustment_GK10 is
Wired to form one thyristor, the same structure as this
(NPN transistor 24, PNP transistor 23
And resistance R for sensitivity adjustment_GK5) Another thyristor
Are connected in parallel in the opposite direction. Structure on chip
The result is N as shown in FIG.⁺ Layer 7, P layer 8 and N ^- sub
The NPN transistor 22 shown in FIG.
And P layer 8 and N^- Figure with layer 3 and P layer 4
The PNP transistor 21 shown in FIG.
It constitutes an iristor, where P layer 2 and N^- By layer 3
The P-N junction thus formed functions as a photodiode.
The other reversely connected thyristor has the same structure.
It Furthermore, R_GK5, 10 and channel stopper
It has a structure including 28.

Next, the operation will be described. In FIG. 4, when the electrode 6 is biased positive and the electrode 11 is biased negative, a current is generated in the photodiode 29 by the incident light 12 and flows into the R _GK 10. However, when a certain value is exceeded, the base of the NPN transistor 22 is exceeded. Flow into. NPN
Since the collector current of the transistor 22 pulls out the base current of the PNP transistor 21, a collector current of the PNP transistor 21 is generated, and this flows into the base of the NPN transistor 22, resulting in a positive feedback state.
The element turns on. At this time, the PNP transistor 23 and the NPN transistor 24 are in the reverse blocking state and do not function. The same operation is performed when biased in the reverse direction.

[0004]

This conventional horizontal bidirectional
In the photothyristor, R to increase the light receiving sensitivity
_GKHigher (hereinafter, measure 1), NPN transistor 2
Increase the current amplification factor of 2 or 25 (hereafter, Measure 2),
Or increase the area of the photodiode 29 or 30
It was common to take the measures of
The problem of false ignition against the increase of leakage current at high temperature, countermeasure 2
If the current amplification factor is less than 1, thyristor operation
The chip area is smaller than the restriction 3
Increase (if double the photosensitivity is required, the chip area is
1.2 times higher) or increase in chip area
There is a problem that it is necessary to widen the incident light corresponding to
It was.

An object of the present invention is to provide a photothyristor capable of improving the light receiving sensitivity without increasing the value of R _GK and without significantly increasing the chip area.

[0006]

The photothyristor of the present invention comprises a phototransistor that receives and amplifies incident light and supplies a current to the gate of the thyristor.

Further, in order to form the thyristor section and the phototransistor on the same chip, these are constructed in each N ^- epi separated by the dielectric.

[0008]

[Operation] When a photocurrent is generated in the phototransistor,
Since the current multiplied by h _FE flows to the gate of the thyristor,
The photosensitivity is improved to about h _FE times that of the phototransistor without increasing the value of R _GK and with a slight increase in the chip area.

[0009]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is a cross-sectional view of a chip when the present invention is applied to a bidirectional photothyristor, and FIG. 2 is an equivalent circuit diagram.

As an equivalent circuit, as shown in FIG.
Transistors 22, 24, PNP transistors 21, 2
3 and R _GK 5,10 constitute a bidirectional thyristor, and the gate terminals 27,2 of this bidirectional thyristor are
7'has a circuit configuration in which phototransistors 25 and 26 are respectively connected. The cross-sectional structure of the chip is shown in FIG. 1, and three N ⁻ layers 3, 15,
Depth of tens of μm separated into 18, specific resistance of 100 Ω · cm
Within a certain tab, a first phototransistor section composed of P layer 13 and N ⁺ 14, a second phototransistor section composed of P layer 16 and N ⁺ layer 17, and P layers 2, 4, 5, In the chip cross section in which the bidirectional thyristor portions composed of 8, 9, 10 and N ⁺ layers 1, 7 are arranged,
The structure is such that the wiring on the surface of the chip is connected as shown in FIG. 2, and the chip size is about 1 to 2 mm square. In addition, the dopant at the time of forming the P layer and the N layer is boron, phosphorus, or the like.

Next, the operation will be described with reference to FIG.

When the electrode 6 is biased positive and the electrode 11 is biased negative, a photocurrent is generated in the phototransistor 25 by the incident light 12, and a current multiplied by h _FE flows into the gate terminal 27. Part of this current flows through R _GK 10 to electrode 11, but part of this current flows through NPN transistor 22.
Flow into. Therefore, the collector current of the NPN transistor 22 flows, and electrons are injected into the base of the PNP transistor 21 to generate a collector current of the PNP transistor 21, and holes are injected into the base of the PNP transistor 22 to cause a positive feedback state. When the sum of the current amplification factors of the PNP transistor 21 and the NPN transistor 22 reaches 1, the ON state is maintained. Here, when the incident light 12 is turned off, the current generated by the phototransistor 25 and flowing into the gate terminal 27 disappears.
The transistor 21 and the NPN transistor 22 are already in the positive feedback state, and the thyristor operation is possible because the element can be kept on only by changing the ratio of the current flowing to the collector side and the base side in the PNP transistor 21. At this time, the PNP transistor 23 and the NPN transistor 2
4 and the phototransistor 26 are in the reverse blocking state,
It doesn't work. Conversely, when the electrode 6 is negatively biased and the electrode 11 is positively biased, the thyristor operation can be similarly performed.

Here, if the thyristor section and the phototransistor section are formed in the same N ⁻ layer, this operation becomes inoperable. Therefore, they are separated by the derivative separation method or the like to be formed in the same chip.

[0015]

As described above, the present invention includes the phototransistor that receives and amplifies incident light and supplies a current to the gate portion of the thyristor, so that the value of R _GK is not increased and the chip area is reduced. 20% increase in photosensitivity to h _FE times that of phototransistors (usually several hundred to several thousand)
Since the value of R _GK is not changed, the self-ignition level due to the leak current at high temperature can be made equal.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a chip according to an embodiment of the present invention.

FIG. 2 is an equivalent circuit diagram of an embodiment of the present invention.

FIG. 3 is a cross-sectional view of a conventional chip.

FIG. 4 is an equivalent circuit diagram of a conventional example.

[Explanation of symbols]

1,7,14,17 N ⁺ layer 2,4,8,9,13,16 P layer 3,15,18 N ^- layer 5,10 R _GK 6,11 Electrode 12 Incident light 19 Dielectric 21,23 PNP Transistor 22,24 NPN transistor 25,26 Phototransistor 27,27 'Gate terminal 28 Channel stopper part 29,30 Photodiode

Claims (2)

[Claims] 1. A photothyristor comprising a phototransistor which receives and amplifies incident light and supplies a current to a gate portion of the thyristor. 2. The photothyristor according to claim 1, wherein the elements are formed on a single chip by a dielectric isolation method.