JPS6148786B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a photosensitive semiconductor device, and particularly to a light control switch (hereinafter referred to as a photothyristor) that can switch from an off state to an on state by irradiating a junction with light.

In general, a photothyristor has a high light sensitivity, that is, it has excellent control performance so that it can be switched from an off state to an on state with a small amount of light energy, and the control circuit can be made simple and inexpensive. However, when the optical sensitivity is further increased, malfunctions are more likely to occur when the power is turned on or due to the voltage increase rate (hereinafter abbreviated as dv/dt) due to external noise. In the conventional photothyristor with a PNPN four-layer structure, the photosensitivity is the number of output light energies of the light emitting diode.
When adapted to mw/cm ² , dv/dt is extremely low;
The limit was about several volts/μs.

The object of the present invention is to provide a new photothyristor that eliminates this drawback.

According to the present invention, it has a PNPNPN6 layer structure, and has a 3-layer structure.
It is characterized by having three or more exposed junctions, which results in high photosensitivity and dv/dt
A photothyristor with high resistance can be obtained.

Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a structural sectional view of a photothyristor that is an embodiment of the present invention. The photothyristor has a six-layer structure of P ₁ , N ₁ , P ₂ , N ₂ , P ₃ , N ₃ , and the P ₁ N ₁ P ₂ N ₂ layer is exposed and these junctions J ₁ , J ₂ , J ₃ is illuminated with light. This photothyristor has P ₁ , N ₁ , P ₂ ,
First thyristor 1 consisting of N ₂ and P ₂ , N ₂ , P ₃ ,
It is equivalently replaced by a second thyristor 2 consisting of N ₃ . First, when the P ₁ N ₂ P ₂ N ₂ layer is irradiated with light, electrons are generated in all the junctions J ₁ , J ₂ , J ₃ of the first thyristor 1 and the gate junction J ₃ on the anode side of the second thyristor 2. - When a pair of holes is generated, the first and second thyristors 1 and 2 are simultaneously switched from the OFF state to the ON state due to the positive feedback effect, similar to a normal thyristor. On the other hand, when the power is turned on and external noise
For dt, the first thyristors P ₁ , N ₁ , P ₂ ,
The cathode side gate layer P ₂ of N ₂ , N ₂ is the second thyristor
Since P ₂ , N ₂ , P ₃ , and N ₃ are short-circuited by the anode side gate layer P ₂ and N ₂ , they constitute the first thyristor.
The current amplification factor of the N ₁ P ₂ N ₂ transistor and the P ₂ N ₂ P ₃ transistor constituting the second thyristor is extremely low to suppress the positive feedback effect. Since the junctions of are connected in series, the junction capacitance Cj becomes small. As a result, the structure has an extremely high dv/dt tolerance.

This example uses a silicon substrate with a specific resistance of 30 to 50 Ωcm and a surface concentration of 2×10 ²⁰ cm obtained by an impurity diffusion method.
^-3 , is a photothyristor with an anode area of 9 mm ² , and the light sensitivity is 0.2 to 0.2 to the output light energy of the light emitting diode.
A light sensitivity of 0.5 mw/cm ² and a dv/dt tolerance of 400v/μs or more and a high dv/dt tolerance were obtained. Note that this photothyristor can be made only by the impurity diffusion method as in the example, but it is also possible to form the N ₂ layer on the P ₂ layer by epitaxial method, and then to form the P ₁ layer by the impurity diffusion method. A photothyristor having a similar function can also be produced by the method of forming the photothyristor.

As described above, according to the present invention, it is possible to obtain a novel photothyristor that has both high photosensitivity and high dv/dt tolerance.

[Brief explanation of the drawing]

FIG. 1 is a structural sectional view of a photothyristor which is an embodiment of the present invention, and FIG. 2 is an equivalent circuit diagram of FIG. 1. In the figure, A...anode, K...cathode, P ₁
~ _P3 ...P-type semiconductor layer, _N1 - _N3 ...N-type semiconductor layer, J1 _{- J5} ...PN junction, Cj...junction capacitance, 1...
...first thyristor, 2...second thyristor.

Claims (1)

[Claims] 1. A photosensitive semiconductor device having a PNPNPN6 layer structure and having three or more exposed junctions.