JPH0719916B2 - Photoelectric conversion element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention connects a base modulation bipolar transistor having a negative resistance characteristic and a phototransistor in Darlington connection in a mode in which the collector regions are common. The present invention relates to a photoelectric conversion element.

[Prior Art and its Problems] Conventionally, as a photoelectric conversion element, a photodiode, a photo diode,
Well known are transistors, photo Darlingtons, and even optical thyristors. These photoelectric conversion elements are
It is widely used for various optoelectronic conversion device devices such as photo couplers, photo interrupters, and optical communication photoelectric switches. Among such various photoelectric conversion devices, a phototransistor or a photo Darlington is widely used when high sensitivity is desired under a DC bias.
However, the phototransistor is inferior to the photo Darlington in terms of sensitivity, and has a drawback that the output cannot take out a large current. On the other hand, the above photo Darlington has extremely high sensitivity and can take out a large current, but on the other hand, the dark current also has a high value,
There is a problem that the sensitivity changes greatly with temperature, and the dark current sharply rises as the temperature rises. Moreover, since the current amplification factor is 10,000 or more, the response becomes extremely slow. Further, most of the phototransistor and the photo Darlington are used as ON or OFF switch-like circuit elements, but since they are linear amplification elements, they are pulse-converted in the next stage. Therefore, with these circuit elements, the waveform is shaped by a Schmitt trigger circuit or the like for the purpose of providing a hysteresis characteristic so that problems such as chattering do not occur, but the number of parts increases, the cost is high, and the current consumption is high. There was a difficulty such as requiring.

On the other hand, an optical thyristor capable of switching a large current with respect to an optical input can be ON-switched under DC bias, but cannot be OFF-switched. Therefore, most of this optical thyristor is used under AC bias.

[Problems to be Solved by the Invention] Accordingly, the present invention is intended to solve various problems found in the semiconductor photoelectric conversion device in the above-mentioned conventional technique, and has high sensitivity to optical input. It is an object of the present invention to provide a photoelectric conversion element that enables high-current bistable switch operation under a DC bias at high speed, is easy to manufacture, and is inexpensive.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention specifically provides a first PN with respect to a collector region made of a semiconductor material of a first conductivity type and the collector region. A base PN region made of a second conductive type semiconductor material formed through the junction, and a second PN for the base PN region.
A phototransistor portion having an emitter region made of a first conductive type semiconductor material formed via a junction; a collector region made of the first conductive type semiconductor material; and a collector region formed in the collector region. On the other hand, a first base region made of a semiconductor material of a second conductivity type formed via the first PN junction portion and the first base region formed via the second PN junction to the first base region. Formed between the emitter region made of a first conductive type semiconductor material, the base contact region spaced apart from the first base region, and the first base region and the base contact region. A base-modulated bipolar transistor section including a second base region formed in the second base region and a gate region having a first conductivity type formed in the second base region. A collector region in the transistor part and a collector region in the base modulation type bipolar transistor part share one another, and an emitter region in the photo transistor part and a base contact region in the base modulation type bipolar transistor part. And a Darlington connection to form a photoelectric conversion element.

[Operation] The photoelectric conversion element according to the present invention configured as described above is
By letting stationary light enter the phototransistor section and energizing the base, collector and gate of the base modulation type bipolar transistor section in the reverse bias state,
The highly sensitive large current output amplified by Darlington connection of the transistor and the base modulation type bipolar transistor shows a negative resistance characteristic. When a load is connected to the photoelectric conversion element having such a negative resistance characteristic and an optical input is given, a bistable output with hysteresis is obtained with high sensitivity to the optical input and a large current at a high speed.

[Examples of the Present Invention] The photoelectric conversion elements according to the present invention will be described below in detail based on specific examples shown in the drawings. In the description of the embodiments of the present invention, an NPN type semiconductor device will be described as an example when silicon is used as a semiconductor material. However, the present invention is also applicable to other compound semiconductors as semiconductor materials,
In addition, it is also possible to construct a PNP type semiconductor device.

In the present invention, a schematic sectional view of the photoelectric conversion element according to the first embodiment is shown in FIG. 1, and a schematic plan view thereof is shown in FIG. In Figure 1, first, N on the N ⁺ heavily doped substrate (1) ^- about an impurity concentration of the collector layer (2) about 10 ¹⁵ atoms / cm ³ 5~15μ
Vapor growth is performed to a thickness of about m. Then P ^- base layer
Epitaxial growth is performed with an impurity concentration of about 10 ¹⁶ atoms / cm ³ to a thickness of about 1 to ³ μm. Then, with the P ⁻ base layer as a base region, diffusion or ion implantation is performed to separate the N ⁻ collector layer (2) into an impurity concentration of about 10 ²⁰ atoms / cm ³ ,
⁺ Region (4) is formed. Isolation been P ^- base region to the base modulation type bipolar transistor (Ba
se Modulation Bipolor Transistor: Hereinafter, abbreviated as BAMBIT) P ⁺ base region (5a) and phototransistor P ⁺ base light-receiving region (5b) are diffused or ion-implanted to about 10 ¹⁸ atoms / cm ^3. I do. Next, the BAMBIT
A partial P ⁺ base contact region (6) is separated from the P ⁺ base region (5a) by the P ⁻ base region (3a).
At this time, the P ⁺ base contact region (6) may be formed simultaneously with the P ⁺ base regions (5a) and (5b). Also, P ⁺
The bases (5a) and (5b) and the P ⁺ base contact region (6) may not reach the N ⁻ collector layer (2), respectively. Subsequently, the emitter region (7a) of the BAMBIT portion and the emitter region (7b) of the phototransistor portion are formed by selecting the impurity concentration and the depth so that the desired current amplification factor is obtained. Subsequently, the N ⁺ gate region (8) is replaced with the P ⁺ base region (5
It is formed by diffusion or ion implantation in the P ^- base region (3a) so as to surround a). In the above process, depending on the characteristics of the BAMBIT part or the current amplification factor, the emitter regions (7a), (7b) and the N ⁺ region (4) are simultaneously formed, and further, the emitter regions (7a), (7b) are formed. Simultaneous formation with the N ⁺ gate region (8) is also possible. Then, by well-known techniques, contact holes are formed in the emitter regions (7a) and (7b), the P ⁺ base contact region (6), and the N ⁺ gate region (8), for example, aluminum. Depending on the desired metal material such as
b) is connected to the base contact region (6) of the BAMBIT section by Darlington connection, and an emitter electrode (11), a collector electrode (12) and a gate electrode (13) of the BAMBIT section are provided to extract the output. Lithography, passivation, etc. between other steps are formed by a well-known technique.

Next, the operating principle of the embodiment shown in FIGS. 1 and 2 will be described. First, the BAMBIT
Regarding the principle of operation of itself, Japanese Patent Application No. Sho 63 by the same applicant
As detailed description is given in −196627, the detailed description is omitted here, but as an example of static characteristics of BAMBIT itself, an example of grounded base characteristics when the gate is set to the same potential as the collector is shown in FIG. And make the gate the same potential as the collector,
Figure 4 shows an example of grounded emitter characteristics when the base voltage V _BE is used as a parameter. Incidentally, in FIGS. 3 and 4, there is a relationship of V _CE (OFF) = V _BE + V _CB (OFF). Next, in the photoelectric conversion element according to the first embodiment shown in FIGS. 1 and 2, an equivalent circuit when the gate has the same potential as the collector is shown in FIG. 5, and shown in the equivalent circuit of FIG. A case will be described in which the photoelectric conversion element is irradiated with constant light. When light is received by the light receiving part of the phototransistor part, the collector-emitter voltage V _CE changes to V _CE (sat) ′ + V
_F (B, E) …… (where V _CE (sat) ′ is the saturation voltage of the phototransistor and V _F (B, E) is the rising voltage between the base and emitter of the BAMBIT) , The input from the phototransistor section is input to the base of the BAMBIT section via Darlington connection, which is amplified and becomes the output current. Due to the original characteristics of BAMBIT, the collector-emitter voltage V _CE becomes V _F (B, E), or the reverse bias is applied between the collector and the gate and the base.
The emitter-to-emitter voltage V _CE is V _CE = V _F (B, E) + V _CB (ON)
(Here, V _CB (ON) reaches the ON voltage shown in FIG. 3), and the output tries to exhibit a negative resistance characteristic. However, in FIG. 5, since the base of the BAMBIT section (the emitter of the phototransistor section) is open, the base voltage of the base section of the BAMBIT section rises as the collector-emitter voltage V _CE increases. It changes to the potential of V _CE -V _CB (ON), and the output current does not show the negative resistance characteristic.

Therefore, next, at the time of irradiating light to the light receiving portion of the phototransistor, with respect to the collector-gate-emitter voltage V _CE , the collector-gate-base V
_{In order to apply} a reverse bias voltage of _CB (OFF) or more, for example, as shown in FIG. 6, a high resistance of about 10 kΩ is inserted as the resistance r _BE . In this state, if V _CE is also increased, the collector-emitter voltage V _CE becomes V _CE (ON) ≈ V
_{From F} (B, E) + V _CB (ON), the input current I _CEL to the base of the BAMBIT section decreases and the amplified output current I _C + I _G + I
_CEL (where I _C and I _G are the collector current and gate current of the BAMBIT part) is also reduced and shows a negative resistance characteristic. The collector-emitter voltage V _CE is V _CE = V _CE (OFF) =
Reaches the _{V CB (OFF) + I CEL} × r BE, all the optical input current I _CEL is to resistor r _BE side as the output current flow photoelectric conversion element, a current I _CEL is no longer amplified, the current I _CEL through a resistor r _BE
Only will flow.

When the illuminance (1x) is used as a parameter, the situation is shown in FIG. As can be understood from the characteristic curve shown in FIG. 7, the photoelectric conversion element according to the present invention, like a normal Darlington transistor, rises at V _CE (sat) ≈0.7V and is a voltage control type even at several hundred mA or more. It shows a negative resistance output characteristic. In addition, since I _C + I _G >> I _CEL , the 7th
As can be seen from the figure, the effect of I _CEL hardly appears. With respect to the negative resistance characteristic, the negative resistance value can be changed by the resistance r _BE , and further, the negative resistance characteristic can be changed by the gate voltage.

Next, the input / output characteristics of the photoelectric conversion element having the characteristics shown in FIG. 7 with respect to light will be described with reference to FIG. 9 when the load R _L is inserted in the collector as a basic circuit example as shown in FIG. . In FIG. 8, when the phototransistor section receives light, a photocurrent flows through the resistors R _L and r _BE .
However, since r _BE >> R _L , the potential V _{A at} point _A is
It rises with almost no effect of resistance R _L. If it is a normal photo darlington, it reaches about 0.7V and flows into the transistor of the output stage, which is amplified and becomes the output of photo darlington. However, the photoelectric conversion element according to the first embodiment shown in FIGS. 1 and 2 is in the state of the A curve in the characteristic curve group shown in FIG. The intersection with R _L is Z
V _CE = V _CC at point X, not point, and the output current is
It does not flow except for I _CEL in the transistor section. Further, when an optical input is given, the characteristic curve of the photoelectric conversion element becomes a B curve from the Z point to the X point, that is, the base voltage V _{A of} BAMBIT is
V _A = V _BE = V _CC −V _CB (OFF) is reached, and the photocurrent I _CEL of the phototransistor section flows into the base of the BAMBIT section, and BAMB
Further amplified in the IT section, the output current I _C + I _G + I _CEL flows out through the load resistance R _L. Then, the potential of the collector decreases, and the photoelectric conversion element of the present invention reverses on its load line in FIG. 9 due to the negative resistance characteristic, and the output current I _C + I _G + I _CEL gradually flows. Due to this positive feedback action, the point of intersection with the load line instantly moves from point X to point Y, and the switch is turned on. Furthermore, even if the optical input is increased,
Since the saturation region of the photoelectric conversion element of the present invention intersects with the load resistance R _L , the output hardly changes anymore.

On the other hand, next, a case where the light input is weakened after the switch is turned on will be described. When the light input becomes weaker, the output characteristic curve group of the photoelectric conversion element according to the present invention also changes according to the light input intensity. However, even if the light input becomes weak, the switch does not switch off unless the curve reaches the C curve, and the intersection with the load resistance _RL is near the point Y. When the light input becomes weaker than the C curve, the photoelectric conversion element of the present invention and the load resistance _RL no longer intersect in the saturation region. Then, the intersection returns to point X again, and the photoelectric conversion element is switched off. Figure 10 shows how the two terminals switch on and off with this hysteresis. In FIG. 9, in order to switch on and off with hysteresis, the negative resistance value of the photoelectric conversion element | R _N |
If R _L and R _L do not satisfy R _L > | R _N |, they will not be switched on / off and a high-sensitivity linear optical amplification element will be obtained.

Next, another usage example of the photoelectric conversion element according to the present invention will be described with reference to FIG. The circuit shown in FIG. 11 is
The resistor r _BE is connected through a constant voltage circuit,
In the curve diagram shown in FIG. 9, a state similar to the A curve is created from the beginning, and the resistance r _BE can be made small, so that more sensitive and high speed switch operation becomes possible. Figure 12 shows
The load resistor R _L is connected to the emitter side, and has hysteresis and switches on and off with two terminals, similar to the usage shown in FIG.

A second embodiment of the photoelectric conversion element according to the present invention is shown in FIG. The photoelectric conversion element according to the second embodiment has a P ⁻ base region formed by ion implantation and is manufactured as follows. In Figure 13, first, N on the N ⁺ heavily doped substrate (1) ^- collector layer (2) is epitaxially grown, the N ^- collector layer relative to (2), the BAMBIT portion P ⁺ base region ( 5a) and the P ⁺ base light receiving area (5b) of the phototransistor section are diffused or ion-implanted to about 10 ¹⁸ atoms / cm ³ . Next, the P ⁺ base contact region (6) of the BAMBIT portion is formed apart from the P ⁺ base region (5a). At this time, the P ⁺ base contact region (6) is
It may be formed simultaneously with the P ⁺ base regions (5a) and (5b). Subsequently, a P ^- base region (3c) is formed between the P ⁺ base contact region (6) and the P ⁺ base region (5a) at 10 ¹⁶ atoms / cm 3.
^{It is} formed by ion implantation with an impurity concentration of about ³ to a thickness of about 1 to 3 μm. Subsequently, the emitter region (7a) of the BAMBIT portion and the emitter region (7b) of the phototransistor portion are formed so as to have a desired current amplification factor. Then, an N ⁺ gate region (8) is formed in the P ⁻ base region (3c).

Also in the second embodiment, depending on the characteristics of the BAMBIT section and the current amplification factor, the emitter regions (7a), (7b)
And N ⁺ region (5) simultaneously formed, emitter region (7a),
It is also possible to simultaneously form (7b) and the N ⁺ gate region (8). In addition, formation of each electrode and lithography, passivation, etc. between steps are performed by known techniques. This manufacturing process eliminates the P ^- base region (3b) and, in some cases, the P ⁺ base region (5a).
A large chip size can be reduced without the need to surround it with the P ^- base region (3a).

The third embodiment shown in FIG. 14 is the same as the first embodiment, except that the resistance r _BE shown in the example of the circuit used is formed in the same chip as the resistance region (14). The resistance region (14) in the device according to the third embodiment is
It can be formed simultaneously in the process of P ⁺ base diffusion. The resistance region can be incorporated in the second embodiment as well.

[Advantages of the Invention] The photoelectric conversion element of the present invention having the above-described configuration has a number of operational effects described below.

(I) Since the photoelectric conversion element has a negative resistance characteristic,
The bistable switch operation with hysteresis can be performed with two terminals for optical input without a post-processing circuit and with an extremely simple structure.

(Ii) Due to the characteristics of the element itself, a bistable switching operation is performed, so that current consumption as in the case of using an integrated circuit is not required.

(Iii) Due to Darlington connection, high current output is switched at high speed even for faint light.

(Iv) The high leakage current, which has been a problem in the conventional photo-darlington, has high sensitivity and high output because the photoelectric conversion element does not amplify the leakage current from the photo-transistor in the switch-off state. Can also be designed.

(V) The threshold level can be set to a high level with almost no drop in output, and like the above (iv), the leakage current from the phototransistor is not amplified in the switch-off state, so that the conventional phototransistor is not amplified. There is no significant increase in leak current due to temperature rise, as in Photo Darlington.

(Vi) By using the gate terminal, the optical input value for switching on can be changed and the switching speed can be improved.

(Vii) It can be manufactured by a process close to that of a conventional phototransistor, photo-Darlington, etc., and is easy to manufacture, and can be provided at low cost and at low cost.

[Brief description of drawings]

FIG. 1 is a first specific example of the photoelectric conversion element according to the present invention.
FIG. 2 is a schematic plan view of the first embodiment device shown in FIG. 1, FIG. 3 is a grounded base characteristic curve diagram of a base modulation type bipolar transistor, and FIG. FIG. 4 is a grounded emitter characteristic curve diagram of a base modulation type bipolar transistor, FIG. 5 is an equivalent circuit diagram of the photoelectric conversion element, and FIG. 6 is a first grounded emitter connection example of the photoelectric conversion element. The circuit diagram shown in FIG. 7 is a grounded emitter characteristic curve diagram when the resistance between the base and the emitter is constant and the light input is used as a parameter in the grounded emitter connection example of FIG. 6, and FIG. A circuit diagram showing a first connection example for obtaining a bistable output with respect to an optical input by connecting a load to the conversion element. FIG. 9 shows that a bistable output can be obtained in the circuit example shown in FIG. 10 is an explanatory view of the operation of FIG. FIG. 11 is a graph showing an example of output characteristics with respect to optical input in the circuit example shown in FIG. 11, and FIG. 11 is a circuit showing a second connection example for obtaining a bistable output with respect to optical input by connecting a load to the photoelectric conversion element. FIG. 12 is a circuit diagram showing a third connection example for connecting a load to the photoelectric conversion element and obtaining a bistable output with respect to an optical input, and FIG. 13 is a photoelectric conversion element according to the present invention. 14 is a schematic cross-sectional view showing a second embodiment of the present invention, and FIG. 14 is a schematic plan view showing a third embodiment in which a high resistance body between a base and an emitter is formed in the same element in the photoelectric conversion element. Is. (1), (2) …… Collector area (3) …… Base area (3a) …… Second base area (4) …… N ⁺ area (5a) …… P ⁺ area of BAMBIT section (5b) …… Base region of phototransistor of phototransistor (6) …… Base contact of BAMBIT (7a) …… Emitter of BAMBIT (7b) …… Emitter of phototransistor (8) …… Gate region (9) …… Oxide film (10) …… Base electrode (11) …… Emitter electrode (12) …… Collector electrode (13) …… Gate electrode (14) …… Base-emitter resistance

Claims (1)

[Claims] 1. A collector region made of a semiconductor material of a first conductivity type, and a base light receiving portion made of a semiconductor material of a second conductivity type formed in the collector region via a first PN junction. And a second area for the base light receiving area
A phototransistor portion comprising an emitter region made of a semiconductor material of a first conductivity type formed via a PN junction portion of the semiconductor device, a collector region made of a semiconductor material of the first conductivity type, and the collector. A first base region made of a semiconductor material of a second conductivity type formed through a first PN junction portion with respect to the region, and a second PN junction formed with respect to the first base region. Between the formed emitter region made of a semiconductor material of the first conductivity type, the base contact region spaced apart from the first base region, and the first base region and the base contact region. A base-modulated bipolar transistor section having a second base region formed in the second base region and a gate region having a first conductivity type formed in the second base region. To The collector region in the transistor part and the collector region in the base modulation type bipolar transistor part share one another, and the emitter region in the photo transistor part and the base contact region in the base modulation type bipolar transistor part. A photoelectric conversion element characterized in that and are connected by Darlington connection.