JP2696300B2 - Two-terminal photoelectric conversion element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoelectric conversion device which operates as a switch with respect to an optical input, and has a quick response and a two-terminal photoelectric switch capable of performing a two-terminal switch operation with hysteresis with respect to an optical input. It relates to a conversion element.

[0002]

2. Description of the Related Art Conventionally, a phototransistor or a photo Darlington transistor has been used as a photoelectric conversion element that performs a switching operation with respect to an optical input.
No. 238, there is known a base modulation type bipolar phototransistor according to the present inventors' invention. Among the above-described conventional photoelectric conversion elements, photoelectric conversion elements such as a phototransistor or a photo-Darlington transistor only perform linear operation with respect to optical input in terms of characteristics, and have a threshold level. And no hysteresis operation could be performed.

Therefore, in the case of this type of conventional photoelectric conversion element, for example, a post-processing circuit such as a Schmitt circuit is provided downstream of a phototransistor or a photodarlington transistor, and waveform processing is performed by this. Further, recently, integrated circuits in which a photodiode, a Schmitt circuit, a constant voltage circuit, and the like are integrated into one chip have been put to practical use. However, this method has the disadvantage that the current consumption by the circuit increases and the cost increases. Further, in a two-terminal device, a switch operation with hysteresis cannot be performed with respect to optical input, and there is a limit to miniaturization.

[0004] Among the above-mentioned conventional photoelectric conversion elements, in order to solve the problems and disadvantages seen in a phototransistor or a photodarlington transistor,
The base modulation type bipolar phototransistor (Photo / Base Mod) according to the invention of the present inventor described above.
ullation Bipolar Transisto
r: hereinafter abbreviated as “photo BAMBIT”) has been developed and provided. This conventional photo BAMBIT
Has a structure as shown in FIG. 7 (plan view of photo BAMBIT), and FIG. 8 (photo BAMBIT).
When used as exemplified in a circuit diagram showing an example of the use of IT, characteristics as shown in FIG. 9 (a graph showing an example of an output characteristic with respect to an optical input of a photo-BAMBIT) are obtained. In other words, the photo BAMBIT has the feature that it does not require any current consumption and operates completely with two terminals for optical input.

[0005]

However, the above-mentioned conventional photo BAMBIT has the following problems. That is, the conventional photo BAMBIT shown in FIG.
The BAMBIT to operate the switch, the base potential _{V B} by light _{input, V B = V B (ON} ) = V cc -V
_P (A _{V P,} the common base view of photo · BAMBIT shown in FIG. 10, the collector current _{I c} pinch OFF
Is the voltage between the collector and the base. The switch does not turn on unless it rises to). In the case of this photo BAMBIT, since V _P ≒ 0 V is an appropriate value, V _B (ON) ≒
_VCC . Therefore, to obtain high sensitivity, r _BE ≒ 1
A high resistance of 0 MΩ or more is required. This has the disadvantage that the CR time constant is increased by the photodiode and the response is deteriorated. Also, 10M in one chip
Inserting a resistor of Ω or more requires an extremely large chip surface, and has the disadvantage of increasing costs.

Accordingly, the present invention has been developed for the purpose of solving these drawbacks and problems in view of the above-mentioned various drawbacks and problems of the photoelectric conversion element in the prior art. It is an object of the present invention to provide a two-terminal photoelectric conversion element having a novel configuration that enables a two-terminal switch operation with hysteresis with respect to light input quickly.

[0007]

According to the present invention, in order to achieve the above object, specifically, a first semiconductor region layer made of a semiconductor material of a first conductivity type; A second semiconductor region layer made of a semiconductor material of the second conductivity type with respect to the first semiconductor region layer, the first semiconductor region layer being formed of a first semiconductor region layer.
A conductive type semiconductor substrate, forming a collector region, for a collector voltage energizing the collector region,
A negative resistance section exhibiting a voltage control type negative resistance characteristic; and a bias voltage applying section provided for applying a bias voltage to an input section of the negative resistance section. The voltage divider divides the voltage between the collector and the emitter by a division ratio of the first and second resistors connected to the collector electrode and the emitter electrode, and divides the third voltage from the divided voltage by the third voltage.
And a two-terminal photoelectric conversion element connected to the input part of the negative resistance part through the above resistor.

[0008]

The two-terminal photoelectric conversion element according to the present invention, which is configured as described above, includes a negative resistance section that performs a switching operation with respect to an optical input, and applies a bias voltage to the negative resistance section in advance. Are provided in the same substrate and biased to switch on with relatively weak input light. As a result, the sensitivity can be increased, and the time constant with respect to the optical input signal can be significantly reduced, which effectively works to improve the responsiveness of the photoelectric conversion element, and further significantly reduces the production cost. Can be reduced.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a two-terminal photoelectric conversion element according to the present invention will be described in detail with reference to specific embodiments shown in the drawings. FIG. 1A is a schematic plan view showing a first embodiment of a two-terminal photoelectric conversion element according to the present invention, and FIG. 1B is a schematic view taken along line BB ′ in FIG. 1A. FIG. In FIG. 1A, a two-terminal photoelectric conversion element according to the present invention includes a negative resistance portion 1, a bias voltage biasing portion 2, a first semiconductor region layer 4 made of a semiconductor material of a first conductivity type, and a BAMBIT structure. 5, a second semiconductor region layer 3 made of a semiconductor material of the second conductivity type, and a PN junction light receiving surface area 3a forming a photodiode
It consists of what contains.

In the two-terminal photoelectric conversion element according to this embodiment, the negative resistance portion 1 includes a P ^- base region 6, a P ⁺ base region 8, a P ⁺ contact region 9, and an emitter region 1.
0, BAMBIT is constituted by the gate region 11.
In the figure, reference numeral 16 is a base electrode of BAMBIT, and reference numeral 17 is an emitter electrode of BAMBIT.

Meanwhile, the bias voltage biasing unit 2 comprise a resistive region indicated by reference numeral 12, 13, 14, act as resistors _{r 1, r 2, r 3} . The emitter region 10 of BAMBIT is connected to the resistance region 13 by the emitter electrode 17 and the bonding pad 19, and the P ⁺ contact region 9 of BAMBIT is provided.
Is the resistance region 1 by the base electrode 16 of BAMBIT.
4 is connected. The PN-junction light receiving surface area 3a forming a photodiode is connected to the P ⁺ contact region 9 of the BAMBIT and the resistance region 1 by the base electrode 16 of the BAMBIT.
4 is connected.

In the present invention, the first semiconductor region layer made of the semiconductor material of the first conductivity type is basically formed as shown by reference numerals 4 and 5 in the embodiment shown in FIG. Consists of a first conductivity type semiconductor substrate and a semiconductor region layer of the same conductivity type grown and formed on one surface thereof. The first semiconductor region layers 4 and 5 indicate a collector region of BAMBIT and a cathode region of a photodiode, respectively.
Is an N ⁺ region, reference numeral 15 indicates an oxide film, and reference numeral 18 indicates a cathode of a photodiode and a collector electrode of BAMBIT.

FIG. 2 shows the principle of operation of the two-terminal photoelectric conversion element according to the first embodiment. Hereinafter, the operation principle of the photoelectric conversion element according to the first embodiment shown in FIG. It will be described in detail based on this. In FIG. 2,
A new symbol mark is used for the BAMBIT.

The operation principle of the two-terminal photoelectric conversion device according to the embodiment shown in FIGS. 1A and 1B is as follows. In FIG. 2, the voltage _Vcc is divided by the resistors r ₁ and r ₂ , and a bias voltage is applied to the base of the BAMBIT through the resistor r ₃ . The ratio between the resistance r ₁ and the resistance r ₂ is approximately 1:
Is about 9, when the voltage _V cc = 5.0V, the anode voltage of the photodiode becomes 4.5V. Of course, the voltage _{V P} of BAMBIT in this case, is designed to _{V P} ≒ 0V as grounded base characteristic example shown in FIG. 10. Thus, BAMBIT remains switched off in the absence of light. So BAMB
In order to switch IT on, unlike the case of the photo BAMBIT, the anode voltage of the photodiode is changed by the resistance r
_By passing the photocurrent Ish of the photodiode through ₃ , the voltage may be increased by about 0.5V. Therefore, it is understood that r ₃ / r _BE ≒ 1/10 may be used in order to switch ON at the same sensitivity as the conventional photo BAMBIT shown in FIG.

In order to further increase the sensitivity, r ₁ / r
Or _two smaller, or increasing the _{r 3,} or may be controlled _{V P} of BAMBIT more positively. Although the current consumption through the resistor _r 1, _{r 2} occurs, each as the resistance _{r 1, r 2, r 1} ≒ 100K
Ω, r ₂ ≒ 900KΩ is good, and current consumption is only 5μ
About A, no problem at all. In addition, the resistor has a high resistance of about 1 MΩ for both r ₂ and r ₃ , but the P− region shown in FIG. 1B can be used.
In A, the resistors r ₁ , r ₂ , and r ₃ are denoted by reference numerals 1 respectively.
2, 13, and 14 and do not occupy a very large area. Therefore, it leads to cost reduction.

FIG. 3 shows an example of input / output characteristics of the two-terminal photoelectric conversion element according to the present invention. As can be understood from FIG. 3, in the two-terminal photoelectric conversion element according to the present invention, an initial voltage of about 0.5 V is generated in the OFF state as compared with the conventional photo BAMBIT shown in FIG. This is due to the current consumption of about 5 μA as described above. However, remarkable improvement in responsiveness can be achieved by greatly reducing the CR time constant. In addition, the degree of freedom of design such as sensitivity is improved. Note that when the collector load is connected, only the low and the high are reversed.

The second embodiment of the two-terminal photoelectric conversion element according to the present invention
4 is shown in FIG. The two-terminal photoelectric conversion element according to the second embodiment of the present invention shown in FIG. 4 is a J-FET (junction field effect transistor) as a voltage-controlled negative resistance.
And a bipolar transistor. FIG. 4 is a cross-sectional view corresponding to the cross section shown in FIG. 1B with respect to the two-terminal photoelectric conversion element according to the second embodiment,
1 schematically shows a negative resistance section 1 according to the present invention. In the case of this embodiment, J-
By using the source 21 of the FET and setting the gate 11 of the J-FET at the same potential as the collector of the transistor, a negative resistance characteristic is realized by a feedback action to the base current. In this case, of course, unlike the conventional BAMBIT, there is no effect of extracting minority carriers from the gate 11 and the switching performance is poor. However, the degree of freedom is increased with respect to the design of the saturation current value between the source and the drain and the withstand voltage, and the negative resistance characteristic can be more controlled. In this embodiment, reference numeral 20 indicates a base region of a transistor, and reference numeral 22 indicates a toluin region of a J-FET.

The third terminal of the two-terminal photoelectric conversion element according to the present invention
5 is shown in FIG. The two-terminal photoelectric conversion element according to the third embodiment includes a negative resistance portion 1 as shown in FIG. The two-terminal photoelectric conversion element according to the third embodiment of the present invention shown in FIG. 5 has a high resistance of several KΩ-cm and a thickness of about 200 to 300 μm in order to bring out higher speed and higher sensitivity. A substrate 23 is used. Thus, compared to those of the first embodiment, N ^- the thickness of the layer to about 10
The sensitivity can be doubled. Also, to use the high-resistance substrate, switching property is approximately 1/10 junction capacitance C ₁ of the photodiode is compared with the first embodiment is improved by an order of magnitude. In this case, the high-concentration region 24 is partially provided in the high-resistance substrate in order to lower the V _CE (sat) of the negative resistance portion and improve the switching performance.
In this embodiment, reference numeral 25 indicates an N ⁺ collector extraction portion.

The fourth aspect of the two-terminal photoelectric conversion element according to the present invention
6 is shown in FIG. In FIG. 6, reference numeral 1 is
4 shows a negative resistance portion of the two-terminal photoelectric conversion element according to the present invention. The two-terminal photoelectric conversion element according to the fourth embodiment of the present invention shown in FIG. 6 uses a phototransistor instead of the photodiode of the circuit example shown in FIG. Can be made about ten times as large as that shown in FIG. 2, and the value of the resistor r ₆ is 1 / several tens or less as compared with the resistor r ₃ . In the fourth embodiment, as shown in FIG. 6, an emitter region is formed in the photodiode shown in FIG. 1A. This connection is made between the emitter region (first conductivity type) and the negative resistance section 1.

Each of the embodiments described above can, of course, be shared with each other.
It is also possible to incorporate them into an integrated circuit.

[0021]

The two-terminal photoelectric conversion element of the present invention having the above-described structure has many effects as described below. (1) Compared to a conventional photoelectric conversion element, switching is performed at the speed of light while having hysteresis characteristics as a complete two-terminal element. (2) By applying an internal bias to the input section of the negative resistance section, the CR time constant can be reduced and the operation speed can be increased as compared with the photo BAMBIT. (3) The sensitivity can be easily increased because the internal bias constant can be freely selected. (4) Since the internal bias constant can be reduced, the photo BAM
Chip size can be reduced as compared with BIT. (5) Since it is a two-terminal element, it can be arrayed,
Various industrial applications are possible. (6) Like a conventional phototransistor, switching with hysteresis is possible for both collector load connection and emitter load connection, and there is no need to have two types of active high and active low as in the case of IC. .

[Brief description of the drawings]

FIG. 1A is a schematic plan view showing a specific first embodiment of a two-terminal photoelectric conversion element according to the present invention;
FIG. 1B is a schematic cross-sectional view taken along a line BB ′ in FIG. 1A.

FIG. 2 is a circuit diagram for explaining an operation principle based on the photoelectric conversion element according to the first embodiment shown in FIGS. 1A and 1B.

FIG. 3 is a graph showing an example of output characteristics with respect to light input in the circuit diagram shown in FIG. 2 in the first embodiment shown in FIGS. 1A and 1B.

FIG. 4 shows a second embodiment of the two-terminal photoelectric conversion element according to the present invention, and is a schematic sectional view corresponding to the section shown in FIG. 1B.

FIG. 5 is a schematic cross-sectional view showing a third embodiment of the two-terminal photoelectric conversion element according to the present invention and corresponding to the cross section shown in FIG. 1B.

FIG. 6 shows a fourth embodiment of the two-terminal photoelectric conversion element according to the present invention, and is an equivalent circuit diagram of the photoelectric conversion element according to the fourth embodiment.

FIG. 7 is a schematic plan view showing an example of a conventional base modulation type bipolar phototransistor (photo BAMBIT).

FIG. 8 is a circuit diagram for explaining an operation of a conventional base modulation type bipolar phototransistor (photo BAMBIT).

FIG. 9 is a graph showing an example of output characteristics with respect to light input of a conventional base modulation type bipolar phototransistor (photo BAMBIT).

FIG. 10 is a graph showing an example of output characteristics of a conventional base modulation type bipolar phototransistor (photo BAMBIT) and a BAMBIT to be used for the photoelectric conversion element of the present invention with respect to an electrical input at a grounded base.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Negative resistance part 2 Bias voltage energizing part 3 Second semiconductor region layer 3a PN junction light receiving surface region 4, 5 First semiconductor region layer 6 P ^- base region of BAMBIT 7 N ⁺ region 8 P ⁺ base of BAMBIT Area 9 P ⁺ contact area of BAMBIT 10 Emitter area 11 Gate area 12, 13, 14 Resistance area 15 Oxide film 16 Base electrode 17 Emitter electrode 18 Cathode of photodiode and collector electrode of BAMBIT 19 Bonding pad for taking out output of photoelectric conversion element 19 Reference Signs List 20 base region of transistor 21 source region of J-FET 22 drain region of J-FET 23 high-resistance substrate 24 N ⁺ high-concentration region 25 N ⁺ collector extraction portion

Claims (1)

(57) [Claims] A first conductive type semiconductor material;
Forming a PN junction light-receiving surface region by a semiconductor region layer of a second semiconductor region layer made of a semiconductor material of a second conductivity type with respect to the first semiconductor region layer. The semiconductor region layer is a semiconductor substrate of the first conductivity type, forms a collector region, and has a negative resistance portion exhibiting a voltage control type negative resistance characteristic with respect to a collector voltage applied to the collector region; A bias voltage energizing section provided to energize the input section of the negative resistance section with a bias voltage, wherein the bias voltage energizing section is connected to a collector electrode and an emitter electrode. And dividing the voltage between the collector and the emitter by a division ratio of the second resistor, and connecting the divided voltage dividing point to the input of the negative resistor through a third resistor. Two-terminal photoelectric conversion element .