JPH01283882A - Lateral photodiode - Google Patents

Abstract

PURPOSE:To reduce an unnecessary part in which light is not directed to a circular spot of incident light, and to decrease a parasitic capacity by composing two or more electrodes in which the arcuate parts of the electrodes are opposed concentrically in the same plane to form the shape of a photodetector in a circular shape. CONSTITUTION:After Si is ion implanted on a GaAs substrate 8 to form an active layer 7 of a photodiode, a first electrode 1 having one arcuate part 1a and a second electrode 2 having two arcuate parts 2d, 2c opposing on a concentric circle with the arcuate part 1a are formed by patterning on the layer 7, and a photodetector 13 is formed in a circular shape. Thus, an unnecessary part irradiated with no light is removed to reduce its capacity, and the end part 2d of the photodiode is effectively operated as an electrode. Accordingly, the diameter of the parts of the shanks 1b, 2b of a comb can be reduced, thereby decreasing its parasitic capacity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrode structure of a semiconductor device, particularly a horizontal photodiode.

[Prior Art] In recent years, with the development of optical communications, optical receivers integrated into ICs have also progressed. The receiver described above converts an optical signal into an electrical signal, and basically uses a light-to-current converter to convert the optical signal to a current signal and a current-to-voltage converter to convert the current signal to a voltage signal. configured. In the above-mentioned receiver, a horizontal photodiode is generally used for the photo-current conversion section.

FIG. 4 shows an example of the electrode structure of a conventional horizontal photodiode. This device has a comb-shaped electrode on a substrate, and the comb teeth portions (1a) and (2a) are rod-shaped.
1) and the second electrode (2) are formed so that their teeth face each other on the same plane. In addition, the light-receiving area of the photodiode (13) is rectangular.

FIG. 5 shows another example of the electrode structure of a conventionally used horizontal photodiode. Its shape is similar to the photodiode described above, and the teeth (la) and (2a) of the comb are rod-shaped, but the light-receiving area (13) is circular.

In the conventional structure shown above, when light is incident with a bias applied between the first electrode (1) and the second electrode (2), carriers are generated at the spot (14) of the incident light and a photocurrent is generated. arise.

In the structure shown in Figure 4, the incident light from the optical fiber (spora) (14) is circular, but the light-receiving area (13) is rectangular and has many unnecessary parts that are not exposed to light. , the parasitic capacitance of the photodiode is correspondingly large. Fifth
The figure shows a structure in which the parasitic capacitance of the photodiode, which impairs the coupling efficiency with the optical 7-eyeper, is reduced by making the light-receiving area (13) circular in consideration of the above-mentioned problem.

[Problem to be solved by the invention] In order to achieve large-capacity information transmission in an IC-based optical receiver, it is necessary to reduce the CR time constant determined by the receiver's light receiving element and electronic circuit, and improve high-speed response. However, the structure shown in FIG. 4 has a problem in that the parasitic capacitance of the photodiode is large, which affects the response speed accordingly. In addition, in the structure shown in FIG. 5, when changing the diameter of the photodiode, the length and number of teeth of the comb,
Since there are many changes to be made, such as changing the curvature of one pole that connects the teeth of the comb, there are problems such as it takes time to make changes and mistakes are likely to occur when making changes.

This invention is rounded to solve the above-mentioned problems, and the photodiode's light-receiving area (13) is circular. By having the W shape, the coupling efficiency with the optical fiber is not impaired, and the parasitic capacitance of the photodiode can be reduced. The object of the present invention is to obtain a horizontal photodiode whose design can be easily changed by having a regular shape.

[Means for Solving the Problems J] The horizontal photodiode in this invention 11 has at least one arc-shaped portion, and the first arc-shaped portion has at least one arc-shaped portion. The 21st one is located on a concentric circle and on the same plane as the arc-shaped part of the first electric plate! The light-receiving area is circular.

[Effect]

In the horizontal photodiode according to the present invention, at least two tWs in which the arc-shaped portions of the electrodes concentrically oppose each other are formed on the same plane, and the shape of the light-receiving portion is circular, so that a circular spot of incident light can be obtained. This reduces parasitic capacitance by reducing unnecessary parts that are not exposed to light. (9) Even in the photodiode which has completed the process because it has the electrode structure, the diameter can be reduced by simple means without damaging the shape of the light receiving part, and the parasitic capacitance can be reduced accordingly.

Furthermore, since the above-mentioned IE groove structure is provided, the number of parts to be changed when changing the design can be reduced, the time required for the change, and the errors that occur during the change can be reduced.

[Example] An example of the present invention will be described below with reference to the drawings. 1st
Figure (a) shows a t-pole structure of a lateral photodiode according to an embodiment of the present invention. Also, Fig. 1(b) shows the above)
The cross-sectional structure of the photodiode is shown when the photodiode is cut between X and Y in the figure. In these figures, the active layer of the photodiode (
7). After this, a first electrode (1) having one arc-shaped part (la) on this active layer (7) and two arc-shaped parts (2a) concentrically opposite to the arc-shaped part (1a) are formed.
(2c) A second electrode (2) is formed by patterning. In this example, the electric current [(1) (2) is changed to W
It is made of Si.

Through the above steps, the Schottky-type horizontal photodiode shown in FIG. 1 can be obtained.

Further, FIG. 2 shows another embodiment of the present invention.

The photodiode shown in this figure is formed by the process described above, and its electrodes are formed into six electrodes (1) (2) (3) (4) (5) (6) from the first electrode to the sixth electrode. It is well structured.

In the embodiment shown in FIGS. 1 and 2 above, the light receiving section (1
3) By making the shape circular, unnecessary parts that are not exposed to light are removed and the capacity is reduced without compromising the coupling efficiency with the optical fiber. Furthermore, [pole arc (la)
(2a) Since (2a) are arranged concentrically, the end portion (2a) of the photodiode also works effectively as an electrode, so it can be used as a comb handle (lb
) There is no need to consider the margin in the part (2b), the diameter can be made small, and the parasitic capacitance can be reduced. Furthermore, in the above-mentioned photodiode which has completed the process, by simply cutting the base of the electrode corresponding to the comb teeth from the outside with a beam or the like according to the spot diameter of the incident light, the photodiode can be made without changing the circular shape of the light-receiving part. The diameter can be made smaller, and the parasitic capacitance can be easily reduced accordingly.

In addition, with this structure, even when redesigning the photodiode to change its diameter, it is only necessary to add or delete only the outermost electrode, reducing the number of changes.
The time required for changes and errors during changes can be reduced.

Next, in the embodiment shown in FIG. 2 described above,! ! The effect caused by having polarity will be explained. In the above embodiment, the function of detecting the spot position of incident light can be added to the function of the conventional photodiode. Furthermore, this detection function makes it possible to adjust the spot position of the incident light to the center position of the photodiode. Figure 3 shows an example of this process. The second electrode (2), the third electrode (1) and the third electrode i (3) of the photodiode shown in FIG.
A bias voltage is applied between the electrodes, and a second monitoring ammeter is connected to the pole (2) to detect the photocurrent generated between the electrodes when light is incident. Also, a bias was applied between the fourth pole (4), the third electrode (3), and the fifth electrode (5), and between the second electrode (2) and the first pole and the third tm. Apply a bias voltage of the same magnitude as the voltage,
A current needle for monitoring photocurrent generated between the t-poles when light is incident is connected to the fourth electrode (4). FIG. 3(a) shows how light is incident on the odd diode in the above state. If light is incident on the spot position in Figure 3 (Inc.), many carriers will be generated on the left side of the center of the figure, so the current value in the first ammeter (9) will be different from the current value in the second iE current meter (10). ) becomes larger. Therefore, 5
The experimenter can know to which side the spot position has shifted by comparing the current values. In addition, the first
It is helpful to move the spot position horizontally in the figure so that the current values of the current needle (9) and the second current needle (10) are equal, as shown in Figure 3 (b). Light can be incident at the central position. Furthermore, from this state, the fourth electrode (4), the third electrode (3), and the fifth electrode (5)
Instead of applying a bias between the 6i-th pole (6) and the 1st
A bias is applied between the pole (1) and the fifth electrode (5), the third ammeter (11) is connected to the 6i-th pole (6),
By comparing the current flowing through the ammeter (11) with the current value of the first ammeter (9), the spot position can be confirmed in the vertical direction of the figure, and the spot position in the vertical direction can be adjusted. Through the above process, it becomes possible to move the sispot position to the center of the photodiode as shown in FIG. 3(c). With the above-mentioned function, light can be efficiently incident on the autodiode, and variations in the amount of incident light due to deviations in spot positions can also be reduced. Also, after adjusting the spot position to the center of the photodiode, the first. Third. Fifth
Short electrodes (1), (3), and (5), '42. Fourth
．． 6th pole (2) (4,) (6) & yaw) L, above 1st. Third. The 5th wl pole (1) (3) (5) and the 2nd wl pole (1) (3) (5). 4th. When a bias is applied between the sixth electrode (2), (4), and (6), the same effect as the photodiode shown in FIG. 1 can be obtained. However, in the photodiode shown in Figure 1, the diameter must be made sufficiently larger than the spot diameter, taking into account the deviation of the spot position, but in the photodiode shown in Figure 2, the spot position must be adjusted to the center of the photodiode. This makes it possible to reduce the margin for spot position deviation. Therefore, the diameter of the photodiode can be smaller than that shown in FIG. 1, and the parasitic capacitance can be reduced accordingly.

In the above example, GaA was applied to the substrate (8) and Wsi was applied to the electrode α) (2), but the substrate (8)
The present invention can be applied as long as the electrode a) (2) is also a Schottky electrode. In this case as well, the above-mentioned effects can be obtained.

Further, in the above embodiment, a Schottky photodiode is formed, but the present invention can also be applied to a Pn junction photodiode. , the above-mentioned effects can also be obtained in this case.

Although the number of t-poles is two or six in the above-mentioned projecting embodiments, if at least one arc-shaped part faces the other ti-arc-shaped part and is arranged on a concentric circle, at least two or more electrodes can be used. The present invention can be applied by forming such a structure. In this case as well, the above-mentioned effects can be obtained.

Furthermore, in the embodiment shown in FIG. 2, the spot position detection function has been described, but there are at least three or more methods for detecting the position. By forming the pole, the present invention can be applied.0 [Effect of the Invention J As described above, according to the present invention, in the horizontal photodiode, the first! It has a pole and at least one arc-shaped part, and this arc-shaped part is the first! Since the light-receiving area is circular, including the arc-shaped part of the pole and the second electrode facing concentrically and on the same plane,
This reduces the portion of the circular spot of incident light that is not illuminated by the light, reducing parasitic capacitance without impairing the coupling efficiency with the optical fiber. Further, even in the photodiode which has been processed to have the tW groove structure, the diameter can be reduced by simple means without damaging the shape of the light receiving portion, and the parasitic capacitance can be reduced accordingly.

Furthermore, since the above structure has a polar structure, the number of parts to be changed when changing the design can be reduced, the time required for the change, and the errors that occur during the change can be reduced.

[Brief explanation of the drawing]

FIG. 1 is an electrode structure diagram and cross-sectional view of a semiconductor device according to an embodiment of the present invention, and FIG. 2 is an electrode structure diagram of a semiconductor device according to an embodiment when six electrodes are used in this invention.
FIG. 3 is a diagram showing the process of moving the spot position of incident light to the center of the photodiode in the photodiode shown in FIG. 2, and FIGS. 4 and 5 are t-pole structure diagrams of a conventional semiconductor device. α) to (6) are the first to sixth electrodes, (7) is the active layer, and (8
) is the substrate, (9) (10) (11) is the first. the second and third ammeters, (12) the spot position of the incident light;
(13) is the light-receiving area of the photodiode, (14)
) is the spot of incident light. In addition, the same reference numerals in each figure indicate the same "i" or corresponding parts.

Claims (1)

[Claims] (1) A first electrode having at least one arc-shaped portion; and a first electrode having at least one arc-shaped portion, the arc-shaped portion being concentric with and on the same plane as the arc-shaped portion of the first electrode. 1. A horizontal photodiode including opposing second electrodes and having a circular light-receiving area.