JPH11233813A - Semiconductor photodetector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain a monitor current being generated by a semiconductor photodetector within the range of a specific amount of current, by adjusting the amount of a monitor current being selected out of current that is generated by a semiconductor photodetector corresponding to the intensity of the emission light from the backside of a DFP-LD. SOLUTION: A device for optical communication is incorporated so that a backside emission beam Pr enters a plurality of p-InP well regions 2 on a light reception surface. A monitor current being generated by the reverse side emission beam Pr is generated between a backside electrode 6 and a pad electrode 5. Then, a drive voltage is applied to a DFB-LD, the intensity of a front surface emission beam Pf is modulated while the front surface emission beam Pf is being detected, and a monitor current that is generated at a semiconductor photodetector by the backside emission beam Pr is adjusted so that the monitor current is within a specific range, namely so that no excessive current flows to the control circuit of the drive current under conditions where a desired intensity of a front surface emission beam P which is required in light communication can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light receiving element for receiving light emitted from a laser diode and converting it into a monitor current used for controlling the laser diode, and more particularly to a semiconductor light receiving element used for controlling a distributed feedback laser diode. It relates to a light receiving element.

[0002]

2. Description of the Related Art FIG. 7 is a top view of an optical communication device for transmitting an optical signal by modulating the intensity of light emitted from a distributed feedback laser diode (hereinafter referred to as "DFB-LD"). In the figure, 12 is a DFB-LD, 13 is a photodiode for monitoring, 14 is a substrate of metal or the like, and Pf is DFB
-The front emission light from the LD, Pr is the back emission light from the DFB-LD, and the back emission light P from the DFB-LD 12
r is received by the monitoring photodiode 13 to be converted into a monitor current, and while monitoring the monitor current, a DF is provided using an externally provided circuit (not shown).
The drive voltage of the B-LD 12 is controlled to perform intensity modulation of the front emission light Pf. Thus, DFB-LD
Is used, the wavelength distribution can be reduced as compared with the case where a normal Fabry-Perot laser (hereinafter, referred to as “FP-LD”) is used, and the propagation efficiency of an optical signal when an optical fiber or the like is used is reduced. Improvement is possible.

FIG. 8A is a top view of a monitor photodiode 13 used in the communication device.
(B) is a cross-sectional view taken along the line CC ′, in which 1 is an n-InP substrate, 2 is a p-InP well region, and 3 is Si
N insulating film (functions as an anti-reflection film in the light receiving section), 4
Is an extraction electrode, 5 is a bonding pad electrode, 6 is a back electrode, 9 is an i-InGaAs layer, and 10 is i-InP.
The layer Pr is light emitted from the back surface of the laser diode.
As shown in FIG. 6B, the laser diode 12, the photodiode 13 and the photodiode 13 are arranged such that the back-side emission light Pr just enters the light receiving region of the photodiode 13, that is, the region where the p-InP well region 2 is formed. Are assembled and n
A current generated by the PN junction region formed by the -InP substrate 1 and the p-InP well region 2 is output as a monitor current between the back surface electrode 6 and the bonding pad electrode 5.

[0004]

SUMMARY OF THE INVENTION Laser diode 12
When a DFB-LD is used as the light source, when the intensity of the front emission light Pf is set to a constant intensity in accordance with the standard, the rear emission light Pr greatly varies between elements, and as shown in FIG. The monitor current generated in the photodiode 13 that has received the light Pr also greatly varies. In the figure, the vertical axis represents the frequency (the number of elements), and the horizontal axis represents the monitor current Im generated by the photodiode. As a result, the monitor current Im generated in the photodiode 13 becomes too small (b in the figure), the detection accuracy of the monitor current Im decreases, or the monitor current Im becomes too large (a in the figure), and the DFB- There is a problem that a circuit for controlling the drive voltage of the LD is broken.

[0005] Then, as a result of examination by the inventor, DFB-
In the LD, the distance between the cleavage plane and the diffraction grating is different at the cleavage position, and due to this, the reflectance at the cleavage plane is different.
It was found that the intensity of light emitted from each cleavage plane also varied depending on the distance between the cleavage plane and the diffraction grating. That is, since the distance between the cleavage plane and the diffraction grating is different between the front side and the back side, and further between the elements, the intensity of the back side outgoing light Pr when the front side outgoing light Pf is constant is also It varied between the elements. Therefore, the present invention provides a semiconductor light-receiving element capable of maintaining a monitor current generated in the semiconductor light-receiving element within a predetermined current amount range even when the intensity of the light Pr emitted from the back surface of the DFB-LD varies between the elements. The purpose is to provide.

[0006]

Accordingly, the inventor of the present invention has conducted intensive studies, and as a result of this research, it has been difficult to avoid such a variation in the back-side emitted light Pr between the elements due to the element structure. Correspondingly, the current to be used as the monitor current is selected from the currents generated in the semiconductor light receiving element, and the amount of the monitor current is adjusted. Can be set within a predetermined current range, and the present invention has been completed.

That is, according to the present invention, a first electrode having a first electrode portion is provided.
A conductive type semiconductor substrate, a plurality of second conductive type semiconductor well regions provided on the semiconductor substrate to form a plurality of PN junctions, and a second conductive type semiconductor well region provided on the semiconductor substrate via an insulating film. A second electrode portion, receiving light emitted from the laser diode on a surface of the semiconductor well region to generate a monitor current between the first electrode portion and the second electrode portion, and A semiconductor light receiving element for detecting and modulating the intensity of light emitted from the laser diode, the semiconductor light receiving element including one or more semiconductor well regions selected from a plurality of the semiconductor well regions and the second electrode portion. A semiconductor light receiving element wherein the monitor current is controlled by changing the light receiving area of the outgoing light or the junction area of the PN junction part by connecting with one connection wiring. In this way, by connecting one or more of the semiconductor well regions and the second electrode portion by the first connection wiring as appropriate in accordance with the intensity of the back surface emitted light Pr, the respective PN junctions are formed. The current used as the monitor current among the currents generated in the section can be selected and used. Thus, even when the intensity of the back surface emitted light Pr differs between the elements, the monitor current can be set within a predetermined current amount range.

The plurality of semiconductor well regions are arranged substantially concentrically with respect to the center of the outgoing light emitted to the semiconductor light receiving element, and such that the area increases as the distance from the center increases. It is preferable that the amount of current generated at the PN junction is substantially equal.
With this structure, the amount of current generated at each PN junction becomes substantially equal, and the monitor current increases substantially in proportion to the number of semiconductor well regions 2 connected.
The number of the well regions electrically connected to the second electrode portion can be easily selected.

Preferably, the first connection wiring is formed of a bonding wire. By using the bonding wires, the monitor current can be adjusted within a predetermined range by increasing the number of the first connection wirings while detecting the monitor current.

The first connection wiring comprises a wiring layer provided on the semiconductor substrate with an insulating film interposed therebetween. The first connection wiring is unnecessary from each wiring layer connecting the semiconductor well region and the second electrode portion. It is preferable to cut the appropriate wiring layer. This is because the remaining wiring layer can be used as the first connection wiring only by cutting the unnecessary wiring layer, and the monitor current can be easily adjusted. In particular, since the working process is simple, it is suitable for use in processing after assembling the optical communication device.

Further, the present invention provides the above-mentioned semiconductor light receiving element,
A third electrode portion connected to the semiconductor substrate on the semiconductor substrate, wherein the semiconductor well region not connected to the second electrode portion is connected to the third electrode portion by a second connection wiring; 3. An electric charge accumulated in said semiconductor well region is discharged to said semiconductor substrate.
The semiconductor light receiving element described in (1). As a result, the semiconductor well region that does not contribute to the generation of the monitor current is short-circuited to the semiconductor substrate, and the charge generated in the PN junction region flows to the semiconductor substrate and is consumed. Therefore, it is possible to prevent the generation of a minute diffusion current generated by the diffusion of the unnecessary charges, and to prevent the detection accuracy of the monitor current from deteriorating and the response characteristics from deteriorating.

It is preferable that the second connection wiring is made of a bonding wire. By using the bonding wire, the monitor current can be adjusted within a predetermined range by increasing the number of the second connection wires while detecting the monitor current.

The second connection wiring comprises a wiring layer provided on the semiconductor substrate with an insulating film interposed therebetween. An unnecessary wiring is formed from the wiring layer connecting the semiconductor well region and the third electrode portion. Preferably, the layer is cut. This is because the remaining wiring layer can be used as the second connection wiring only by cutting off the unnecessary wiring layer, and the monitor current can be easily adjusted.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 Embodiment 1 of the present invention will be described with reference to FIG. FIG.
(A) is a top view of the semiconductor light receiving element according to the present embodiment, and (b) of FIG. 1 is a cross-sectional view taken along the line AA ′ of (a) of FIG. In the figure, the same reference numerals as those in FIG. 8 indicate the same or corresponding portions, and 4a indicates a connection wiring, 4b indicates a lead electrode, and 4c indicates a cut portion of the connection wiring.

The above-mentioned semiconductor light receiving element is formed by forming an i-InGaAs layer (low concentration n
-InGaAs layer) 9, i-InP layer (low concentration n-In)
P layers) 10 are sequentially laminated, and a plurality of p-I
An nP well region 2 is provided to form a plurality of PN junctions. Here, six p-InP well regions 2 having the same shape are formed at equal intervals. Also, i-In
On the P layer 10 and the p-InP well region 2, SiN
Layer 3 is formed. The SiN film 3 functions as an electrical insulating film and also functions as an anti-reflection film of the light receiving unit on the p-InP well region 2. Furthermore,
A lead electrode 4b connected to the pad electrode 5 is provided on the SiN film 3, and the lead electrode 4b and six n-I
The nP well regions 2 are formed in a state where they are connected to each other by the connection wiring 4a. The pad electrode 5, the lead electrode 4b, and the connection wiring 4a are formed from a conductive metal such as gold.

In such a semiconductor light receiving element, a plurality of p-I
The surface on which the nP well region 2 is formed is a light receiving surface, and the back surface emitting light Pr is formed on the p-InP well region 2 on the light receiving surface.
Is incorporated in the optical communication device such that the light is incident.
The monitor current generated by the back surface emitted light Pr is generated between the back surface electrode 6 and the pad electrode 5.

Next, while applying a driving voltage to the DFB-LD 12, the front emission light Pf is detected by a detector (not shown), the intensity of the front emission light Pf is modulated, and a desired light required for optical communication is obtained. Under the condition that the front emission light intensity is obtained, the monitor current generated in the semiconductor light receiving element 13 by the rear emission light Pr is measured. At this point, the semiconductor light receiving element 13
Are not connected to the drive voltage control circuit of the DFB-LD 12.

Next, the monitor current is adjusted so that the monitor current is within a predetermined range, that is, so that an excessive current does not flow through the drive current control circuit. Specifically, six p-InP well regions 2 and extraction electrodes 4b
Is cut by laser cutting or the like so that part of the current generated at the six PN junctions does not become the monitor current.

Thus, when the intensity of the back-side emitted light Pr when the intensity of the front-side emitted light Pf is the standard intensity is larger than the upper limit of the standard value required by the control circuit of the DFP-LD connected to the semiconductor light receiving element. However, by lowering the conversion efficiency of the semiconductor light receiving element, it is possible to shift the monitor current to a lower current side and prevent an excessive current from being supplied to the control circuit. In the present semiconductor light receiving element, the monitor current can be shifted to the low current side, but cannot be shifted to the high current side. Therefore, the intensity of the back surface emitted light Pr corresponding to the intensity of the front surface emitted light Pf is: Even when the intensity is lower than the standard intensity, p-InP is set in advance so that a larger monitor current is obtained so that the monitor current does not become lower than the lower limit of the standard value of the control circuit.
It is necessary to form the well region 2 in advance.

FIG. 2 shows another semiconductor light receiving element according to the present embodiment, which is obtained by partially changing the structure of FIG. 1A. In the figure, the same reference numerals as those in FIG. 1 indicate the same or corresponding parts. In such a semiconductor light receiving element, six p-InP
Connection wiring 4 for connecting well region 2 and extraction electrode 4b
a is formed in a state where it is cut 4c in the middle, and while detecting the monitor current, the cut portion of the connection wiring 4a is electrically connected by bonding such as a gold wire, and the monitor current supplied to the control circuit is detected. Is adjusted to fall within a predetermined standard range.

In such a semiconductor light receiving element, the p-InP well region 2 is formed so that the monitor current when all the connection wirings 4a are connected is larger than the lower limit of the standard value of the control circuit. Required.

Embodiment 2 FIG. Embodiment 2 of the present invention will be described with reference to FIG. FIG. 3A is a top view of the semiconductor light receiving element according to the present embodiment, and FIG. 3B is a cross-sectional view taken along line BB ′ of FIG. 3A. In the figure, the same reference numerals as those in FIG. 1 indicate the same or corresponding parts.

In the semiconductor light receiving element according to the present embodiment, the plurality of p-InP well regions 2 are formed substantially concentrically from the center of the back surface outgoing light Pr applied to the semiconductor light receiving element and from the center. The farther away, the larger the area becomes, and the respective p-InP well regions 2 and i-InG
The amount of current generated at each PN junction formed at the connection with the aAs layer 9 is formed to be substantially equal at each PN junction.

In the present embodiment, as in the first embodiment, first, a drive voltage is applied to the DFB-LD 12, and the front emission light Pf is detected by a detector (not shown). Under the condition that the intensity of the emitted light Pf is modulated and the desired front emission light Pf intensity required for optical communication is obtained, the monitor current generated in the semiconductor light receiving element 13 by the back emission light Pr is measured. Subsequently, the connection wiring 4a connecting the p-InP well region 2 and the extraction electrode 4b is cut by laser cutting or the like so that the monitor current falls within a predetermined range, and the current generated at the four PN junctions is cut. Some of them do not become the monitor current.

Thus, when the intensity of the back-side emitted light Pr when the intensity of the front-side emitted light Pf is set to the standard intensity is larger than the upper limit of the standard value required by the control circuit of the DFP-LD connected to the semiconductor light receiving element. However, it is possible to shift the monitor current to the low current side and prevent an excessive current from being supplied to the control circuit. In particular, in the present embodiment, since the amount of current generated at each PN junction is substantially equal, it is easy to predict the amount of current when the connection wiring 4a is cut by laser cutting or the like, and it is necessary to adjust the monitor current. It is easy to predict a cut portion of the connection wiring 4a. In the present semiconductor light receiving element, the monitor current can be shifted to the low current side, but cannot be shifted to the high current side. Therefore, the intensity of the back emission light Pr corresponding to the intensity of the front emission light Pf is: Even if the intensity is lower than the standard intensity, the p-InP well region 2 may be formed in advance so that a larger monitor current is obtained so that the monitor current does not become lower than the lower limit of the standard value of the control circuit. Required.

FIG. 4 shows another semiconductor light receiving element according to the present embodiment, which is obtained by partially changing the structure of FIG. 3A. In the figure, the same reference numerals as those in FIG. 3 indicate the same or corresponding parts. In such a semiconductor light receiving element, a connection wiring 4a connecting the four p-InP well regions 2 and the extraction electrode 4b is provided.
Is formed in a state of being cut 4c in the middle, and while monitoring the monitor current, the cut portion of the connection wiring 4a is electrically connected by a bonding 11 such as a gold wire to supply the monitor current supplied to the control circuit. Is adjusted to fall within a predetermined standard range.

In the present embodiment, as described above, since the amount of current generated at each PN junction is substantially equal,
The amount of current when the connection portion 4c of the connection wiring 4a is connected by the bonding 11 can be easily predicted, and the connection position of the bonding 11 necessary for adjusting the monitor current can be easily predicted.

Embodiment 3 Embodiment 3 of the present invention will be described with reference to FIG. FIG. 5 is a top view of the semiconductor light receiving element according to the present embodiment.
The same reference numerals indicate the same or corresponding parts. In the present embodiment, the semiconductor light receiving element is provided on the n-InP substrate 1 with the n-InP substrate.
A p-InP well region 2 having a third electrode portion 8 connected to the InP substrate 1 and not connected to the lead-out wiring 4b
Are connected to the third electrode unit 8 by the connection wiring 7a and the extraction electrode 7b.

That is, in this embodiment, first, in addition to the connection wiring 4a and the extraction electrode 4b according to the first embodiment, the third
Connection wiring 7a connected to electrode portion 8, extraction electrode 7b
Is formed. Connection wiring 7a, lead electrode 7b
Is formed on the SiN film 3 and connected to the third electrode portion 8 electrically connected to the n-InP substrate 1.
The connection wiring 7a and the lead electrode 7b are preferably formed from a conductive material such as gold.

Next, according to the method of the first embodiment, after the predetermined connection wiring 4a is cut, as shown in FIG. 5, the connection connected to the p-InP well region 2 where the connection wiring 4a is cut. The connection wiring 7 connected to the p-InP well region 2 while the connection wiring 4a remains connected, leaving the wiring 7a
a is cut by laser cutting or the like. Thereby, p connected to the pad electrode 5 and contributing to the generation of the monitor current
P-InP well region 2 other than -InP well region 2
Is electrically connected to the n-InP substrate 1 via the connection wiring 7a, the extraction electrode 7b, and the third electrode unit 8.

As a result, the p-InP well region 2 which does not contribute to the generation of the monitor current is short-circuited to the n-InP substrate 1, and the carriers generated in the PN junction region are n-InP
It flows to the substrate 1 and is consumed. Therefore, pI
Unnecessary carriers formed in the nP well region 2 are n-
It is possible to prevent the generation of a minute diffusion current generated by diffusing into the InP substrate 1 and to prevent the detection accuracy of the monitor current from being reduced due to the diffusion current and the response characteristics from deteriorating. Become.

FIG. 6 shows another semiconductor light receiving element according to the present embodiment. As described in the first embodiment, p-I
A connection wiring 4a connecting the nP well region 2 and the extraction electrode 4b is formed in a state where it is cut 4c in the middle, and
The connection wiring 7a connecting the p-InP well region 2 and the extraction electrode 7b is also formed in a state where it is cut 7c in the middle. Subsequently, according to the method described in the first embodiment,
After the cut portion of the predetermined connection wire 4a is electrically connected by bonding 11 such as a gold wire, the pad electrode 5 and the cut 7c region of the connection wire 7a corresponding to the p-InP well region 2 which has not been known to the world Are electrically connected by bonding 11 such as a gold wire.

As a result, similarly to the case shown in FIG. 5, it is possible to prevent the detection accuracy of the monitor current from deteriorating and the response characteristics from deteriorating. Note that the structure according to the present embodiment can be similarly applied to the structure according to the second embodiment.

In the first to third embodiments, the case where the DFP-LD is used for the laser diode has been described.
Even in a normal FP-LD, the back-side emission light Pr intensity when the front-side emission light Pf intensity is constant may vary between elements due to the thickness of the antireflection film provided on the cleavage plane, and the like. In such a case, the present invention is applied to a normal FP-LD
And other types of laser diodes,
A similar effect can be obtained.

[0035]

As is clear from the above description, by using the semiconductor light receiving element according to the present invention, the current used as the monitor current is selected from the currents generated at the respective PN junctions and used. Even if the intensity of the back-side emitted light Pr differs between the elements, the monitor current can be set within a predetermined current amount range. Therefore, it is possible to prevent the detection accuracy from being lowered due to an excessively small monitor current, and to prevent the control circuit from being broken due to an excessively large monitor current.

In the present invention, among the carriers generated in the PN junction region, the carriers that do not contribute to the generation of the monitor current can be flowed to the semiconductor substrate and consumed, so that such unnecessary carriers are diffused and generated. It is possible to prevent the generation of a minute diffusion current, and prevent the detection accuracy of the monitor current from deteriorating, the response characteristic from deteriorating, and the like.

[Brief description of the drawings]

FIG. 1A is a top view of a semiconductor light receiving element according to a first embodiment of the present invention; (B) It is sectional drawing in AA '.

FIG. 2 is a top view of another semiconductor light receiving element according to the first embodiment of the present invention.

FIG. 3A is a top view of a semiconductor light receiving element according to a second embodiment of the present invention; (B) It is sectional drawing in BB '.

FIG. 4 is a top view of another semiconductor light receiving element according to the second embodiment of the present invention.

FIG. 5 is a top view of a semiconductor light receiving element according to a third embodiment of the present invention.

FIG. 6 is a top view of another semiconductor light receiving element according to the third embodiment of the present invention.

FIG. 7 is a schematic diagram of an optical communication device incorporating a laser diode and a semiconductor light receiving element.

FIG. 8A is a top view of a semiconductor light receiving element according to a conventional structure. (B) It is sectional drawing in CC '.

FIG. 9 shows a monitor current I between the DFB-LD and the FP-LD.
It is a comparison of the distribution of m.

[Explanation of symbols]

1 n-InP substrate, 2 p-InP well region, 3
SiN insulating film, 4, 4b extraction electrode, 4a connection wiring, 4c cutting part, 5 bonding pad electrode, 6
Back electrode, 7a Connection wiring, 7b Leader electrode, 8
Third electrode part, 9 i-InGaAs layer, 10 i-In
P layer, 11 bonding wire, 12 laser diode, 13 photodiode, 14 substrate.

Claims (7)

[Claims] A first conductivity type semiconductor substrate having a first electrode portion; a plurality of second conductivity type semiconductor well regions provided on the semiconductor substrate so as to form a plurality of PN junctions; A second electrode portion provided on the semiconductor substrate via an insulating film, and receiving light emitted from a laser diode on a surface of the semiconductor well region, the first electrode portion and the second electrode portion. A semiconductor light receiving element for detecting the monitor current and modulating the intensity of the emitted light of the laser diode, wherein one or two of the semiconductor well regions are selected from the plurality of semiconductor well regions.
The above-described semiconductor well region and the second electrode portion are connected by a first connection wiring, and the monitor current is controlled by changing the light receiving area of the emitted light or the junction area of the PN junction. Semiconductor light receiving element. 2. A semiconductor device according to claim 1, wherein the plurality of semiconductor well regions are arranged substantially concentrically with respect to a central portion of the outgoing light irradiated on the semiconductor light receiving element, and such that the area increases as the distance from the central portion increases. 2. The semiconductor light receiving device according to claim 1, wherein the amount of current generated in each of the PN junctions is substantially equal. 3. The semiconductor light receiving device according to claim 1, wherein said first connection wiring is made of a bonding wire. 4. The semiconductor device according to claim 1, wherein the first connection wiring comprises a wiring layer provided on the semiconductor substrate with an insulating film interposed therebetween, and the first connection wiring comprises a wiring layer connecting the semiconductor well region and the second electrode portion. 3. The semiconductor light receiving device according to claim 1, wherein an unnecessary wiring layer is cut. 5. The semiconductor light-receiving element further includes a third electrode portion connected to the semiconductor substrate on the semiconductor substrate, the semiconductor well region not connected to the second electrode portion, and the third electrode 3. The semiconductor light-receiving element according to claim 1, wherein the first and second portions are connected by a second connection wiring, and charges accumulated in the semiconductor well region are discharged to the semiconductor substrate. 6. The semiconductor light receiving device according to claim 5, wherein said second connection wiring is made of a bonding wire. 7. The semiconductor device according to claim 7, wherein the second connection wiring comprises a wiring layer provided on the semiconductor substrate with an insulating film interposed therebetween, and the second connection wiring is unnecessary from a wiring layer connecting the semiconductor well region and the third electrode portion. 6. The semiconductor light receiving device according to claim 5, wherein the wiring layer is cut off.