JP3768099B2 - Light receiving element and optical semiconductor device including the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a light receiving element suitable for monitoring the light output of a device that outputs a single wavelength, such as a light emitting diode or semiconductor laser for optical communication, and an optical semiconductor device including the same.
[0002]
[Prior art]
As typified by a semiconductor laser device, an optical semiconductor device that controls the light output of an element to a constant includes a light receiving element for monitoring the element output. In a semiconductor laser device, a semiconductor laser element is provided as a light emitting element, and this element is disposed on a submount (see Japanese Patent Laid-Open No. 6-53603). As shown in FIG. 7, there is a case where a silicon light receiving element is built in the submount and the submount and the light receiving element 1 are used together by utilizing the fact that the submount is mainly composed of silicon. In this case, the electrode 10 for disposing the laser element 18 is formed in a region outside the light receiving region 4 on the surface of the submount. The electrode 10 is formed on the upper surface of the submount via an insulating film 8 such as silicon oxide.
[0003]
[Problems to be solved by the invention]
As described above, when the semiconductor laser element is disposed on the submount with the built-in light receiving element, if the distance L between the laser element 18 and the light receiving region 4 varies, the output of the light receiving element may vary accordingly. For example, as shown by the solid line in FIG. 6, when the height H from the surface of the light receiving element to the light emitting point of the laser element is 130 μm, the output current Im of the light receiving element is substantially constant regardless of the interval L. When the height H is 10 μm, the output current Im of the light receiving element decreases rapidly as the interval L increases as shown by the broken line. The tendency as shown by the broken line in FIG. 6 appears when the height H is 120 μm or less, for example, when the active layer of the semiconductor laser is disposed on the lower side, and the tendency as shown by the solid line is the height H of 130 μm or more. In this case, for example, it appears when the active layer of the semiconductor laser is arranged on the upper side.
[0004]
Therefore, when the active layer is disposed on the lower side in order to effectively release the heat generated in the active layer through the submount, the output current Im is likely to fluctuate depending on the interval L as shown by the broken line in FIG. There is a problem that the current Im is different for each light receiving element depending on the mounting state of the laser element.
[0005]
As described above, when the electrode for arranging the laser element is formed on the upper surface of the submount built in the light receiving element, the charge formed by the voltage applied to the electrode for arranging the element may adversely affect the output of the light receiving element. Yes. Such a tendency is due to the case where the electrode for element arrangement is arranged in direct contact with the semiconductor layer without interposing an insulating film in order to improve the heat dissipation characteristics of the light emitting element, or along with the miniaturization of the element shape, This becomes conspicuous when the distance between the element placement electrode and the light receiving region of the light receiving element is shortened.
[0006]
Therefore, an object of the present invention is to reduce fluctuations in the output current of the light receiving element and maintain good output characteristics. Another object is to improve the heat dissipation characteristics of the element placement electrode. Another object is to provide an optical semiconductor device that is easy to use. Another object is to provide an optical semiconductor device that is downsized.
[0007]
[Means for Solving the Problems]
The light receiving element of the present invention is a light receiving element having a light emitting element arranging electrode and a light receiving region on an upper surface thereof as claimed in claim 1, wherein the element arranging electrode and the light receiving region overlap in a plane. It is characterized by that. With this configuration, it is possible to suppress the variation in the distance between the light emitting point of the light emitting element and the light receiving region, and to reduce the output fluctuation of the light receiving element due to the attached state.
[0008]
According to a second aspect of the present invention, there is provided a light receiving element having a light emitting element arrangement electrode and a light receiving region on an upper surface thereof, wherein a concave portion as viewed in a plan view of the element arrangement electrode is provided on the light receiving element. A convex portion is formed in the region in plan view, and the concave portion and the convex portion are arranged so as to fit into each other. With this configuration, it is possible to suppress the variation in the distance between the light emitting point of the light emitting element and the light receiving region, and to reduce the output fluctuation of the light receiving element due to the attached state. Further, the light emitting element can be stably mounted on the electrode.
[0009]
According to a third aspect of the present invention, there is provided an optical semiconductor device in which a light emitting element having a light emitting point on an end face is disposed adjacent to a light receiving region on an upper surface of the light receiving element. It arrange | positions so that it may overlap with the said light reception area | region planarly. With this configuration, it is possible to suppress the variation in the distance between the light emitting point of the light emitting element and the light receiving region, and to reduce the output fluctuation of the light receiving element due to the attached state.
[0010]
The optical semiconductor device according to the present invention is the optical semiconductor device according to claim 4, wherein a light emitting element having a light emitting point on an end face is arranged on an element arrangement electrode adjacent to the light receiving area on the upper surface of the light receiving element. A convex portion protruding in a plan view is formed on the side facing the element arranging electrode of the electrode, and a depressed concave portion into which the convex portion is fitted is formed on the side facing the light receiving region of the element arranging electrode. The light emitting element is arranged so that an end surface having the light emitting point crosses a portion where the convex portion and the concave portion are fitted. With this configuration, it is possible to suppress the variation in the distance between the light emitting point of the light emitting element and the light receiving region, and to reduce the output fluctuation of the light receiving element due to the attached state. Further, the light emitting element can be stably mounted on the electrode.
[0011]
The light emitting element can be arranged such that the height of the light emitting point with respect to the surface of the light receiving element is 120 μm or less. Even in the light emitting element having such an arrangement, the light emitting state can be reliably detected by the light receiving element.
[0012]
An electrode for disposing the light emitting element is disposed in an adjacent region adjacent to the light receiving region, and the electrode for disposing the light emitting element passes through an insulating film so as to contact a semiconductor layer constituting the adjacent region. Can be configured. With such a configuration, it is possible to improve the heat dissipation of the element arranged on the element arrangement electrode. In addition, a high voltage discharge path applied to the light emitting element can be secured, and the electrostatic withstand voltage of the element can be increased.
[0013]
A high-concentration impurity layer may be formed on the surface of the semiconductor layer constituting the light receiving element so as to be positioned between the light emitting element arranging electrode and the light receiving region. With this configuration, unnecessary charges around the light receiving region can be absorbed by this layer, and the characteristics of the light receiving element can be improved.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. First, a first embodiment will be described with reference to FIGS. FIG. 1 is a sectional view showing an embodiment of an optical semiconductor device comprising the light receiving element 1 and the light emitting element 18 of the present invention, and FIG. 2 is a plan view thereof. FIG. 1 is a cross-sectional view taken along the line II of FIG.
[0015]
The light receiving element 1 is composed of a PN-type or PIN-type light receiving element, and a p-type high-concentration impurity layer 3 is formed in an island shape by selectively diffusing p-type impurities such as boron (B) into the silicon substrate 2. is doing. The p-type high concentration impurity layer 3 substantially becomes the light receiving region 4 of the light receiving element 1. In the case of a PN type light receiving element, the silicon substrate 2 can be formed of only an n type high concentration impurity layer (n + silicon layer). In this example, in order to obtain a PIN type light receiving element, an n type high concentration impurity is used. An n-type low concentration impurity layer (n-silicon layer) 6 is stacked on the layer (n + silicon layer) 5.
[0016]
A region adjacent to the light receiving region 4 of the light receiving element 1 is referred to as an adjacent region 7. That is, the upper surface of the silicon substrate 2 that is not covered with the p-type high concentration impurity layer 3 is substantially the adjacent region 7. The upper surface of the light receiving element 1, that is, the light receiving region 4 and the adjacent region 7 are substantially covered with an insulating film 8 such as silicon oxide (SiO 2). A signal electrode 9 made of aluminum (Al) or the like is provided on the upper surface of the light receiving element 1 so as to penetrate the hole 8 a of the insulating film 8 on the light receiving region 4 and to be connected to the high concentration impurity layer 3. An element placement electrode 10 made of gold (Au) or the like is provided on the insulating film 8 on the adjacent region 7.
[0017]
The light-emitting element 18 is an edge-emitting semiconductor laser element having light emitting points 18a and 18b on the side end faces in the front-rear direction, and its active layer is disposed close to the lower part of the element in order to improve heat dissipation. The light emitting element 18 includes positive and negative electrodes, and in this example, they are arranged on the upper and lower surfaces.
[0018]
As shown in FIG. 2, the light receiving region 4 has a planar overlap with the electrode 10 by forming a protruding portion 4 a on the side facing the electrode 10. The convex portion 4 a serves to fill the gap between the light emitting element 18 and the light receiving region 4. The light emitting element 18 is arranged so that the rear end surface having the light emitting point 18b for monitoring slightly protrudes from the rear edge of the electrode 10, so that the light emitting point 18b overlaps the convex portion 4a in a plane. In this way, the front end of the convex portion 4 a is arranged in front of the rear edges of the electrode 10 and the light emitting element 18. Therefore, even if the mounting position of the light emitting element 18 slightly varies, the state of L = 0 in FIG. 6 can be maintained.
[0019]
Next, a second embodiment will be described with reference to FIGS. The description of the configuration common to the first embodiment will be omitted, and the description will focus on the differences.
[0020]
The first difference is that the electrode 10 disposed on the insulating film 8 is disposed so as to penetrate most of the electrode 2 through the insulating film 8 and directly contact the substrate 2. In general, the through-hole 8b is provided in the insulating film 8 that is not excellent in thermal conductivity, and the electrode 10 passes through the insulating film 8 so that most of the electrode 10 is in direct contact with the substrate 2. Compared with the case where it is provided only on the upper surface, the heat dissipation characteristics of the element 18 disposed on the electrode 10 can be improved. If the resistance value of the substrate 2 is optimized, the electrode 10 and the silicon substrate 2 can function as a discharge path when an undesired high voltage such as static electricity is applied to the element 18. The withstand voltage of 18 can be increased.
[0021]
The second difference is that the high-concentration impurity is set on the upper surface of the silicon substrate 2 along the edge of the element placement electrode 10 so that the impurity concentration is set to be equal to or higher than that of the p-type high-concentration impurity layer 3. This is the point where the layer 11 is formed. The high-concentration impurity layer 11 is formed by selectively diffusing n-type impurities such as phosphorus (P). However, like the p-type high-concentration impurity layer 3, it can be made p-type. The conductivity type can be selectively changed according to the polarity of the voltage applied to the electrode 10.
[0022]
The high concentration impurity layer 11 is formed below the insulating film 8 so as to be separated from the electrode 10 and surround the periphery of the electrode 10. Since the high concentration impurity layer 11 is located between the p-type high concentration impurity layer 3 forming the light receiving region 4 and the electrode 10, unnecessary charges generated on the surface of the silicon substrate 2 due to the voltage applied to the electrode 10 are effective. It functions as a region for absorbing unwanted charges that are absorbed. Therefore, the charge generated on the surface of the silicon substrate 2 due to the voltage applied to the electrode 10 affects the output of the signal electrode 9, and the illuminance-output current characteristics of the light receiving element 1 are adversely affected. it can. Further, the element shape can be reduced by setting the distance between the light receiving region 4 and the electrode 10 shorter than in the case where the impurity layer 11 is not provided. A back electrode 12 such as gold is formed on the back surface of the light receiving element 1.
[0023]
The third difference is that the planar shape of the electrode 10 that has overlapped the light receiving region 4 is changed so as not to have a planar overlap with the light receiving region 4. The electrode 10 has a shape such that the electrode 10 sandwiches both sides of the convex portion 4a by forming a concave portion 10a for receiving the convex portion 4a on the side facing the light receiving region 4. As a result, the electrode 10 is arranged so as not to have a planar overlap with the light receiving region 4.
[0024]
The light-emitting element 18 is arranged so that the convex portion 4a of the light-receiving region fits into the concave portion 10a of the electrode 10 when seen in a plan view, and the rear end surface having the light-emitting point 18b crosses the portion in which both are fitted. . As a result, the light emitting point 18b at the center of the end face of the light emitting element 18 is located on the convex portion 4a, and both ends of the rear end face are located on the electrode 10. Thus, the presence of the convex portion 4a and the concave portion 10a allows the tip portion of the convex portion 4a to be disposed in front of the tail end of the electrode 10, and to be disposed in front of the rear end surface of the light emitting element 18. And the state of the interval L = 0 shown in FIG. 6 can be maintained.
[0025]
Next, an embodiment in which the optical semiconductor device shown in FIGS. 1 to 4 described above is mounted in a package will be described with reference to FIG. The embodiment shown in FIG. 5 shows a frame type semiconductor laser device 13 that includes a semiconductor laser element as the light emitting element 18 and includes the light receiving element 1 as a light receiving element that also serves as a submount.
[0026]
The laser device 13 is configured by arranging the light receiving element 1 and the semiconductor laser element 18 in a package formed by connecting and fixing a plurality of leads 14, 15, and 16 by a resin frame 17 and wire bonding wiring. The leads 14, 15, 16 are of a lead frame type, and a pair of sub leads 14, 16 are arranged on the left and right of the main lead 15 having an element arrangement region at the tip. The main lead 15 is integrally formed with right and left wings for heat dissipation, and these protrude from the resin frame 17 to the left and right. The light receiving element 1 is fixed by adhering the back electrode 12 to the element arrangement portion at the tip of the main lead 15 with a conductive adhesive such as silver paste. On the electrode 10 on the upper surface of the light receiving element 1, the element 18 is arranged so that the light emitting points 18a and 18b are located below the element, that is, the light emitting point height H with reference to the surface of the light receiving element is 120 μm or less. It is fixed using a conductive agent such as solder or silver paste. As a result, the back electrode of the element 18 is electrically connected to the element arrangement electrode 10. A wiring 19 made of a wire bond line is provided between a portion of the element placement electrode 10 exposed without being covered by the element 18 and the sub lead 16. Between the surface electrode 20 of the element 18 and the main lead 15, a wiring 21 made of a wire bond line is provided. Between the signal electrode 9 of the light receiving element 1 and the sub lead 14, a wiring 22 made of a wire bond line is provided.
[0027]
In the laser device 13, when a predetermined laser driving voltage is applied between the main lead 15 and the sub lead 16, the driving voltage is supplied to the front and back electrodes of the element 18, the element 18 oscillates, and the laser light travels along the axis X. Is output. A part of the laser beam output in the backward direction is incident on the light receiving region 4 of the light receiving element 1, whereby a predetermined current output Im (monitor signal) is generated at the signal electrode 9. The voltage applied to the element 18 can be controlled by taking this signal out from between the sub lead 14 and the main lead 15 and performing a predetermined process.
[0028]
In the above embodiment, the case where a semiconductor laser element is used as the light-emitting element 18 is taken as an example. However, the present invention is a light-emitting diode that has a relatively single wavelength and can be used for optical communication and other semiconductor light-emitting elements. An element or the like can also be the target of the element 18.
[0029]
In addition, the present invention can include the case where the conductivity of P and N is reversed in each of the above embodiments.
[0030]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the light receiving element excellent in the light reception sensitivity characteristic can be provided. In addition, it is possible to provide a light receiving element with excellent heat dissipation. In addition, a light receiving element suitable for downsizing can be provided. In addition, the optical semiconductor device including such a light receiving element can have excellent characteristics.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an embodiment of an optical semiconductor device of the present invention.
FIG. 2 is a plan view of the same embodiment.
FIG. 3 is a cross-sectional view showing another embodiment of the present invention.
FIG. 4 is a plan view of the embodiment.
FIG. 5 is a plan view showing another embodiment of the present invention.
FIG. 6 is a characteristic diagram showing a distance L between a light emitting point and a light receiving surface and an output current of the light receiving element.
FIG. 7 is a cross-sectional view of a conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Light receiving element 4 Light receiving area | region 7 Adjacent area | region 8 Insulating film 10 Element arrangement | positioning electrode 11 High concentration impurity layer (unnecessary charge absorption layer)
13 Semiconductor Laser Device 18 Light Emitting Element (Laser Element)

Claims (7)

A light receiving element comprising a light emitting element arrangement electrode and a light receiving area on an upper surface, wherein the element arrangement electrode and the light receiving area overlap in a plane. A light receiving element having a light emitting element arrangement electrode and a light receiving region on an upper surface, wherein the element arranging electrode has a concave portion when viewed in plan, and a convex portion when viewed in plan on the light receiving region, and the concave portion And a convex portion are arranged so as to fit into each other. In an optical semiconductor device in which a light emitting element having a light emitting point on an end face is disposed adjacent to a light receiving region on the upper surface of the light receiving element, the light emitting element is disposed so that the light emitting point overlaps the light receiving region in a plane. An optical semiconductor device. In an optical semiconductor device in which a light emitting element having a light emitting point on an end face is arranged on an element arranging electrode adjacent to a light receiving region on the upper surface of the light receiving element, the light receiving region is viewed in plan on the side facing the element arranging electrode. A protruding convex part is formed, a concave concave part into which the convex part is fitted is formed on a side of the element arrangement electrode facing the light receiving region, and an end surface having the light emitting point is fitted into the convex part and the concave part. An optical semiconductor device, wherein the light emitting element is disposed so as to cross a portion to be jammed. 5. The optical semiconductor device according to claim 3, wherein the light emitting element is arranged such that a height of the light emitting point with respect to a surface of the light receiving element is 120 μm or less. An electrode for disposing the light emitting element is disposed in an adjacent region adjacent to the light receiving region, and the electrode for disposing the light emitting element passes through an insulating film so as to contact a semiconductor layer constituting the adjacent region. 5. The optical semiconductor device according to claim 3, wherein the optical semiconductor device is arranged. 7. The optical semiconductor device according to claim 6, wherein a high concentration impurity layer is formed on a surface of a semiconductor layer constituting the light receiving element so as to be positioned between the electrode for arranging the light emitting element and the light receiving region. .

Images