JP2003168837A - Semiconductor laser device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce noise even at the time of using high-speed APC without making a return light be incident on a photodetector for monitoring. <P>SOLUTION: The semiconductor laser device is provided with a mount board 10 for which a pin photodiode is formed by stacking an i-type Si layer 12 and a p-type Si layer 13 on a part of an n-type Si substrate 11, and a part of a side face of the Si layers 12 and 13 is formed on a slope 15; a semiconductor laser element 40 mounted on the Si substrate 11 where the Si layers 12 and 13 are not formed of the mount board 10, so as to make a light emitting end face opposed to the slope 15; and a total reflection mirror 30 formed at a part of the slope 15. The total reflection mirror 30 is formed in a stripe shape in a direction orthogonal to an inclining direction of the slope 15, and is arranged so as to reflect the light 51 at an optical axis center part of output light beams of the laser element 40; output it to the outside; and make peripheral lights 53 and 54 be incident on a light receiving part of the photodiode. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser device used as a light source for optical communication technology, optical transmission technology, and optical information recording technology.

[0002]

2. Description of the Related Art Currently, in the fields of optical communication, optical transmission, optical information recording, etc., semiconductor lasers are widely used as a light source because of their coherency of emitted light, high-speed operation, and small size. Semiconductor lasers emit stimulated emission light by injecting current from the outside, and because the light intensity changes sensitively to thermal fluctuations, it is necessary to secure a heat dissipation path. It is mounted on metal members such as frames and metal blocks. Here, in order to reduce the difference in thermal expansion coefficient between the metal member and the semiconductor material forming the semiconductor laser, the semiconductor laser is mounted on a base material called a submount made of Si, AlN, or the like, and then mounted on the metal member. To be implemented.

On the other hand, the semiconductor laser sensitively changes its optical output due to environmental temperature changes, so that both the semiconductor laser and the mounting substrate (metal member) are collectively temperature-controlled on an element such as a Peltier element. To be implemented. However, since the mounting board and the submount also have a small amount of heat capacity, when precise light output control is required, a method of monitoring actual output light and causing the drive current circuit to perform feedback control is adopted. This is the automatic light output control (Auto
matic power control (APC). In an edge-emitting semiconductor laser, both front and rear light can be monitored, but in general, a front APC that monitors a part of light from the front is preferable.

As an example of using a semiconductor laser in the front APC system, there is a configuration shown in FIG. 8 (see, for example, Patent Document 1). In this configuration, not the writing beam 106 emitted from the semiconductor laser 105 and passing through the APC-controlled focusing lens 103, but the beam peripheral portion 107 deviating from the effective diameter 101 of the focusing lens 103 is received by the light receiving element. Monitored by 102. As a result, APC can be performed without consuming a part of the writing beam 106. However, this method has a problem in that the semiconductor laser 105, the lens 103, and the light receiving element 102 are independently positioned and positioned, and accurate position adjustment is required for each component, which increases the manufacturing cost.

As an example of avoiding this problem, a configuration shown in FIG. 9 has been proposed (for example, see Patent Document 2). In the figure, 10 is a submount substrate made of Si, and this substrate 10 is obtained by epitaxially growing an i-type Si layer 12 and a p-type Si layer 13 on an n-type Si substrate 11.
A pin photodiode is composed of 1, 12, and 13. This diode applies a reverse bias voltage to Si
A depletion layer extending over the entire layer 12 is used as a light receiving portion.

A recess is formed in a part of the submount substrate 10 by anisotropic etching or the like, and a semiconductor laser element 40 is mounted on the bottom of this recess. Further, one side surface of the recess is formed on the inclined surface 15, and a semi-transmissive film 70 made of a dielectric multilayer film or thin metal is formed on a part of the inclined surface 15.

Emitted light 51 from the semiconductor laser device 40
Is partially reflected by the semi-transmissive film 70 formed on the inclined surface 15, and is output as output light 52 above the substrate. A part of the light 55 transmitted through the semi-transmissive film 70 enters the depletion layer spread in the i-type Si layer 12, and is absorbed and becomes a photocurrent. The output light of the semiconductor laser device 40 is controlled by inputting this current into the APC circuit. Usually, the band of the APC circuit is set as low as several tens to several hundreds of Hz, and it is designed to identify and control the slow component of the output light fluctuation of the semiconductor laser. This is because the temperature of the semiconductor laser beam largely changes.

On the other hand, in consideration of application to an optical disk, the output light is reflected on the surface of the optical disk, is branched by a hologram element inserted in the middle, and is input to a signal receiving element. However, the branching in the hologram element uses diffraction, and 100% of the reflected light cannot be diffracted due to the difference in the birefringence of the optical disc medium and there is return light returning to the light source. Therefore, on the semiconductor laser side,
The high-frequency superimposition technology that keeps constant modulation at a frequency higher than the signal frequency is aimed at reducing the return light noise of the semiconductor laser.

In FIG. 9, the return light is indicated by 57, and the light incident on the light receiving portion is indicated by 56. In FIG. 9, most of the return light 57 is reflected by the semi-transmissive film 70, but a part of the return light 57 is incident on the light receiving portion of the photodiode for monitoring, that is, the depletion layer spreading around the i-type Si layer 12, and the original light is transmitted. AP is added to the photocurrent generated by the semiconductor laser emission light 55,
The noise is input to the C circuit and becomes noise. The frequency of the signal light included in the return light from the optical disk is normally several tens of MHz to 10 MHz.
It has a high frequency of 0 MHz and has a gain only in the low range.
Only the average value is detected in the PC circuit, and only a slight offset occurs. Since this is an almost constant minute value, it can be canceled by the gain adjustment of the APC circuit.

However, in the optical disc application for writing,
In order to precisely control the light pulse during writing, high-speed A
It has been reported that it is effective to use a PC,
In order to control the write light pulse intensity and reduce the return light noise,
High-speed APC is effective. When the band of the APC circuit becomes equal to or higher than the signal frequency, there is a problem that all the monitor noise due to the return light is amplified as noise and eventually APC becomes impossible.

Although a circular mirror is used instead of the semi-transmissive film 70 in the configuration of FIG. 9 (for example, Patent Document 3), good APC can be performed even by using such a device. It was difficult.

[0012]

[Patent Document 1] Japanese Unexamined Patent Publication No. 4-332185

[0013]

[Patent Document 2] Japanese Patent Laid-Open No. 2001-15849

[0014]

[Patent Document 3] Japanese Unexamined Patent Publication No. 8-320166

[0015]

As described above, in the conventional semiconductor laser device in which the semiconductor laser element and the light receiving element are mounted on the same submount substrate, a part of the laser light from the semiconductor laser element is partially divided for front APC. In the configuration in which the light is input to the light receiving element through the transparent film, the return light from the optical disk or the like enters the light receiving element through the semitransparent film, and the AP
There is a problem that it becomes noise of the C circuit.

The present invention has been made in consideration of the above circumstances. An object of the present invention is to provide a structure in which a semiconductor laser element and a light receiving element are mounted on the same submount substrate, and the return light is a light receiving element for monitoring. Without making it incident on
An object of the present invention is to provide a semiconductor laser device capable of significantly reducing noise even when using high-speed APC.

[0017]

(Structure) In order to solve the above problems, the present invention adopts the following structure.

That is, according to the present invention, a semiconductor substrate for forming a light receiving element is laminated on a part of a semiconductor substrate, and at least a part of a side surface of the semiconductor layer is formed as an inclined surface. , A semiconductor laser element mounted on a semiconductor substrate of the mount substrate on which the semiconductor layer is not formed so that the light emitting end face faces the inclined surface, and total reflection formed on a part of the inclined surface. A semiconductor laser device comprising a mirror, wherein the total reflection mirror is formed on a part of the inclined surface in a stripe shape in a direction orthogonal to an inclination direction of the inclined surface, and an output of the semiconductor laser device. Part of the light beam including at least the center of the optical axis is reflected and output to the outside, and the remaining part is arranged to be incident on the light receiving portion of the light receiving element without being reflected. This The features.

According to the present invention, a light-receiving element is formed on the surface of a semiconductor substrate, a recess is formed on a part of the surface of the substrate, and at least one side surface of the recess is an inclined surface. And a semiconductor laser device mounted on the bottom surface of the recess so that the light emitting end face faces the inclined surface, and a total reflection mirror formed on a part of the inclined surface. The total reflection mirror is
A part of the inclined surface is formed in a stripe shape in a direction orthogonal to the inclination direction of the inclined surface, and a part of the output light beam of the semiconductor laser device including at least the central portion of the optical axis is reflected. It is characterized in that it is arranged so that it is output to the outside and the remaining part is incident on the light receiving part of the light receiving element without being reflected.

The following are preferred embodiments of the present invention.

(1) The semiconductor substrate is a high-concentration impurity-doped Si substrate of the first conductivity type, and the semiconductor layer includes a low-concentration impurity-doped Si layer sequentially stacked from the Si substrate side and a high-concentration impurity of the second conductivity type. Consists of a doped Si layer. This should form a pin diode.

(2) The total reflection mirror is formed so as to cover a part of the low-concentration impurity-doped Si layer exposed on the inclined surface.

(3) The total reflection mirror is formed in a stripe shape except the upper and lower portions of the low concentration impurity-doped Si layer exposed on the inclined surface.

(4) The total reflection mirror is formed in a stripe shape except the upper and lower portions of the low-concentration impurity-doped Si layer exposed on the inclined surface, and the high-concentration impurity of the first conductivity type exposed on the inclined surface. The doped Si substrate and the second-conductivity-type high-concentration impurity-doped Si layer should be covered with a total reflection mirror or a light-shielding film.

(5) The total reflection mirror is formed in a pattern having a slit-shaped opening along a direction orthogonal to the inclination direction of the inclined surface, and the position of the slit-shaped opening is part of the low-concentration impurity-doped semiconductor layer. It corresponds to.

(6) A groove having an inclined surface continuous with the inclined surfaces of the low-concentration impurity-doped semiconductor layer and the high-concentration impurity-doped semiconductor layer is formed on the surface of the semiconductor substrate. And a stripe-shaped first pattern formed so as to cover a part of the side surface of the low-concentration impurity-doped semiconductor layer located at, and a side surface of the second conductivity type high-concentration impurity-doped semiconductor layer located at the inclined surface. A stripe-shaped second pattern, and a stripe-shaped third pattern formed so as to cover a portion of the high-concentration impurity-doped semiconductor substrate of the first conductivity type located on the inclined surface,
Each of the first pattern, the second pattern, and the third pattern is
Arrange along the direction orthogonal to the direction of inclination of the inclined surface.

(7) A groove having an inclined surface continuous with the inclined surface of the semiconductor layer is formed on the surface portion of the semiconductor substrate.

(8) A non-reflection film is formed on the inclined surface.

(9) The inclined surface of the side surface of the semiconductor layer is (111)
The surface of the semiconductor substrate is inclined by a predetermined angle from the (100) plane so that the inclined surface is 45 degrees with respect to the surface of the semiconductor substrate.

(Operation) According to the present invention, a total reflection mirror is provided instead of the semi-transmissive film for reflecting the output light beam from the semiconductor laser device, and the total reflection mirror is provided only near the optical axis of the output light beam. Since it is provided so as to cover, the light near the optical axis is extracted to the outside, and the peripheral light is incident on the light receiving element for monitoring. Since the return light from the optical disc or the like enters near the optical axis, the return light does not enter the light receiving element due to the presence of the total reflection mirror. Therefore,
It is possible to prevent the returning light from entering the monitor light receiving element, and it is possible to significantly reduce noise even when using the high-speed APC.

Moreover, since the positional relationship between the semiconductor laser mounting portion and the total reflection mirror can be defined by the precision of the semiconductor process, it is possible to manufacture with high precision without requiring special equipment or control. This is advantageous in reducing manufacturing costs.

[0032]

DETAILED DESCRIPTION OF THE INVENTION The details of the present invention will be described below with reference to the illustrated embodiments.

(First Embodiment) FIG. 1 shows a first embodiment of the present invention.
2A is a perspective view and FIG. 1B is a cross-sectional view for explaining a schematic configuration of the semiconductor laser device according to the embodiment.

In the figure, 10 is a submount substrate made of Si or the like, 30 is a total reflection mirror, and 40 is a semiconductor laser element. The submount substrate 10 has a low impurity concentration i on a portion of the n-type Si substrate 11 that is highly doped with impurities.
-Type Si layer 12 and p heavily doped with impurities
Type Si layer 13 is formed by sequentially epitaxially growing,
A concave portion is formed by partially removing the surface portion of the substrate 10. Specifically, the Si layers 12 and 13 are removed by anisotropic etching or the like while leaving a part thereof. And
The remaining i-type Si layer 12, p-type Si layer 13, and n-type Si substrate 11 form a pin photodiode (light-receiving element) as a light-receiving element.

The insulating layer 2 is formed on the surface of the submount substrate 10.
1 is formed, the insulating film 21 is partially removed on the p-type Si layer 13, and the p-side electrode 2 is formed so as to contact the Si layer 13.
2 is formed. The n-side electrode 23 is provided on the back surface of the substrate 11.
Are formed. Then, a reverse bias voltage is applied between these electrodes 22 and 23, and the depletion layer spreading over the entire i-type Si layer 12 is used as a light receiving portion.

The side surface formed by etching, that is, the pin
The side surface of the photodiode is an inclined surface. Here, the etching side surface obtained by anisotropic etching is generally likely to be a (111) plane. Therefore, by tilting the surface of the Si substrate 11 from the (100) plane by 9.7 degrees, the inclined surface 15 serving as the (111) plane can be set at 45 degrees with respect to the surface of the substrate 11.

A total reflection mirror 30 is formed on the inclined surface 15. Specifically, the Au layer is formed so as to cover the Si layer 12 except the upper and lower portions of the i-type Si layer 12 exposed on the inclined surface 15.
The total reflection mirror 30 is formed in a stripe shape. A positioning marker 27 is formed on the upper surface of the light receiving element. The positioning marker 27 may be formed by etching the p-type Si layer 13.
A pattern of a metal film may be formed on the insulating layer 21.

The semiconductor laser element 40 is mounted on the bottom surface of the recess of the submount substrate 10, that is, the portion where the Si layers 12 and 13 are not formed. Specifically, an electrode 24 is formed on the bottom surface of the recess via the insulating film 21, and the semiconductor laser element 40 is mounted thereon by a conductive adhesive 25 made of solder or the like. At this time, the semiconductor laser element 40 is mounted so that the light emitting end surface faces the inclined surface 15.

The light beam emitted from the semiconductor laser element 40 is emitted in a direction parallel to the surface of the Si substrate 11 and often becomes a vertically elongated elliptical beam (50 in the figure) on the inclined surface 15. A part of the light beam 51 near the center of the optical axis is reflected by the total reflection mirror 30 made of Au or the like formed on the inclined surface 15 and becomes output light 52 which is output above the substrate. The peripheral light beams 53 and 54 are generated by the low concentration layer (i-type Si layer) 1
2 enters the depletion layer that spreads within 2 and is absorbed into a photocurrent.

In FIG. 1, the upper and lower peripheral portions of the elliptical beam 50 correspond to the peripheral light beams 53 and 54, which are incident on the light receiving region and serve as a monitor current. Return light 57 from the optical disk or the like is reflected by the total reflection mirror 30 and returns to the semiconductor laser element 40. At this time, the return light 57 is completely reflected by the total reflection mirror 30.
In order to prevent the return light 57 from being incident on the light receiving region of the monitor light receiving element, the width of the total reflection mirror 30 is set larger than the beam diameter at the time when the return light 57 reaches the inclined surface 15. APC noise can be reduced. In addition,
The beam diameter of the returning light 57 is the numerical aperture (N.
A. ) And so on.

Since the light receiving region of the monitor light receiving element is a depletion layer formed at substantially the same position as the low concentration layer 12, the depth of the recess in which the semiconductor laser element 40 is mounted is determined by the anisotropic etching time. By controlling with the control, the semiconductor laser mounting position and the height can be precisely adjusted by a method such as adjusting the relative height with the epitaxial layer. In particular, by forming the positioning marker 27 and the like as shown in FIG. 1, the relative positions of the light receiving region, the total reflection mirror 30, and the semiconductor laser device 40 can be precisely determined, and a special adjustment process is required. A configuration that does not do is feasible.

In the configuration of FIG. 1, since the total reflection mirror 30 extends in the lateral direction in a strip shape, the lateral mounting error has almost no effect on the monitor current value. Further, although the vertical position shift has some influence, the influence of the position shift is reduced by monitoring both above and below.

In FIG. 1, the groove 14 is formed on the surface of the Si substrate 10 so as to be continuous with the inclined surface of the side surface of the light receiving element, and the light emitting portion (that is, the active layer) of the semiconductor laser element 40 is recessed. The output light beam is prevented from being kicked at the bottom surface of the recess even when the light beam is relatively close to the bottom surface.

This structure is realized as follows.
First, a low concentration Si layer 12 and a high concentration p type Si layer 13 are formed on a high concentration n type Si substrate 11 by epitaxial growth or the like.
The wafer on which the film is formed is patterned into a thermal oxide film, a nitride film, or the like by using a photolithography method or the like, and the bottom portion of the substrate 1 is covered with a solution such as KOH using these films as a mask.
Etch the recess until 1 is reached. Subsequently, the groove 14 is formed by patterning and etching a part of the bottom portion in the same manner. In this case, by using an anisotropic etching solution such as KOH, the slope of the concave portion becomes (11
1) A specific crystal face such as a face can be formed, and a flat face can be obtained. After that, a dielectric film 21 such as an oxide film is formed for the purpose of passivation and insulation. afterwards,
On the dielectric film 21 on the inclined surface 15, the Au film 3 is provided as a total reflection mirror.
0 is formed by a method such as ordinary photolithography or lift-off. At this time, the total reflection mirror 30 is etched so that a part of the low-concentration Si layer 12 is exposed on the inclined surface 15, and then the extraction electrode 22 and the back surface electrode 23 of the photodiode are formed and the chip is formed by dicing or the like. cut.

As described above, according to this embodiment, the submount substrate 1 for mounting the semiconductor laser device 40 is mounted.
A light-receiving element is integrally formed at 0, and light in the vicinity of the optical axis of the output light beam from the semiconductor laser element 40 is extracted to the outside via the total reflection mirror 30, and ambient light is detected by the light-receiving element. Therefore, returning light can be prevented from entering the light receiving element, noise can be significantly reduced even when a high-speed APC is used, and it is possible to realize an integrated semiconductor device that is small in size and good in mass productivity.

Moreover, since the positional relationship between the semiconductor laser element 40 and the total reflection mirror 30 can be defined by the accuracy of the semiconductor process, it is possible to manufacture with high accuracy without requiring special equipment or control. It is also possible to reduce the manufacturing cost. Further, by designing the thickness and the like so that the dielectric film 21 is a non-reflective film at the wavelength of the semiconductor laser device 40, reflection can be reduced, and monitor efficiency can be improved and stray light can be reduced. .

(Second Embodiment) FIG. 2 shows a second embodiment of the present invention.
2A is a perspective view and FIG. 1B is a cross-sectional view for explaining a schematic configuration of the semiconductor laser device according to the embodiment. The same parts as those in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted.

The basic structure is the same as that of the first embodiment, and the difference of this embodiment from the first embodiment described above is the arrangement of the total reflection mirrors. As shown in FIG. 2, the total reflection mirrors 30 are arranged in stripes so as to cover a part of the i-type Si layer 12 as in FIG. 1, and the p-type Si layer 13 exposed on the inclined surface 15 is formed. The total reflection mirror 31 covers the
Total reflection mirrors 32 are formed in stripes so as to cover the n-type Si substrate 11 exposed on the inclined surface 15.
In other words, the total reflection mirror is formed on the entire inclined surface, and the inclined surface 15 is provided with a slit in a part of the total reflection mirror so that the upper portion and the lower portion of the i-type Si layer 12 are exposed.

With such a structure, the n-type Si substrate 1
It is possible to prevent the slow component of the photocurrent absorbed by the 1 and p-type Si layer 13 from being diffused and diffused into the i-type Si layer 12 to become a slow-responding current component (so-called tail portion of the received waveform). Therefore, it is of course possible to obtain the same effect as that of the first embodiment, and it is possible to provide a faster response.

(Reference Example) FIG. 3 is a perspective view showing a schematic configuration of a semiconductor laser device according to a reference example of the present invention. The same parts as those in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted.

The basic structure is the same as that of the first embodiment, and the difference of this reference example from the first embodiment described above is the arrangement of the total reflection mirrors. As shown in FIG. 3, the total reflection mirror 35 is not formed in a stripe shape, but is formed in an elliptical shape centered on the optical axis of the output light beam from the semiconductor laser element 40. As a result, a light receiving area can be provided in the lateral direction of the inclined surface 15.

However, in this configuration, the first and second
Unlike the embodiment described above, the lateral mounting deviation between the total reflection mirror 35 and the semiconductor laser device 40 greatly affects the light receiving sensitivity. Therefore, higher mounting accuracy (lateral direction) is required as compared with the first and second embodiments.
That is, the relative position between the total reflection mirror 35 and the semiconductor laser device 40 must be precisely determined, which causes a problem that a special adjustment process is required.

(Third Embodiment) FIG. 4 shows the third embodiment of the present invention.
For explaining the embodiment of FIG.
(B) is a sectional view. The same parts as those in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted.

The basic structure of this embodiment is the same as that of the first embodiment, and the difference of this embodiment from the first embodiment lies in the structure of the light receiving portion and the structure of the total reflection mirror 30. That is, the separation groove 60 reaching the Si substrate 11 is provided in the portion where the i-type Si layer 12 and the p-type Si layer 13 are stacked. The separation groove 60 is for separating a portion of each of the Si layers 12 and 13 that functions as a light receiving element from another portion.

When the output light beam of the semiconductor laser device 40 reaches the inclined surface 15, the beam 50 has an elliptical shape as shown in the figure. The portion of the inclined surface 15 outside the light beam 50 is an unnecessary portion. In particular, the light receiving element
Since the electrostatic capacity is determined by the surface area of the depletion layer, it is preferable to eliminate unnecessary portions as much as possible. Therefore, as in the present embodiment, by limiting the size of the light receiving element portion to the required minimum size, higher speed operation becomes possible.

Further, since the light receiving element is separated by the separation groove 60 and is located inside the laminated portion of the Si layers 12 and 13, the light receiving element itself is diced when cut into individual chips by processing such as dicing. Never be done. Therefore, there is no inconvenience such as increase in leak current of the light receiving element due to the fracture layer included in the interface when cut out by processing such as dicing. Further, by adopting a structure in which the electrode 24 and the total reflection mirror 30 are not diced, it is possible to prevent defects such as metal peeling and short circuit due to redeposition of metal on the cut surface.

The total reflection mirror 30 includes the semiconductor laser electrode 24.
It is formed integrally with. Generally, in a process using photolithography, a resist pattern is formed by coating a resist on a workpiece and then exposing the resist to a desired pattern. At this time, the groove 14
If there is such a steep dent, the resist thickness between the flat portion and the bottom of the groove greatly differs due to the flow of the resist. For this reason, the process may be difficult due to a large difference in exposure conditions. If the semiconductor laser electrode 24 and the total reflection mirror 30 are integrated as in the present embodiment, fine patterning in the groove 14 can be avoided, which is effective in the process.

The upper electrode 22 for the light receiving element has a shape that extends over the flat portion and the upper portion of the inclined surface 15, and the lower end side of the upper electrode 22 is located substantially at the center of the i-type Si layer 12 on the inclined surface 15. . As a result, it is possible to prevent light from entering the non-depleted portion of the p-type Si layer 13, and to prevent generation of a current component having a slow response when operating at high speed. Further, on the inclined surface 15, a slit 65 is formed between the upper surface of the total reflection mirror 30. This slit 65
The position of is set to a portion where only the beam in the peripheral portion away from the optical axis of the output light of the semiconductor laser element 40 is irradiated.

Here, FIG. 5 shows the positional relationship of the respective parts as seen from the direction of the emitting surface of the semiconductor laser. Semiconductor laser device 40
The active layer is shown at 41, the light emitting portion is shown at 64, and the central axes of the light emitting portion within the laser output end face are shown at 62 and 63. The horizontal axis 62 and the vertical axis 63 substantially coincide with the center of the active layer 41. In general, AlGaInP-based and AlGaAs-based lasers used in optical disks such as DVDs and CDs are becoming higher in output and, in order to improve heat dissipation, junction down mounting with the surface on which the active layer is grown as the mounting surface is usually performed. Be seen. Therefore, the position of the active layer 41 is about 5 to 10 μm above the recess of the submount substrate.

On the other hand, the slit 65 of the electrode is located near the center of the i-type Si layer 12 and off the center of the output light beam of the semiconductor laser device 40. A beam in the vicinity of the optical axis of the output light beam of the semiconductor laser device 40 is irradiated on the total reflection mirror 30 and reflected to become output light. Similarly, since the return light is applied to the total reflection mirror 30, it does not enter the light receiving element. This functions as an output light monitor that is not affected by the return light.

Further, reference numeral 61 in FIG. 4 is a metal mask for preventing stray light from penetrating into a portion other than the light receiving element, generating electric carriers and causing a current due to diffusion and noise.

As described above, according to this embodiment, the same effects as those of the first embodiment can be obtained, and the following effects can be obtained. That is, since the separation groove 60 is provided to limit the size of the light receiving element to the minimum necessary size, high speed operation of the light receiving element becomes possible. Further, it is possible to avoid the adverse effects of the crushed layer during dicing, prevent metal peeling and short circuit due to redeposition of metal on the cut surface, and avoid fine patterning in the groove portion 14. .

(Fourth Embodiment) FIG. 6 shows a fourth embodiment of the present invention.
FIG. 3 is a cross-sectional view showing a schematic configuration of a semiconductor laser device according to the embodiment. The same parts as those in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted.

The present embodiment differs from the first embodiment described above in that the p layer of the pin photodiode is formed by impurity diffusion.

The submount substrate 10 is constructed by laminating an i-type Si layer 12 having a low impurity concentration on a part of an n-type Si substrate 11 which is highly impurity-doped.
A recess is formed by partially removing 0. In particular,
The i-type Si layer 12 is removed by anisotropic etching or the like except for a part thereof. After that, the remaining S that was not removed
A p-type Si layer 13 in which a high concentration of impurities is doped by diffusion is formed on a part of the surface of the i layer 12. These i-type Si layer 12, p-type Si layer 13, and n-type Si substrate 11 form a pin photodiode (light-receiving element) as a light-receiving element.

With such a structure, the same effects as those of the first embodiment can be obtained, and the following effects can be obtained. That is, since the p-type Si layer 13 is not exposed on the inclined surface 15, it is possible to prevent light from entering the non-depleted portion of the p-type Si layer 13, and a current component with a slow response when operating at high speed. Can be prevented. Moreover, i
Since the incident surface of the mold Si layer 12 can be increased, the sensitivity can be improved.

(Fifth Embodiment) FIG. 7 shows the fifth embodiment of the present invention.
FIG. 3 is a cross-sectional view showing a schematic configuration of a semiconductor laser device according to the embodiment. The same parts as those in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted.

The present embodiment is different from the above-described first embodiment in that a p photodiode is used instead of the p photodiode.
This is the formation of an n-junction photodiode.

The submount substrate 10 is composed of an n-type Si substrate 11 which is highly doped with impurities.
A part of 1 is removed to form a recess. Specifically, part of the substrate 11 is removed by anisotropic etching or the like. After that, a p-type Si layer 13 in which a high concentration of impurities is doped by diffusion or the like is formed on a part of the surface of the substrate 11 which remains without being removed. These p-type Si layer 1
A pn photodiode (light receiving element) as a light receiving element is formed by the 3 and n-type Si substrate 11.

In this pn junction photodiode, when a reverse bias voltage is applied, the p-type Si layer layer 13 and the n-type S layer are formed.
The depletion layer 13-2 is formed in the vicinity of the boundary of the i substrate 11 and serves as a light receiving portion.

In this embodiment, compared with the pin structure, the depletion layer thickness cannot be made large with the same bias, so that the sensitivity is low and the frequency response is low, but there is an advantage that the mount substrate can be realized at low cost.

(Modification) The present invention is not limited to the above embodiments. In the embodiment, Si is used as the material of the mount substrate, but a light receiving element capable of receiving the output light wavelength of the semiconductor laser element used can be configured, and a flat inclined surface can be formed by anisotropic etching or the like. Any semiconductor material may be used, and for example, GaAs can be used.

Further, in the embodiment, the high-speed pin structure is shown as the light receiving element structure, but the same effect can be obtained by using a normal pn type light receiving element. In that case, i-type Si
Although a low concentration layer such as the layer 12 is unnecessary, a depletion layer is formed near the boundary between the p-type high concentration layer and the n-type high concentration layer to form a light receiving portion. Therefore, compared with the pin structure, the depletion layer thickness cannot be made large with the same bias, so that the sensitivity is low and the frequency response is low, but there is an advantage that the mount substrate can be realized at low cost.

Although the conductivity type of the semiconductor substrate is n-type, when p-type is used as the semiconductor substrate, the same effect can be obtained by reversing the conductivity type of the other portions. Other,
Various modifications can be implemented without departing from the scope of the present invention.

[0075]

As described above in detail, according to the present invention, the return light from the optical disk or the like can be returned only to the total reflection mirror portion, and the return light is incident on the monitor light receiving element. Can be prevented. Therefore, noise can be significantly reduced even when using high-speed APC. Moreover, since the positional relationship between the semiconductor laser mounting portion and the total reflection mirror can be defined by the accuracy of the semiconductor process, it is possible to manufacture with high accuracy without requiring special equipment or control, and the cost increase due to adjustment It becomes possible to prevent it. Therefore, it is possible to realize at low cost a semiconductor laser device suitable for writing optical disc applications and the like, which produces less noise even when using a high-speed APC.

[Brief description of drawings]

FIG. 1 is a perspective view and a sectional view showing a schematic configuration of a semiconductor laser device according to a first embodiment.

FIG. 2 is a perspective view and a sectional view showing a schematic configuration of a semiconductor laser device according to a second embodiment.

FIG. 3 is a perspective view showing a schematic configuration of a semiconductor laser device according to a reference example of the present invention.

FIG. 4 is a perspective view and a sectional view showing a schematic configuration of a semiconductor laser device according to a third embodiment.

FIG. 5 is a schematic diagram showing the positional relationship of each part as seen from the emission end face direction of the semiconductor laser device according to the third embodiment.

FIG. 6 is a sectional view showing a schematic configuration of a semiconductor laser device according to a fourth embodiment.

FIG. 7 is a sectional view showing a schematic configuration of a semiconductor laser device according to a fifth embodiment.

FIG. 8 is a sectional view showing a schematic configuration of a conventional semiconductor laser device.

FIG. 9 is a sectional view showing a schematic configuration of a conventional semiconductor laser device.

[Explanation of symbols]

10 ... Submount substrate 11 ... n-type Si substrate (first conductivity type high-concentration impurity-doped Si substrate) 12 ... i-type Si layer (low-concentration impurity-doped Si layer) 13 ... p-type Si layer (second conductivity type High concentration impurity doped S
i layer) 14 ... Groove 15 ... Inclined surface 21 ... Insulating layer 22 ... Light receiving element p-side electrode 23 ... Light receiving element n-side electrode 24 ... Laser element electrode 25 ... Adhesive 27 ... Positioning markers 30, 31, 32, 35 ... Total reflection mirror 40 ... Semiconductor laser element 50 ... Elliptical beam 51 ... Optical axis center output light beam 52 ... Output light beams 53, 54 ... Peripheral light beam 57 ... Return light

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Claims (9)

[Claims] 1. A mount substrate comprising a semiconductor substrate and a semiconductor layer laminated on a part of the semiconductor substrate such that at least a part of its side surface is an inclined surface, and a light emitting end surface is provided. A semiconductor laser element mounted on the mount substrate so as to face the inclined surface, a light receiving element having a part of the inclined surface as a light receiving portion, and a total reflection mirror formed on a part of the inclined surface. The total reflection mirror is formed in a stripe shape on a part of the inclined surface in a direction orthogonal to the inclination direction of the inclined surface, and at least the central portion of the optical axis of the output light beam of the semiconductor laser device. Part of the light beam including is reflected and output to the outside,
A semiconductor laser device, wherein the remaining part is arranged to be incident on the light receiving part of the light receiving element. 2. The semiconductor substrate is a first-conductivity-type high-concentration impurity-doped Si substrate, and the semiconductor layer is a low-concentration impurity-doped Si layer sequentially stacked from the Si substrate side and a second-conductivity-type high-concentration layer. 2. The semiconductor laser device according to claim 1, wherein the semiconductor laser device comprises a concentration impurity-doped Si layer, and a pin photodiode as the light receiving element is provided. 3. The semiconductor laser device according to claim 2, wherein the total reflection mirror is formed so as to cover a part of the low-concentration impurity-doped Si layer exposed on the inclined surface. 4. The total reflection mirror comprises a plurality of stripe-shaped patterns, slit-shaped openings are provided between adjacent patterns, and the positions of the openings correspond to a part of the low-concentration impurity-doped semiconductor layer. 3. The method according to claim 2, wherein
The semiconductor laser device described. 5. A groove having an inclined surface continuous with the inclined surfaces of the low-concentration impurity-doped semiconductor layer and the high-concentration impurity-doped semiconductor layer is formed on a surface portion of the semiconductor substrate, and the total reflection mirror includes: A stripe-shaped first pattern formed so as to cover a part of the side surface of the low-concentration impurity-doped semiconductor layer located on the inclined surface, and a second conductivity type high-concentration impurity-doped semiconductor layer located on the inclined surface. A stripe-shaped second pattern formed so as to cover the side surface of the groove, and a stripe-shaped second pattern formed so as to cover a portion of the high-concentration impurity-doped semiconductor substrate of the first conductivity type located on the inclined surface of the groove. And a third pattern, each of the first pattern, the second pattern, and the third pattern
The semiconductor laser device according to claim 2, wherein the semiconductor laser device is arranged along a direction orthogonal to an inclination direction of the inclined surface. 6. The semiconductor laser according to claim 1, wherein a groove having an inclined surface continuous with the inclined surface of the semiconductor layer is formed on a surface portion of the semiconductor substrate. apparatus. 7. The inclined surface of the side surface of the semiconductor layer is (111)
And the inclined surface is 4 with respect to the surface of the semiconductor substrate.
2. The surface of the semiconductor substrate is tilted at a predetermined angle from the (100) plane so as to be 5 degrees.
The semiconductor laser device according to any one of 1 to 6. 8. A mount substrate comprising a semiconductor substrate having a recess formed in a part of a surface portion thereof, wherein at least one side surface of the recess is an inclined surface, and a light emitting end face is provided on the bottom surface of the recess. A semiconductor laser element mounted on the mount substrate so as to face each other, a light receiving element having a part of the inclined surface as a light receiving portion, and a total reflection mirror formed on a part of the inclined surface. The total reflection mirror is formed in a stripe shape on a part of the inclined surface in a direction orthogonal to the inclination direction of the inclined surface, and includes at least the optical axis center portion of the output light beam of the semiconductor laser device. Part of the light beam is reflected and output to the outside,
A semiconductor laser device, wherein the remaining part is arranged to be incident on the light receiving part of the light receiving element. 9. The semiconductor laser device according to claim 1, wherein a non-reflection film is formed on the inclined surface.