JP3257219B2 - Multi-beam semiconductor laser - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-beam semiconductor laser in which a plurality of laser elements are arranged one-dimensionally or two-dimensionally.

[0002]

2. Description of the Related Art In various optical communication technologies and OEICs, the use of a multi-beam semiconductor laser as a light emitting element for optical multiplex communication and optical parallel processing is being studied. In a multi-beam semiconductor laser, a plurality of laser elements are arranged one-dimensionally or two-dimensionally, and the light emission of each laser element is controlled individually or collectively. Each laser element in such a multi-beam semiconductor laser includes:
Uniformity of characteristics such as emission wavelength, emission efficiency or light output is required.

[0003]

However, when a large number of laser elements arranged one-dimensionally are manufactured, for example,
The characteristics of the laser element located outside (hereinafter also referred to as a peripheral laser element for description) are better than those of laser elements located in other parts (hereinafter also referred to as a central laser element for description). There is a problem of inferiority. It is considered that such characteristic deterioration is due to the causes described below.

In general, when a laser structure is formed on a substrate made of a compound semiconductor, it is necessary to grow a compound semiconductor crystal layer by, for example, the MOCVD method. in this case,
Depending on the state of diffusion and flow of the source gas in MOCVD, the growth rate of the compound semiconductor crystal in the region where the peripheral laser element is formed is higher than the growth rate of the compound semiconductor crystal in the region where the central laser element is formed. Become slow.
As a result, for example, the thickness of the active layer is smaller in the peripheral laser element than in the central laser element (see FIG. 8). When the active layer has, for example, a quantum well structure, variations in the thickness of the active layer cause variations in the emission wavelength.

After forming a laser structure on a substrate,
In order to separate laser elements from each other, it is necessary to form a concave portion by, for example, etching a compound semiconductor crystal layer or a substrate. In this case, depending on the state of the flow of the etching solution or the etching gas, the etching rate in the region where the peripheral laser element is formed is faster than the etching rate in the region where the central laser element is formed. As a result, the depth of the recess formed in the vicinity of the peripheral laser element becomes larger than that in the vicinity of the central laser element. When a multi-beam semiconductor laser having, for example, an SDH structure is manufactured based on such a state, as shown in a schematic cross-sectional view of FIG. This is different from the local laser element. As a result, a current leak component occurs in the peripheral laser element, causing a problem that the light output is reduced and the luminous efficiency is reduced. Alternatively, there arises a problem that the series resistance of the laser element increases and power consumption increases.

In a multi-beam semiconductor laser, an electrode is formed for each laser element. Usually, a multi-beam semiconductor laser is mounted on a substrate for leading out wiring, and an electrode provided for each laser element and a conductor formed on the substrate for leading out wiring are electrically and mechanically soldered or the like. Connect to When the multi-beam semiconductor laser is mounted on a wiring drawing substrate, the multi-beam semiconductor laser is usually transported using a collet provided with vacuum suction means as shown in FIG. Mount. At this time, with the increase in the size of the multi-beam semiconductor laser, FIG.
As shown in (1), the peripheral laser element may hit the substrate for drawing out the wiring more strongly. As a result, a short circuit is likely to occur when soldering or the like is performed, and there is a problem that the peripheral laser element is less reliable than the central laser element. Hereinafter, such a phenomenon may be referred to as “variation in an assembling process due to the size of the multi-beam semiconductor laser”.

Furthermore, after the multi-beam semiconductor laser is mounted on a substrate from which wiring is drawn out, while the multi-beam semiconductor laser is being used, the difference in thermal expansion coefficient causes
There is also a problem that stress concentration occurs in the peripheral laser element, and the reliability of the peripheral laser element is reduced.

As described above, variations in various processing and film forming conditions in a manufacturing process of a multi-beam semiconductor laser, variations in an assembling process due to the size of the multi-beam semiconductor laser, heat in using the multi-beam semiconductor laser, Due to the stress, there is a problem that the characteristics of the peripheral laser element are degraded compared to those of the central laser element.

Accordingly, an object of the present invention is to provide a multi-beam semiconductor laser in which the characteristics such as the emission wavelength, emission efficiency, and light output of each laser element are uniform.

[0010]

According to a first aspect of the present invention, there is provided a multi-beam semiconductor laser in which a plurality of laser elements are arranged one-dimensionally or two-dimensionally. A pseudo laser element that does not emit light during use is provided in a region outside the region where the laser device is formed.

Here, the pseudo laser element may have the same structure as the laser element on which electrodes are formed,
For example, it may have the same structure as a laser element except that no electrode is formed. The point is that any device that does not emit light when a multi-beam semiconductor laser is used may be used.
The pseudo-laser element may be provided in at least one portion of a region outside the region where the laser device is formed.
At least one, and if necessary, a plurality of them may be provided in this outer region.

According to a second aspect of the present invention, there is provided a multi-beam semiconductor laser in which a plurality of laser elements are arranged one-dimensionally or two-dimensionally. A raised portion or a groove portion is provided in a region outside the bent region.

In the multi-beam semiconductor laser according to the second aspect of the present invention, a groove is provided in a region outside a region where a plurality of laser elements are formed, and the groove is used for positioning during bonding of the multi-beam semiconductor laser. It can be used as a mark.

The ridge may be formed from the substrate or the compound semiconductor crystal layer when etching the substrate or the compound semiconductor crystal layer, or may be formed from thick solder or the like, or may be formed by wiring a multi-beam semiconductor laser. It can also be composed of an adhesive layer for fixing to a drawer substrate. The groove can be formed by etching the substrate or the compound semiconductor crystal layer.

[0015]

In the process of fabricating the multi-beam semiconductor laser according to the first aspect of the present invention, a plurality of laser devices are fabricated, and at the same time, a pseudo laser device is fabricated outside a region where the laser devices are formed. As a result, (A) variations in various processing and film forming conditions in the manufacturing process of the multi-beam semiconductor laser, and (B) variations in the assembly process due to the size of the multi-beam semiconductor laser, and (C) use of the multi-beam semiconductor laser Thermal stress at the time is absorbed by the pseudo laser element. This pseudo laser element does not contribute to light emission. Therefore, a multi-beam semiconductor laser in which a plurality of laser elements having uniform characteristics are formed can be obtained.

In the multi-beam semiconductor laser according to the second aspect of the present invention, a protrusion or a groove is provided outside the region where the laser element is formed. As a result, variations in the assembling process due to the size of the multi-beam semiconductor laser can be absorbed by the protrusions or the grooves.

Further, by forming the groove which also serves as the alignment mark, in the bonding step of the multi-beam semiconductor laser, the electrode formed on each laser element and the conductor formed on the wiring drawing substrate are formed. When performing position alignment, or when applying die bonding to the electrodes formed on the respective laser elements, the position alignment can be easily performed.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A multi-beam semiconductor laser according to the present invention will be described below based on embodiments with reference to the drawings. Example 1
Example 5 to Example 5 relate to the first embodiment of the multi-beam semiconductor laser of the present invention. Examples 6 and 7 relate to the second mode of the multi-beam semiconductor laser of the present invention.

Example 1 Example 1 relates to a multi-beam semiconductor laser according to the first embodiment of the present invention, and as shown in a schematic sectional view of FIG. They are arranged one-dimensionally. Specifically, Example 1
In the multi-beam semiconductor laser described above, a plurality of laser elements 20 are formed on a substrate 10 made of a p-type compound semiconductor. This multi-beam semiconductor laser, for example,
The anode of the laser device 20 is a common electrode, and the cathode is an independent common electrode.

The laser element 20 corresponding to the light emitting portion includes a first clad layer 22 and an active layer 2 formed on the substrate 10.
4, the second cladding layer 26;
An independent electrode 30 is formed thereon. Independent electrode 30
Is, for example, Au-Ge / N from the second cladding layer 26 side.
It is composed of an n-type ohmic electrode having a three-layer structure of i / Au. An element isolation region 28 formed of a groove is formed between each laser element 20, whereby the laser elements 20 are electrically insulated from each other. On the back surface of the substrate 10, a p-type common electrode 32 is formed.

Two pseudo laser elements 42 that do not emit light during use are provided in two areas 40 outside the area where the plurality of laser elements 20 are formed. This pseudo laser element 42 has the same structure as the laser element 20. That is, the pseudo laser element 42 includes the first clad layer 22, the active layer 24, and the second clad layer 26 formed on the substrate 10, and the dummy independent electrode 44 is formed on the second clad layer 26. ing. Dummy independent electrode 4
4 is, for example, Au-Ge /
It is composed of an n-type ohmic electrode having a three-layer structure of Ni / Au. No current is supplied to the dummy independent electrode 44 from outside. An element isolation region 46 composed of a groove is formed between the laser element 20 and the pseudo laser element 42, whereby the pseudo laser element 42 is electrically insulated from the laser element 20.

Since the crystal growth speed in the region where the pseudo laser element 42 is formed is lower than the crystal growth speed in the other regions, the active layer 24 of the pseudo laser element 42 is more active than the active layer 24 of the laser element 20. Also thin. The etching rate of the region where the pseudo laser element 42 is formed is:
The depth of the element isolation region 46 is deeper than that of the element isolation region 28 because it is faster than the etching rate in the other regions.

As described above, when a compound semiconductor crystal layer is grown or etched on a substrate made of a compound semiconductor, the crystal growth speed is reduced in a region where the pseudo laser element 42 is formed, or The etching rate increases. However, since the pseudo-laser element 42 is formed in substantially the same process, variations in the growth and etching of the compound semiconductor crystal layer occur only in the pseudo-laser element 42. Therefore, the adverse effects of these variations on the laser element 20 can be suppressed. In addition, when mounting the multi-beam semiconductor laser to the wiring drawing substrate, a pseudo-laser element is present, so that the reliability of the laser element is prevented from deteriorating due to variations in the assembly process due to the size of the multi-beam semiconductor laser. I can do it. Furthermore, during the use of the multi-beam semiconductor laser, it is possible to prevent stress concentration on the laser element due to a difference in thermal expansion coefficient.

FIG. 1B shows a state in which the multi-beam semiconductor laser is mounted on a wiring drawing substrate 60. In FIG. 1B, reference numeral 62 denotes a conductor portion formed on a wiring lead substrate 60, and reference numeral 64 denotes an electrode provided on each laser element and a wiring portion on the wiring lead substrate. This is a solder layer for electrically and mechanically connecting the formed conductor.

Since the pseudo laser element 42 does not contribute to light emission, it does not cause variations in the characteristics of the multi-beam semiconductor laser, and is composed of a plurality of laser elements 20 having uniform characteristics. A laser can be made.

(Embodiment 2) Embodiment 2 is a modification of Embodiment 1. In the first embodiment, the structure of the pseudo laser element 42 is the same as that of the laser element 20. On the other hand, in the second embodiment, one pseudo laser element 42 that does not emit light during use is provided in each of two areas 40 outside the area where the plurality of laser elements 20 are formed. The width of the independent electrode 44A is wider than the width of the independent electrode 30 formed on the laser element 20 (see the schematic sectional view of FIG. 2). Thus, the independent electrode 44 of the pseudo laser element
By increasing the width of A, the measurement terminal of the inspection device can be easily and reliably brought into contact with the independent electrode 44A, and the electrical characteristics of the pseudo laser element 42 can be easily inspected. By examining the electrical characteristics of the pseudo laser device 42, it is possible to easily predict the electrical characteristics of the laser device 20 before the completion of the multi-beam semiconductor laser.

(Embodiment 3) Embodiment 3 is a modification of Embodiment 2. In Example 2, the structure of the pseudo laser element 42 was the same as that of the laser element 20 except that the width of the independent electrode 44A was different. On the other hand, in the third embodiment, FIG.
As shown in a schematic cross-sectional view of FIG. 2, the entire width of the pseudo laser element 42 is larger than the width of the laser element 20. By forming the pseudo laser element 42 in such a structure, the probability that defects during crystal growth and etching occur in the outer region 40 is increased. By checking the formation state of the pseudo laser element 42, the multi-beam semiconductor The uniformity and yield of the laser manufacturing process can be monitored better.

(Embodiment 4) Embodiment 4 is also a modification of Embodiment 1. In the fourth embodiment, a plurality of laser elements are two-dimensionally arranged as shown in a schematic perspective view in FIG. The basic structure of each laser element can be the same as in the first embodiment. In the fourth embodiment, a total of four rows of pseudo laser elements 42 are provided in four regions 40 outside the region where a plurality of laser elements are formed. The structure of the pseudo laser element 42 can be the same as that of the laser element 20. Note that the pseudo laser element 42 is indicated by a black square to distinguish it from the laser element 20.

Embodiment 5 Embodiment 5 also relates to a multi-beam semiconductor laser according to the first aspect of the present invention, and as shown in a schematic cross-sectional view of FIG. Are arranged. Unlike the first embodiment, the fifth embodiment
In, the element isolation region of the laser element was formed by ion implantation. Other structures of the laser element 20 are the same as those of the first embodiment.

In the fifth embodiment, a plurality of laser elements 2
Two pseudo laser elements 42 that do not emit light during use are provided in two regions 40 outside the region where 0 is formed. This pseudo laser element 42 has the same structure as the laser element 20 except that no independent electrode is provided. Between the laser element 20 and the pseudo laser element 42,
An element isolation region 46 formed by an ion implantation method is formed, whereby the pseudo laser element 42
0 is electrically insulated.

When a compound semiconductor crystal layer is grown or etched on a substrate made of a compound semiconductor, the crystal growth rate is reduced in a region where the pseudo laser element 42 is formed. However, since the pseudo laser device 42 is formed in substantially the same process except for the process of forming the independent electrode, the adverse effect on the laser device 20 due to the variation in the growth of the compound semiconductor crystal layer can be eliminated. Note that, unlike the first embodiment, since the element isolation regions 28 and 46 are formed by the ion implantation method, there is no variation in etching.

In the fifth embodiment, the pseudo laser element 42
Does not contribute to light emission, so that it is possible to produce a highly reliable multi-beam semiconductor laser composed of a plurality of laser elements 20 having uniform characteristics without causing variations in the characteristics of the multi-beam semiconductor laser. it can.

Example 6 Example 6 relates to a multi-beam semiconductor laser according to the second aspect of the present invention, and as shown in a schematic sectional view of FIG. Are arranged one-dimensionally. The structure of the laser element 20 can be the same as the structure of the laser element described in the first embodiment.

A plurality of grooves 50 are provided in two regions 40 outside the region where the plurality of laser elements 20 are formed. The groove 50 is formed in the element isolation region 28 composed of a groove.
Can be formed at the same time as the formation of the element isolation region 28, or when the element isolation region 28 is formed by ion implantation, it can be formed by etching before or after the formation of the element isolation region. In the outer region 40,
A pseudo laser element having substantially the same structure as the laser element may or may not be formed. The outer region 4
It is desirable to provide a dummy independent electrode 44 on the surface of 0. Since the plurality of grooves 50 are provided in the outer region 40, the width of the dummy independent electrode 44 is small.

When no pseudo laser element is formed in the outer region 40, a compound semiconductor crystal layer is grown or etched on a substrate made of a compound semiconductor. It is not possible to avoid adverse effects on the laser element 20 due to the above.

However, since the groove 50 is formed, after the multi-beam semiconductor laser is mounted on the substrate for leading out the wiring, the laser element 20 due to the difference in the coefficient of thermal expansion while using the multi-beam semiconductor laser is used. Can be prevented from being concentrated. That is, since the width of the dummy independent electrode 44 is small, the contact area between the independent electrode 44 and the conductor provided on the wiring lead-out board is reduced, and the thermal stress can be reduced.

Further, even if a short circuit occurs when soldering or the like is performed in the outer region 40, the laser element 20 is not affected. In addition, it is possible to prevent the reliability of the laser element 20 from being lowered. Furthermore, the grooves 50 can also prevent solder or adhesive from flowing into the region where a plurality of laser elements are formed. The solder and the adhesive play a role of fixing the multi-beam semiconductor laser to the wiring drawing substrate.

The cross section of the groove may be formed in a zigzag shape as shown in FIG.

As shown in FIG. 6C, a large groove 50A is formed in the outer region 40.
Is used as a positioning mark, in the bonding step of the multi-beam semiconductor laser, the independent electrode 30 formed on each laser element 20 is aligned with the conductor formed on the wiring lead-out substrate. At this time, or when die bonding is performed on the independent electrode 30 formed on each laser element 20, the alignment can be easily performed.

Example 7 Example 7 also relates to a multi-beam semiconductor laser according to the second embodiment of the present invention, and as shown in a schematic sectional view of FIG. Are arranged. Also in the seventh embodiment, the structure of the laser element 20 can be the same as the structure of the laser element described in the first embodiment.

In the seventh embodiment, unlike the sixth embodiment,
Region 4 outside the region where a plurality of laser elements 20 are formed
At 0, a raised portion 52 is provided. The raised portion 52 can be composed of, for example, a solder layer.
0 protrudes from the top surface of the independent electrode 30. Alternatively, the raised portion 52 can be formed by etching a compound semiconductor crystal layer or the like, or can be formed of an adhesive layer for fixing the multi-beam semiconductor laser to a wiring leading substrate.

By providing the protruding portion 52 in the outer region 40 in this manner, when the multi-beam semiconductor laser is transported using a collet provided with a vacuum suction means and is mounted on a substrate from which wiring is drawn, FIG. Can solve the problem that the reliability of the laser element 20 becomes poor even when the edge of the multi-beam semiconductor laser strongly hits the wiring leading substrate. If the protruding portion 52 is formed of, for example, a solder layer, when the multi-beam semiconductor laser is mounted on a wiring lead-out substrate, the solder melts and the protruding portion 52 disappears. In the outer region 40, the laser element 2
Since 0 is not formed, the independent electrode is not short-circuited by the melting of the solder.

Although the present invention has been described based on the preferred embodiments, the present invention is not limited to these embodiments. The structure described in the second to seventh embodiments can be applied to a multi-beam semiconductor laser in which a plurality of laser elements are two-dimensionally arranged. The structure of the laser element may be any structure other than the structure described in the embodiment, such as the SDH structure.

[0044]

According to the present invention, variations in various processing and film forming conditions in a manufacturing process of a multi-beam semiconductor laser, and variations in an assembling process due to the size of the multi-beam semiconductor laser are reduced or eliminated. According to the present invention, it is possible to obtain a multi-beam semiconductor laser in which a laser element having uniform characteristics is formed in which thermal stress during use of the multi-beam semiconductor laser is relaxed.

In a preferred embodiment of the multi-beam semiconductor laser according to the present invention, the electric characteristics of the pseudo-laser element are examined to easily predict the electric characteristics of the laser element before completion of the multi-beam semiconductor laser. It becomes possible. Alternatively, in the bonding step of the multi-beam semiconductor laser, it is possible to easily perform the alignment of the electrode formed on each laser element with the conductor formed on the wiring drawing substrate.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a multi-beam semiconductor laser according to a first embodiment.

FIG. 2 is a schematic sectional view of a multi-beam semiconductor laser according to a second embodiment.

FIG. 3 is a schematic sectional view of a multi-beam semiconductor laser according to a third embodiment.

FIG. 4 is a schematic sectional view of a multi-beam semiconductor laser according to a fourth embodiment.

FIG. 5 is a schematic sectional view of a multi-beam semiconductor laser according to a fifth embodiment.

FIG. 6 is a schematic sectional view of a multi-beam semiconductor laser according to a sixth embodiment.

FIG. 7 is a schematic sectional view of a multi-beam semiconductor laser according to a seventh embodiment.

FIG. 8 is a cross-sectional view schematically showing a state in which the thickness of an active layer is smaller in a peripheral laser element due to a difference in crystal growth rate in a conventional technique.

FIG. 9 is a cross-sectional view schematically showing a position shift of a current blocking layer with respect to an active layer in a conventional multi-beam semiconductor laser having an SDH structure.

FIG. 10 is a diagram for explaining a problem when assembling a multi-beam semiconductor laser.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Substrate 20 Laser element 22 1st cladding layer 24 Active layer 26 2nd cladding layer 30 Independent electrode 32 Common electrode 28, 46 Element isolation region 40 Outside area 42 Pseudo laser element 44, 44A Independent electrode 50 Groove 52 Ridge 60 Wiring Substrate for drawing 62 Conductor 64 Solder layer

Claims (2)

(57) [Claims] 1. A multi-beam semiconductor laser in which a plurality of laser elements are arranged one-dimensionally or two-dimensionally, and a pseudo laser which does not emit light during use in a region outside a region where the plurality of laser devices are formed. element is provided with, the pseudo laser element, dummy independent electrodes are formed
Multi-beam semiconductor laser, characterized in that that. 2. A multi-beam semiconductor laser in which a plurality of laser elements are arranged one-dimensionally or two-dimensionally,
The area outside the area where the plurality of laser elements are formed is
A multi-beam semiconductor laser, wherein a plurality of laser elements are provided with ridges protruding from the top surface .