JPH10247328A - Semiconductor laser device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent light from being re-reflected by the light-emitting end face of a semiconductor light emitting element by forming a reflection-preventing coat on an area where the light reflected by a reflection film hits, in the light- emitting end faces of the semiconductor light emitting element. SOLUTION: Such a semiconductor light emitting element 5 is made beforehand on the light-emitting end face 51, a dielectric film 6 with a prescribed reflectance in a part having a light-emitting point is formed and a reflection- preventing coat 8 with almost zero reflectance is formed in a part having no light-emitting point 7. This semiconductor light emitting element 5 is arranged so that the emitting end face 51 is opposed to a micro-mirror and the side where reflection-preventing coat 8 is formed is upward, and is mounted on an insulating coat 3 of a flat part of an epitaxial layer 2. When an emitting angle of the emitting light on the emitting end face 51 exceeds a fixed value, reflecting light 9 from a bottom end part of the reflection coat 4 constituting the micro-mirror is returned to the emitting end face 51, but all the reflecting light transmits the reflection-preventing coat 8 without being reflected since the reflection-preventing coat 8 is formed thereon and guided as refracted light.

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 having a structure in which a light emitting axis of light emitted by a semiconductor light emitting element is changed by using an inclined surface formed on a semiconductor substrate or the like, and more particularly, to a semiconductor light emitting element. The present invention relates to a semiconductor laser device having a structure for preventing light from being re-reflected by an emission end face of the semiconductor laser device.

[0002]

2. Description of the Related Art As a light source for reading information recorded on an optical recording medium such as an optical disk, for example, a semiconductor laser device having a micromirror having a 45-degree tilt angle on a semiconductor substrate is used. .

FIG. 2 is a structural sectional view showing a conventional semiconductor laser device having a micromirror having a 45-degree tilt angle on a semiconductor substrate.

In FIG. 1, 1 is a semiconductor substrate, 2 is an epi layer formed on the semiconductor substrate 1, 3 is an insulating film formed on the epi layer 2, and 4 is formed on the inclined surface 21 of the epi layer 2. Reflective film (metallized), 5 is a semiconductor light emitting element, 6 is a dielectric film for reducing return light noise when used in an optical pickup or the like, 7 is a light emitting point of the semiconductor light emitting element 5, 9
Is a reflected light of the light emitted from the semiconductor light emitting element 5 reflected by the reflection film 4, 10 is a refracted light of the reflected light 9 refracted by the dielectric film 6, 21 is an inclined surface of the epi layer 2, and 51 is a semiconductor light emission. This is an emission end face of the element 5.

A semiconductor laser device having a 45-degree micromirror shown in FIG. 2 has a semiconductor light emitting element 5 arranged on a semiconductor substrate 1 so that an emission end face 51 thereof is oriented in a horizontal direction, and a semiconductor light emitting element 5 And a micro-mirror having a 45-degree inclination angle and disposed so as to face the emission end face 51 of the light-emitting device.

The semiconductor substrate 1 is made of Si (silicon),
It is made of a semiconductor substrate such as GaAs (gallium arsenide), and has a role of disposing the semiconductor light emitting element 5 thereon and diffusing the heat generated by the semiconductor light emitting element 5. On this semiconductor substrate 1, an epitaxial layer 2 formed by crystal growth of Si, GaAs or the like by a desired crystal growth method is formed. The epitaxial layer 2 has an inclined surface 21 having an inclination angle of 45 degrees with respect to the substrate surface of the semiconductor substrate 1 in a part thereof. Also, this 45
The insulating layer 3 made of a SiO ₂ film, a SiN film, or the like is formed so as to cover the entire surface of the epi layer 2 having the inclined surface 21 with a certain degree. The insulating film 3 serves to protect the surface of the epi layer 2 and electrically insulate the semiconductor light emitting element 5 mounted on the semiconductor substrate 1.

A micromirror arranged on the semiconductor substrate 1 is formed by Au (gold) on the inclined surface 21 of the epi layer 2.
And a reflection film (metallized) 4 on which a metal such as a metal film is formed. The reflection film 4 is formed on the insulating film 3 covering the surface on the 45-degree inclined surface 21 formed by the epi layer 2. Therefore, the micromirror made of the reflection film 4 has a 45-degree inclination angle, similarly to the inclined surface 21 of the epi layer 2.

The semiconductor light emitting element 5 is mounted on a flat portion of the epi layer 2 by soldering or the like. As the semiconductor light emitting device 5, various types such as a GaAs semiconductor laser and an InP semiconductor laser are used, and the semiconductor light emitting device 5 is disposed so that the emission end face 51 faces the micromirror made of the reflection film 4. Further, the semiconductor light emitting element 5 is arranged such that the emission end face 51 is perpendicular to the substrate surface of the semiconductor substrate 1. Therefore, since the semiconductor light emitting element 5 emits light whose emission axis is perpendicular to the emission end face 51, the emission light is reflected by the micromirror having an inclination angle of 45 degrees and the emission axis is 90 degrees. Is changed to Further, a dielectric film 6 having a reflectance of several to several tens% is formed on the emission end face 51 of the semiconductor light emitting element 5. This dielectric film 6 is formed to reduce return light noise when the semiconductor laser device is used for an optical pickup or the like. The dielectric film 6 is formed of, for example, SiO _x in a multilayer structure, and the reflectance is set by appropriately adjusting the thickness of each layer formed in the multilayer structure.

Next, a method for manufacturing the semiconductor laser device will be described. First, a semiconductor layer such as Si or GaAs is grown on the semiconductor substrate 1 by a known crystal growth method such as the MOCVD method. Next, an inclined surface 21 having an inclination angle of 45 degrees is formed on the semiconductor layer by photolithography, etching, or the like. As a result, the epi layer 2 having the inclined surface 21 having the inclination angle of 45 degrees is formed on the semiconductor substrate 1. Then, an insulating film 3 made of SiO ₂ , SiN or the like is formed on the entire surface of the epi layer 2 by various film forming methods such as normal pressure CVD, low pressure CVD, and plasma enhanced CVD. After this, the inclination angle becomes 4
A metal such as aluminum is formed on the insulating film 3 at the 5 ° inclined surface 21 to form the reflective film 4. A micromirror having an inclination angle of 45 degrees is formed by the reflection film 4 thus formed. Next, a dielectric film 6 having a reflectivity of several to several tens% in advance on the emission end face 51.
The semiconductor light emitting element 5 having the light emitting end face 5
The semiconductor laser device shown in FIG. 2 is completed by disposing the semiconductor laser device 1 so as to face the micromirror and mounting it on the insulating film 3 in the flat portion of the epi layer 2 by soldering or the like.

Next, the operation of the semiconductor laser device will be described. When a forward bias voltage is applied to the semiconductor light emitting element 5, light is emitted from the light emitting point 7 with a spread of the radiation angle θ having an angle of θ in the vertical direction. The emitted light is reflected on a 45 arranged on the front surface of the semiconductor light emitting element 5.
Reflected light 9 reflected by a micromirror (reflection film 4) having a tilt angle of 90 degrees and having its emission axis changed by 90 degrees.
Will be radiated. And this reflected light 9
When the semiconductor laser device is used for an optical pickup, the light is focused on an optical recording medium such as an optical disk.

[0011]

By the way, the reflected light 9 reflected by the micromirror comprising the reflection film 4 is used.
Is that the emission angle θ of the emitted light at the emission end face 51 of the semiconductor light emitting element 5 is given by the following equation:

[0012]

(Equation 1)

(Where H is the light emitting point 7 of the semiconductor light emitting element 5)
, The distance from the position to the lower end face on the side in contact with the insulating layer 3, L
Is the distance from the light-emitting point 7 to the point where the line intersects the reflective film 4 when a line is drawn in the horizontal direction, and T indicates the distance from the lower end face to the upper end face of the semiconductor light-emitting element 5). Then, the light 9 reflected by the lower end of the reflection film 4 returns to the semiconductor light emitting element 5. This returned reflected light 9 is
When the light reaches the dielectric film 6 formed on the emission end face 51 of the semiconductor light emitting element 5, part of the light is further recycled by the dielectric film 6 due to a predetermined reflectance ratio of the dielectric film 6. The reflected light is transmitted through the dielectric film 6 and the refracted light 1
As 0, the light is guided into the semiconductor light emitting element 5. The light re-reflected by the dielectric film 6 in this manner is shown in FIG.
As shown by A in the figure, interference occurs with the reflected light 9 from the micromirror. For this reason, it adversely affects the wavefront aberration and the like of the reflected light 9 reflected by the micromirror, and as a result, there is a problem that the laser characteristics are deteriorated, for example, a distortion is generated in a laser light focusing spot.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems. In particular, even when the emission angle at the light emitting point of a semiconductor device is large, reflected light from a micromirror can be applied to a semiconductor light emitting device. To provide a semiconductor laser device capable of preventing the light from being re-reflected by the emission end face.

[0015]

A semiconductor laser device according to the present invention comprises: a semiconductor light emitting element for emitting light at a predetermined radiation angle from a light emitting point on a semiconductor substrate or a semiconductor layer; A micromirror that reflects emitted light emitted from the light emitting point to change the light emitting axis thereof, wherein a portion of the light emitting point of the semiconductor light emitting element has a predetermined reflectance. And a non-reflection film is formed in a portion where the light reflected by the micromirror shines.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a semiconductor laser device according to the present invention will be described below. FIG. 1 is a structural sectional view showing a semiconductor laser device according to an embodiment of the present invention.

In the figure, 1 is a semiconductor substrate, 2 is an epilayer formed on the semiconductor substrate 1, 3 is an insulating film formed on the epilayer 2, and 4 is formed on the inclined surface 21 of the epilayer 2. Reflective film (metallized), 5 a semiconductor light emitting element, 6 a dielectric film for reducing return light noise when used in an optical pickup or the like, 7 a light emitting point of the semiconductor light emitting element 5, 8
Is a non-reflective film whose reflectance is almost 0%, 9 is a reflected light of the light emitted from the semiconductor light emitting element 5 reflected by the reflective film 4, and 10 is a refracted light of the reflected light 9 refracted by the dielectric film 6. , 21 are inclined surfaces of the epi layer 2 and 51 is an emission end face of the semiconductor light emitting element 5.

The semiconductor laser device according to the above-described embodiment is a semiconductor laser device having a micromirror having an inclination angle of 45 degrees on the semiconductor substrate 1.
The semiconductor light-emitting device 5 includes a semiconductor light-emitting element 5 disposed thereon such that the light-emitting end face 51 faces in the horizontal direction, and a micromirror disposed so as to face the light-emitting end face 51 of the semiconductor light-emitting element 5.

The semiconductor substrate 1 is made of Si (silicon),
It is made of a semiconductor substrate such as GaAs (gallium arsenide), and has a role of disposing a semiconductor light emitting element 5 thereon and dissipating heat generated by the semiconductor light emitting element 5. On this semiconductor substrate 1, an epitaxial layer 2 formed by crystal growth of Si, GaAs or the like by a desired crystal growth method is formed. The epi layer 2 has an inclination angle of 45 with respect to the substrate surface of the semiconductor substrate 1 in a part thereof.
A suitable inclined surface 21 is formed. The epi layer 2 having the inclined surface 21 having an inclination angle of 45 degrees is provided with an insulating film 3 made of a SiO ₂ film, a SiN film, or the like so as to cover the entire surface. This insulating film 3
Plays a role of, for example, protecting the surface of the epi layer 2 and electrically insulating the semiconductor light emitting element 5 mounted on the semiconductor substrate 1.

The micromirror arranged on the semiconductor substrate 1 is formed of Au (gold) on the inclined surface 21 of the epi layer 2.
And a reflection film (metallized) 4 on which a metal such as a metal film is formed. The reflection film 4 is formed on the insulating film 3 which covers the surface of the inclined surface 21 formed by the epi layer 2 and having an inclination angle of 45 degrees. Therefore, the micromirror made of the reflection film 4 has a 45-degree inclination angle, similarly to the inclined surface 21 of the epi layer 2.

The semiconductor light emitting device 5 is mounted on the insulating film 3 in a flat portion of the epi layer 2 by soldering or the like. As the semiconductor light emitting device 5, various types such as a GaAs semiconductor laser and an InP semiconductor laser are used, and the semiconductor light emitting device 5 is disposed so that the emission end face 51 faces the micromirror made of the reflection film 4. Also,
The semiconductor light emitting element 5 is arranged such that the light emitting end face 51 is perpendicular to the substrate surface of the semiconductor substrate 1. Therefore, the semiconductor light emitting element 5 emits light whose emission axis is perpendicular to the emission end face 51. When the emitted light is reflected by a micromirror having an inclination angle of 45 degrees, its emission axis becomes 90 degrees. Can be changed.

The emission end face 5 of the semiconductor light emitting device 5
In FIG. 1, a dielectric film 6 having a reflectance of several to several tens of percent is formed in a portion having a light emitting point 7, and the reflectance is substantially reduced in a portion where light reflected by the reflective film 4 shines. 0%
Is formed. That is, as shown in FIG. 1, on the emission end face 51 of the semiconductor light emitting element 5, a two-part region is formed into a lower part including the light emitting point 7 and an upper part not including the light emitting point 7. In the same manner as in the prior art, a dielectric film 6 of several to several tens% is formed, and a non-reflection film 8 having a reflectance of almost 0% is formed in a lower portion including a light emitting point 7. The dielectric film 6 is formed to reduce return light noise when the semiconductor laser device is used for an optical pickup or the like, similarly to the conventional one. on the other hand,
The non-reflective film 8 is formed to prevent light 9 reflected by the reflective film 4 from being re-reflected. The dielectric film 6 and the antireflection film 8 are made of, for example, (SiO ₂ ) _X
(Si ₃ N ₄ ) _1-X is formed from a multi _- layered structure, and the reflectance is set by appropriately adjusting the thickness and the like of each of the multi-layered layers.

Next, a method for manufacturing the semiconductor laser device will be described. First, a semiconductor layer such as Si or GaAs is grown on the semiconductor substrate 1 by a known crystal growth method such as the MOCVD method. Then, the semiconductor layer has an inclination angle of 4 by photolithography and etching.
A 5-degree inclined surface 21 is formed. Thus, the epi layer 2 having the 45-degree inclined surface 21 is formed on the semiconductor substrate 1. Then, normal pressure CVD is performed on the entire surface of the epi layer 2.
An insulating film 3 made of SiO ₂ , SiN, or the like is formed by various film forming methods such as a low-pressure CVD method, a low-pressure CVD method, and a plasma enhanced CVD method. Thereafter, a metal such as aluminum is formed on the insulating film 3 at the 45-degree inclined surface 21 to form the reflective film 4. The reflection film 4 thus formed is
A micromirror having a tilt angle of 5 degrees is configured. Next, on the emission end face 51, a portion having the light emitting point 7 and a portion having no light emitting point 7 are divided into two portions, and the portion having the light emitting point 7 is provided with the dielectric film 6 having a reflectance of several to several tens%. The semiconductor light-emitting element 5 is formed in advance, and the anti-reflection film 8 having a reflectance of almost 0% is formed in a portion where no light-emitting point 7 is formed. The semiconductor light emitting element 5 is arranged such that the emission end face 51 faces the micromirror and the side on which the antireflection film 8 is formed faces upward, and the insulating film 3 on the flat portion of the epi layer 2 is formed. Mount on top by soldering or the like. Thus, the semiconductor laser device shown in FIG. 2 is manufactured.

Next, the operation of the semiconductor laser device will be described. When a forward bias voltage is applied to the semiconductor light emitting element 5, light is emitted from the light emitting point 7 with a spread of the radiation angle θ having an angle of θ in the vertical direction. The emitted light is reflected on a 45 arranged on the front surface of the semiconductor light emitting element 5.
The light is reflected by the micromirror (reflection film 4) of a degree and is emitted as reflected light 9 whose emission axis is changed by 90 degrees. When the semiconductor laser device is used for an optical pickup, the reflected light 9 is focused on an optical recording medium such as an optical disk.

The reflected light 9 is applied to the semiconductor light emitting element 5
The emission angle θ of the outgoing light at the outgoing end face 51 is

[0026]

(Equation 2)

(Where H is the light emitting point 7 of the semiconductor light emitting element 5)
, The distance from the position to the lower end face on the side in contact with the insulating layer 3, L
Is the distance from the light-emitting point 7 to the point where the line intersects the reflective film 4 when a line is drawn in the horizontal direction, and T indicates the distance from the lower end face to the upper end face of the semiconductor light-emitting element 5). The light 9 reflected from the lower end of the reflection film 4 constituting the micromirror is returned to the emission end face 51 of the semiconductor light emitting element 5, and at this time, the emission end face 51 to which the reflected light 9 strikes
The anti-reflection film 8 is formed on the portion. for that reason,
All of the reflected light 9 returning to the emission end face 51 is transmitted through the non-reflection film 8 without being re-reflected at the emission end face 51 and guided as refracted light 10 into the semiconductor light emitting element 5.

As described above, in the semiconductor laser device according to the above-described embodiment, even when the emission angle θ of the emitted light becomes larger than a predetermined angle, the semiconductor light emitting element 5
Since the non-reflection film 8 is formed on the portion of the emission end face 51 where the reflected light 9 from the reflection film 4 shines, it is possible to prevent the light from being re-reflected by the emission end face 51 of the semiconductor light emitting element 5. . Therefore, the reflected light 9 from the micromirror is not reflected again by the exit end face 51 as in the conventional case, and this re-reflected light does not interfere with the reflected light 9 from the micromirror. As a result, wavefront aberration and the like are improved. There is an effect that a good spot for narrowing down the laser beam can be obtained.

It should be noted that the semiconductor laser device of the present invention is not limited to the above-described embodiment. For example, the semiconductor light emitting element 5 may have a portion where the reflected light 9 from the micromirror shines on the emission end face 51 thereof. If a non-reflective film 8 is formed on the GaAs semiconductor laser,
Various semiconductor lasers such as an InP-based semiconductor laser can be used, and the inclination angle of the micromirror can be appropriately changed according to the usage mode of the semiconductor laser device. As the formed anti-reflection film 8, various types can be used as long as the reflectance of the light can be made almost 0%, and in the above-mentioned embodiment, it becomes a micro mirror. Although the reflection film 4 is formed by using the inclined surface 21 formed on the epi layer 2, the semiconductor substrate 1 is processed without forming such an epi layer 2 to directly provide the inclined surface on the substrate 1. Alternatively, this inclined surface may be used.

[0030]

According to the semiconductor laser device of the present invention, a semiconductor light emitting element which emits light at a predetermined radiation angle from a light emitting point on a semiconductor substrate or a semiconductor layer;
A micromirror that reflects emitted light emitted from the light emitting point of the semiconductor light emitting element and changes the light emitting axis thereof, wherein a portion of the light emitting point of the semiconductor light emitting element has a light emitting point. Is characterized in that a dielectric film having a predetermined reflectivity is formed, and a non-reflective film is formed in a portion where light reflected by the micromirror shines, and thereby,
Even if the emission angle θ of the outgoing light becomes larger than a predetermined angle, the non-reflective film is formed in the area of the outgoing end face of the semiconductor light emitting element where the light reflected by the reflective film hits. In addition, since it is possible to prevent light re-reflected by the emission end face of the semiconductor light emitting element, light reflected by the micromirror does not interfere with light re-reflected by the emission end face unlike the conventional one, and as a result, the wavefront This has the effect that aberrations and the like are improved, and a laser beam with good laser characteristics, such as no distortion of the focused spot of the laser beam, is obtained.

[Brief description of the drawings]

FIG. 1 is a structural sectional view showing a conventional semiconductor laser device having a 45-degree micromirror on a semiconductor substrate.

FIG. 2 is a structural sectional view showing a semiconductor laser device according to an embodiment of the present invention.

[Explanation of symbols]

Reference Signs List 1 semiconductor substrate, 2 epilayer formed on semiconductor substrate 1, 3 insulating film formed on epilayer 2, 4 reflection film (metallized) formed on inclined surface 21 of epilayer 2, 5
A semiconductor light emitting device, 6 a dielectric film for reducing return light noise when used in an optical pickup, 7 a light emitting point of the semiconductor light emitting device 5, 8 a non-reflective film having a reflectance of almost 0%, 9 a semiconductor light emitting device The reflected light reflected from the element 5 by the reflective film 4 is reflected by the reflective film 10, the refracted light reflected from the reflected light 9 by the dielectric film 6, the inclined surface of the epilayer 2, and the emission end face of the semiconductor light emitting element 5.

Claims (1)

[Claims] 1. A semiconductor light emitting element that emits light at a predetermined radiation angle from a light emitting point on a semiconductor substrate or a semiconductor layer, and the light emitted from the light emitting point of the semiconductor light emitting element is reflected and reflected. A semiconductor mirror device having a micromirror that changes an emission axis, wherein a dielectric film having a predetermined reflectance is formed on a portion of the emission end face of the semiconductor light emitting element, the portion having the emission point; A non-reflective film formed on a portion to which light reflected by the laser beam is applied.