JPH1022522A - Optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a light reception in a confocal position possible without generating any external feedback offset, by forming an insulation film stripe on a GaAs substrate to provide a specific structure in the vicinity of the insulation film stripe. SOLUTION: On an n-type GaAs semiconductor substrate 11 having a crystalline plane [100] as its principal surface, respective semiconductor layers 12-15 configuring a semiconductor laser are subjected to epitaxial growths by an MOCVD method, etc. Then, after forming an insulation film stripe 16 out of SiN, a stripe ridge to become a pattern on the stripe 16 is formed by etching. Thereafter, a current blocking layer comprising an n-type GaAs layer 18 is formed to complete the structure of the semiconductor laser. Subsequently, an n-type GaAs layer 19 and an i-type GaAs layer 20 are made to grow, and further, a p-type GaAs layer 21 is laminated thereon. In this way, since a halved structure can be given in a self-aligning way to a photodiode formed on the semiconductor laser, a light reception in a confocal position is made possible.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical device suitable for reading / writing an optical recording medium such as an optical disk.

[0002]

2. Description of the Related Art Conventionally, compact discs (CDs)
An optical device called an optical pickup is used to read data from an optical recording medium such as a disk or a magneto-optical disk or to write data to the optical recording medium. recent years,
In this type of apparatus, optical components such as a semiconductor laser, a photodiode, and a beam splitter are combined and formed on the same substrate, and an astigmatism method and a push-pull method are often used for defocusing and tracking processing.

In the push-pull method using one beam, there is no stability against skew (tilt due to warpage or distortion) of the disk. An optical device having a so-called confocal laser coupler configuration in which a light emitting unit is disposed and a light receiving unit is formed near a confocal position where the light emitting unit is located has been proposed.

FIG. 10 is a diagram showing a schematic configuration of such an optical device. In this figure, reference numeral 10 denotes an optical device arranged at a confocal position. Reference numeral 20 denotes an objective lens, and reference numeral 30 denotes an optical disk. The optical device 10 has a structure in which a light emitting unit 4 forming a semiconductor laser LD and a light receiving unit 5 forming a photodiode PD are monolithically laminated on the same semiconductor substrate.

Here, the laminated structure of the optical device 10 will be described with reference to FIG. Note that the optical device 10 shown in this figure is an example in which the light receiving unit 5 is stacked right above the light emitting unit 4. As shown in FIG. 11, the light emitting unit 4 includes:
Buffer layer 41 made of n-type GaAs, n-type AlGaAs
A first cladding layer 42 of s, an active layer 43 of i-type GaAs, a second cladding layer 44 of p-type AlGaAs, and a gap layer 45 of p-type GaAs are formed epitaxially by MOCVD or the like. Further, n-type GaAs is further formed on the second clad layer 44.
The current constriction layer 46 is provided to provide a semiconductor laser device LD having a slab waveguide horizontal resonator.

On the other hand, the light receiving section 5 has a pin junction surface parallel to the horizontal cavity direction of the light emitting section 4 via a light absorbing layer 50 provided on the light emitting section 4 and has an end face on the resonator end face. As desired vertically, the first semiconductor layer (p-type GaAs)
s) 51, a second semiconductor layer (i-type GaAs) 52, and a third semiconductor layer (n-type GaAs) 53 are stacked and PIN
Type photodiode PD is formed.

A groove 10A is formed in the center of the first to third semiconductor layers 51 to 53 constituting the light receiving section 5 by etching, whereby the light receiving section 5 is divided into two photodiodes PD ₁ and PD ₁ . ₂ to be divided into two parts. Therefore, the two photodiodes PD ₁ and PD ₂ have their p
The in-junction surface is provided so as to face the resonator end face of the semiconductor laser element LD described above.

In the optical device 10 having the above structure, FIG.
As shown in, the optical disk 30 the emitted light L _F from the semiconductor laser device LD of the light-emitting portion 4 via the objective lens 20
The return light L _R convergently radiated upward and further reflected from the optical disk 30 passes through a coaxial path before and after being reflected by the optical disk 30, that is, passes through the same path as the outgoing light L _F, and again passes through the objective lens 20. And is received by the light receiving unit 5 of the optical device 10. In the push-pull method, the light reflected and diffracted by the tracking guide groove formed on the optical disc 30 is detected by the _two-part photodiodes PD ₁ and PD ₂ symmetrically arranged in the light receiving unit 5 and the detected output difference is determined. Tracking processing.

[0009]

In the conventional optical device 10 described above, the light receiving section 5 is divided into _two photodiodes PD ₁ and PD ₂ by forming a groove 10A by etching using a mask. But,
As shown in FIG. 12, a groove 1 formed by etching
0A is sometimes deviated from the emission center of the light-emitting portion 4, there is a possibility that the received light amount balance of the returning light L _R for collapses, a problem arises.

[0010] The present invention has been made in view of the above circumstances, and an object without causing the offset of the returning light L _R, to provide an optical device capable of receiving at the confocal position .

[0011]

In order to achieve the above object, according to the first aspect of the present invention, an insulating film stripe is formed in a [01-1] direction on a GaAs substrate having a {100} crystal plane as a main surface. Is formed near the insulating film stripe, a vertical end face in the {110} plane direction, a {111} A plane,
It has a structure surrounded by a {111} B plane.

According to a second aspect of the present invention, in the structure according to the first aspect, a light emitting element is formed below the insulating film stripe, and a pn junction or a pin junction is formed near the insulating film stripe. The light receiving element is provided.

Further, according to the third aspect of the present invention, a high-resistance layer or a p-layer is provided between the light emitting element and the student element.
It is characterized by having either an np junction or an npn junction.

According to a fourth aspect of the present invention, in the structure of the first aspect, at a position apart from the end face of the light emitting element,
A first light-receiving element directly above the light-emitting element end face, and p
a second formed by either an n-junction or a pin junction
Is provided.

In the invention according to claim 5, the growth temperature is in the range of 650 ° C. to 750 ° C.
It is characterized in that the a / As ratio is formed in the range of 100 to 1000.

According to the present invention, an insulating film stripe is formed in a [01-1] direction on a GaAs substrate having a crystal plane of {100} as a main surface, and {110} is formed near the insulating film stripe.
Vertical end face in plane direction, {111} A plane, {111} B
Since the light-receiving element is formed on the light-emitting element, the light-receiving element formed on the light-emitting element can be divided into two parts by self-alignment, thereby preventing the return light _LR from being offset.
Enables light reception at the confocal position.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The optical device according to the present invention can be applied to an optical pickup such as a compact disk (CD) or a magneto-optical disk. Hereinafter, an optical device according to an embodiment of the present invention will be described as an example with reference to the drawings.

First, FIG. 1 is a view for explaining a manufacturing process of an optical device according to one embodiment of the present invention. In this figure, reference numeral 11 denotes an n-type crystal plane {100} as a principal plane. Is a semiconductor substrate made of GaAs. Each semiconductor layer 12 constituting the semiconductor laser LD is formed on the semiconductor substrate 11.
To 15 are epitaxially grown by MOCVD or the like.
That is, the n-type AlGaAs layer 1 is formed on the semiconductor substrate 11.
2. An i-type AlGaAs layer 13, a p-type AlGaAs layer 14, and a p-type GaAs layer 15 are sequentially stacked.

Next, as shown in FIG.
An insulating film stripe 16 is formed on the As layer 15 using SiN or SiO ₂ . Thereafter, as shown in FIG. 3, wet etching or dry etching (ion etching) is performed to form a stripe ridge 17 having a stripe pattern. Next, as shown in FIG. 4, a current block layer of the n-type GaAs layer 18 is formed by the second crystal growth to complete the semiconductor laser structure. The crystal growth conditions up to this point are as follows.
0 ° C, V / III ratio is generally about 20 to 50.

Next, the growth temperature is set to 650 ° C. to 750 ° C.
When the V / III ratio is between 100 and 1000,
As shown in FIG. 6, an n-type GaAs layer 19 is grown, and then, as shown in FIG. 6, an i-type GaAs layer 20 is grown.
Then, as shown in FIG. 7, the p-type GaAs layer 2 is formed.
1 is laminated. At this time, as the growth temperature is lower and the V / III ratio is higher, the growth rate of the crystal plane {111} A plane is higher,
A crystal plane {110} plane appears.

This will be described with reference to FIG. When the growth temperature is high (800 ° C. or more), as shown in FIG. 8A, the growth near the side of the insulating film stripe 16 grows with the crystal plane {111} A appearing. In this case, since the growth rate of the crystal plane {111} A plane is extremely slow, {11}
Only 1｝ A surface.

On the other hand, when the growth temperature is lowered (up to 7
50 ° C), and as shown in FIG.
Since the 11 @ A plane grows little by little, a crystal plane {111} B plane obtained by folding the {111} A plane appears. This $ 1
The growth rate of the 11 ° B plane is much lower than that of other crystal planes, and is almost zero.

As the growth temperature further decreases (750 ° C. or lower), the growth rate of the crystal plane {111} A increases, as shown in FIG.
A {110} crystal plane appears between the first and second planes.
As described above, the crystal plane {111} A plane depends on the growth temperature, but also greatly depends on the V / III ratio.
When the ratio is high, the growth rate of the crystal plane {111} A plane increases. Therefore, it can be said that increasing the V / III ratio is equivalent to decreasing the growth temperature. The {110} plane is also {11}
It has growth temperature and V / III ratio dependence similar to the 1A plane.

[0024] Now, albeit at completed structure shown in FIG. 7, the region of the dead zone for receiving the return light L _R described above,
That is, it is necessary to reduce a region on the insulating film where no growth occurs. Therefore, the growth temperature and the V / III ratio (Ga / A
(s ratio) is controlled to grow the crystal plane {110} plane to some extent, and to narrow the gap between the opposing crystal plane {110} plane.

As described above, according to the present invention, since the photodiode formed on the semiconductor laser LD can be formed into a two-part structure by self-alignment, the groove formed by the etching process is shifted from the center of light emission as in the related art. Return light L
It can be removed drawback that break the light amount balance of _R, without causing the offset of the returning light L _R, it is possible to light of a confocal position.

The gist of the present invention is not limited to the optical device having the structure shown in FIG. 7, but is applicable to, for example, the optical device having the structure shown in FIG. That is, in the optical device shown in FIG. 9, in the structure shown in FIG. 7, an insulating film is further formed on the first light receiving element (PIN photodiode) formed near the laser end face, and crystal growth occurs in this region. Not to be. Next, the second light receiving element is grown in the same manner as described above. If a second light receiving element is formed in addition to the first light receiving element in this manner, the first light receiving element receives the push-pull signal at the confocal position, while the second light receiving element receives the return light of the far field. L _R
To receive the push-pull signal.

[0027]

According to the present invention, an insulating film stripe is formed in a [01-1] direction on a GaAs substrate having a {100} crystal plane as a main surface, and a {1} is formed near the insulating film stripe.
A vertical end face in the direction of the {10} plane, {111} A plane, and {11}
Since the structure is surrounded by the 1｝ B surface, the light receiving element formed on the light emitting element can be divided into two by self-alignment,
Thus the return light L without causing the offset of _R, it is possible to allow the receiving of a confocal position.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a manufacturing process of an optical device according to an embodiment of the present invention.

FIG. 2 is a view showing formation of an insulating film stripe 16 in a manufacturing process according to the embodiment.

FIG. 3 is a view showing formation of a stripe ridge 17 in a manufacturing process according to the embodiment.

FIG. 4 shows n-type GaAs in a manufacturing process according to the embodiment.
FIG. 4 is a diagram showing formation of a layer 18 (current blocking layer).

FIG. 5 shows n-type GaAs in the manufacturing process according to the embodiment.
FIG. 4 is a diagram showing growth of an s-layer 19;

FIG. 6 shows i-type GaAs in the manufacturing process according to the embodiment.
FIG. 4 is a diagram showing growth of an s layer 20.

FIG. 7 shows a p-type GaAs in a manufacturing process according to the embodiment.
FIG. 4 is a diagram showing growth of an s-layer 21.

FIG. 8 is a diagram for explaining a relationship between a growth temperature and a V / III ratio.

FIG. 9 is a perspective view showing a structure according to another embodiment.

FIG. 10 is a diagram for explaining a conventional example.

FIG. 11 is a diagram for explaining a conventional example.

FIG. 12 is a diagram for explaining a conventional example.

[Explanation of symbols]

4 ... light emitting section, 5 ... light receiving section, 10 ... optical device, 11
... n-type GaAs layer, 12 ... n-type AlGaAs layer, 1
3 ... i-type AlGaAs layer, 14 ... p-type AlGaAs
Layers, 15: p-type GaAs layer, 16: insulating film stripe, 17: stripe ridge, 18: n-type GaAs
s, 19: n-type GaAs layer, 20: i-type GaAs
Layer, 21 ... i-type GaAs layer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location H01S 3/18 H01L 27/15 C // H01L 27/15 27/14 Z

Claims (5)

[Claims] GaAs having a {100} crystal plane as a main surface
An insulating film stripe is formed in the [01-1] direction on the s substrate, and is surrounded by a vertical end face in the {110} plane direction, a {111} A plane, and a {111} B plane near the insulating film stripe. An optical device having a structured structure. 2. The structure according to claim 1, wherein a light emitting element is formed below the insulating film stripe, and a light receiving element formed by either a pn junction or a pin junction is provided near the insulating film stripe. The optical device according to claim 1, wherein: 3. Between the light emitting element and the student element,
3. The optical device according to claim 2, wherein the optical device has one of a high resistance layer, a pnp junction, and an npn junction. 4. The structure according to claim 1, further comprising: a first light receiving element directly above the light emitting element end face at a position distant from the light emitting element end face; 2. The optical device according to claim 1, wherein a second light receiving element formed by either a pn junction or a pin junction is provided at a separated position. 5. The optical device according to claim 1, wherein the growth temperature is in the range of 650 ° C. to 750 ° C., and the Ga / As ratio is in the range of 100 to 1000.