JP2003060303A - Semiconductor laser and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor laser that is resistant to external feedback noise, can satisfactorily correct or reduce astigmatic differences, can be reduced in operation current, and stably oscillates at high-temperature output time, and to provide a method of manufacturing the laser. SOLUTION: In this self-pulsation semiconductor laser, the width of the central waveguide stripe of a stripe section 107 is fixed and the width (ridge separation width) W2 of the recessed section between ridges at the central part of the stripe section 107 (central part of a resonator) is set to a narrow width. In addition, the ridge separation width W2' near the end face of the laser 100 is set to a width broader than the separation width W2 at the central part and light guide layers 109a-109c, which function as channel stoppers at the manufacturing time are selectively formed in the bottom sections of the ridges of the stripe section 107 and sidewall ridge sections 108a and 108b on both sides of the section 107, respectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser having a ridge type waveguide structure and a method for manufacturing the same.

[0002]

2. Description of the Related Art A ridge structure is an index guide (Ind
ex Guide) type, self-oscillation type, gain guide (Gain Guide)
It is used in semiconductor lasers of all materials (wavelengths) such as molds, and has an excellent general-purpose structure. These semiconductor lasers are applied to optical disk devices and the like.

For reproduction of an optical disk, a laser beam emitted from a semiconductor laser element is applied to the disk surface of the optical disk, and a light receiving element (photodiode) reflected from the disk surface and returned.
By receiving the information, the information on the board is read and the information is reproduced.

However, the laser light reflected by the surface of the board actually returns not only to the light receiving element but also to the semiconductor laser element which emits light, which causes the semiconductor laser element to have an extra phase difference. Receives light energy. As a result, the semiconductor laser device increases noise such as mode hopping noise, phase shift noise, and quantum noise.

When light is mixed with noise, the signal amplitude becomes small and the amount of jitter becomes large, so that a reading error is likely to occur. In order to avoid this, it is necessary to take measures to reduce the return light noise. For that purpose, it is effective to make the semiconductor laser element self-pulsation (self-pulsation) or to make a gain guide structure.

FIG. 33 is a sectional view showing an example of the structure of a conventional self-excited oscillation type semiconductor laser adopting a so-called buried ridge structure. Here, a case where a self-excited oscillation type semiconductor laser is made of an AlGaAs material is shown.

As shown in FIG. 33, this self-excited oscillation type semiconductor laser 10 has an n-type Al substrate on an n-type Al substrate 11.
GaAs clad layer 12, AlGaAs active layer 13, p
Type AlGaAs clad layer 14 and p type GaAs cap layer 15 are sequentially stacked. And p-type Al
Upper layer of GaAs clad layer 14 and p-type GaAs
The cap layer 15 has a mesa-shaped stripe shape extending in one direction. That is, these p-type AlGaA
A stripe portion 16 is composed of the upper layer portion of the s cladding layer 14 and the p-type GaAs cap layer 15. A GaAs current constriction layer 17 is buried in both sides of the stripe portion 16, thereby forming a current confinement structure.

P-type GaAs cap layer 15 and GaA
On the s current confinement layer 17, for example, Ti / Pt / Au
A p-side electrode 18 such as an electrode is provided. On the other hand, n
On the back surface of the type GaAs substrate 11, for example, AuGe / N
An n-side electrode 19 such as an i / Au electrode is provided.

FIG. 34 is a schematic diagram showing the refractive index distribution of the self-excited oscillation type semiconductor laser 10 shown in FIG. here,
The refractive index distribution in the direction parallel to the pn junction of the self-excited oscillation type semiconductor laser 10 and perpendicular to the cavity length direction (hereinafter, this direction is referred to as the lateral direction) is shown in correspondence with FIG.

As shown in FIG. 34, the self-excited oscillation type semiconductor laser 10 has a stripe portion 1 having a lateral refractive index.
6 has a high refractive index n1 in the portion corresponding to 6 and a low refractive index n2 in the portions corresponding to both sides of the stripe portion 16, and has a so-called stepwise refractive index distribution.

As described above, in the self-excited oscillation type semiconductor laser 10, the optical waveguide is laterally guided by changing the refractive index in the lateral direction stepwise. In this case, the refractive index difference Δn (= n1−n2) between the portion corresponding to the stripe portion 16 and the portions corresponding to both sides thereof is set to about 0.003 or less, and light is confined in the lateral direction of the AlGaAs active layer 13. Has been eased.

During operation of the self-excited oscillation type semiconductor laser 10 configured as described above, as shown in FIG.
The width WP of the optical waveguide region 22 becomes larger than the width WG of the gain region 21 inside the aAs active layer 13,
The optical waveguide region 22 outside the area becomes the saturable absorption region 23.

In this self-excited oscillation type semiconductor laser 10, the amount of light leaking out in the lateral direction is increased by reducing the change in refractive index in the lateral direction, and the saturable absorption region inside the light and the AlGaAs active layer 13 is absorbed. Self-excited oscillation is realized by increasing the interaction with 23. Therefore, it is necessary to sufficiently secure the saturable absorption region 23.

As described above, the self-excited oscillation type semiconductor laser 10 has a so-called ridge structure as shown in FIG.
Saturable Absorbing R
eagions) are provided on both sides of the optical waveguide in the active layer to cause self-sustained pulsation. In this case, as shown in FIG. 35, the gain region in the active layer (whose width is G) caused by the current spread is made as narrow as possible, and conversely, the optical waveguide spot size (whose width is P) is made relatively large. To P>
When the relationship of G is satisfied, this difference functions as a saturable absorber and causes self-sustained pulsation. This relationship is satisfied as an intermediate guide between an index guide and a gain guide having a waveguide refractive index difference Δn of about 0.005 to 0.001.

The self-oscillation type semiconductor laser having such a structure is self-oscillated at a frequency of about several hundred MHz by forming a saturable absorber in the element.
As a result, the spectral line width is chirped as if high-frequency superposition is applied, the coherence is reduced, and the return light noise is reduced. Also, this noise characteristic is better than the conventional gain guide laser by 10 dB or more.

FIG. 36 is a perspective view showing a configuration example of a conventional gain guide type semiconductor laser, FIG. 37 is a plan view showing a configuration example of a conventional gain guide type semiconductor laser, and FIG. 38 is a conventional gain guide type semiconductor laser. It is sectional drawing which shows the structural example of a laser.

As shown in the figure, the gain guide type semiconductor laser 30 has an n-type Al substrate on an n-type GaAs substrate 31.
GaAs clad layer 32, AlGaAs active layer 33, p
Type AlGaAs clad layer 34 and p type GaAs cap layer 35 are sequentially stacked. And p-type Al
Upper layer of GaAs clad layer 34 and p-type GaAs
The cap layer 35 has a mesa-shaped stripe shape extending in one direction. That is, these p-type AlGaA
Upper layer of s clad layer 34, p-type GaAs cap layer 3
The stripe portion 36 is composed of five. A current confinement layer 37 is formed on both sides of the stripe portion 36 with a high resistance, for example, by ion implantation of B ⁺ ions.

A p-side electrode 38 such as a Ti / Pt / Au electrode is provided on the p-type GaAs cap layer 35 and the current confinement layer 37. On the other hand, n-type GaA
On the back surface of the s substrate 31, for example, AuGe / Ni / Au
An n-side electrode 39 such as an electrode is provided.

Further, in the case of a gain guide type semiconductor laser, from a practical point of view, the waveguide has a taper shape in which the stripe width is wide in the central portion and narrow in the vicinity of the end face as shown in FIG. It is configured as a tapered waveguide.
In FIG. 37, L is the total cavity length, l1 is the taper region length, l2 is the wide stripe region length in the central portion, w1 is the stripe width near the end face, and w2 is the central stripe width.

In the gain guide type semiconductor laser 30 having such a structure, a current flows through the stripe portion during operation, and this current is injected into the active layer 33, but the current confinement layer 37 is provided. The current injection to both sides of the active layer 33 is suppressed. As a result, a light emitting region having a predetermined width is formed and laser oscillation is performed.

In the case of the gain guide type semiconductor laser having almost no refractive index difference Δn, since the multimode oscillation in the longitudinal direction is performed, the return light noise characteristic is relatively good, and the electrostatic breakdown voltage is high, so that it is resistant to surge breakdown. . Further, there is an advantage that the structure is relatively simple and easy to manufacture. In the case of this gain guide type semiconductor laser, the noise level required for the semiconductor laser is the relative noise intensity (RIN;
The value of ive intensity noise) is about 1% for the amount of return light and about -120 dB to -125 dB at the time of output of several mW, which is suitable as a light source for optical disk devices such as CDs.

[0022]

By the way, in recent years, as the use in a higher temperature environment, the downsizing of a pickup, and the lower power consumption progress, further improvement in noise characteristics and lower power consumption of a semiconductor laser device are required. It has become possible to be.

However, the conventional semiconductor lasers described above have the following problems in both the self-excited oscillation type and the gain guide type.

That is, in the case of the self-excited oscillation type semiconductor laser, the noise characteristic is good in the low temperature region, but when the temperature becomes higher than 60 ° C., the pulsation oscillation stops, so that the noise is suddenly increased. It has the disadvantage of deteriorating the characteristics. Also, in the case of self-excited oscillation type semiconductor laser,
It has the disadvantage of having a relatively large astigmatic difference of the order of a few tens of μm.

Further, in the case of the conventional gain guide type semiconductor laser, since it has a gain guide structure, the optical loss is large, and both the threshold current value Ith and the operating current value Iop are high. Its noise characteristic is 10
Bad over dB. In addition, the gain guide laser is 30 μm
Although there is an astigmatic difference As in the front and back, an astigmatic difference correction window cap is used to correct this astigmatic difference in a CD pickup or the like, or an astigmatic difference correction plate is provided between the laser element and the lens. Have been inserted into. On the other hand, in the semiconductor laser integrated device (LC), the astigmatic difference correction window cap cannot be used. For these reasons, realization of a laser device having a small astigmatic difference is strongly demanded.

The present invention has been made in view of the above circumstances, and its object is to be strong against return light noise, to satisfactorily correct or reduce astigmatic difference, to reduce operating current, and at high temperature output. The present invention also provides a semiconductor laser that stably oscillates and a manufacturing method thereof.

[0027]

In order to achieve the above object, the present invention provides a first conductivity type first cladding layer, an active layer formed on the first cladding layer, and the active layer. A semiconductor laser having a second conductivity type second clad layer formed above, the central part and both sides of the second clad layer having a ridge structure, and having a stripe-shaped current injection structure. An optical guide layer having a refractive index higher than that of the second cladding layer is formed at the bottom of each ridge structure except for the bottom of the groove formed between the ridge structures, and the ridge separation is performed. The widths of the parts are set so as to be different between the central part in the stripe direction and the vicinity of the end faces.

Further, in the present invention, the width of the ridge separating portion is set to be narrower in the central portion in the stripe direction and wider than the central portion in the vicinity of at least one end face.

Further, in the present invention, the width of the ridge separation portion is set so that a narrow portion and a wide portion are alternately repeated in the stripe direction.

Further, in the present invention, the width of the waveguide stripe in the center is constant.

Further, in the present invention, the width of the waveguide stripe in the center is set to be narrower in the central portion in the stripe direction and wider than the central portion in the vicinity of at least one end face.

Further, in the present invention, the width of the waveguide stripe in the center is set to be wide at the central portion in the stripe direction and narrower than the central portion in the vicinity of at least one end face.

Further, in the present invention, the insulating film is formed on at least a part of the upper surface of the second cladding layer except the upper surface of the second cladding layer forming the central ridge structure.

Further, in the present invention, the groove portion formed between the ridge structure portions is filled with an insulating material.

Further, in the present invention, current injection is performed on the upper surface of the second clad layer forming the central ridge structure and a part of the upper surface of the second clad layer forming the ridge structure portions on both sides. A cap layer is formed.

Further, according to the present invention, the current injection cap layer is formed on the upper surface of the second cladding layer forming the central ridge structure, and the second cladding forming the upper and lower ridge structure portions. A high resistance layer is formed on a part of the upper surface of the second cladding layer forming the second ridge structure portion on a part of the upper surface of the layer.

Further, in the present invention, the first cladding layer includes a layer having a refractive index higher than that of the first cladding layer.

The present invention also provides a first conductivity type first clad layer, an active layer formed on the first clad layer, and a second conductivity type second clad layer formed on the active layer. A second clad layer, wherein the central part and both side parts of the second clad layer have a ridge structure and a stripe-shaped current injection structure.
A step of forming an etching stop layer at a predetermined distance from the active layer in the second cladding layer when forming the ridge structure portions in the central portion and both sides of the cladding layer Includes a first step of selectively forming an etching protection layer on the second cladding layer, and a first step
A second step of etching the second cladding layer to the vicinity of the etching stop layer with the etchant of
It includes a third step of etching the second cladding layer to the etching stop layer with the second etchant, and a fourth step of etching off the ching stop layer exposed by the third etchant.

Further, in the present invention, the cap layer is formed on the upper surface of the second cladding layer, and remains in the region where the second cladding layer is removed by the etching after the third step. And a fifth step of removing the cap layer with a fourth etchant.

Further, in the present invention, the second cladding layer contains AlGaAs, and in the second step, non-selective etching is performed using a hydrochloric acid / hydrogen peroxide solution / water-based first etchant, and the third cladding layer is formed. In the process, AlGaAs with a second etchant of hydrofluoric acid / ammonium fluoride system
Selective etching is performed, and in the fourth step, non-selective etching is performed using phosphoric acid / hydrogen peroxide / water-based third etchant.

Further, in the present invention, in the fifth step,
GaAs selective etching is performed with a fourth etchant based on ammonia water / hydrogen peroxide solution.

Further, the present invention has a step of diffusing predetermined ions into a region to be a stripe portion to insulate a region other than the stripe.

Further, in the present invention, the diffusion step is performed before forming the ridge structure portion.

According to the present invention, for example, the center waveguide stripe width is constant, and the width of the ridge separation portion is set to be narrower in the central portion in the stripe direction and wider than the central portion in the vicinity of the end face. In the case of the type semiconductor laser, the spread of light in the lateral direction is larger than the stripe width of the second cladding layer. That is, in the central waveguide, the light is spread laterally and the current remains narrow, so that a saturable absorption region effective for pulsation is sufficiently obtained. As a result, the light is narrowed down like a so-called index guide, and the pulsation does not stop, and the pulsation is stably and continuously generated. On the other hand, near the end face, the optical mode is narrowed to the center and the effective refractive index difference Δ
Since n becomes large, it becomes close to an index type waveguide. As a result, the astigmatic difference is corrected and the beam divergence angle θ // in the parallel direction of the FFP is expanded. Further, since the optical guide layer having a refractive index higher than that of the second cladding layer is formed at the bottom of each ridge structure except for the bottom of the groove formed between the ridge structures, the refractive index difference is adjusted. As a result, the FFP can be made narrower (the angle can be made smaller), the change in the wavefront in the vertical direction can be caused gently, and the astigmatic difference can be favorably corrected while reducing the energy loss.

Further, for example, in the case of a semiconductor laser in which the width of the central waveguide stripe is constant and the width of the ridge separation portion is set to be narrow at the central portion in the stripe direction and wider than the central portion in the vicinity of the end face, the waveguide mode Is narrow at the center and wide near the end face. In order to ensure its reliability, high output lasers with high end face light density and materials with large end face deterioration are required.
It is necessary to reduce the light density on the end face.

Further, according to the present invention, since the gain guide region is provided with the waveguide mechanism in which the index guide region is connected, the longitudinal mode property of the gain guide can be utilized, that is, the low noise characteristic strong against the returning light can be obtained. The astigmatism difference is reduced and the converging spot system becomes small while maintaining the above.

Further, in the semiconductor laser provided with the optical guide layer, the wavefront in the vertical direction is corrected from the concavely curved wavefront to the convexly curved wavefront.

[0048]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment FIG. 1 is a plan view showing a first embodiment of a semiconductor laser according to the present invention, FIG. 2 is a sectional view taken along line AA of FIG.
FIG. 3 is a diagram for explaining a ridge structure of a semiconductor laser according to the present invention. Here, a case is shown where a saturable absorber is formed inside the laser resonator on both sides of the active layer using an AlGaAs-based material.

As shown in the figure, this semiconductor laser 100
Is a buffer layer 102, an n-type AlGaAs cladding layer (first cladding layer) 103, an AlGaAs active layer 104, a p-type (second conductivity type) AlGaAs cladding layer on an n-type (first conductivity type) GaAs substrate 101. (Second cladding layers) 105a to 105d and a p-type GaAs cap layer 106 (high resistance layers 106a and 106b on both sides) are sequentially laminated. The upper layer portion of the p-type AlGaAs clad layer 105a, that is, the clad layer 105c and the p-type GaAs cap layer 106 has a mesa stripe shape extending in one direction. That is, the p-type AlGaAs cladding layer 105c and the p-type GaAs cap layer 106 form a stripe portion 107.

Sidewall ridges 108a and 108b are formed on both sides of the stripe portion 107 with a predetermined space therebetween. The sidewall ridge 108a is made of p-type AlGaA.
The s clad layer 105b and the high resistance layer 106a. Similarly, the sidewall ridge 108b is
p-type AlGaAs cladding layer 105d and high resistance layer 106
b.

That is, as shown in FIGS. 1 to 3, the present semiconductor laser 100 is formed in a so-called W-type ridge shape having a second ridge structure portion with both side (lateral) portions raised. . Furthermore, the waveguide stripe width at the center of the stripe portion 107 is constant, and the width of the clad layer recess between the ridges, in other words, the ridge portions 108a and 108b on both sides and the central ridge portion (stripe portion).
The width of the thin region of the p-type AlGaAs cladding layer 104 between 107 (ridge separation width) is several tens of μm, which is a normal value.
Is not constant but is non-uniform with a narrower portion (in the first embodiment, the central portion of the resonator is formed narrow).

Specifically, in the semiconductor laser 100, the stripe width W1 of the so-called mesa-shaped bottom is 4 μm.
The width of the recess between ridges (width of the ridge separation portion; hereinafter referred to as ridge separation width) W2 is set to, for example, 5 μm or less at the center portion of the stripe portion 107 (resonator center portion).
The ridge separation width W2 ′ near the end face side is set wider than the ridge separation width W2 in the central portion.

When the ridge separation width W2 at the central portion of the stripe portion 107 is set to about 5 μm or less, the central ridge portion 1
The stripe width W1 of 10 (about 4 μm, W1 is described as larger than W2 in order to clarify the description of the waveguide mode width in FIGS. 2 and 3) is almost the same, The tail starts to act on the large refractive index portions of the ridge portions 108a and 108b on both sides. When this happens,
The effective refractive index difference Δn becomes smaller, and the guided mode tends to broaden. In this way, the refractive index difference Δn can be controlled by controlling the ridge separation width W2 that can be achieved by a simple etching process.
Can be controlled. Therefore, it is possible to freely change the guided state in the resonator direction without changing the shape of the central portion of the stripe portion 107, that is, to change the guided mode while keeping the current distribution narrow and uniform. Is possible.

Further, it is desirable that the length L1 in the resonator direction in which the width W2 is set to 5 μm or less is 20 μm or less. This is because if the thickness is 20 μm or more, the index property becomes too strong, and the noise characteristic with respect to the return light deteriorates.

Further, in order to stably generate the pulsation, the current does not spread in the lateral direction of the active layer, the light spot is spread and the difference between them is enlarged to secure a wide saturable absorption region. The thickness of the AlGaAs cladding layer 104a, in other words, the active layer 104 and the optical guide layer 109a-
109c has a thickness d of, for example, d ≦ 800 nm,
It is preferable to set d ≦ 450 nm. Thickness d is 8
This is because when the thickness is 00 nm or more, the saturable absorption region is not formed in the active layer 104, and self-sustained pulsation does not occur.

The refractive index difference Δn (= n1−) between the portion corresponding to the stripe portion 107 and the portions corresponding to both sides thereof.
n2) is set to about 0.003 or less, and light confinement in the lateral direction of the AlGaAs active layer 103 is relaxed.

The p-type AlGaAs clad layer 10a forming the stripe portion 107 and the p-type AlGaAs clad layer 105a formed on the AlGaAs active layer 104 are also included.
The p-type AlGaAs clad layer 10 is formed at the boundary with 5c.
5a, 105c Al composition ratio (0.47: Al _0.47 G
Al _0.3 Ga _0.7 As light guide layer 109a lower than a _0.53 As) is formed. Similarly, a p-type AlGaAs clad layer 1 formed on the AlGaAs active layer 104
05a and the p-type AlGaAs clad layer 105b forming the sidewall ridge 108a, Al having a lower Al composition ratio than the p-type AlGaAs clad layers 105a and 105b (0.47: Al _0.47 Ga _0.53 As) is used.
_{A 0.3} Ga _0.7 As light guide layer 109b is formed. P-type Al formed on the AlGaAs active layer 104
GaAs cladding layer 105a and sidewall ridge 1
P-type AlGaAs clad layer 105d constituting 08b
The p-type AlGaAs cladding layer 105 is
a, 105d Al composition ratio (0.47: Al _0.47 Ga
_The Al _0.3 Ga _0.7 As light guide layer 109c lower than _0.53 As)) is formed. The light guide layer is formed by the ridge of the stripe portion 107 and the groove portions 110a and 110b between the sidewall ridges 108a and 108b on both sides.
Is not formed on the p-type AlGaAs cladding layer 105a. In this way, the light guide layer 109 is selectively
By forming a to 109c, the refractive index difference can be adjusted, the FFP can be narrowed (the angle can be made small), the change of the wavefront in the vertical direction can be gently caused, and the astigmatism can be reduced while reducing the energy loss. It becomes possible to satisfactorily correct the gap.

On the p-type GaAs cap layer 106, the high resistance layers 106a and 106b, the ridge of the stripe portion 106 and the sidewall ridges 108a and 108b on both sides.
On the p-type AlGaAs cladding layer 105a between them, the stripe portion 106, the sidewall ridges 108a and 108b.
A p-side electrode 111 such as a Ti / Pt / Au electrode is provided on the entire side wall of the. On the other hand, n-type GaA
On the back surface of the substrate 101, for example, AuGe / Ni / A
An n-side electrode 112 such as a u electrode is provided.

Next, a method of manufacturing the semiconductor laser 100 having the above structure will be described with reference to FIGS.

First, as shown in FIG. 4A, n-type Ga
On the As substrate 101, the n-type buffer layer 102 and the n-type Al
GaAs cladding layer 103, AlGaAs active layer 10
4, p-type AlGaAs clad layer 105a and etching stop layer 10 serving as optical guide layers 109a to 109c
9. The p-type AlGaAs cladding layer 105a and the p-type GaAs cap layer 106 are sequentially grown by, for example, a metal organic chemical vapor deposition (MOCVD) method. next,
On the p-type GaAs cap layer 106, an etching protection layer 20 for forming a ridge shape is selectively formed on both sides of the stripe portion 106 as shown in FIG.

Then, FIGS. 4 (B), (C) and FIG.
As shown in (D) and (E), the distance d from the active layer 104 to the bottom of the ridge is 800 nm or less, and the p-type GaAs cap layer 106 and the p-type AlGaAs clad are formed so that the ridge does not penetrate the active layer 104. The layer 105a is etched to form a ridge. This is because, as described above, when the bottom of the ridge is separated from the active layer by 800 nm or more, a saturable absorption band is not formed in the active layer 104, so that pulsation oscillation does not occur.

In the present embodiment, as shown in FIG. 4 (B), the etching stop layer is first formed with a hydrochloric acid / hydrogen peroxide solution / water mixture (1: 1 to 10:10 to 60) to form the ridge. Non-selective etching is performed up to the vicinity of 109.

Next, as shown in FIG. 4C, hydrofluoric acid:
P-type Al with ammonium fluoride mixed solution (1: 1 to 20)
Only the GaAs cladding layer 105a is selectively etched so that the etching does not proceed deeper than the etching stop layer 109. By this selective etching, the distance d from the bottom of the ridge to the active layer 104 can be kept constant and the characteristics of the laser element can be stabilized. Further, by this step, as shown in FIG. 4C, the p-type GaAs cap layer 106 is formed on the ridge.
As shown in FIG. 5 (D), the eaves are formed, and as shown in FIG. 5 (D), a mixture of ammonia water and hydrogen peroxide water (1:10 to 1
00) to remove. However, even if the eaves are left, the characteristics of the semiconductor laser do not change.

Further, as shown in FIG. 5 (E), phosphoric acid: hydrogen peroxide water: water (1 to 10: 1: 10 to 100)
The GaAs and AlGaAs non-selective etching etches off the etching stop layer 109 at the bottom of the ridge, and the etching protection layer 20 is peeled off as shown in FIG. 5 (F).

Next, as shown in FIG. 6G, the gap between the stripe portion 107 and the ridge is protected by the ion implantation protection layer 21. Then, as shown in FIG. 6H, ions such as boron are added to the sidewall ridge portions 108a and 108a.
By implanting into the GaAs cap layer 106 forming 8b, high resistance layers 106a and 106b are formed. afterwards,
As shown in FIG. 6I, the ion implantation protection layer 21 is peeled off. After that, a high resistance layer is formed by ion implantation from the P electrode side.

Finally, after removing the ion implantation protection layer 21, the p-type GaAs cap layer 106 and the high resistance layer 106 are formed.
a, 106b, the ridge of the stripe portion 106, the p-type AlGaAs cladding layer 105a between the sidewall ridges 108a, 108b on both sides, and the stripe portion 10.
6. A p-side electrode 111 is formed on the entire sidewalls of the sidewall ridges 108a and 108b (entire front walls of the trenches 110a and 110b), and on the back surface of the n-type GaAs substrate 101.
By forming the n-side electrode 112, the semiconductor laser 100 as shown in FIG. 7 is manufactured.

As described above, the self-pulsation type semiconductor laser 10
0 is completed.

In the manufacturing process described above, after selectively forming a resist (etching protection layer 20) for forming a ridge shape, four types of etchants are used,
It forms a ridge. Specifically, in the process of FIG. 4B, non-selective etching of “hydrochloric acid / hydrogen peroxide solution / water system (first etchant)” is performed, and in the process of FIG. 4C, [S
O21 (hydrofluoric acid / ammonium fluoride system (second etchant) "AlGaAs selective etching", FIG. 5D)
In the process of, the GaAs selective etching of "ammonia water / hydrogen peroxide water system (4th etchant)", and FIG.
In the process of (E), "phosphoric acid / hydrogen peroxide water / water system (3rd
Etchant) 'non-selective etching.

By the way, in practice, at the end of each etching step of FIGS. 4 (B) to 5 (E), heat treatment of the wafer (for example, baking at 120 ° C. for 10 minutes) is performed, and the resist and the wafer are re-etched. Adhesion is desirable.
The reason is that the adhesion of the resist immediately after each etching process to the wafer has deteriorated, and if the next etching is performed in that state, erosion of the etching solution occurs on the GaAs surface layer, and after each etching, the resist This is because it is considered difficult to include the peeling / resist window opening step due to the accuracy of the resist window opening and the complexity of the process steps.

The reason why the GaAs cap layer 106 of the stripe portion 107 is protected is as follows. In order to easily pass a current through the active layer 104, Ga on the p-side surface is
It is necessary to take an ohmic contact between As and p-type metal (electrode). In the ridge portion, since AlGaAs of the p-type cladding layer is exposed and the distance from the bottom portion of the ridge to the active layer 104 is very short, Zn diffusion cannot be performed after forming the ridge. Therefore, before forming the ridge, GaAs
It is necessary to perform high-concentration Zn diffusion on the layer surface. Therefore, in the so-called "ridge formation process" described above, the GaAs layer of the stripe portion 107 (particularly the surface Zn high-concentration layer) must be protected from the etchant at the time of forming the ridge.

Next, the operation of the above configuration will be described. When the self-pulsation type semiconductor laser 100 operates, a current flows through the stripe portion 107. In this case, p-type AlGaAs is used.
The thickness d between the clad layer 105a and the bottom of the ridge is 80.
Since it is set to a sufficiently small value of 0 nm or less, the spread of the current in the lateral direction can be suppressed to the stripe width W1 of the p-type AlGaAs cladding layer 105c. On the other hand, in the central portion of the stripe portion 107 (central portion of the resonator), the recess width between ridges (ridge separation width) W2 is, for example, 5 μm.
The ridge separation width W2 ′ near the end face side is set wider than the ridge separation width W2 in the central portion, and the difference in refractive index between the portion corresponding to the stripe portion 107 and the portions corresponding to both sides thereof is set as follows. Δn is set to about 0.003 or less, and light confinement in the lateral direction of the AlGaAs active layer 104 is relaxed.

Therefore, in the central waveguide, the spread of light in the lateral direction is larger than the stripe width W1 of the p-type AlGaAs cladding layer 105a. That is, in the central waveguide the light is spread laterally and the current remains narrow,
A sufficient saturable absorption region effective for pulsation is obtained. As a result, the light is narrowed down like a so-called index guide, and the pulsation does not stop, and the pulsation is stably and continuously generated.

On the other hand, in the vicinity of the end face, the optical mode is narrowed to the center and the effective refractive index difference Δn becomes large, so that it becomes close to the index type waveguide. In other words, as it becomes closer to the guided wave of a plane wave, astigmatic difference is less likely to occur,
The astigmatic difference is corrected and the beam divergence angle θ // in the parallel direction of the FFP is expanded.

Further, the p-type AlGaAs cladding layer 105
a and the p-type AlGaAs clad layer 105c forming the stripe portion 107, the optical guide layer 109a is formed at the boundary portion.
To form the p-type AlGaAs cladding layer 105a and the sidewall ridge 108a.
The optical guide layer 10 is formed at the boundary with the s clad layer 105b.
9b is formed, and the p-type AlGaAs cladding layer 105a is formed.
And the p-type AlG forming the sidewall ridge 108b
An optical guide layer 109c is formed at the boundary with the aAs clad layer 105d, and the ridge of the stripe portion 107 and
Since no optical guide is formed on the p-type AlGaAs cladding layer 105a in the trenches 110a and 110b between the sidewall ridges 108a and 108b on both sides, the refractive index difference can be adjusted to narrow the FFP (angle It can be made small), and the change in the wavefront in the vertical direction can be caused gently, and the astigmatic difference can be satisfactorily corrected while reducing the energy loss.

The results of actual driving of the semiconductor laser 100 constructed as described above will be described with reference to FIGS.

FIG. 8 is a characteristic diagram showing the relationship between the CW (Continuous Wave) output light and the injection current of the semiconductor laser according to the present invention at room temperature of 25 ° C. In FIG. 8, the horizontal axis represents the injection current, the left vertical axis represents the output power, and the right vertical axis represents the voltage. As shown in FIG. 8, the threshold current of this device was 18 mA, and the operating current at 3 mW was 22 mA. Further, the kink at about 20 mW is sufficiently high as a light source for reading the optical disk system.

FIG. 9 is a diagram showing a far field pattern (FFP) of the semiconductor laser according to the present invention at 3 mW. In FIG. 9, the horizontal axis indicates the angle.
As shown in FIG. 9, the beam divergence angle θ // in the parallel direction of the FFP was 15 °, and the beam divergence angle θ | in the vertical direction of the FFP was 35 °.

FIG. 10 shows the CW emission spectrum of the semiconductor laser according to the present invention at an output power level of 3 mW. In FIG. 10, the horizontal axis represents wavelength. As shown in FIG. 10, the oscillation wavelength λ of this semiconductor laser is
Was about 795 nm. Also, multi-longitudinal mode operation is achieved, and the coherence degree of the first peak is
It was 0.7. This indicates that this semiconductor laser maintains self-sustained pulsation.

FIG. 11 shows the output power and relative noise intensity (R) of the semiconductor laser according to the present invention at room temperature of 25 ° C.
It is a figure which shows the relationship with (IN). In FIG. 11, the horizontal axis represents output power and the vertical axis represents relative noise intensity (RIN). As shown in FIG. 11, in the optical feedback (PFB) of 1%, the relative noise intensity (RI
N) level is -130d with output power of 3mW or more.
B / Hz or less was maintained. This indicates that self-sustained pulsation was maintained at the output power between 3 mW and 8 mW.

FIG. 12 shows the cavity position (c
It is a figure which shows the dependence of the near-field spot size in avity position). In FIG. 12, the horizontal axis represents the cavity position, the left vertical axis represents the spot size,
The right vertical axis shows the intensity. As shown in FIG. 12, the astigmatic difference is 20 μm which is not desired, but it can be applied to the optical disc system. The reason is that the spot size of the beam in the direction parallel to the joint surface is -3 ± 10 μm.
This is because there is a very slight change in the cavity position range of m.

As described above, according to the first embodiment, in the self-pulsation type semiconductor laser 100, the waveguide stripe width at the center of the stripe portion 107 is constant, and the central portion of the stripe portion 107 ( The width of the recess between ridges (ridge separation width) W2 is set to be narrower in the resonator center portion, the ridge separation width W2 ′ near the end face side is set to be wider than the ridge separation width W2 in the center portion, and the ridge bottom portion of the stripe portion 107 is set. , And the sidewall ridges 108a on both sides,
Optical guide layers 109a to 109c functioning as channel stoppers at the time of manufacturing are selectively formed at the bottom of 108b, and the refractive index difference Δn between the portion corresponding to the stripe portion 107 and the portions corresponding to both sides thereof is 0. Since it is set to about 003 or less, light confinement in the lateral direction of the AlGaAs active layer 103 is relaxed, so that the waveguide mode at the central portion of the stripe can be laterally widened and the current can be kept in a narrow region. Therefore, a saturable absorption region can be formed in the lateral region inside the active layer, and pulsation can be stably induced. In addition, regarding the astigmatic difference, since the effective refractive index difference Δn near the end face can be increased and the waveguide can be used as an index guide, the astigmatic difference can be brought close to zero. In addition, fixing the mode at the end face also makes it possible to suppress a change in the beam divergence angle θ // in the parallel direction of the FFP depending on the output. As a result, there is an advantage that it can be applied to an optical system for an optical disc and has high versatility. Further, since the ridge portion is formed using four types of etchants after selectively forming the resist (etching protection layer 20) for forming the ridge shape, the ridge structure can be realized with high accuracy. There are advantages.

In the first embodiment, Al
Although a GaAs / GaAs self-excited oscillation type semiconductor laser has been described as an example, the present invention is applicable to AlGaInP / GaInP, A
lGaN / InGaN, ZnMgSSe / ZnS system, etc.
It goes without saying that it can be applied to various lasers.

Second Embodiment FIG. 13 is a sectional view showing a second embodiment of the semiconductor laser according to the present invention.

The difference of the second embodiment from the first embodiment described above is that the sidewall ridge portions 108a, 108a,
08b p-type AlGaAs cladding layers 105b and 105
Instead of forming the high resistance layer on the upper part of d, the GaAs cap layer other than the stripe portion 107 is removed. Other configurations are the same as those in the first embodiment.

According to the second embodiment, the above-described first
It is possible to obtain the same effect as that of the embodiment.

Third Embodiment FIG. 14 is a sectional view showing a third embodiment of the semiconductor laser according to the present invention.

The difference of the third embodiment from the above-mentioned first embodiment is that the sidewall ridge portions 108a, 108a, 1b.
08b p-type AlGaAs cladding layers 105b and 105
Ga is formed on the upper part of d by ion implantation without providing a high resistance layer.
The side wall ridge portion 10 is formed so that the As cap layer 106 is left as it is and no current is passed except for the stripe.
8a, the upper surface and the side surface of the cap layer 106, and the groove portion 110.
a side surface of the p-type AlGaAs clad layer 105b, upper surface of the p-type AlGaAs clad layer 105a, side surface of the p-type AlGaAs clad layer 105c of the stripe portion 107,
P-type AlGaAs in the stripe portion 107 of the groove portion 110b
The side surface of the clad layer 105c, the upper surface of the p-type AlGaAs clad layer 105a, the upper surface and side surface of the cap layer of the sidewall ridge portion 108b, and the p-type Al of the groove portion 110b.
On the side surface of the GaAs cladding layer 105d, for example, SiO
_This is because the insulating film 113 made of ₂ was formed. Other configurations are the same as those in the first embodiment.

FIG. 15 shows the steps of forming this SiO ₂ .
A description will be made in association with (A) to (C) and FIGS. 16 (D) to (F).

Since a current is passed only through the stripe portion 107, first, as shown in FIG. 15A, the SiO ₂ film 113 is first formed.
15 is deposited on the entire surface of the p-type layer on which the ridge is formed, and then FIG.
As shown in (B), a resist 30 is formed on the entire surface of the vapor-deposited SiO ₂ film, and as shown in FIGS. 15 (C) and 16 (D), stripes are formed by a self-alignment method by incomplete exposure of the resist. The resist is removed only from the portion 107. Next, as shown in FIG. 16 (E), the SiO film on the stripe portion 107 is removed by SO1 (hydrofluoric acid / ammonium fluoride based etchant), and the resist 30 is removed as shown in FIG. 16 (F). To do.

According to the third embodiment, the above-mentioned first embodiment
It is possible to obtain the same effect as that of the embodiment.

Fourth Embodiment FIG. 17 is a sectional view showing a fourth embodiment of the semiconductor laser according to the present invention.

The fourth embodiment differs from the third embodiment described above in that the sidewall ridge portions 108a, 108a,
08b p-type AlGaAs cladding layers 105b and 105
High resistance layers 106a and 106b are formed on the upper part of
This is because the O ₂ film 113 is formed only on the side surfaces of the p-type cladding layers 105b to 105d and the upper surface of the p-type cladding layer 105a. Other configurations are similar to those of the third embodiment.

According to the fourth embodiment, the above-mentioned first
It is possible to obtain the same effect as that of the embodiment.

Fifth Embodiment FIG. 18 is a sectional view showing a fifth embodiment of the semiconductor laser according to the present invention.

The fifth embodiment is different from the fourth embodiment described above in that the p-type electrode 111 is arranged in the stripe portion 10.
7 upper surface of the GaAs cap layer 106 and the high resistance layer 106 of the sidewall ridge portions 108a and 108b.
It is formed only on the upper surfaces of a and 106b. Other configurations are similar to those of the fourth embodiment.

According to the fifth embodiment, the above-mentioned first embodiment
It is possible to obtain the same effect as that of the embodiment.

Sixth Embodiment FIG. 19 is a sectional view showing a sixth embodiment of the semiconductor laser according to the present invention.

The sixth embodiment differs from the fifth embodiment described above in that instead of using a SiO ₂ film as an insulating material, polyimide 114 is used to form both groove portions 110a, 1a.
10b is the upper surface of the GaAs cap layer 106 and the high resistance layer 1 of the sidewall ridges 108a and 108b.
This is because the p-type electrodes 111 were formed on the upper surfaces of the upper surfaces of the layers 06a and 106b to the same height. Other configurations are similar to those of the fifth embodiment.

According to the sixth embodiment, the above-mentioned first embodiment
It is possible to obtain the same effect as that of the embodiment.

Seventh Embodiment FIG. 20 is a sectional view showing the seventh embodiment of the semiconductor laser according to the present invention.

The seventh embodiment differs from the sixth embodiment described above in that a polyimide layer 114 is formed instead of the high resistance layers 106a and 106b. In this configuration, the GaAs cap layer 106 of the stripe portion 107 has a configuration protruding toward the groove portions 110a and 110b like a so-called eaves. Other configurations are similar to those of the sixth embodiment.

According to the seventh embodiment, the above-mentioned first embodiment
It is possible to obtain the same effect as that of the embodiment.

Eighth Embodiment FIG. 21 is a sectional view showing an eighth embodiment of the semiconductor laser according to the present invention.

The eighth embodiment differs from the sixth embodiment described above in that the GaAs cap layer 106 of the stripe portion 107 and the sidewall ridge portion 108a,
The high resistance layers 106a and 106b of the groove 108b
The structure is such that it projects like a so-called eave on the a and 110b sides. Other configurations are similar to those of the sixth embodiment.

According to the eighth embodiment, the above-mentioned first embodiment
It is possible to obtain the same effect as that of the embodiment.

Ninth Embodiment FIG. 22 is a sectional view showing the ninth embodiment of the semiconductor laser according to the present invention.

The ninth embodiment differs from the seventh embodiment described above in that the high resistance layers 106a and 106b are not formed and the polyimide layer 114 is replaced with the p-type cladding layers 105b-1.
The GaAs cap layer 106 of the stripe portion 107 is filled with the groove portion 110a,
The structure is such that it protrudes on the 110b side like a so-called eaves, and the p-type electrode 111 is formed on the upper surface thereof. Other configurations are similar to those of the seventh embodiment.

According to the ninth embodiment, the above-mentioned first embodiment
It is possible to obtain the same effect as that of the embodiment.

Tenth Embodiment FIG. 23 is a sectional view showing a tenth embodiment of a semiconductor laser according to the present invention.

The tenth embodiment is different from the above-described fourth embodiment in that the vertical loss is corrected symmetrically at the skirt portion of the optical mode in correcting the vertical concave curvature to the convex curvature. To form n-type Al with the active layer 104 in between,
The optical guide layer 115 having a higher refractive index than the n-type AlGaAs clad layer 103 is formed in the GaAs clad layer 103.

The n-side light guide layer 115 is made of n-type Al.
Al having a lower Al composition ratio than the GaAs cladding layer 103
It is formed as a GaAs layer.

In the present semiconductor laser 100I, since the wave front is delayed due to the loss effect of the n-side optical guide layer 115, the concave wave front becomes a wave surface close to a flat surface, and if the loss becomes large, it becomes a convex curvature.

According to the tenth embodiment, by performing the wavefront shaping as described above, it is possible to form a curve close to the lateral wavefront curve and eliminate the astigmatic difference.

Eleventh Embodiment FIG. 24 is a plan view showing an eleventh embodiment of the semiconductor laser according to the present invention.

The eleventh embodiment is the above-mentioned first to first
In the semiconductor laser 100J, the ridge separation width W2 ′ in the vicinity of the end face side is set to be wider than the ridge separation width W2 in the central portion in the semiconductor laser 100J, instead of gradually widening toward the end face. The configuration is such that the width is the same in the vicinity of the end face. Other configurations are first
~ It is similar to the tenth embodiment.

According to the eleventh embodiment, the same effect as the effect of the first embodiment described above can be obtained.

Twelfth Embodiment FIG. 25 is a plan view showing a twelfth embodiment of the semiconductor laser according to the present invention.

The twelfth embodiment is the above-mentioned first to first
The semiconductor laser 100K is different from that of the first embodiment in that the width of the waveguide stripe at the center of the stripe portion 107K is not constant but is gradually narrowed from the end face side toward the center portion. . Other configurations are similar to those of the first to tenth embodiments.

According to the twelfth embodiment, it is possible to obtain the same effects as those of the first embodiment described above.

13th Embodiment FIG. 26 is a plan view showing a 13th embodiment of a semiconductor laser according to the present invention.

The thirteenth embodiment is the above-mentioned first to first
The difference from the 0th embodiment is that in the semiconductor laser 100L, the waveguide stripe width at the center of the stripe portion 107L is made constant, but is gradually widened from the end face side toward the center portion. . Other configurations are similar to those of the first to tenth embodiments.

According to the thirteenth embodiment, it is possible to obtain the same effects as those of the first embodiment described above.

Fourteenth Embodiment FIG. 27 is a plan view showing a fourteenth embodiment of the semiconductor laser according to the present invention.

The fourteenth embodiment is the above-mentioned first to first
In the semiconductor laser 100M, the waveguide stripe width at the center of the stripe portion 107M is constant in the semiconductor laser 100M, but gradually widens from the rear end face side toward the central portion, and further from the central portion to the front end. It is configured to gradually widen toward the surface side. Other configurations are similar to those of the first to tenth embodiments.

According to the fourteenth embodiment, the same effect as that of the above-described first embodiment can be obtained.

Fifteenth Embodiment FIG. 28 is a plan view showing a fifteenth embodiment of the semiconductor laser according to the present invention.

The fifteenth embodiment is the above-mentioned first to first
In the semiconductor laser 100N, the ridge separation width W2 ′ in the vicinity of both end faces is set to be wider than the ridge separation width W2 in the central portion in the semiconductor laser 100N, instead of gradually widening toward the end faces. The width is the same from the rear end face side to the central portion, and gradually widens toward the front end face. Other configurations are first to tenth
It is similar to the embodiment.

According to the fifteenth embodiment, it is possible to obtain the same effects as the effects of the first embodiment described above.

Sixteenth Embodiment FIG. 29 is a plan view showing a sixteenth embodiment of the semiconductor laser according to the present invention.

The sixteenth embodiment is the above-mentioned first to first
In the semiconductor laser 100O, the ridge separation width W2 ′ in the vicinity of both end surfaces is set to be wider than the ridge separation width W2 in the central portion in the semiconductor laser 100O, instead of gradually widening toward the end surface. It is configured so that it spreads stepwise. Other configurations are first to tenth
It is similar to the embodiment.

According to the sixteenth embodiment, it is possible to obtain the same effects as the effects of the first embodiment described above.

17th Embodiment FIG. 30 is a plan view showing a 17th embodiment of a semiconductor laser according to the present invention.

The seventeenth embodiment is the above-mentioned first to first
The semiconductor laser 100P is different from the first embodiment in that the ridge separation width W2 ′ in the vicinity of both end surfaces is set wider than the ridge separation width W2 in the central portion in the semiconductor laser 100P, instead of gradually widening toward the end surface. That is, it is configured to have a so-called comb shape (having a plurality of steps). Other configurations are similar to those of the first to tenth embodiments.

According to the seventeenth embodiment, the same effect as that of the above-described first embodiment can be obtained.

Eighteenth Embodiment FIG. 31 is a plan view showing an eighteenth embodiment of a semiconductor laser according to the present invention.

The eighteenth embodiment is the above-mentioned first to first
In the semiconductor laser 100Q, the ridge separation width W2 ′ in the vicinity of both end surfaces is set wider than the ridge separation width W2 in the central portion in the semiconductor laser 100Q, instead of gradually widening toward the end surface. That is, it is configured to have a plurality of steps including so-called a plurality of triangular waves. Other configurations are similar to those of the first to tenth embodiments.

According to the eighteenth embodiment, it is possible to obtain the same effects as the effects of the first embodiment described above.

19th Embodiment FIG. 32 is a plan view showing a 19th embodiment of a semiconductor laser according to the present invention.

The nineteenth embodiment is the above-mentioned first to first
In the semiconductor laser 100S, the ridge separation width W2 ′ in the vicinity of both end faces is set to be wider than the ridge separation width W2 in the central portion in the semiconductor laser 100S, instead of gradually widening toward the end faces. , Having a plurality of steps including a so-called plurality of trapezoidal waves. Other configurations are similar to those of the first to tenth embodiments.

According to the nineteenth embodiment, the same effects as the effects of the first embodiment described above can be obtained.

[0141]

As described above, according to the present invention,
The following effects can be obtained. It is possible to laterally spread the guided mode in the central portion of the stripe and yet keep the current in a narrow region. Therefore, a saturable absorption region can be formed in the lateral region inside the active layer, and pulsation can be stably induced.

As for the astigmatic difference, since the effective refractive index difference Δn near the end face can be increased and the waveguide can be index-guided, the astigmatic difference can be brought close to zero. In addition, fixing the mode at the end face also makes it possible to suppress a change in the beam divergence angle θ // in the parallel direction of the FFP depending on the output.
As a result, there is an advantage that it can be applied to an optical system for an optical disc and has high versatility.

Since the ridge portion is formed by using four kinds of etchants after selectively forming the resist for forming the ridge shape, there is an advantage that the ridge structure can be realized with high accuracy. .

[Brief description of drawings]

FIG. 1 is a plan view showing a first embodiment of a semiconductor laser according to the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a diagram for explaining a ridge structure of a semiconductor laser according to the present invention.

FIG. 4 is a drawing for explaining the manufacturing method of the semiconductor laser according to the present invention.

FIG. 5 is a drawing for explaining the manufacturing method of the semiconductor laser according to the present invention.

FIG. 6 is a drawing for explaining the manufacturing method of the semiconductor laser according to the present invention.

FIG. 7 is a diagram showing a semiconductor laser manufactured by the manufacturing method according to the present invention.

FIG. 8 is a characteristic diagram showing the relationship between CW (Continuous Wave) output light and the injection current of the semiconductor laser according to the present invention at room temperature of 25 ° C.

FIG. 9 is a diagram showing a far-field pattern (FFP) of the semiconductor laser according to the present invention at 3 mW.

FIG. 10 shows a CW emission spectrum of a semiconductor laser according to the present invention at an output power level of 3 mW.

FIG. 11 is a diagram showing the relationship between the output power and the relative noise intensity (RIN) of the semiconductor laser according to the present invention at room temperature of 25 ° C.

FIG. 12: Cavity position near the front surface (cavity)
It is a figure which shows the dependence of the near-field spot size in (position).

FIG. 13 is a sectional view showing a second embodiment of a semiconductor laser according to the present invention.

FIG. 14 is a sectional view showing a third embodiment of a semiconductor laser according to the present invention.

FIG. 15 is a diagram for explaining a process of forming a SiO ₂ film according to the present invention.

FIG. 16 is a diagram for explaining a process of forming a SiO ₂ film according to the present invention.

FIG. 17 is a sectional view showing a fourth embodiment of a semiconductor laser according to the present invention.

FIG. 18 is a sectional view showing a fifth embodiment of a semiconductor laser according to the present invention.

FIG. 19 is a sectional view showing a sixth embodiment of a semiconductor laser according to the present invention.

FIG. 20 is a sectional view showing a seventh embodiment of a semiconductor laser according to the present invention.

FIG. 21 is a sectional view showing an eighth embodiment of a semiconductor laser according to the present invention.

FIG. 22 is a sectional view showing a ninth embodiment of a semiconductor laser according to the present invention.

FIG. 23 is a sectional view showing a tenth embodiment of a semiconductor laser according to the present invention.

FIG. 24 is a plan view showing an eleventh embodiment of a semiconductor laser according to the present invention.

FIG. 25 is a perspective view showing a twelfth embodiment of a semiconductor laser according to the present invention.

FIG. 26 is a perspective view showing a thirteenth embodiment of a semiconductor laser according to the present invention.

FIG. 27 is a perspective view showing a fourteenth embodiment of a semiconductor laser according to the present invention.

FIG. 28 is a perspective view showing a fifteenth embodiment of a semiconductor laser according to the present invention.

FIG. 29 is a perspective view showing a sixteenth embodiment of a semiconductor laser according to the present invention.

FIG. 30 is a perspective view showing a seventeenth embodiment of a semiconductor laser according to the present invention.

FIG. 31 is a perspective view showing an eighteenth embodiment of a semiconductor laser according to the present invention.

FIG. 32 is a perspective view showing a nineteenth embodiment of a semiconductor laser according to the present invention.

FIG. 33 is a sectional view showing a configuration example of a conventional self-excited oscillation type semiconductor laser.

34 is a schematic diagram showing a refractive index distribution of the self-excited oscillation type semiconductor laser shown in FIG.

FIG. 35 is a schematic diagram showing the relationship between the gain width and the light spot width of a conventional self-pulsation semiconductor laser.

FIG. 36 is a perspective view showing a configuration example of a conventional gain guide type semiconductor laser.

FIG. 37 is a plan view showing a configuration example of a conventional gain guide type semiconductor laser.

FIG. 38 is a sectional view showing a configuration example of a conventional gain guide type semiconductor laser.

[Explanation of symbols]

100, 100A to 100S ... Semiconductor laser, 101 ...
n-type GaAs substrate, 102 ... buffer layer, 103 ... n-type AlGaAs cladding layer, 104 ... AlGaAs active layer, 105, 105a to 105d ... p-type AlGaAs cladding layer, 106 ... p-type GaAs cap layer, 106
a, 106b ... High resistance layer, 107 ... Stripe portion, 1
08a, 108b ... Sidewall ridge portion, 109a
... 109c ... p-side optical guide layer (etching stop layer), 110a, 110b ... groove part, 111 ... p-side electrode,
112 ... N-side electrode, 113 ... SiO ₂ insulating film, 114 ...
Polyimide layer, 115 ... N-side light guide layer.

Continued front page    F-term (reference) 5D119 AA12 AA33 BA01 FA05 FA17                       HA38 NA04                 5F073 AA13 AA45 AA53 AA86 BA06                       CA05 CB02 DA05 DA22 EA01                       EA13 EA19

Claims (23)

[Claims] 1. A first conductivity type first cladding layer, an active layer formed on the first cladding layer, and a second conductivity type second cladding layer formed on the active layer. And a central portion and both side portions of the second cladding layer having a ridge structure and a stripe-shaped current injection structure, wherein a groove portion formed between the ridge structure portions is formed. An optical guide layer having a refractive index higher than that of the second cladding layer is formed at the bottom of each ridge structure except the bottom, and the width of the ridge separation portion is different between the central portion in the stripe direction and near the end face. Laser that is set to. 2. The semiconductor laser according to claim 1, wherein the width of the ridge separation portion is set to be narrower in the central portion in the stripe direction and wider than the central portion in the vicinity of at least one end face. 3. The semiconductor laser according to claim 1, wherein the width of the ridge separation portion is set so that a narrow portion and a wide portion are alternately repeated in the stripe direction. 4. The semiconductor laser according to claim 1, wherein the width of the waveguide stripe in the center is constant. 5. The semiconductor laser according to claim 1, wherein the width of the waveguide stripe in the center is set to be narrower in the central portion in the stripe direction and wider than the central portion in the vicinity of at least one end face. 6. The semiconductor laser according to claim 1, wherein the width of the waveguide stripe in the center is set to be wide at the central portion in the stripe direction and narrower than the central portion in the vicinity of at least one end face. 7. A second ridge structure for forming the central ridge structure
2. The semiconductor laser according to claim 1, wherein an insulating film is formed on at least a part of the upper surface of the second cladding layer except the upper surface of the cladding layer. 8. The semiconductor laser according to claim 1, wherein a groove formed between the ridge structure portions is filled with an insulating material. 9. A second structure for forming the central ridge structure
2. The semiconductor laser according to claim 1, wherein a current-injection cap layer is formed on an upper surface of the clad layer and a part of an upper surface of the second clad layer forming the ridge structure portions on both sides. 10. A current injection cap layer is formed on the upper surface of the second cladding layer forming the central ridge structure, and an upper surface of the second cladding layer forming upper ridge structure portions is formed. 2. The semiconductor laser according to claim 1, wherein a high resistance layer is formed on a part of the upper surface of the second cladding layer which partially forms the second ridge structure portion. 11. The semiconductor laser according to claim 1, wherein the first cladding layer includes a layer having a refractive index higher than that of the first cladding layer. 12. A first conductivity type first cladding layer, an active layer formed on the first cladding layer, and a second conductivity type second cladding layer formed on the active layer. And a central portion and both side portions of the second cladding layer having a ridge structure and a stripe-shaped current injection structure, wherein the central portion of the second cladding layer is And when forming the ridge structure portions on both sides, an etching stop layer is formed on the second cladding layer at a predetermined distance from the active layer, and the step of forming the ridge structure portion is performed by the second step. A first step of selectively forming an etching protection layer on the clad layer, a second step of etching the second clad layer up to the vicinity of the etching stop layer by the first etchant, and a second step of etching by the second etchant. Third step and method of manufacturing a semiconductor laser and a fourth step of etching off the quenching stop layer exposed by the third etchant for etching up to the second cladding layer to the etching stop layer. 13. The second cladding layer is AlGaA.
In the second step, non-selective etching is performed using a hydrochloric acid / hydrogen peroxide solution / water-based first etchant, and in the third step, AlGaAs is used using a hydrofluoric acid / ammonium fluoride-based second etchant. Selective etching is performed, and in the fourth step, phosphoric acid / hydrogen peroxide water / water-based third
The non-selective etching is performed by the etchant of claim 1.
2. The method for manufacturing a semiconductor laser described in 2. 14. A cap layer is formed on an upper surface of the second clad layer, and a cap layer remaining in a region where the second clad layer is removed by the etching is formed after the third step. , 4th
13. The method for manufacturing a semiconductor laser according to claim 12, further comprising a fifth step of removing with an etchant. 15. A cap layer is formed on an upper surface of the second clad layer, and a cap layer remaining in a region where the second clad layer is removed by the etching after the third step is formed. , 4th
14. The method of manufacturing a semiconductor laser according to claim 13, further comprising a fifth step of removing the GaAs by an etchant, wherein in the fifth step, GaAs selective etching is performed by a fourth etchant of an aqueous ammonia / hydrogen peroxide solution system. 16. The method of manufacturing a semiconductor laser according to claim 12, further comprising the step of diffusing predetermined ions into a region to be a stripe portion to insulate a region other than the stripe. 17. The method of manufacturing a semiconductor laser according to claim 12, further comprising a step of diffusing predetermined ions into a region to be a stripe portion to insulate a region other than the stripe. 18. The method of manufacturing a semiconductor laser according to claim 14, further comprising a step of diffusing predetermined ions into a region to be a stripe portion to insulate a region other than the stripe. 19. The method of manufacturing a semiconductor laser according to claim 15, further comprising a step of diffusing predetermined ions into a region to be a stripe portion to insulate a region other than the stripe. 20. The method for manufacturing a semiconductor laser according to claim 16, wherein the diffusion step is performed before forming the ridge structure portion. 21. The method of manufacturing a semiconductor laser according to claim 17, wherein the diffusion step is performed before forming the ridge structure portion. 22. The method for manufacturing a semiconductor laser according to claim 18, wherein the diffusion step is performed before forming the ridge structure portion. 23. The method of manufacturing a semiconductor laser according to claim 19, wherein the diffusion step is performed before forming the ridge structure portion.