JPH11177180A - Self-excited oscillation type semiconductor laser and method of its operation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a self-excited excitation type semiconductor laser and a method for operating the same, by which range of operating conditions permitting self-excited oscillation can be enlarged, and self-excited oscillation exhibiting a high stability and reliability with respect to change in operating conditions can be realized, by controlling the expansion of current in horizontal direction by a simple method. SOLUTION: An AlGaAs base self-excited oscillation type semiconductor laser has a current narrowing structure which is formed by burying an n type current narrowing layer 10 on both sides of a ridge stripe part disposed on the upper layer of a p type cladding layer. A p side electrode 12 is disposed on a p type GaAs cap layer 11. An n side electrode 14 is disposed on the rear side of an n type GaAs substrate. An electrode 13 electrically separated from the p side electrode 12 and the n side electrode 14 is disposed on a specified part of the n type current narrowing layer 10. At the time of operation, a specified positive voltage is applied to the n type current narrowing layer 10 through the electrode 13 independently of the voltage for laser driving.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a self-pulsation type semiconductor laser and an operation method thereof.

[0002]

2. Description of the Related Art In applying a semiconductor laser as a light source for an optical disk recording / reproducing apparatus, it is important to suppress return light noise. As one of measures for suppressing the return light noise, a so-called self-excited oscillation type semiconductor laser in which a multi-mode is achieved by self-oscillating the semiconductor laser has been known.

Conventionally, in such a self-pulsation type semiconductor laser, for example, an n-type cladding layer, an active layer and a p-type cladding layer are sequentially laminated on an n-type GaAs substrate. It has a current confinement structure in which an n-type current confinement layer is embedded in both sides of a stripe portion provided in an upper layer portion, and a difference in refractive index between a portion corresponding to the stripe portion and portions on both sides of the current portion is a normal index. The size is smaller than that of the guide type semiconductor laser, and light confinement in the lateral direction is moderated. In operation, self-excited oscillation is realized by allowing portions corresponding to both sides of the stripe portion in the active layer to act as saturable absorbers.

[0004]

However, in the conventional self-pulsation type semiconductor laser, when the operating conditions change, specifically, for example, when the operating temperature rises to a high temperature of about 70 ° C., the n-type current is reduced. The blocking rate of the current by the narrowing layer is lower than that at the time of operation at room temperature, so that the carriers pass through the n-type current narrowing layer, and the carriers spread in the lateral direction (perpendicular to the cavity length direction and parallel to the junction). In the active layer, the proper state of the light distribution and the carrier distribution is destroyed, and the portion that has been acting as a saturable absorber cannot play its role, and the self-sustained pulsation stops. . As described above, in the conventional self-pulsation type semiconductor laser, the operating conditions under which self-pulsation can be performed are limited to a narrow range, and the stability and reliability of the self-pulsation oscillation with respect to changes in the operating conditions are lacking. there were.

By the way, as a method of suppressing the spread of current in the lateral direction due to an increase in operating temperature or the like, when manufacturing a self-pulsation type semiconductor laser, the thickness and impurity concentration of an n-type current confinement layer, or the p-type It is conceivable to control the thickness of the cladding layer (particularly, the thickness on both sides of the stripe portion) and the impurity concentration, but none of them is perfect and has limitations. Specifically, for example, in order to suppress the spread of current in the lateral direction, it is effective to reduce the thickness of the p-type cladding layer on both sides of the stripe portion. It is difficult to strictly control the thickness of the portion, and there are inconveniences such as a decrease in the margin for self-sustained pulsation and a change in other parameters of the laser.

Therefore, an object of the present invention is to control the spread of current in the lateral direction by a simple method,
The range of operating conditions that enable self-oscillation can be widened,
Moreover, it is an object of the present invention to provide a self-pulsation type semiconductor laser capable of realizing self-pulsation with high stability and reliability against changes in operating conditions, and a method of operating the same.

[0007]

To achieve the above object, a first aspect of the present invention is to provide a first conductive type first cladding layer, an active layer on the first cladding layer, A second cladding layer of a second conductivity type on the second layer, and a current confinement structure in which a current confinement layer is embedded in portions on both sides of a stripe portion provided in an upper layer portion of the second cladding layer. The excitation oscillation type semiconductor laser is characterized in that an electrode electrically separated from a laser driving electrode is connected to the current confinement layer.

According to a second aspect of the present invention, there is provided a first conductive type first cladding layer, an active layer on the first cladding layer, and a second conductive type second cladding layer on the active layer. A current confinement layer having a stripe-shaped opening on the second cladding layer;
In a self-pulsation type semiconductor laser having a second conductive type third cladding layer provided on the second cladding layer in a portion of an opening of the current confinement layer, the current confinement layer is electrically connected to a laser driving electrode. Characterized in that electrically separated electrodes are connected.

According to a third aspect of the present invention, there is provided a first conductive type first cladding layer, an active layer on the first cladding layer, and a second conductive type second cladding layer on the active layer. And the second
A current confinement structure in which a current confinement layer is embedded on both sides of a stripe portion provided in an upper layer portion of the cladding layer, and an electrode electrically separated from a laser driving electrode is connected to the current confinement layer A method of operating a self-sustained pulsation type semiconductor laser, comprising applying a laser driving voltage to a laser driving electrode from the outside and independently of the laser driving voltage through an electrode to a current confinement layer. The present invention is characterized in that a predetermined voltage is applied.

In a fourth aspect of the present invention, there is provided a first conductive type first cladding layer, an active layer on the first cladding layer, and a second conductive type second cladding layer on the active layer. A current confinement layer having a stripe-shaped opening on the second cladding layer;
An electrode electrically separated from the laser driving electrode, the third electrode having a second conductivity type third cladding layer provided on the second cladding layer in the opening portion of the current confinement layer. Is a method of operating a self-pulsation type semiconductor laser to which a laser driving voltage is externally applied to a laser driving electrode and a laser driving voltage is applied to the current confinement layer through the electrode. It is characterized in that a predetermined voltage is applied independently.

In the present invention, the current confinement layer is typically of the first conductivity type. However, in some cases, the current confinement layer may be of an insulating or semi-insulating type.

In the third and fourth aspects of the present invention, the voltage applied to the current confinement layer is controlled according to the operating conditions of the self-pulsation type semiconductor laser, such as the operating temperature. You may.

In the third aspect of the present invention, when the second cladding layer is a p-type cladding layer and the conductivity type of the current confinement layer is n-type, a positive voltage is applied to the current confinement layer. If the second cladding layer is a p-type cladding layer and the current confinement layer is insulating or semi-insulating, a negative voltage is applied to this current confinement layer. On the other hand, in the third aspect of the present invention, when the second cladding layer is an n-type cladding layer and the conductivity type of the current confinement layer is p-type, a negative voltage is applied to the current confinement layer, The second cladding layer is n
In the case where the current confinement layer in the mold cladding layer is insulating or semi-insulating, a positive voltage is applied to this current confinement layer.

In a fourth aspect of the present invention, when the second and third cladding layers are p-type cladding layers and the conductivity type of the current confinement layer is n-type, the current confinement layer is When a positive voltage is applied and the second and third cladding layers are p-type cladding layers and the current confinement layer is insulating or semi-insulating, a negative voltage is applied to the current confinement layer. Apply voltage. On the other hand, in the fourth invention of the present invention, when the second cladding layer and the third cladding layer are n-type cladding layers and the conductivity type of the current confinement layer is p-type, the current confinement layer is negative. Voltage of the second
If the cladding layer and the third cladding layer are n-type cladding layers and the current confinement layer is insulating or semi-insulating, a positive voltage is applied to the current confinement layer.

According to the present invention configured as described above, since the electrode that is electrically separated from the laser driving electrode is connected to the current confinement layer, the current can flow through this electrode during operation. A predetermined voltage can be externally applied to the constriction layer independently of the laser driving voltage. By applying a predetermined voltage to the current confinement layer as described above, fixed charges are generated in the current confinement layer, and further, an electrostatic induction effect due to the fixed charges generated in the current confinement layer. As a result, fixed charges having opposite polarities are generated in the second clad layer or in both the second clad layer and the third clad layer. Get focused. For this reason, even if the operating conditions change, the spread of carriers injected into the active layer in the horizontal direction is suppressed, and as a result, the portions corresponding to both sides of the stripe portion in the active layer can be removed. The saturated absorption region is formed stably, and for example, when the operating temperature is high, self-excited oscillation can be performed under severe operating conditions in which self-excited oscillation was conventionally impossible.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

First, a first embodiment of the present invention will be described. FIG. 1 shows an AlGa according to the first embodiment.
1 shows an As-based self-pulsation type semiconductor laser. This AlGaAs
The s-based self-oscillation type semiconductor laser is SCH (Separate Confi
The active layer has a multiple quantum well (MQW) structure.

As shown in FIG. 1, in the AlGaAs-based self-pulsation type semiconductor laser according to the first embodiment, for example, an n-type Al _x2 Ga
N-type Al _x1 Ga _1-x1 A via _1-x2 As buffer layer 2
s cladding layer 3, n-type Al _x2 Ga _1-x2 As optical waveguide layer 4,
An active layer 5 having an MQW structure using a non-doped Al _x3 Ga _1-x3 As layer as a quantum well layer, a p-type Al _x2 Ga _1-x2 As optical waveguide layer 6, a p-type Al _x1 Ga _1-x1 As clad layer 7, Non-doped Al _x2 Ga _1-x2 As optical waveguide layer 8 and p-type Al _x1 G
a _1-x1 As clad layer 9 is sequentially laminated.

The Al _x2 Ga _1-x2 As optical waveguide layer 8 and the p-type Al _x1 Ga _1-x1 As clad layer 9 have a ridge stripe shape of a predetermined width extending in one direction. On both sides of the ridge stripe portion, for example, n-type Al _x1 Ga _1-x1
As clad layer 10a and n-type GaAs layer 10 thereon
The n-type current confinement layer 10 of FIG.
In this case, the n-type current confinement layer 10 is provided on the entire surface including the portion on the ridge stripe portion, and has a predetermined width reaching the p-type Al _x1 Ga _1-x1 As clad layer 9 at a predetermined portion on the ridge stripe portion. Has a stripe-shaped opening 10c. Here, of the n-type current confinement layer 10, the upper n-type G
The aAs layer 10b has a role of improving contact with an electrode (described later) provided thereon.

[0020] p-type in the portion of the n-type current blocking layer 10 and the opening 10c, except a portion of the lateral ends Al _x1 Ga
_A p-type GaAs cap layer 11 is provided on the _1-x1 As clad layer 9 so as to fill the opening 10c.

Here, the n-type Al _x1 Ga _1-x1 As clad layer 3, the p-type Al _x1 Ga _1-x1 As clad layer 7, the p-type Al
_x1 Ga1 _-x1 As clad layer 9 and n-type _Alx1 Ga1 _-x1
X1 in the As layer 10a is n-type Al _x2 Ga _1-x2 As
Buffer layer 2, n-type Al _x2 Ga _1-x2 As optical waveguide layer 4, p
Type Al _x2 Ga _1-x2 As optical waveguide layer 6 and Al _x2 Ga _1-x2
It is made larger than x2 in the As optical waveguide layer 8, and this x2 is Al _x3 Ga as the quantum well layer of the active layer 5.
_1-x3 It is made larger than _{x3 in the} As layer. That is, x1>x2> x3. For example, x1 = 0.47, x2 = 0.3, x3
= 0.13.

In this AlGaAs-based self-pulsation type semiconductor laser, Al _x2 G is provided between the p-type Al _x1 Ga _1-x1 As clad layer 7 and the p-type Al _x1 Ga _1-x1 As clad layer 9.
a _1-x2 As optical waveguide layer 8 is inserted,
A step-like refractive index distribution is created in the lateral direction, and thereby, the optical waveguide in the lateral direction is performed,
In this case, the difference in the refractive index between the high refractive index portion in the ridge stripe portion and the low refractive index portion on both sides of the ridge stripe portion is smaller than that in the case of an ordinary index guide type semiconductor laser, and confinement of light in the lateral direction is suppressed. Has been moderate.

Further, as an example of the thickness of each semiconductor layer constituting this AlGaAs-based self-pulsation type semiconductor laser, the thickness of the n-type Al _x2 Ga _{1 -x2} As buffer layer 2 is 1 μm.
The thickness of the m, n-type Al _x1 Ga _1-x1 As clad layer 3 is 1.
5 μm, n-type Al _x2 Ga _1-x2 As optical waveguide layer 4, p-type Al
_The thicknesses of the _x2 Ga1 _-x2 As optical waveguide layer 6 and the _Alx2 Ga1 _-x2 As optical waveguide layer 8 are each 70 nm, and the p-type _Alx1 Ga
The thickness of the _1-x1 As cladding layer 7 is 0.35 μm, p-type Al
The thickness of the _x1 Ga _{1 -x1} As clad layer 9 is 1.3 μm, and the n-type Al _x1 Ga _{1 -x1} As layer 10 of the n-type current confinement layer 10.
a has a thickness of 0.8 μm, the n-type GaAs layer 10 b has a thickness of 0.5 μm, and the p-type GaAs cap layer 11 has a thickness of 1.0 μm.
5 μm.

On the p-type GaAs cap layer 11, a p-side electrode 12 such as a Ti / Pt / Au electrode is provided in ohmic contact. At both ends in the lateral direction, predetermined portions on the n-type current confinement layer 10 not covered with the p-type GaAs cap layer 11 are, for example, Au.
An electrode 13 such as a Ge / Ni electrode is used for the n-type GaAs layer 1.
0b is provided in ohmic contact. On the other hand, on the back surface of the n-type GaAs substrate 1, for example, AuGe /
An n-side electrode 14 such as a Ni electrode is provided in ohmic contact. As described above, in this AlGaAs-based self-pulsation type semiconductor laser, the n-type current confinement layer 1
Since the electrode 13 separated from the p-side electrode 12 and the n-side electrode 14 is provided on 0, the n-type current confinement layer 10 is externally applied to the n-type current confinement layer 10 through the electrode 13 independently of the laser driving voltage. Can be applied with a predetermined voltage.

Next, the AlG having the above-described structure is used.
The operation of the aAs-based self-pulsation type semiconductor laser will be described.

That is, when oscillating this AlGaAs-based self-excited oscillation type semiconductor laser, for example, the p-side electrode 1
2, a positive voltage of about 2 to 3 V is applied, and the n-side electrode 14 is grounded. Here, the operation in the case where the operating temperature is about room temperature and no voltage is applied to the electrode 13 will be described first.
In this case, as shown in FIG. 2, a current (here, n-type Al _x1 Ga _{1 -x1} A
The electron e ⁻ injected from the s cladding layer 3 side)
While the light spreads substantially to the portion corresponding to the ridge stripe portion, the light spreads beyond the portion corresponding to the ridge stripe portion due to the gradual confinement in the lateral direction. The saturable absorption regions 15 are formed in portions corresponding to both sides of the ridge stripe portion. Therefore, when the operating temperature is about room temperature, the saturable absorption region 15 is formed in the active layer 5 as described above, so that the AlGaAs-based self-excited oscillation can be performed without applying a voltage to the electrode 13. The type semiconductor laser oscillates by itself.

On the other hand, when the operating temperature rises from room temperature to a high temperature of, for example, about 70 ° C., if no voltage is applied to the electrode 13, the current rejection rate of the n-type current confinement layer 10 is reduced. Lower than at room temperature operation,
In the active layer 5, the current spread in the lateral direction is larger than that at the time of the room temperature operation, and carriers are injected into the portion where the saturable absorption region 15 was formed at the time of the room temperature operation. Oscillation stops. Therefore, this Al
In the GaAs-based self-pulsation type semiconductor laser, when the operating temperature rises, a predetermined positive voltage is applied to the n-type current confinement layer 10 through the electrode 13 independently of the laser driving voltage, and the operation is started. The current is prevented from spreading in the horizontal direction due to a rise in temperature.

When a positive voltage is applied to the n-type current confinement layer 10 through the electrode 13, electrons are attracted to the electrode 13 side in the n-type current confinement layer 10 as shown in FIG. A positive (+) fixed charge due to the n-type impurity is left. On the other hand, the p-type Al _x1 Ga _1-x1 As cladding layer 7 near the junction with the n-type current confinement layer 10
Al _x1 Ga _{1 -x1} As clad layer 9 and p-type GaAs
In the cap layer 11, holes are repelled by the static induction effect of the positive (+) fixed charges generated in the n-type current confinement layer 10, and as a result, negative (-) fixed charges are generated by the p-type impurities. I do. Therefore, of the carriers, the electrons e ⁻ are _{supplied to} the p-type Al _x1 Ga _1-x1 As clad layer 7, the p-type Al _x1 Ga _1-x1 As clad layer 9 and the p _- type Al _x1 Ga _1-x1 As clad layer 9.
(-) Generated in the GaAs type cap layer 11
Is repelled by the influence of the fixed charge of the ridge stripe, and is concentrated at the center of the ridge stripe portion, and a hole (not shown)
It is repelled by the influence of the fixed charges plus that occurred in the n-type current confinement layer 10 (+), electrons e ^- so concentrated as well in the middle of the ridge stripe portion in the case of.

As described above, in the AlGaAs-based self-pulsation type semiconductor laser, by applying a predetermined positive voltage to the n-type current confinement layer 10, even if the operating temperature rises, the current is reduced. Saturable absorption region 15 is formed in the portion corresponding to both sides of the ridge stripe portion in active layer 5 as in the case of operation at room temperature, and stable self-pulsation can be performed. Become. In the case of the AlGaAs-based self-pulsation type semiconductor laser, when the operating temperature is 70 ° C., 5 to 10
By applying a positive voltage of about V, self-excited oscillation up to an output of about 5 mW is possible.

When this AlGaAs-based self-excited oscillation type semiconductor laser is used as a light source of, for example, an optical disk recording / reproducing apparatus, the n-type current confinement layer 10 is passed through the electrode 13 during reproduction when self-excited oscillation is required. And a self-excited oscillation of the AlGaAs-based self-oscillation type semiconductor laser is performed at an output of, for example, 5 mW. At this time, the operating temperature of the AlGaAs-based self-excited oscillation semiconductor laser is constantly monitored using a combination of, for example, a temperature sensor and a microprocessor.
Is controlled according to the operating temperature (specifically, as the operating temperature increases, the n-type current confinement layer 10
Is controlled so as to increase the voltage applied to the AlGaAs-based self-pulsation type semiconductor laser.
It is also possible to cause self-sustained pulsation in a substantially constant state irrespective of a change in operating temperature. On the other hand, at the time of recording, since it is not necessary to perform the self-sustained pulsation operation, the application of the voltage to the n-type current confinement layer 10 is stopped, and the AlGaAs-based self-sustained pulsation semiconductor laser is operated at a high output of, for example, 20 to 30 mW. Output operation.

Next, the first device configured as described above is used.
A method for manufacturing an AlGaAs-based self-excited oscillation semiconductor laser according to the embodiment will be described.

That is, in order to manufacture the AlGaAs-based self-pulsation type semiconductor laser, first, as shown in FIG. 4, an n-type Al _x2 Ga _1-x2 As is formed on an n-type GaAs substrate 1.
Buffer layer 2, n-type Al _x1 Ga _1-x1 As clad layer 3,
n-type Al _x2 Ga _1-x2 As optical waveguide layer 4, MQW structure active layer 5, p-type Al _x2 Ga _1-x2 As optical waveguide layer 6, p-type Al _x1
The Ga1 _-x1As clad layer 7, the _{Alx2Ga1 -x2As} optical waveguide layer 8, and the p-type _{Alx1Ga1 -x1As} clad layer 9 are sequentially grown by, for example, MOCVD.

Next, an SiO ₂ film or a SiN film is formed on the entire surface of the p-type Al _x1 Ga _1-x1 As clad layer 9 by, for example, the CVD method, and is patterned by etching to form a stripe-shaped mask having a predetermined width. (Not shown), and using this mask as an etching mask, etching is performed by a wet etching method until the surface of the p-type Al _x1 Ga _1-x1 As clad layer 6 is exposed. Thereby, as shown in FIG. 5, the Al _x2 Ga _1-x2 As optical waveguide layer 8 and the p-type Al _x1 Ga _1-x1 As clad layer 9 are patterned into a ridge stripe shape having a predetermined width extending in one direction. . After that, the mask used as the etching mask is removed.

[0034] Next, as shown in FIG. 6, the n-type Al _x1 Ga _1-x1 As layer 10a and the n-type GaAs layer 10b of the n-type current confinement layer 10 on the entire surface, for example, are successively grown by MOCVD. Next, by selectively etching the n-type current confinement layer 10 in a predetermined portion on the ridge stripe portion, an opening 10c is formed in this portion. Next, a p-type GaAs cap layer 11 is formed on the entire surface so as to fill the opening 10c of the n-type current confinement layer 10 by, for example, M
It is grown by OCVD.

Next, as shown in FIG. 7, a p-side electrode 12 is formed on the entire surface of the p-type GaAs cap layer 11.

Next, for example, CVD is performed on the entire surface of the p-side electrode 12.
After a SiO ₂ film or a SiN film is formed by a method, it is patterned by etching to cover a portion corresponding to the vicinity of the ridge stripe portion, and has a mask of a predetermined shape having openings at a part of both ends in the lateral direction (FIG. (Not shown).
Next, by using this mask as an etching mask, etching is performed until the surface of the n-type current confinement layer 10 is exposed, thereby forming the p-type GaAs cap layer 11 as shown in FIG.
Then, the p-side electrode 12 is patterned into a predetermined shape.

Next, a portion excluding a predetermined portion on the n-type current confinement layer 10 exposed at both ends in the lateral direction is covered with a resist pattern (not shown), and an AuGe / Ni film is formed on the entire surface. AuGe / N on the pattern
By removing (lifting off) together with the i film, FIG.
As shown in (1), an electrode 13 is formed at a predetermined portion on the n-type current confinement layer 10.

Next, the n-type GaAs substrate 1 is wrapped from its back surface to a predetermined thickness. Thereafter, as shown in FIG. 1, an n-side electrode 14 is formed on the back surface of the n-type GaAs substrate 1. As described above, the target A
An lGaAs-based self-excited oscillation semiconductor laser is manufactured.

As described above, according to the first embodiment, the electrode 13 that is electrically separated from the p-side electrode 12 and the n-side electrode 14 is connected to the n-type current confinement layer 10, and during operation, By applying a predetermined positive voltage to the n-type current confinement layer 10 through the electrode 13 independently of the laser driving voltage, the operating conditions change, for example, when the operating temperature rises. Even if you do
The spread of carriers injected into the active layer 5 in the lateral direction can be suppressed. For this reason, according to the first embodiment, the range of operating conditions under which the self-sustained pulsation of the AlGaAs-based self-sustained pulsation semiconductor laser can be broadened as compared with the related art, and the n-type current confinement layer can be formed. By controlling the voltage applied to 10 according to the operating conditions, the state of self-oscillation can be maintained even when the operating conditions change. In addition, the reliability can be improved.

Further, according to the first embodiment, the self-excited oscillation operation is controlled and maintained by a simple method of applying a positive voltage to the n-type current confinement layer 10 during operation. As a result, as compared with the structure of a normal self-pulsation type semiconductor laser, only the connection of the electrode 13 to the n-type current confinement layer 10 is required.
Since the margin for the self-excited oscillation can be increased, manufacturing is easy, and the control of the self-excited oscillation operation is as follows.
Since this is realized only by suppressing the spread of the current flowing in the element in the lateral direction, there is also an advantage that the degree of freedom in designing other laser characteristics is increased.

Next, a second embodiment of the present invention will be described. FIG. 10 shows the AlG according to the second embodiment.
FIG. 2 is a sectional view of an aAs-based self-pulsation type semiconductor laser. This AlGaAs-based self-pulsating semiconductor laser has an SCH structure, and the active layer has an MQW structure.

As shown in FIG. 10, in the AlGaAs-based self-pulsation type semiconductor laser according to the second embodiment, for example, an n-type Al _x2 Ga
N-type Al _x1 Ga _1-x1 via _1-x2 As buffer layer 22
As cladding layer 23, n-type Al _x2 Ga _1-x2 As optical waveguide layer 24, active layer 25 of MQW structure using non-doped Al _x3 Ga _1-x3 As layer as a quantum well layer, p-type Al _x2 Ga _1-x2 A
The s optical waveguide layer 26 and the p-type Al _x1 Ga _1-x1 As clad layer 27 are sequentially laminated.

On the p-type Al _x1 Ga _1-x1 As clad layer 27, for example, an n-type Al _x1 Ga _1-x1 As clad layer 28a
And an n-type GaAs layer 28b thereon, and an n-type current confinement layer 28 having a stripe-shaped opening 28c of a predetermined width extending in one direction is laminated. A non-doped Al _x2 Ga _1-x2 As optical waveguide layer is provided on the p-type Al _x1 Ga _1-x1 As clad layer 27 at the portion of the n-type current confinement layer 28 and the opening 28c except for a part of both ends in the lateral direction. A p-type Al _x1 Ga _1-x1 As clad layer 30 is laminated through the intervening layer 29. On the p-type Al _x1 Ga _1-x1 As clad layer 30, a p-type GaAs cap layer 31 is provided.

Here, the n-type Al _x1 Ga _1-x1 As clad layer 23, the p-type Al _x1 Ga _1-x1 As clad layer 27, the n-type Al _x1 Ga _1-x1 As layer 28a and the p-type Al _x1 Ga _{1 -x1}
X1 in the As cladding layer 30 is n-type Al _x2 Ga
_{From x2 in the 1-x2} As buffer layer 22, the n-type _{Alx2Ga1 -x2As} optical waveguide layer 24, the p-type _{Alx2Ga1 -x2As} optical waveguide layer 26, and the _{Alx2Ga1 -x2As} optical waveguide layer 29. The value x2 is larger than the value _{x3 in} the Al _x3 Ga _1-x3 As layer as the quantum well layer of the active layer 25. That is, x1>x2> x3. For example, x1 = 0.47, x
2 = 0.3 and x3 = 0.13.

In this AlGaAs-based self-pulsation type semiconductor laser, the p-type Al _x1 Ga _1-x1
Since the Al _x2 Ga _1-x2 As optical waveguide layer 29 is inserted between the As cladding layer 27 and the p-type Al _x1 Ga _1-x1 As cladding layer 30, a step-like refractive index distribution is formed in the lateral direction. Built-in, which provides lateral light guiding. In this case, the difference in the refractive index between the high-refractive-index portion in the ridge stripe portion and the low-refractive-index portions on both sides of the ridge stripe portion is smaller than that in the case of a typical index guide type semiconductor laser, and the light in the lateral direction is reduced. The confinement has been loosened.

As an example of the thickness of each semiconductor layer constituting the AlGaAs-based self-pulsation type semiconductor laser, the thickness of the n-type Al _x2 Ga _{1 -x2} As buffer layer 22 is 1
μm, the thickness of the n-type Al _x1 Ga _1-x1 As cladding layer 23 is 1.5 μm, and the n-type Al _x2 Ga _1-x2 As optical waveguide layer 24, p
Type Al _x2 Ga _1-x2 As optical waveguide layer 26 and Al _x2 Ga
The thickness of the _1-x2 As optical waveguide layer 29 is 70 nm, and the thickness of the p-type Al _x1 Ga _1-x1 As clad layer 27 is 0.35 μm.
Of the m and n-type current confinement layers 28, n-type Al _x1 Ga _1-x1 A
The thickness of the s layer 28a is 0.4 μm, and the n-type GaAs layer 28b
Is 0.3 μm, the thickness of the p-type Al _x1 Ga _1-x1 As cladding layer 30 is 1 μm, and the thickness of the p-type GaAs cap layer 31 is 0.5 μm.

On the p-type GaAs cap layer 31, a p-side electrode 32 such as a Ti / Pt / Au electrode is provided in ohmic contact. At both ends in the lateral direction, the p-type GaAs cap layer 31 and the p-type Al _x1
Ga _1-x1 As clad layer 30 and Al _x2 Ga _1-x2 As
An electrode 33 such as an AuGe / Ni electrode is provided in a predetermined portion on the n-type current confinement layer 28 not covered with the optical waveguide layer 29 in ohmic contact with the n-type GaAs layer 28b. On the other hand, an n-side electrode 3 such as an AuGe / Ni electrode is
4 is provided in ohmic contact. As described above, in the AlGaAs-based self-pulsation type semiconductor laser, since the p-side electrode 32 and the electrode 33 separated from the n-side electrode 34 are provided on the n-type current confinement layer 28, Through this electrode 33, a predetermined voltage can be applied to the n-type current confinement layer 28 independently of the laser driving voltage.

The AlGaAs-based self-pulsating semiconductor laser according to the second embodiment configured as described above can perform the same operation as the AlGaAs-based self-pulsating semiconductor laser according to the first embodiment. .

Next, a method of manufacturing the AlGaAs-based self-pulsation type semiconductor laser according to the second embodiment having the above-described configuration will be described.

That is, in order to manufacture this AlGaAs-based self-excited oscillation semiconductor laser, first, as shown in FIG. 11, an n-type Al _x2 Ga _{1 -x2 is formed} on an n-type GaAs substrate 21.
As buffer layer 22, n-type Al _x1 Ga _1-x1 As clad layer 23, n-type Al _x2 Ga _1-x2 As optical waveguide layer 24, active layer 25, p-type Al _x2 Ga _1-x2 As optical waveguide layer 26, p-type Al
_x1 Ga _{1 -x1} As clad layer 27 and n-type current confinement layer 2
N-type Al _x1 Ga _1-x1 As layer 28a and n-type G
The aAs layer 28b is sequentially grown by, for example, the MOCVD method.

Next, on the n-type current confinement layer 28, SiO ₂
A mask (not shown) formed of a film, a SiN film, or the like and having a stripe-shaped opening of a predetermined width extending in one direction is formed. Next, using this mask as an etching mask, an n-type current confinement layer 28 is formed by wet etching.
Is selectively etched. As a result, as shown in FIG. 12, a striped opening 28c extending in one direction is formed in the n-type current confinement layer 28. Thereafter, the mask used for the etching is removed.

Next, as shown in FIG. 13, the opening 28c is buried in the entire surface of the n-type current confinement layer 28,
Al _x2 Ga _1-x2 As optical waveguide layer 29 and p-type Al _x1 Ga
_{The 1-x1} As clad layer 30 is sequentially grown by, for example, MOCVD, and a p-type GaAs cap layer 31 is formed, for example, by MOCVD on the entire surface of the p _- type Al _x1 Ga _1-x1 As clad layer 30.
Grow by the method.

Next, as shown in FIG.
A p-side electrode 32 is formed on the entire surface of the cap layer 31.

Next, for example, CVD is performed on the entire surface of the p-side electrode 32.
After a SiO ₂ film or a SiN film is formed by a method, it is patterned by etching to cover a portion corresponding to the vicinity of the ridge stripe portion, and has a mask of a predetermined shape having openings at a part of both ends in the lateral direction (FIG. (Not shown).
Next, by using this mask as an etching mask, etching is performed until the surface of the n-type current confinement layer 28 is exposed, so that the Al _x2 Ga _1-x2 As optical waveguide layer 29, the p-type Al _x1 The Ga _1-x1 As clad layer 30, the p-type GaAs cap layer 31, and the p-side electrode 32 are patterned into a predetermined shape.

Next, a portion excluding a predetermined portion on the n-type current confinement layer 28 exposed at both ends in the lateral direction is covered with a resist pattern (not shown), and an AuGe / Ni film is formed on the entire surface. AuGe / N on the pattern
By removing (lifting off) together with the i-film, FIG.
As shown in FIG. 6, an electrode 33 is formed at a predetermined portion on the n-type current confinement layer 28.

Next, the n-type GaAs substrate 21 is wrapped from the back surface to a predetermined thickness. Thereafter, as shown in FIG. 10, an n-side electrode 34 is formed on the back surface of the n-type GaAs substrate 21. As described above, the intended AlGaAs-based self-pulsation type semiconductor laser is manufactured.

According to the second embodiment, the same advantages as in the first embodiment can be obtained.

Next, a third embodiment of the present invention will be described. FIG. 17 shows an AlG according to the third embodiment.
FIG. 2 is a sectional view of an aAs-based self-pulsation type semiconductor laser. This AlGaAs-based self-pulsation type semiconductor laser is of a surface emitting type having a vertical resonator structure. In FIG.
The same or corresponding portions as those in FIG. 10 are denoted by the same reference numerals.

As shown in FIG. 17, in this AlGaAs-based self-pulsation type semiconductor laser, a laser structure is formed on an n-type GaAs substrate 21 via an n-type Al _x1 Ga _1-x1 As buffer layer 22. The semiconductor layers to be formed are stacked similarly to the AlGaAs-based self-pulsation type semiconductor laser according to the second embodiment. However, in this case, the n-type current confinement layer 28 includes an n-type GaAs layer 28d on the p-type Al _x1 Ga _1-x1 As clad layer 27 and an n-type Al _x2 Ga _1-x2 on the n-type GaAs layer 28d. And an As layer 28e. Here, of the n-type current confinement layer 28, the n-type GaAs layer 28d
Is 0.1 μm, for example. In addition, this AlGa
In an As-based self-excited oscillation type semiconductor laser, a reflecting mirror (not shown) is provided at a predetermined portion.
A resonator structure is formed in a direction perpendicular to the main surface of the aAs substrate 21, and a groove 21 a for extracting laser light is provided in a predetermined portion on the back surface side of the n-type GaAs substrate 21.

Further, in this AlGaAs-based self-pulsation type semiconductor laser, a p-type G
After stacking up to the aAs cap layer 31, etching is performed from the back side of the n-type GaAs substrate 21, so that the n-type GaAs of the n-type current confinement layer 28 is provided at both ends in the lateral direction.
The layer 28d is exposed. Therefore, in this case, the electrode 33 is formed of the p-type Al _x1 Ga
_1-x1 n-type G provided on the side in contact with As clad layer 27
It is in contact with the aAs layer 28d.

Here, _x1 in the n-type Al _x1 Ga _1-x1 As clad layer 23, the p-type Al _x1 Ga _1-x1 As clad layer 27 and the p-type Al _x1 Ga _1-x1 As clad layer 30.
_Are n-type Al _x2 Ga _1-x2 As buffer layer 22, n-type Al
_{x2Ga1 -x2As} optical waveguide layer 24, p-type _{Alx2Ga1 -x2As}
It is larger than x2 in the optical waveguide layer 26, the n-type Al _x2 Ga _1-x2 As layer 28e and the Al _x2 Ga _1-x2 As optical waveguide layer 29. It is greater than x3 in _x3 Ga _1-x3 As layer. That is, x1>x2> x3. For example, x1 = 0.47, x
2 = 0.3 and x3 = 0.13.

The other configuration of this AlGaAs-based self-pulsation type semiconductor laser is similar to that of the AlGaAs self-excited oscillation type semiconductor laser according to the second embodiment.
The description is omitted because it is the same as that of the s-system self-pulsation type semiconductor laser.

In this AlGaAs-based self-pulsation type semiconductor laser, a predetermined positive voltage is applied to the n-type current confinement layer 28 through the electrode 33 electrically separated from the p-side electrode 32 and the n-side electrode 34. By doing so, the same operation as the AlGaAs-based self-pulsation type semiconductor laser according to the first embodiment can be performed.

According to the third embodiment, the same advantages as in the first embodiment can be obtained in a surface-emitting type AlGaAs-based self-excited oscillation semiconductor laser having a vertical resonator structure.

Although the embodiments of the present invention have been specifically described above, the present invention is not limited to the above embodiments, and various modifications based on the technical concept of the present invention are possible. For example, the numerical values, materials, structures, and the like described in the embodiments are merely examples, and the present invention is not limited to these.

Specifically, the n-type current confinement layers 10 and 28 in the above-described first to third embodiments are each formed of an n-type Al _x1 Ga
_1-x1 As layers 10a, 28a and n-type GaAs layers 10b, 2
8b or an n-type GaAs layer 28d and n
It has a laminated structure with a type Al _x2 Ga ₁ -x2 As layer 28 e, which is made of, for example, a single-layer n-type AlGaAs.
It may be an s layer or an n-type GaAs layer.

In place of the n-type current confinement layers 10 and 28 in the first to third embodiments, an insulating or semi-insulating current confinement layer may be used. Specifically, for example, when the current confinement layer is made semi-insulating, a semi-insulating AlGaAs layer doped with Co or Fe or a GaAs
A current confinement layer is formed using the layer. In the first to third embodiments, when the current confinement layer is made of an insulating or semi-insulating material, a negative voltage is applied to the current confinement layer during operation. The operation principle at this time is the same as the operation principle described in the first embodiment. Specifically, for example, a case where a semi-insulating current confinement layer is used instead of the n-type current confinement layer 10 in the first embodiment will be described. By applying a negative voltage, a positive (+) charge is induced in a portion of the current confinement layer opposite to the electrode, while a p-type Al _x1 Ga near the junction with the current confinement layer is applied.
_{In the 1-x1} As clad layer 7, the p-type Al _x1 Ga _1-x1 As clad layer 9 and the p-type GaAs cap layer 11, the static induction effect due to the positive (+) fixed charge generated in the current confinement layer. As a result of the repulsion of the holes, a negative (-) fixed charge is generated. Therefore, of the carriers, the electrons e ⁻ are transferred to the p-type Al _x1 Ga _1-x1 As clad layer 7, the p-type Al _x1 Ga _1-x1 As clad layer 9, and the p-type G
It is repelled by the influence of the negative (-) fixed charge generated in the aAs cap layer 11 and is concentrated at the center of the ridge stripe portion, and a hole (not shown) is generated in the current constriction layer. The repulsion is caused by the influence of the fixed charge (+), and is concentrated at the center of the ridge stripe portion as in the case of the electron e ⁻ .

For example, in the first to third embodiments, the conductivity types of the substrate and each semiconductor layer may be reversed. In this case, as the current confinement layer, a p-type conductivity type or an insulating or semi-insulating type is used. When a p-type current confinement layer is used,
In operation, a negative voltage is applied to the p-type current confinement layer. When an insulating or semi-insulating current confinement layer is used, the insulating or semi-insulating current confinement layer is used in operation. Is applied with a positive voltage.

In the first to third embodiments,
Although the present invention has been described for the case where the present invention is applied to an AlGaAs-based self-pulsation type semiconductor laser having a SCH structure, the present invention relates to an AlGaAs having a DH (Double Heterostructure) structure.
It is also possible to apply to an s-system self-excited oscillation type semiconductor laser. Further, the active layer may have a structure other than the MQW structure.

Further, in the first to third embodiments, the case where the present invention is applied to an AlGaAs self-pulsation type semiconductor laser has been described.
In addition to GaAs self-excited oscillation type semiconductor lasers, AlGaI
nP-based self-pulsating semiconductor laser, self-pulsating semiconductor laser using II-VI compound semiconductor, and nitride-based I
It is also possible to apply to a self-pulsation type semiconductor laser using a II-V group compound semiconductor. Usually, II-V
In a self-pulsation type semiconductor laser using a group I compound semiconductor, Al ₂ O ₃ is used as a material of a current confinement layer, and a self-pulsation type semiconductor laser using a nitride group III-V compound semiconductor. In this case, SiO ₂ is used as the material of the current confinement layer. However, even when such an insulator is used as the material of the current confinement layer, the same effect as that described in the above embodiment is obtained. The effect of can be obtained.

The technical idea similar to that of the present invention can be applied to ordinary semiconductor lasers other than the self-pulsation type semiconductor laser. In this case, a predetermined current confinement layer is applied to the current confinement layer during operation of the semiconductor laser. By applying the above voltage, it is also possible to cause a normal semiconductor laser to perform a self-sustained pulsation operation. Further, when the lateral refractive index difference Δn is small and the light confinement is moderate as in a self-pulsation type semiconductor laser, the light spread in the lateral direction is caused by the injection of carriers into the active layer. Although hardly affected by the state, as in the case of an index guide type semiconductor laser, when the refractive index difference Δn in the lateral direction is larger than that of a self-pulsation type semiconductor laser and light confinement is enhanced, By applying a voltage to the current confinement layer to change the state of carrier injection into the active layer, it is possible to directly control the beam shape. Specifically, in this case, by applying a voltage to the current confinement layer, the spread of carriers in the active layer in the lateral direction is smaller than when no voltage is applied (the carrier injection region Becomes narrower), so that the beam spread angle θ // in the horizontal direction of the far-field image (FFP) can be increased.

[0072]

As described above, according to the present invention, since the electrode which is electrically separated from the laser driving electrode is connected to the current confinement layer, the current confinement is performed externally through the electrode during operation. By a simple method of applying a predetermined voltage to the layer independently of the laser driving voltage,
It is possible to control the self-pulsation oscillation, thereby providing a self-pulsation type semiconductor laser having a wide range of operating conditions in which self-pulsation can be performed, and having high stability and high reliability of self-pulsation with respect to changes in operation conditions. Can be realized.

[Brief description of the drawings]

FIG. 1 shows an AlGaAs according to a first embodiment of the present invention.
FIG. 3 is a cross-sectional view of an s-system self-excited oscillation type semiconductor laser.

FIG. 2 shows AlGaAs according to the first embodiment of the present invention.
FIG. 4 is a cross-sectional view for explaining the operation of the s-system self-pulsation type semiconductor laser.

FIG. 3 shows AlGaAs according to the first embodiment of the present invention.
FIG. 4 is a cross-sectional view for explaining the operation of the s-system self-pulsation type semiconductor laser.

FIG. 4 shows AlGaAs according to the first embodiment of the present invention.
FIG. 4 is a cross-sectional view for describing a method for manufacturing an s-system self-pulsation type semiconductor laser.

FIG. 5 shows AlGaAs according to the first embodiment of the present invention.
FIG. 4 is a cross-sectional view for describing a method for manufacturing an s-system self-pulsation type semiconductor laser.

FIG. 6 shows AlGaAs according to the first embodiment of the present invention.
FIG. 4 is a cross-sectional view for describing a method for manufacturing an s-system self-pulsation type semiconductor laser.

FIG. 7 shows AlGaAs according to the first embodiment of the present invention.
FIG. 4 is a cross-sectional view for describing a method for manufacturing an s-system self-pulsation type semiconductor laser.

FIG. 8 shows AlGaAs according to the first embodiment of the present invention.
FIG. 4 is a cross-sectional view for describing a method for manufacturing an s-system self-pulsation type semiconductor laser.

FIG. 9 shows an AlGaAs according to a second embodiment of the present invention.
FIG. 3 is a cross-sectional view of an s-system self-excited oscillation type semiconductor laser.

FIG. 10 shows an AlGa according to a second embodiment of the present invention.
It is sectional drawing for demonstrating the manufacturing method of an As-system self-excited oscillation type semiconductor laser.

FIG. 11 shows an AlGa according to a second embodiment of the present invention.
It is sectional drawing for demonstrating the manufacturing method of an As-system self-excited oscillation type semiconductor laser.

FIG. 12 shows an AlGa according to a second embodiment of the present invention.
It is sectional drawing for demonstrating the manufacturing method of an As-system self-excited oscillation type semiconductor laser.

FIG. 13 shows an AlGa according to a second embodiment of the present invention.
It is sectional drawing for demonstrating the manufacturing method of an As-system self-excited oscillation type semiconductor laser.

FIG. 14 shows an AlGa according to a second embodiment of the present invention.
It is sectional drawing for demonstrating the manufacturing method of an As-system self-excited oscillation type semiconductor laser.

FIG. 15 shows an AlGa according to a second embodiment of the present invention.
It is sectional drawing for demonstrating the manufacturing method of an As-system self-excited oscillation type semiconductor laser.

FIG. 16 shows an AlGa according to a second embodiment of the present invention.
It is sectional drawing for demonstrating the manufacturing method of an As-system self-excited oscillation type semiconductor laser.

FIG. 17 shows an AlGa according to a third embodiment of the present invention.
FIG. 2 is a sectional view of an As-based self-pulsation type semiconductor laser.

[Explanation of symbols]

1,21 ... n-type GaAs substrate, 3,23 ... n-type Al _x1 Ga _1-x1 As clad layer, 4,24 ... n-type A
1 _x2 Ga _1-x2 As optical waveguide layer, 5, 25... active layer,
6, 26... P-type Al _x2 Ga ₁ -x2 As optical waveguide layer, 7,
9,27,30 ··· p-type Al _x1 Ga _1-x1 As cladding _{layer, 8,29 ··· Al x2 Ga 1-} x2 As optical waveguide layer, 1
.., N-type current confinement layers, 10a, 28a,.
n-type Al _x1 Ga _1-x1 As layer, 10b, 28b, 28d
..N-type GaAs layer, 28e... N-type Al _x2 Ga _1-x2
As layer, 11, 31,... P-type GaAs cap layer, 1
2, 32 ... p-side electrode, 13, 33 ... electrode, 1
4, 34 ... n-side electrode

Claims (12)

[Claims] 1. A first cladding layer of a first conductivity type, an active layer on the first cladding layer, and a second cladding layer of a second conductivity type on the active layer, In a self-excited oscillation type semiconductor laser having a current confinement structure in which a current confinement layer is embedded on both sides of a stripe portion provided in an upper layer portion of a second clad layer, a laser drive electrode A self-sustained pulsation type semiconductor laser characterized by being connected to electrically separated electrodes. 2. The self-pulsation type semiconductor laser according to claim 1, wherein a conductivity type of said current confinement layer is a first conductivity type. 3. The self-pulsation type semiconductor laser according to claim 2, wherein said electrode is in ohmic contact with said current confinement layer. 4. The self-pulsation type semiconductor laser according to claim 1, wherein said current confinement layer is insulating or semi-insulating. 5. A first cladding layer of a first conductivity type; an active layer on the first cladding layer; a second cladding layer of a second conductivity type on the active layer; A current confinement layer having a stripe-shaped opening on the cladding layer; and a third cladding layer of the second conductivity type provided on the second cladding layer at the opening of the current confinement layer. A self-pulsation type semiconductor laser, wherein an electrode electrically separated from a laser driving electrode is connected to the current confinement layer. 6. The self-pulsation type semiconductor laser according to claim 5, wherein the conductivity type of the current confinement layer is a first conductivity type. 7. The self-pulsation type semiconductor laser according to claim 6, wherein said electrode is in ohmic contact with said current confinement layer. 8. The self-pulsation type semiconductor laser according to claim 5, wherein said current confinement layer is insulating or semi-insulating. 9. A semiconductor device, comprising: a first cladding layer of a first conductivity type; an active layer on the first cladding layer; and a second cladding layer of a second conductivity type on the active layer. A current confinement structure in which a current confinement layer is embedded on both sides of a stripe portion provided in an upper layer portion of the second cladding layer, wherein the current confinement layer is electrically separated from a laser driving electrode An operation method of a self-pulsation type semiconductor laser to which an electrode is connected, wherein a laser driving voltage is externally applied to the laser driving electrode, and the laser is passed through the electrode to the current confinement layer. A method of operating a self-pulsation type semiconductor laser, wherein a predetermined voltage is applied independently of a driving voltage. 10. The self-pulsation type semiconductor according to claim 9, wherein the voltage applied to the current confinement layer is controlled in accordance with operating conditions of the self-pulsation type semiconductor laser. How the laser works. 11. A first cladding layer of a first conductivity type; an active layer on the first cladding layer; a second cladding layer of a second conductivity type on the active layer; A current confinement layer having a stripe-shaped opening on the cladding layer; and a second conductivity type third cladding layer provided on the second cladding layer at the opening of the current confinement layer. An operation method of a self-excited oscillation type semiconductor laser in which an electrode electrically separated from a laser driving electrode is connected to the current constriction layer. A method of operating a self-pulsation type semiconductor laser, comprising applying a voltage and applying a predetermined voltage to said current confinement layer through said electrode independently of said laser driving voltage. 12. The self-excited oscillation semiconductor according to claim 11, wherein the voltage applied to the current confinement layer is controlled in accordance with operating conditions of the self-excited oscillation semiconductor laser. How the laser works.