JPH05183231A - Semiconductor laser and manufacturing method thereof - Google Patents

Abstract

PURPOSE:To easily manufacture a true refractive index wave guide type AlGaInP base semiconductor laser. CONSTITUTION:An n type AlGaInP clad layer 2, an active layer 3, a p type AlInP clad layer 4, etc., are successively and epitaxially grown by MOCVD process on an n<+> type GaAs substrate 1 whereon a protrusion 1a having a slanting side surface toward the main surface is formed. At this time, the band gaps of the parts epitaxially grown on the slanting side surface of the protrusion 1a out of said layers 2, 3 and 4 are made larger than that of the part epitaxially grown on the surface of the protrusion 1a. In such a constitution, a laser resonator in double hetero-structure can be formed by said layers 2, 3 and 4 epitaxially grown on the surface of this protrusion 1a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser and a method for manufacturing the same, and more particularly to an AlGaInP-based semiconductor laser.

[0002]

2. Description of the Related Art In recent years, AlGa, a visible light semiconductor laser
InP semiconductor lasers have attracted attention as a light source for optical information processing and are being actively researched. Several refractive index guided structures have been proposed for practical use. FIG. 4 shows the most reliable and widely used AlGaInP-based semiconductor laser of the index guided type.

As shown in FIG. 4, in this conventional refractive index guided AlGaInP semiconductor laser, an n-type GaAs buffer layer 102 and an n-type AlGaInP are provided on an n ⁺ -type GaAs substrate 101.
A clad layer 103, for example, an active layer 104 made of a non-doped GaInP layer and a p-type AlGaInP clad layer 105 are sequentially provided. In this case, a stripe-shaped ridge 105a is formed on the p-type AlGaInP cladding layer 105. The n-type AlGaInP clad layer 103, the active layer 104 and the p-type AlGaInP clad layer 105 in the ridge 105a form a laser cavity having a double hetero (DH) structure.

A p-type GaInP contact layer 106 is provided on the ridge 105a. Also, the ridge 105a
The current confinement layer 107 made of an n-type GaAs layer is formed on both sides of the
Is provided. Furthermore, p-type GaInP contact layer 1
A p-type GaAs cap layer 108 is provided on the 06 and the current confinement layer 107. p-type GaAs cap layer 108
A p-side electrode 109 is provided on the top surface of the n ⁺ -type GaAs substrate 101, and an n-side electrode 110 is provided on the back surface of the n ⁺ -type GaAs substrate 101.

In the conventional index-guided AlGaInP-based semiconductor laser having the above-described structure, the current flowing between the electrodes 109 and 110 for causing laser oscillation is a current composed of an n-type GaAs layer. Due to the current blocking effect of the constriction layer 107, the current flows only through the stripe-shaped ridge 105a. In this case, the current confinement layer 107 made of the n-type GaAs layer serves as a light absorption layer, and the ridge 1
The light is confined by the difference in the refractive index between 05a and the current confinement layer 107 on the outer side. Therefore,
This conventional index-guided AlGaInP semiconductor laser is
It is a so-called loss guide type index guided laser, not a real index guided laser.

[0006]

As described above, the conventional index-guided AlGaInP semiconductor laser shown in FIG.
Since it is a loss guide type semiconductor laser utilizing light absorption by the current constriction layer 107, it cannot be said to be sufficient in terms of characteristics.

The active layer 10 is used as a material for the current confinement layer 107.
When n-type AlInP or the like having a band gap larger than 4 is used, the absorption of light by the current confinement layer 107 does not occur and a real refractive index guided laser is obtained, so that improvement in characteristics is expected. However, with the current epitaxial growth technique, it is extremely difficult to epitaxially grow an AlInP layer or the like on an uneven surface such as the surface of the p-type AlGaInP cladding layer 105 on which the ridge 105a is formed. At present, it is difficult to use n-type AlInP or the like.

In manufacturing the conventional index-guided AlGaInP semiconductor laser shown in FIG. 4, the n-type GaAs buffer layer 102, the n-type AlGaInP clad layer 103, the active layer 104, and the p-type AlGaInP clad layer are used. 105 and p-type GaInP
There is also a problem that manufacturing takes time because three epitaxial growth steps of the contact layer 106, the current confinement layer 107, and the p-type GaAs cap layer 108 are required.

Therefore, an object of the present invention is to provide a semiconductor laser which can easily realize an AlGaInP type semiconductor laser of the real refractive index guided type by a single epitaxial growth and a manufacturing method thereof.

[0010]

In order to achieve the above object, a semiconductor laser according to the present invention has a convex portion (1a) or a concave portion (1) having side surfaces inclined with respect to its main surface.
b) a compound semiconductor substrate (1) provided on the main surface, and a first cladding layer (2) made of a first conductivity type AlGaInP layer sequentially vapor-phase epitaxially grown on the compound semiconductor substrate (1), and an active layer. A layer (3) and a second cladding layer (4) consisting of a second conductivity type AlGaInP layer.

According to the method of manufacturing a semiconductor laser of the present invention, a convex portion (1) having a side surface inclined with respect to its main surface is used.
a) A first clad layer (2) made of an AlGaInP layer of the first conductivity type, an active layer (3) and a second conductivity type on a compound semiconductor substrate (1) having a major surface provided with a recess (1b) Al
The second clad layer (4) made of a GaInP layer is sequentially grown in the vapor phase one axial manner.

[0012]

[Function] When an AlGaInP layer is epitaxially grown on a GaAs substrate or the like by metal organic chemical vapor deposition (MOCVD) or the like, the plane orientation of the GaAs substrate used is (100).
The band gap of the AlGaInP layer increases as the index becomes higher from the surface and saturates at a constant value (Electronic
s Letters, Vol.25, No.12 (1989) 758). The same applies to the GaInP layer.

Therefore, for example, a GaAs substrate having a (100) plane orientation is used as the compound semiconductor substrate (1), and the main surface of the GaAs substrate has a convex portion (1a) or a concave portion having a side surface inclined with respect to the main surface. Provide (1b) and place it on this GaAs substrate
First clad layer (2) composed of AlGaInP layer, active layer (3) and second clad layer (4) composed of AlGaInP layer
When vapor-phase epitaxial growth was sequentially performed by MOCVD or the like, the convex portions (1a) or concave portions (1b) of the AlGaInP layers forming the first cladding layer (2) and the second cladding layer (4) were inclined. The portion epitaxially grown on the side surface has a larger band gap than the portion epitaxially grown on the upper surface or the bottom surface composed of the (100) plane at the center of the convex portion (1a) or the concave portion (1b).

As a result, the first cladding layer (2) made of the AlGaInP layer epitaxially grown on the upper surface or the bottom surface of the central portion of the convex portion (1a) or the concave portion (1b),
The laser cavity formed by the active layer (3) and the second cladding layer (4) composed of the AlGaInP layer has a structure in which both sides of the laser cavity are surrounded by a layer having a larger band gap. An AlGaInP semiconductor laser is realized. Moreover, since this semiconductor laser can be manufactured by one-time epitaxial growth, the manufacturing process can be greatly simplified.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. In all the drawings of the embodiments, the same or corresponding parts are designated by the same reference numerals. FIG. 1 shows a semiconductor laser according to the first embodiment of the present invention. As shown in FIG. 1, in the semiconductor laser according to the first embodiment, for example, a {911} plane, a {511} plane, and a {311} plane are formed on the main surface of the n ⁺ -type GaAs substrate 1 having a {100} plane orientation.
Plane, a stripe-shaped convex portion 1a having a side surface inclined with respect to this main surface such as a {111} plane, and the n-type AlGaInP cladding layer 2, for example, is formed on the main surface on which the convex portion 1a is formed. An active layer 3, a p-type AlGaInP clad layer 4 and a p-type GaInP which are made of non-doped GaInP layer or AlGaInP layer
The contact layers 5 are sequentially provided by vapor phase epitaxial growth.

In this case, of the n-type AlGaInP clad layer 2, the active layer 3, the p-type AlGaInP clad layer 4, and the p-type GaInP contact layer 5, the portions on both side surfaces of the convex portion 1a of the n ⁺ -type GaAs substrate 1 ( The portion marked with stippling) is completely mixed crystal, and the band gap is larger than the portion above the upper surface of the convex portion 1a composed of the {100} plane. The band gap difference between the two portions becomes larger as the index of the crystal plane on the side surface of the convex portion 1a is lower. In the first embodiment, the n-type AlGaInP cladding layer 2, the active layer 3 and the p-type AlGaInP cladding layer 4 on the upper surface of the convex portion 1a
A laser resonator having a DH structure is formed.

A p-type GaAs cap layer 6 is provided on the p-type GaInP contact layer 5 above the convex portion 1a.
Further, a p-side electrode 7 is provided on the p-type GaAs cap layer 6 and the p-type GaInP contact layer 5, and the n ⁺ -type GaAs is formed.
An n-side electrode 8 is provided on the back surface of the substrate 1. In this case, the junction between the p-side electrode 7 and the p-type GaInP contact layer 5 is a Schottky junction. Therefore, the current flowing between the electrodes 7 and 8 for causing laser oscillation does not pass through this Schottky junction portion, and the electrode 7 and the p-type
It flows only through the ohmic contact with the GaAs cap layer 6.

Next, a method of manufacturing the semiconductor laser according to the first embodiment configured as described above will be described. As shown in FIG. 1, an n ⁺ type GaAs substrate 1 having a {100} plane orientation
Of the n ⁺ -type GaAs substrate 1 on which the convex portion 1a is formed, the n-type AlGaInP cladding layer 2, the active layer 3 and the p-type The AlGaInP clad layer 4, the p-type GaInP contact layer 5, and the p-type GaAs cap layer 6 are sequentially epitaxially grown. Next, the p-type GaAs cap layer 6 is patterned by etching to leave only the portion above the convex portion 1a. Then, the p-side electrode 7 and the n-side electrode 8 are formed to complete the intended semiconductor laser.

As described above, according to this first embodiment,
An n-type AlGaInP clad layer 2, an active layer 3, a p-type AlGaInP clad layer 4, and a p-type which are vapor-phase epitaxially grown on an n ⁺ -type GaAs substrate 1 on which a convex portion 1a having a side surface inclined with respect to the main surface is formed. Convex portion 1a of GaInP contact layer 5
The bandgap of the portion grown on the inclined side surface is larger than that of the portion grown on the upper surface of the convex portion 1a, so that a real refractive index guided AlGaInP semiconductor laser can be realized. Further, this real refractive index waveguide type structure can efficiently confine light and current in the stripe-shaped laser resonator, thereby improving characteristics such as reduction of threshold current. Can be planned. Moreover, since the epitaxial growth required for manufacturing this semiconductor laser only needs to be performed once, the manufacturing process can be greatly simplified.

FIG. 2 shows a semiconductor laser according to the second embodiment of the present invention. As shown in FIG. 2, in the semiconductor laser according to the second embodiment, for example, a {911} plane is formed on the main surface of the n ⁺ -type GaAs substrate 1 having a {100} plane orientation,
A stripe-shaped concave portion 1b having side surfaces inclined with respect to this main surface such as a {511} surface, a {311} surface, and a {111} surface is formed, and on the main surface where the concave portion 1b is formed,
An n-type AlGaInP clad layer 2, for example, an active layer 3 composed of a non-doped GaInP layer or an AlGaInP layer, a p-type AlGaInP clad layer 4, a p-type GaInP contact layer 5 and a p-type GaAs cap layer 6 are sequentially provided by vapor phase epitaxial growth. ..

In this case, portions of the n-type AlGaInP clad layer 2, the active layer 3, the p-type AlGaInP clad layer 4 and the p-type GaInP contact layer 5 on both side surfaces of the recess 1b of the n ⁺ -type GaAs substrate 1 (dotted pattern). (The part marked with) is {10
The band gap is larger than that of the upper part of the bottom surface composed of the 0 plane. In the second embodiment, the DH structure laser resonator is formed by the n-type AlGaInP cladding layer 2, the active layer 3, and the p-type AlGaInP cladding layer 4 on the bottom surface of the recess 1b.

For example, SiN is formed on the p-type GaAs cap layer 6.
An insulating film 9 such as an _x film is provided. This insulating film 9
Has a stripe-shaped opening 9a formed above the recess 1b, and the p-side electrode 7 is formed through the opening 9a.
The cap layer 6 is contacted. Then, in this case, the current passed between the electrodes 7 and 8 for causing the laser oscillation flows only through the stripe portion defined by the opening 9a of the insulating film 9.

In the method of manufacturing the semiconductor laser according to the second embodiment, the p-type GaAs cap layer 6 is not patterned, and the insulating film 9 is formed after the insulating film 9 is formed on the p-type GaAs cap layer 6. The method is the same as the method for manufacturing the semiconductor laser according to the first embodiment, except that Also according to the second embodiment, as in the first embodiment, it is possible to easily realize an AlGaInP-based semiconductor laser of the real index guiding type.

FIG. 3 shows a semiconductor laser according to the third embodiment of the present invention. As shown in FIG. 3, in the semiconductor laser according to the third embodiment, the p-type GaAs cap layer 6 is provided on the entire surface, and the insulating film 9 having the opening 9a is formed on the p-type GaAs cap layer 6. The p-side electrode 7 is provided through the opening 9a so that the p-type GaAs cap layer 6 is formed.
The semiconductor laser has the same structure as the semiconductor laser according to the first embodiment except that it is in contact with the semiconductor laser.

The method of manufacturing the semiconductor laser according to the third embodiment is different from the method of manufacturing the semiconductor laser according to the second embodiment except that the n ⁺ type GaAs substrate 1 having the convex portion 1a formed on the main surface is used. Is the same as. Also in this third embodiment, similar to the first embodiment, the real refractive index guided AlGaInP is used.
A semiconductor laser can be easily realized.

Although the embodiments of the present invention have been specifically described above, the present invention is not limited to the above-mentioned embodiments, and various modifications can be made based on the technical idea of the present invention. For example, although the MOCVD method is used as the vapor phase epitaxial growth method in the above-described embodiments, the molecular beam epitaxy (MBE) method can also be used as the vapor phase epitaxial growth method.

Further, the convex portion 1a is formed on the main surface of the n ⁺ type GaAs substrate 1.
And the recesses 1b are formed alternately, and the n-type AlGaInP cladding layer 2, the active layer 3, and the p-type AlGaInP are formed on the n ⁺ -type GaAs substrate 1.
A semiconductor laser array can be formed on the n ⁺ type GaAs substrate 1 by sequentially performing vapor phase epitaxial growth of the cladding layer 4 and the like. Further, although the n ⁺ type GaAs substrate 1 is used in the above-mentioned embodiment, a p ⁺ type GaAs substrate can be used instead of the n ⁺ type GaAs substrate 1. In this case, the conductivity type of each layer forming the laser structure is opposite to that of the above-described embodiment.

[0028]

As described above, according to the present invention,
A real-index-guided AlGaInP-based semiconductor laser can be easily realized.

[Brief description of drawings]

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

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

FIG. 3 is a sectional view showing a semiconductor laser according to a third embodiment of the present invention.

FIG. 4 is a sectional view showing a conventional AlGaInP-based semiconductor laser.

[Explanation of symbols]

1 n ⁺ type GaAs substrate 1a convex part 1b concave part 2 n type AlGaInP clad layer 3 active layer 4 p type AlGaInP clad layer 7, 8 electrode

Claims (2)

[Claims] 1. A compound semiconductor substrate in which a convex portion or a concave portion having a side surface inclined with respect to the main surface is provided on the main surface, and a first conductivity type which is sequentially vapor-phase epitaxially grown on the compound semiconductor substrate. A semiconductor laser comprising: a first clad layer composed of an AlGaInP layer; an active layer; and a second clad layer composed of an AlGaInP layer of a second conductivity type. 2. A first clad layer and an active layer made of an AlGaInP layer of a first conductivity type on a compound semiconductor substrate having a convex portion or a concave portion having a side surface inclined with respect to the main surface, which is provided on the main surface. And a method for manufacturing a semiconductor laser in which a second cladding layer composed of a second conductivity type AlGaInP layer is sequentially grown by vapor phase epitaxial growth.