JP2721274B2 - Semiconductor laser device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an AlGaAs semiconductor laser produced by a molecular beam epitaxy (MBE) method, and more particularly to a laminated structure thereof.

[0002]

2. Description of the Related Art The following are known as characteristic growth characteristics of the MBE method. For example, AlGaAs
In semiconductor lasers, Si is used as an amphoteric impurity as an impurity for controlling the conductivity type of the Al _x Ga ₁ -x As system, and the p-type and n-type conductivity types can be arbitrarily controlled by appropriately controlling the growth conditions. Can be formed. That is, (100)
A (n11) A plane (n = 1,
2, 3, 4, 5) are formed in advance so that facets (crystal faces) appear, and a predetermined amount of As, Ga, A
at a predetermined substrate temperature while irradiating l and Si beams.
_{When X} Ga _{1 -X} As is grown by MBE, on the (100) plane, an Al _x Ga _{1 -X} As layer of n-type conductivity and (n 1
1) It is known that a p-type conduction Al _x Ga ₁ -x As layer grows on the facet of the A plane (n = 1, 2, 3, 4, 5) (DL Miller, Appl. Phys. Lett. 47 (1985)
1309, etc.). More recently, utilizing such growth characteristics, as shown in FIG. 4 , a normal mesa stripe having a (100) surface and a (311) A inclined surface is formed on a p-type GaAs substrate 1. And Al _X Ga _{1 -X} As
FIG later system semiconductor laser structure (each layer symbols 1 to 3
), A p-type Si-doped current confinement layer 6 is automatically formed on the inclined surface (311) A, and an internally confined laser device is realized (H.
Jaeckel et al., Appl. Phys. Lett. 55 (1989) 1059).

However, this internal confinement type laser (see FIG.
In the case of 4 ), the upper current confinement layer 6 of p-type Al _x Ga ₁ -x As (x = 0.5) doped with Si in the inclined portion is obtained, but the region (100) other than the light emitting portion is obtained.
In the region formed on the surface, an Al _x Ga ₁ -x As (x = 0.5) layer 15 exhibiting n-type conductivity doped with Si is formed, so that the luminous efficiency is improved and the single mode emission is improved. For this purpose, as shown in FIG. 4 , an insulating layer 14 such as Si ₃ N ₄ is used.
It is necessary to form an opening (patterning) of the insulating layer 14 in accordance with the current path portion 11.

In order to reduce the threshold current of the semiconductor laser and to make the oscillation mode uniform, the width of the current path portion 11 must be 5 μm.
m or less. Therefore, in the opening step of the insulating layer 14, 5 μm
It is necessary to perform the process with the following stripe width (accuracy of 1 μm or less). However, patterned GaAs
Since the process is performed after the crystal growth on the substrate 1, it is very difficult to align the openings due to deformation of the stripe structure formed below. As a result, there is a problem that the yield for obtaining a good laser device becomes very poor.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and has as its object to solve the above-mentioned problems and to provide an internal confinement type utilizing the growth characteristics of the MBE method. An object of the present invention is to provide a semiconductor laser device having a low threshold current as a device characteristic, a simple manufacturing process, and a high production yield.

[0006]

SUMMARY OF THE INVENTION A semiconductor laser element according to the present invention is provided.
The semiconductor chip forms one current path on the compound semiconductor substrate having the (100) substrate plane orientation, and is formed on both sides of the current path on both sides of the current path (n11).
(However, n = 1 to 5) and a multi-channel structure which covers the entire area Do Ri and excluding said current passage portion from the groove of the plurality of rows having a facet, superimposed on the region of the multi-channel structure
Crystal-grown by molecular beam epitaxy Te, the Fase
A current confinement layer having p-type conduction according to the plane orientation of the unit, and an n-type conduction layer formed so as to overlap the region of the current passage portion, thereby achieving the above object. . Ma
Further, the semiconductor laser device of the present invention has a (100) substrate surface.
N-type conduction formed on compound semiconductor substrate with orientation
A current path portion in the current constriction layer of
Formed on both sides of the current path portion.
(N11) (where n = 1 to 5)
And the entire area excluding the current path portion is formed of a plurality of rows of grooves.
The covering multi-channel structure and the area of the multi-channel structure
Crystal growth by molecular beam epitaxy
And the current made p-type conduction by the face orientation of the facet
The constriction layer and the n formed so as to overlap the region of the current path portion
And the above-mentioned purpose is achieved.
Is done.

[0007]

(N11) (where n11 is formed on both sides of one stripe-shaped current path portion provided on the substrate )
= Such a groove in the plurality of rows having facets 1-5) Ri且
Heavy by providing a multi-channel structure, the area of the multi-channel structure which covers the entire area except the One current path portion
All tatami to molecular beam epitaxy (MBE) grown by layer automatically becomes a current constricting layer of p-type conduction. An n-type conductive layer is grown on the current path. Therefore, even if the electrodes are formed on the entire upper surface of the element, no current leaks. Therefore, the manufacturing process of the semiconductor laser device is simplified, and the yield is improved. In addition, the semiconductor laser element
In addition to the current confinement layer of p-type conduction,
In the case where a constriction layer is further provided, current leakage
Can be more reliably prevented.

For example, in the case of a semiconductor laser in which the substrate is formed of GaAs, the surface orientation of the substrate is set to (100), and the surface of the portion other than the stripe-shaped current path (on both sides) is formed of a large number of triangular or trapezoidal columns. (N11) (n = 1)
5) Make facets appear. By irradiating Al, Ga, As, and Si thereon by MBE to grow the layer, Si-doped p-type conductive Al _x Ga _{1 -x} As (0 ≦ x ≦ 1) on the multi-channel stripe. A current confinement layer is formed. The thickness of this growth layer is 0.5 μm
It is desirable to make the above. In addition, the width of the stripe-shaped current path can be about 1 to 20 μm.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments.

FIG. 1 shows a laminated structure of a semiconductor laser according to a first embodiment of the present invention. This embodiment is manufactured by a single growth process by the MBE method. Hereinafter, the laminated structure of this embodiment will be described according to the manufacturing order.

First, a plurality of (n11) (n = 1 to 5) facets are formed on a GaAs substrate 1 having a (100) plane orientation by p-type conduction by a single photolithography and etching process. A multi-channel section 10 and a current path section 11 formed of columnar stripes are formed. The GaAs substrate 1 having a step structure formed in this manner is
The substrate is charged into the apparatus, the substrate temperature is increased while irradiating an As molecular beam, and the substrate is heated to about 720 ° C. At this temperature, the p-type conductive Al _0.5 Ga _0.5 As lower cladding layer 2 doped with Be at about 1 μm and then undoped Al _0.15 Ga _0.85 As
An active layer 3 and an upper clad layer 4 of Al _0.5 Ga _0.5 As doped with Si are formed. Here, the upper Al _0.5 Ga
_{Under the} growth conditions described above, the _0.5 As
11) On the facet surface (n = 1 to 5) (shaded portion in FIG. 1), since the Si dopant grows so as to be arranged at the As site, the hatched portion is Al _0.5 Ga showing p-type conduction.
It becomes the _0.5 As upper current confinement layer 6. In addition, the current path 11
In the upper to selectively position the Al or Ga site, the Al _0.5 Ga _0.5 As upper cladding layer 5 having n-type conduction. Next, the substrate temperature is lowered to 400 to 500 ° C.
An n-type GaAs cap layer 7 doped with Si is formed. Thus, the growth in the MBE apparatus is completed, the GaAs substrate is polished, and then the n-type conduction electrode 8 and the p-type conduction electrode 9 are formed by vacuum evaporation to complete the semiconductor laser.

FIG. 2 shows a laminated structure of a semiconductor laser according to a second embodiment of the present invention. In this embodiment, the threshold current is further reduced by providing an n-type GaAs current confinement layer 12 on the P electrode side. Hereinafter, the laminated structure of this embodiment will be described according to the manufacturing order.

A p-type (100) GaAs substrate 1 has M
An n-type GaAs current confinement layer 12 having a thickness of about 200 to 500 nm is epitaxially grown by BE or metal organic chemical vapor deposition (MOCVD), liquid phase epitaxy (LPE), or the like. In the GaAs epitaxial substrates 1 and 12 thus obtained, a triangular prism-shaped multi-channel portion 10 having (n11) (n = 1 to 5) and a current passage portion 11 are formed in the same steps as in the first embodiment. And are formed. Here, the current path portion 11 is formed by forming the current confinement layer 1.
It is necessary to perform etching until the GaAs substrate 1 is reached by opening the hole 2.

The subsequent steps are the same as those in the first embodiment, and the Al _0.5 Ga doped with Be by MBE is used.
_0.5 As lower cladding layer 2, undoped Al _0.15 Ga
_0.85 As active layer 3, Si-doped Al _0.5 Ga _0.5
The upper cladding layer 4 of As (the Al _0.5 Ga _0.5 As upper cladding layer 4 has an n-type conduction A
l _{0. 5} Ga _0.5 As upper cladding layer 5 next, the Al _0.5 Ga _0.5 As upper current confinement layer 6 of p-type conduction on a multi-channel unit 10), GaAs cap n-type conduction and Si doping layer 7 Are sequentially formed. The GaAs substrate thus grown is taken out of the MBE apparatus,
The n-type conduction electrode 8 and the p-type conduction electrode 9 are formed by polishing and vacuum deposition, thereby completing the semiconductor laser shown in FIG.

FIG. 3 shows a laminated structure of a semiconductor laser according to a third embodiment of the present invention. In the first and second embodiments, a triangular prism-shaped multi-channel structure 10 having (n11) (n = 1 to 5) facets is used to obtain a p-type conduction Al _0.5 Ga _0.5 As upper current confinement layer. Adopted
In this embodiment, a multi-channel structure 13 having a trapezoidal column shape is employed. In the multi-channel structure 13 of this embodiment, trapezoidal channels are arranged at a period of 2 to 3 μm, and the width of the upper base of each trapezoid is 1 to 2 μm. Also in this trapezoidal multi-channel structure 13, the first and second
Layer growth was performed by the MBE method in exactly the same manner as in the embodiment.
Al _0.5 Ga _0.5 As lower cladding layer 2 of about 0 type conduction.
By growing 5 μm or more (preferably about 1 μm), a trapezoidal columnar multi-channel having (n11) (n = 1 to 5) facets as shown in FIG. Undoped A with shape
l _0.5 Ga _0.5 As active layer 3 and Al exhibiting p-type conduction
A semiconductor laser including the _0.5 Ga _0.5 As upper current confinement layer 6 can be obtained.

Although the semiconductor laser of the present embodiment outputs a 780 nm band laser, other output bands can be handled by changing the composition ratio and structure of each layer. For example, Al _0.5 Ga _0.5 As Al composition ratio of the lower cladding layer 2 and the Al of the n-type conductivity _0.5 Ga _0.5 As upper cladding layer 5, Al of p-type conductivity _0.5 Ga _0.5 As upper current confinement layer 6 of p-type conduction 0 It can be changed in the range of 0.4 to 0.8. In addition, undoped Al _0.15 Ga _0.85
Instead of the As active layer 3, an active layer 16 composed of an Al _x Ga _{1 -x} As layer (x ≒ 0.1) having a GRIN (GRaded INdex) type SCH (Separate Confinement Hetero) structure
It is also possible to use Further, by using active layers having different composition ratios (for example, x ≒ 0), the present invention can be applied to an 830 nm wavelength band laser.

[0017]

The present invention is also applicable to semiconductor lasers of other materials, and includes S as an impurity for controlling the electric conduction type when forming the upper cladding layer 5 and the current confinement layer 6.
In the case of a stacked example of a semiconductor laser formed by MBE growth using i, InGaAsP, InGaAlAs, InG
Also in a semiconductor laser structure composed of an aAlP-based material system, a triangular prism (or trapezoidal column) multi-channel structure 10 (or 13) composed of the above (n11) (n = 1 to 5) facets is used. Thus, a semiconductor laser structure having the upper current confinement layer 6 can be formed.

[0019]

According to the present invention, a strap provided on a substrate is provided.
Formed on both sides of one current path portion
(N11) (where n = 1 to 5)
Covering the entire area except for and the current path portion Do Ri from the groove of the plurality of rows that
It is provided with the cormorant multi-channel structure, this multichannel
All of the layers superimposed on the region of the MBE structure by MBE automatically become p-type conduction current confinement layers. An n-type conductive layer is grown on the current path. Therefore, even if the electrodes are formed on the entire upper surface of the element, no current leaks. Therefore, in an internal current confinement type laser by the MBE method, a complicated process such as alignment by photolithography after crystal growth becomes unnecessary. Therefore, MB
The controllability of the E growth is improved and the quality is improved, and the yield and mass productivity are improved and the cost is reduced. M
By using the BE method, a quantum well structure can be adopted, and a semiconductor laser having good characteristics can be obtained with a lower threshold. Also, the semiconductor laser device is connected to a p-type conduction electrode.
In addition to the current confinement layer, an n-type conduction current confinement layer is further provided.
More reliably prevent current leakage
It is possible to do.

[Brief description of the drawings]

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

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

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

FIG. 4 is a sectional view of a conventional semiconductor laser.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 GaAs substrate 2 Be-doped p-type lower cladding layer 3 undoped Al _0.15 Ga _0.85 As active layer 4 Si-doped upper Al _0.5 Ga _0.5 As layer 5 Si-doped n-type conduction Al _0.5 Ga _0.5 As upper cladding layer 6 Si-doped p-type conduction Al _0.5 Ga _0.5 As upper current confinement layer 7 n-type GaAs cap layer 8 n-type conduction electrode 9 p-type conduction electrode 10 triangular prism-shaped multi-channel part having (n11) (n = 1 to 5) facet crystal face Reference Signs List 11 current path portion 12 n-type conduction GaAs lower current confinement layer 13 column-shaped multi-channel portion having (n11) (n = 1 to 5) facet crystal plane 14 insulating layer of Si ₃ N ₄ 15 Si-doped Al _0.5 Ga _0.5 As layer 16 GRIN-SCH (GRraded INdex Separate Con
finement Hetero) Active layer including guide layer

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masafumi Kondo 22-22 Nagaikecho, Abeno-ku, Osaka City Inside Sharpe Corporation (72) Inventor Naohiro Suyama 22-22 Nagaikecho, Abeno-ku, Osaka City Inside Sharpe Corporation ( 72) Inventor Matsui Kanei 22-22, Nagaike-cho, Abeno-ku, Osaka-shi Inside Sharpe Co., Ltd. (56) References JP-A-2-103989 (JP, A) JP-A-2-291190 (JP, A) International application PCT / US90 / 3993 (International Publication No. 91/10263 pamphlet) APPL. PHYS. LETT. 55 to 11! (1989) P.A. 1059−1061

Claims (1)

(57) [Claims] 1. A current path portion is formed on a compound semiconductor substrate having a (100) substrate plane orientation, and is formed on both sides of the current path portion on both sides thereof (n1).
1) A plurality having facets (where n = 1 to 5)
Columns and Ma <br/> Ruchi channel structure which covers the entire area except Do Ri and the said current path portion from the groove of crystal-grown by molecular beam epitaxy to be superimposed on the region of the multi-channel structure, the surface of the facet Depending on direction
Ri p-type and the current confinement layer which is a conductive, semiconductor laser device having an n-type conductive layer formed by superimposing the area of the current passage. 2. A compound half having a (100) substrate plane orientation.
An n-type conduction current confinement layer formed on a conductive substrate
The current path portion is formed, and the current path portion is interposed therebetween.
(N11) formed on both sides thereof (where n
= 1-5) consisting of a plurality of rows of grooves having facets
Multi-channel structure covering the entire area except for the current path portion
And molecular beam epitaxy superimposed on the region of the multi-channel structure.
The crystal is grown by the C method and depends on the face orientation of the facet.
A current confinement layer having p-type conduction and an n-type conduction layer formed so as to overlap the region of the current passage portion.
A semiconductor laser device having: