JPH01181585A - Semiconductor laser - Google Patents

Abstract

PURPOSE:To emit two beams of light of different wavelengths or of variable wavelengths by providing on a partial region of a deposition layer a stripe- shaped impurity diffusion region of an opposite conductivity type to that of a semiconductor substrate, and further providing electrodes on said region, on other regions, and on the lower surface of the semiconductor substrate. CONSTITUTION:Stripe-shaped impurity diffusion regions 11, 12 of an opposite conductivity type to that of a semiconductor substrate 1 are provided on a partial region of a deposition layer such that they penetrate the upper part of a third cladding layer 6 and then a first active cladding layer 2. Electrodes are provided on a region 10, on another region 8, and on the lower surface 9 of the semiconductor substrate 1. Hereby, there are established two current paths, so that the two active layers 3, 5 emit respectively independently two light beams located in close vicinity to each other, which beams can be changed in wavelengths by changing compositions and structures of the first and second active layers 3, 5.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a semiconductor laser which can be driven independently and which can emit two beams of the same or different wavelengths or variable wavelength light.

[Conventional technology]

Conventionally, this type of semiconductor laser has been manufactured by patterning two stripe structures close to a semiconductor wafer and arranging independent electrodes on each stripe.

[Problem that the invention seeks to solve]

However, the conventional semiconductor laser described above has the following drawbacks due to its structure.

First, it is difficult to make the distance between the two light beams (usually several microns) closer to each other than a certain degree. This is because the confinement of light by the stripe structure is usually weak in the direction perpendicular to the substrate forming the DH (double hetero) structure. This is because light coupling occurs between the lasers, making it impossible to drive the two lasers independently.

Further, when the stripes are placed close to each other, the electrodes and the structure for current confinement must be prepared, and a complicated electrode formation process is required. Second, if you want to change the oscillation wavelength of the two beams or change the far field pattern, for example, as disclosed in Japanese Patent Application Laid-Open No. 56-80195,
After creating one laser structure, a part of the laminated structure is removed by etching, and the crystal is regrown in that part to create a laser structure with a different band gap and film thickness from the originally created laser structure. It required a complicated process.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems and provide a semiconductor laser with a simple structure that emits two beams of different wavelengths or a variable wavelength.

[Means for solving problems]

The semiconductor laser of the present invention includes, on a semiconductor substrate, a first cladding layer of the same conductivity type as the semiconductor substrate, a first active layer, a second cladding layer of the opposite conductivity type to the semiconductor substrate, and a second active layer. A semiconductor laser comprising a deposited layer formed by sequentially stacking a third cladding layer and a third cladding layer of the same conductivity type as the semiconductor substrate, wherein a third cladding layer of the conductivity type opposite to that of the semiconductor substrate is formed in a partial region of the deposited layer. A live impurity diffusion region is provided to penetrate the first active layer from the top of the third cladding layer and further reach the first cladding layer, and an electrode is provided on the region. It is characterized in that it is provided on other regions and on the lower surface of the semiconductor substrate.

(Function) The present invention having the above structure has two paths of current, and each light wave oscillates independently in the two active layers, so that two luminous fluxes with close light emission points can be obtained. Moreover, the first
By changing the composition and structure of the active layer and the second active layer, a semiconductor laser that emits three beams of light with different wavelengths can be easily manufactured. In addition, by adopting a structure in which the distance between the two active layers is shortened, a composite resonator is formed, and by changing the resonant frequency by current injection, it is possible to construct a tunable wavelength semiconductor laser in which the longitudinal mode can be freely selected. .

(Example) Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic perspective view showing an embodiment of the semiconductor laser of the present invention, and FIGS. 2(a) to 2(f) are schematic front views showing the steps of its manufacturing method.

(too) plane on an n-type GaAs substrate 1.
Type GaAlAs cladding layer 2, GaAs active layer 3, P type GaAlAs cladding layer 4, GaAs active layer 5, n type G
The aAlAs cladding layer 6 and two separated GaAs cap layers 7 are laminated. Furthermore, n-type GaAs substrate 1
A cathode electrode 9 is provided on the lower surface of the GaAs cap layer 7, a cathode electrode 8 is provided on one upper surface of the GaAs cap layer 7, and an anode electrode 10 is provided on the other upper surface. In addition, striped P
After the '' type impurity diffusion region 12 penetrates from the top surface of the n-type GaAlAs cladding layer 6 to the GaAs active layer 3, the n-type G
aAlAs cladding layer 2 has been reached. in this way,
The P'' type impurity diffusion region 12 is provided to divide the semiconductor laser into two regions. One region is a P'' type impurity diffusion region 12.
- type impurity diffusion region 11.

Next, a typical example of a method for manufacturing the semiconductor laser shown in FIG. 1 will be described with reference to FIGS. 2(a) to 2(f).

On the n-type GaAs substrate 1, an n-type GaAlAs cladding layer 2 (film thickness 12 μm),
GaAs active layer 3 (0.35 μm), P type G
aAlAs cladding layer 4 (3 μts), Ga
As active layer 5 (0.35μ11), n-type GaAl s
A cladding layer 6 (3 μm thick) was laminated (Fig. 2(a)
).

Next, GaAs is deposited on the top surface of the n-type GaAlAs cladding layer 6.
A cap layer 7 is laminated and patterned by a photolithography process (FIG. 2(b)).

Next, a SiO□ layer I3 is formed on the 91 layer 7 by electron beam evaporation so as not to cover half of the cap layer 7, and a diffusion window 20 is formed by a lift-off method (FIG. 3(C)). ).

Next, the wafer configured as described above is Zn3P2
, Zn, As, and a mixture using a quartz sealed tube method.
n was diffused until it reached the n-type AlGaAs cladding layer 2. Thereafter, the wafer is taken out from the quartz tube and heat-treated at 500° C. in an inert gas flow containing phosphine gas. In this way, a P-type impurity diffusion region 11% P'' impurity diffusion region 12 was formed. Due to the blocking effect of the 5102 layer 13, both impurity diffusion regions 11 and 12 are formed on one side of the wafer (Figure P1 (d)). .

Thereafter, the Sin layer 13 is removed (FIG. 4(e)).

Further, ^u-5n is deposited on the lower surface of the n-type GaAs substrate 1 to form a cathode electrode M9, and Au-5n and Au-Zn are deposited on the upper surface of the GaAs cap layer to form cathode electrodes 8, respectively. , an anode electrode 10 is formed (FIG. 1(f)).

Furthermore, after that, a resonator surface is formed by cleavage, and the first
A semiconductor laser capable of emitting two beams as shown in the figure is formed.

Next, the operation of the embodiment shown in FIG. 1 will be explained. In the semiconductor laser capable of emitting two beams of this embodiment, the anode electrode I
O serves as a common anode terminal, and cathode electrode 8 and cathode electrode 9 serve as cathode terminals of lasers that emit respective luminous fluxes. When a current is passed from the anode electrode lO to the cathode electrode 8, as shown in FIG.
From the p-type impurity diffusion region ■ formed by diffusion,
The light is injected into the GaAs active layer 5 through the p-GaAlAs cladding layer 4, a gain is generated, and a light beam 21 is emitted from the GaAs active layer 5. On the other hand, when a current is passed from the anode electrode 10 to the cathode electrode 9, the current flows from the p-type impurity diffusion region 11 formed by Zn diffusion to the p-type GaAl
It is injected into the GaAs active layer 3 through the As cladding layer 4, a gain for light is generated in the GaAs active layer 3, and the GaAs
A light beam 22 is emitted from the active layer 3 . At this time, p-type Ga
Since the current injected from the AlAs cladding layer 4 to the GaAs active layer 5 and the current injected from the p-GaAlAs cladding layer 4 to the GaAs active layer 3 are almost independent, the GaAs
It is possible to drive the light beam 21 emitted from the s-active layer 5 and the light beam 22 emitted from the GaAs active layer 3 independently. In addition, since the light fluxes 21 and 22 are aligned in the direction perpendicular to the substrate with relatively strong light confinement, the P-type Ga
The thickness of the ^1^S cladding layer 4 can be made considerably thinner. Therefore, it is possible to fabricate a laser array having a structure as if two beams of light 21 and 22 were emitted from the same point light source. Furthermore, since this laser structure has a nearly symmetrical structure vertically with the p-type GaAlAs cladding layer 4 as a boundary, the optical properties such as far-field pattern and astigmatism are almost the same between the light beams 22 and 21.
The characteristics such as threshold current and differential quantum efficiency are also almost the same.

FIG. 4 is a schematic sectional view showing a second embodiment of the present invention.

1 shows a configuration diagram of a semiconductor laser that emits two beams of light with different wavelengths from one chip.

This example uses GRIN-5CH (Graded-1nd
ej 5eparateconfined heter
structure), and the quantum well structures of each active layer 15 and 18 are different.6 In other words, there are graded index separate layers on both sides of the active layer I5, which corresponds to the GaAs active layer 3 in FIG. - Combination layers 14 and 16 are provided, and separate confinement layers 17 and 19 are provided on the inner surface of the active layer 18 corresponding to the GaAs active layer 5. The composition of the active layer 15 is Gao, , ^11°85 (60 people)
From Ga,, ,AI. ,, As (300 people),
It has an MQW (multiple quantum well) structure with 5 6-El numbers, and the composition of the active layer 18 ranges from GaAs (60 people) to Gao, ? The AI is 0.3AS (100 people) and the number of wells is an MQW structure with 5 wells. In addition, the composition of the separate confinement layers 14.16 and 17.19 ranges from Gao, A1.3As to GaAlAs, ,
, As, O. Since the active layers 15 and 18 have different compositions, their quantum well structures are different. As a result, the wavelengths of the light beams emitted from the active layers 15 and 18 are different, and two light beams with different wavelengths can be obtained using the same principle as in FIG. 1. According to the present invention, it is possible to provide a semiconductor laser capable of emitting two light beams of different wavelengths without using a complicated process such as double growth.

Note that in this example, the active layer has different quantum structures,
Although the GRIN-5C)I structure was explained as an example, the structure of the active layer is not limited to this, but is a normal DH structure.
The active layers may have mutually different compositions.

FIG. 5 is a schematic diagram showing a third embodiment of the present invention.

Although the basic configuration is exactly the same as the embodiment shown in FIG. 1, a variable wavelength can be obtained in this embodiment. The difference from the embodiment shown in FIG. 1 is that the thickness of the p-type GaA IAs cladding layer 4 in the embodiment shown in FIG. In this embodiment, the p-type GaAlAs cladding layer 4 is constructed such that the two light waves 23 and 24 are coupled by evanescent waves.
The thickness of is set to 1.0 μm. Furthermore, the active layer 3a is made of GaAlAs, .

Next, seven principles by which a variable wavelength can be obtained by this embodiment will be explained. First, from the anode electrode i10 to the cathode electrode 8
A current is injected to cause the GaAs active layer 5 to oscillate a light wave 23. At this time, since the laser structure of the first embodiment originally does not have a step in the refractive index in the horizontal direction, it becomes like a gain waveguide and oscillates in longitudinal multimode, but in the semiconductor laser of this embodiment, the GaAs active layer 5 A composite resonator is constructed because the waveguide with the active layer 3a as the core and the waveguide with the active layer 3a as the core are coupled by evanescent waves.
Oscillation occurs only where the resonant frequencies of the resonators of the active layer 5 and the resonator of the active layer 3a match, and oscillation occurs in a single mode. At this time, when a current is passed from the anode electrode lO to the cathode electrode 9, the current is injected into the GaAs active layer 3, and the effective refractive index of the GaAs active layer 3 changes.

As a result, the resonator length of the resonator formed by the waveguide having the GaAs active layer 3 as its core changes, and the resonant frequency changes. Therefore, since the resonant wavelength of the composite resonator changes, the oscillation longitudinal mode can be continuously changed by passing a current from the anode electrode 10 to the male sword electrode 9, thereby making it possible to tune the wavelength.

(Effects of the Invention) As explained above, the semiconductor laser of the present invention can be manufactured by a simple manufacturing process and can provide two luminous fluxes with a very small interval between light emitting points.

Therefore, the conventional complicated electrode formation process is no longer necessary, improving yield and productivity. Furthermore, it is also possible to provide a tunable wavelength laser that can select two beams of light with different wavelengths or a longitudinal mode.

[Brief explanation of the drawing]

FIG. 1 is a schematic perspective view showing an embodiment of the semiconductor laser of the present invention, FIG. 2 is a schematic view showing the process of its manufacturing method, FIG. 4 and 5 respectively show the second embodiment of the present invention. FIG. 7 is a schematic perspective view showing a third embodiment. 1......n-type GaAs substrate, 2...
...Hem-shaped GaAlAs cladding layer, 3.5...
...GaAs active layer, 3a, 15.18 ... active layer, 4 ......P-type GaAlAs cladding layer,
6......n-type GaAlAs cladding layer,
7II...--GaAs cap layer, 8.9
......Cathode electrode, 10......Anode electrode, 11...
...P-type impurity diffusion region, 12...
...P+ type impurity diffusion region, 13...
...5i02, +4.16.17.19... Separate confinement layer, 20... Diffusion window, 21, 22... Luminous flux, 23, 24 ...Light waves.

Claims (1)

[Claims] 1) On a semiconductor substrate, a first cladding layer and a first active layer of the same conductivity type as the semiconductor substrate, a second cladding layer of the opposite conductivity type to the semiconductor substrate, and a second cladding layer of the opposite conductivity type to the semiconductor substrate. A semiconductor laser comprising a deposited layer in which at least a second active layer and a third cladding layer of the same conductivity type as the semiconductor substrate are laminated in sequence, wherein a partial region of the deposited layer is opposite to the semiconductor substrate. a striped impurity diffusion region of a conductivity type is provided to penetrate the first active layer from the top of the third cladding layer and further reach the first cladding layer,
A semiconductor laser characterized in that electrodes are provided on the region, on other regions, and on the lower surface of the semiconductor substrate. 2) The semiconductor laser according to claim 1, wherein the first active layer and the second active layer have different energy gaps. 3) The semiconductor laser according to claim 1, wherein each of the first active layer and the second active layer is formed including a quantum well structure. 4) The semiconductor laser according to claim 1, wherein each of the first active layer and the second active layer is formed including a quantum well structure, and the first active layer and the second active layer have different quantum well structures. . 5) The semiconductor laser according to claim 1, wherein the light wave guided through the first active layer and the light wave guided through the second active layer are optically coupled.