JPH03145787A - Semiconductor laser element - Google Patents

Abstract

PURPOSE:To obtain a distorted quantum well semiconductor laser element which outputs a high power and is long in service life by a method wherein a distorted quantum well active layer is sandwiched between clad layers to constitute an InGaAs double hetero-structure, where the clad layers are formed of InzGa1-zAsyP1-y. CONSTITUTION:An N-type GaAs buffer layer 2, an N-type In0.49Ga0.51P clad layer 3, an active and light trapping layer 4, a P-type In0.49Ga0.51P clad layer 5, and a P-type contact layer 6 are successively laminated on an N-type GaAs substrate 1 through an MBE method or an MOCVD method. The active and light trapping layer 4 is formed in such a structure that a GaAs barrier layer 8 and an InGaAs distorted quantum well layer 9 are laminated in multilayer to constitute an active layer, which is sandwiched between GaAs light trapping layer 7. Even if a clad layer is formed of InGaAsP whose energy gap is 1.5eV or above, light and carriers can be trapped, and a regrowth interface and a cleavage plane are hardly oxidized, so that a laser long in service life can be manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to improvements in strained quantum well semiconductor laser devices.

[Conventional technology]

I n XG a + - xA s (x = 0.1~0
．． 5) A strained quantum well semiconductor laser device in which an active layer with a strained quantum well layer structure consisting of a strained quantum well layer and a GaAs barrier layer is formed on a GaAs substrate is different from the conventional GaAs/Al2Ga
For lattice matched lasers such as As and Ga1nAsP/InP, the wavelength ranged from 0.9 to 1.1/2, which was just in the valley.
It is expected to be a 1m light source.

Incidentally, in order to confine carriers and light in the active layer, a semiconductor laser element is transparent to light at the oscillation wavelength, has a lower refractive index than the active layer (or an optical confinement layer near the active layer), and has a lower energy It is necessary to use a semiconductor with a large gap as the cladding.

In the conventional strained quantum well semiconductor laser device, where w>0.3, A Itl, Ga + - wA
S is used as the cladding.

A conventional example will be explained using FIG. 2. ■ is an n-type GaAs substrate with a thickness of approximately 350 mm, and MBE or MO
Two or less layers are stacked by epitaxial growth such as CVD. 2 is a 0.5-thick n-type GaAs buffer layer, and 3 is a 1.5-thick n-type Aj! o, 3Gao, 7As
This is the cladding layer.

4 is l n@, 35Ga6.6s AS strained quantum well, G
These are an active layer and a light confinement layer consisting of an aAs barrier layer or the like.

5 is a p-type A lo, s Ga o with a film thickness of 1.5
, 7 A S cladding layer, 6 is a 0.2-thick p
type contact layer.

The details of 4 will be explained using FIG. 7 are As optical confinement layers with a thickness of 1,500,500 mm each on the upper and lower sides, 8 are GaAs barrier layers each with a thickness of 100 mm, and 9 are each with a thickness of 40 mm.
It is a strained quantum well layer of I n 6.3SG a O, 65A S with a human thickness.

The double heterostructure uniformly formed on the GaAs substrate is subjected to fine processing such as current confinement layer formation, electrode formation, and element isolation to obtain a laser chip.

Note that the above is an example of a conventional example, and the composition ratio of the mixed crystal, the number of quantum well layers, the film thickness of each layer, etc. may vary. Further, as the optical confinement layer, a GRIN-3CH structure using AjIC;aAs in which the /l composition ratio is varied is also often used.

[Problem to be solved by the invention]

The main uses of lasers with a wavelength of 0.9 to 1.1 - are for pumping fiber amplifiers doped with rare earth elements such as Er, or for pumping S
It is a visible light source etc. in combination with HG, and generally requires a high output of several tens of mW or more and a long life.

The conventional strained quantum well semiconductor laser device uses AffGaAs for the cladding layer as described above, but has the following problems.

In, Ap, , Ga, As, P constituting a compound semiconductor
, Sb, and the like, Ap is the element that is most easily oxidized. Therefore, if oxidation occurs during the fabrication of the laser chip, such as at the regrowth interface during buried growth, it will cause non-emissive centers to occur and deterioration of crystallinity, making it impossible to obtain good laser characteristics.

Further, if the cleavage plane is used as a laser end face, end face oxidation progresses during the period of use of the laser, resulting in a decrease in reflectance and an increase in absorption, resulting in deterioration of laser characteristics. Particularly during high injection, the temperature becomes high and oxidation progresses rapidly.

Therefore, in order to suppress such oxidation of AN, great efforts must be made to remove oxygen and moisture during the laser manufacturing process, and efforts must be made to protect the end faces.

That is, there was a problem in that it was not easy to obtain a laser with high output and long life.

[Means and actions to solve the problem]

The present invention provides a semiconductor laser device that solves the above-mentioned problems, and includes an active layer having a strained quantum well structure in which a quantum well layer is made of T n The cladding layers placed above and below are G
In a semiconductor laser device formed by epitaxial growth on an aAs substrate, the cladding layer is In
It is characterized by being composed of zG a l-mA S yP +-y.

The upper and lower cladding layers of the active layer can sufficiently confine light and carriers in the strained quantum well active layer and optical confinement layer, so G
It is lattice matched to the aAs substrate and has a refractive index of A/! for light with a wavelength of 0.9 to 1.1-. wGa+-wAS(W-0,5~
0.6), and the energy gap is A
p, wG a 1-wA s (w ~0.5~0.6
) is required to be as large as . In, IG a
Since I-zA syP +-y satisfies the above conditions by adjusting the composition, it can be used as a cladding layer, and since it does not contain Aff, it can be used as a cladding layer.
It is possible to prevent the above-mentioned problems caused by the oxidation of . In the present invention, at least the upper and lower cladding layers of the active layer are made of materials that do not contain Aj2, but it is desirable that all constituent materials of the strained quantum well semiconductor laser device be made of materials that do not contain Affi. Needless to say.

〔Example] Examples of the present invention will be described below.

In one embodiment of the present invention, the cladding layers 3 and 5 in FIG. 2 used to explain the conventional example are replaced with n-type and p-type I
No, aqGao, s+P.

That is, MB is formed on an n-type GaAs substrate 1 with a film thickness of about 350 mm.
By E or MOCVD method, an n-type GaAs buffer layer of 0.51 m1 thickness is formed.
411G ao, s+ P cladding layer 3, active layer and optical confinement layer 4.1.5-thick p-type 1 no,
aqG ao, 5+P cladding layer 5 and 0.2-
Thick p-type contact layers 6 were sequentially laminated. As shown in FIG. 3, the active layer and optical confinement layer 4 are composed of a GaAs barrier layer 8 with a thickness of 100 mm and a thickness of I n Q, 3SG with a thickness of 40 mm.
It has a structure in which an active layer made up of multiple layers of ao, 6sA S strained quantum well layers 9 is covered above and below with a GaAs light confinement layer 7 with a thickness of 1500 μm. The oscillation threshold current density of a full electrode type semiconductor laser device having such a structure during room temperature pulse driving is 290 A/ci, and A1. o, 5
Values equivalent to those of Gao and 5AS were obtained.

The second embodiment of the present invention, as shown in FIG.
Au metal n-type electrode, 11 is n-type GaA type, n-type In
Current blocking is performed at this p/n junction in the GaP layer.

17, p-type 1nGaP cladding layer, 18, p-type CaA
S key! 7. 19 is a p-type electrode of AuZn. 14 is a strained quantum well active layer and an optical confinement layer.

The width of the active layer and optical confinement layer 14 is approximately 1.5/IT
In II, the resonator length was 300 -, and the cleavage plane was made into a mirror without a protective film.

When this semiconductor laser device is operated, a current of 7 mA is generated at room temperature c.
W optical oscillation was obtained, and an output of 100 mW was obtained when 150 mA was injected. No change was observed in the 1-L characteristics even after laser driving at 50 mW for 2000 hours, and a long life with high output was obtained.

In the above examples, InGaP was used for the cladding layer, but TnGaP with an energy gap of 1.5 eV or more
Even if sP is used in the ground layer, light and carriers can be confined, and A! Since it does not contain oxidation at the regrowth interface and cleavage interface, a long-life laser can be produced.

InGaAsP only needs to be lattice matched to the GaAs substrate to the extent that no dislocation occurs.

Further, the film thickness and composition of each layer, the number of strained quantum well layers, etc. are not limited to those in the embodiment. Furthermore, a GRIN structure in which the composition of InGaAsP is changed in stages may be used for the optical confinement layer.

Note that the semiconductor laser element structure is not limited to the above embodiments, and the cleavage end face may be coated for the purpose of reducing the threshold value, improving efficiency, and further increasing output.

〔Effect of the invention〕

As explained above, according to the present invention, in the InGaAs-based tuple heterostructure in which the strained quantum well active layer is sandwiched between the upper and lower sides by the cladding layers, the cladding layer is made of In, lGa 1-ZA.
Since it is composed of S yP ly, there is an excellent effect that a strained quantum well semiconductor laser device with high output and long life can be obtained.

[Brief explanation of the drawing]

FIG. 1 is an explanatory sectional view of one embodiment of a semiconductor laser device according to the present invention, FIG. 2 is an explanatory sectional view of another embodiment and a conventional example, and FIG. 3 is a partially enlarged view of FIG. 2. , 1,
11-G a As substrate, 2, 12... buffer layer, 3. 5.13.17...Clad layer, 4.1
4... Active layer and light confinement layer, 6... Contact layer, 7... Light confinement layer, 8... Barrier layer,
9...Strained quantum well layer, 15...p-type 1nGaP layer, 16...=n-type TnGaP layer, 18-...k+7 layer, 19...p-type electrode, 20...n-type electrode .

Claims (1)

[Claims] Ga with In_xGa_1_-_xAs as quantum well layer
In a semiconductor laser device in which an active layer having a strained quantum well structure with As as a barrier layer and cladding layers disposed above and below this active layer are formed by epitaxial growth on a GaAs substrate, the cladding layer is In_zGa_1_
A semiconductor laser device comprising: -_zAs_yP_1_-_y.