JP3027664B2 - 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 improvement in a current blocking function of a semiconductor laser device.

[0002]

2. Description of the Related Art FIG. 5 is an example of a schematic sectional view of a conventional general AlGaAs semiconductor laser. 501 Zn-doped p-GaAs substrate in the figure, 502 is Zn-doped p-Al _0.5 Ga _0.5 As cladding layer, an undoped Al _0.13 Ga _0.87 As active layer 503, 504, 506 Se-doped n-Al _0.5 Ga _0.5 As Cladding layer, 505
Denotes a Zn-doped p-GaAs current blocking layer, 507 denotes a Se-doped n-GaAs contact layer, and 508 and 509 denote n.
Side, p-side electrode. In this element, the current blocking function is performed by a single layer of 505 p-GaAs.

In general, a GaAs material having a large laser light absorption coefficient is used for the current blocking layer as in the above-described elements, and in many cases, light mode control is performed in addition to the current blocking function. That is, the design is performed so that the fundamental transverse mode, which is hardly absorbed by the current blocking layer, oscillates in a laser. However, when the light absorption in the current blocking layer is large, the luminous efficiency of the device is reduced, and a problem of an increase in the threshold value occurs. In order to solve this problem, the structure shown in FIG. 4 has been improved.

That is, FIG. 4 is an example of a schematic cross-sectional view of an AlGaAs semiconductor laser realizing a lower threshold current. The threshold is reduced by performing a current blocking function and an optical confinement function in three layers. In the figure, reference numeral 401 denotes a Si-doped n-GaAs substrate, and 402 denotes Se-doped n-Al
_0.5 Ga _0.5 As clad layer, 403 is non-doped Al
_0.13x Ga _0.77 As active layer, 404 is Zn-doped p-A
l _0.25 Ga _0.75 As clad layer, 405 and 407 are Se
Doped n-Al _0.2 Ga _0.8 As current blocking layer, 406 is S
e-doped n-GaAs mode confinement layer, 408 is Zn
Doped p-Al _0.5 Ga _0.5 As layer, 409 is a Zn-doped p-GaAs contact layer, 410 and 411 are p-side, n
Side electrode.

That is, the GaAs layer is made of Al having a high mixed crystal ratio.
_{The 0.2} Ga _0.8 As layer is interposed, the 406 layer that strongly absorbs light is made thin as a mode confinement layer, and the 405 and 406 layers having a small light absorption coefficient are used as current blocking layers.

[0006]

However, the MOC
When an element is manufactured by using a crystal growth method such as VD, MBE, or LPE, the element is heated to a high temperature (for example, 750 ° C. in MOCVD growth) because the temperature in the growth step is high.
Will be done. Therefore, diffusion of impurities may occur during crystal growth, and the current blocking function may be lost due to a decrease in carrier concentration or pn inversion.

Accordingly, an object of the present invention is to provide a layer for suppressing the diffusion of impurities and to obtain a good current blocking function without impairing the light emitting function.

[0008]

According to the present invention ( claim 1).
Semiconductor laser device is an AlxGa1-xAs type or (AlxGa1-x)
Semiconductor laser with stacked structure of 1-yInyP-based semiconductor material
In the device, any of Zn, Mg, and Be as p-type impurities
Doped first semiconductor layer and n-type impurity
Between the second semiconductor layer with a relatively high Al
Or Al-doped with n-type impurities
Having a low or Al-free third semiconductor layer
It is characterized by the following . The half according to the present invention (claim 2)
The semiconductor laser element is an n-type doped third semiconductor layer.
Wherein the impurity is Se or Te.
You. The semiconductor laser device according to the present invention (claim 3) is
The third semiconductor layer has an Al mixed crystal ratio x of 0 ≦ x ≦ 0.05.
It is characterized by having. The present invention (Claim 4)
The semiconductor laser device according to the above, wherein the third semiconductor layer,
Characterized in that the layer thickness d is 0.05 μm ≦ d ≦ 0.3 μm
Things.

[0009]

In the case of Al _x Ga _{1 -x} As, the diffusion coefficient of Zn tends to increase as the Al liquid crystal ratio increases.
For example, in the case of Al _0.7 Ga _0.3 As, the diffusion rate of Zn is G
It is known that it is about 7 times as large as aAs (Japanese Patent Application No. 3-84782). The inventors show that the diffusion coefficients of Mg and Be show the same tendency, and that (Al _x Ga _{1 -x} ) _Y In _{1 -Y}
It was also found that the same phenomenon occurred in P with respect to the Al liquid crystal ratio.

In addition, Se or Te is set to 10 ¹⁷ to 10 ¹⁸ cm
^-3 doped low Al mixed crystal AlGaAs (X ≦ 0.0
5) or (Al _x Ga _x-1 ) _Y In _Y-1 P (X ≦ 0.05)
Has also found that the diffusion of Zn, Mg, and Be is extremely suppressed.

For example, non-doped, Se or Te
6 and 7 show the profiles of Zn diffusion into the AlGaAs layer or the AlGaInP layer doped with Al. This sample was manufactured by MOCVD at a growth temperature of 750 ° C. and a growth rate of about 1 μm / h. In both cases of FIGS. 6 and 7, a large amount of Zn is diffused from the Zn-doped surface layer to the layer having an Al mixed crystal ratio of 0.7. Spreading is suppressed. In addition, it can be seen that the diffusion is further suppressed in the case of Se or Te doping as compared with the non-doped sample. Also, X
= 0.05 is approximately 0.0
It turns out that it is 5-0.3 micrometers. Similar results have been obtained for the diffusion of Mg and Be.

[0012] Based on these facts, the present invention provides a method for forming an Al layer near an interface between a current blocking layer and a guide layer or a cladding layer.
By forming a diffusion prevention layer having a mixed crystal ratio X ≦ 0.05 and a layer thickness 0.05 ≦ d ≦ 0.3 μm, diffusion of impurities can be sufficiently suppressed, and sufficient diffusion can be achieved without greatly increasing light absorption. The purpose is to obtain a current blocking characteristic.

[0013]

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

<Embodiment 1> FIG. 1 shows the SAS (S
1 shows a sectional view of a semiconductor laser according to a first embodiment applied to an elf-aligned structure) structure. In FIG. 1, reference numeral 101 denotes a Si-doped n-GaAs substrate;
2 n-Al _0.5 Ga _0.5 As cladding layer, an undoped Al _0.13 Ga _0.87 As active layer 103, 104, 110 p-Al _0.5 Ga _0.5 As cladding layer, 105 and 109 non-doped GaAs diffusion barrier layer (thickness 0 .1 μm), 1
06 and 108 are n-Al _0.2 Ga _0.8 As current blocking layers, 1
07 is an n-GaAs mode confinement layer, 111 is p-G
The aAs contact layers 112 and 113 are p-side and n-side electrodes. MBE is used for crystal growth, and Be is used as a p-type impurity and Si is used as an n-type impurity.

In FIG. 1, the non-doped GaAs diffusion preventing layers 105 and 109 are connected to the Si-doped current blocking and mode confinement layers 106 and 108, respectively.
Be diffusion from the p-cladding layer could be effectively prevented. For this reason, 106-108
P inversion due to Be diffusion into each layer did not occur, and generation of a leak current was prevented. In this device, the threshold current was as small as 30 mA, and no current leakage outside the stripe was observed.

<Embodiment 2> FIG. 2 shows a VSIS according to the present invention.
(V-Channeled SubstrateInn
FIG. 4 is a cross-sectional view of a semiconductor laser according to a second embodiment applied to an (er Strip) structure. In FIG. 2, 201 is a Zn-doped p-GaAs substrate, and 202 and 206 are Te-doped n.
-Al _0.05 Ga _0.95 As diffusion prevention layer (thickness 0.05μ)
m), 203 and 205 are Te-doped n-Al _0.2 Ga _0.8
As current blocking layer, 204 is a Te-doped n-GaAs mode confinement layer, 207 is Mg-doped p-Al _0.5 Ga _0.5
As clad layer 208 is non-doped Al _0.13 Ga _0.87
As active layer, 209 is Te-doped n-Al _0.5 Ga _0.5 A
An s cladding layer, 210 is a Sn-doped n-GaAs contact layer, and 211 and 212 are n-side and p-side electrodes. This element uses the LPE method as a crystal growth method.

In FIG. 2, Zn and p of the GaAs substrate 201 are formed by the Te-doped diffusion preventing layers 202 and 206.
-The diffusion of Mg in the cladding 207 into the current block layer was suppressed, no current leakage outside the stripe was observed, and the threshold current was a low value of 35 mA.

<Embodiment 3> FIG. 3 shows a GaAs-based S according to the present invention.
FIG. 9 shows a sectional view of a semiconductor laser according to a third embodiment applied to an AS structure. In FIG. 3, reference numeral 301 denotes Zn-doped p-GaAs.
Substrate, 302 is Zn-doped p-Al _0.5 Ga _0.5 As cladding layer, an undoped Al _0.13 Ga _0.87 As active layer 303, 304 Se-doped n-Al _0.5 Ga _0.5 As cladding layer, 305 Se-doped n-Al _0.05 Ga _0.95 As diffusion preventing layer (thickness 0.3 μm), 306 is Zn-doped p-
GaAs current blocking layer, 307 is Se-doped n-Al _0.5
Ga _0.5 As clad layer, 308 is Se-doped n-Ga
As contact layers 309 and 310 are n-side and p-side electrodes. The MOCVD method was used as the crystal growth method.

In FIG. 3, the diffusion of Zn doped in the current blocking layer 306 is suppressed by the diffusion preventing layer 305.
The carrier concentration of the p-current blocking layer 306 and the n-cladding layer 304 was sufficiently maintained. As a result, the occurrence of current leakage outside the stripe was prevented, and the threshold current was as low as 40 mA.

<Embodiment 4> The present invention relates to an AlGaInP-based S
A fourth embodiment applied to an AS structure is shown. The structure is the same as in FIG. 1, 101 is a Si-doped n-GaAs substrate, 102
Are n- (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P clad layer, 10
3 is a Ga _0.5 In _0.5 P active layer, 104 and 110 are p-
(Al _0.5 Ga _0.5 ) _0.5 In _0.5 P clad layer, 105,
109 is an n- (Al _0.05 Ga _0.95 ) _0.5 In _0.5 P diffusion preventing layer; 106 and 108 are n-Al _0.2 Ga _0.8 As current blocking layers; 107 is an n-GaAs mode confinement layer;
Is a p-GaAs cap layer, and 112 and 113 are p-side and n-side electrodes. MOCVD is used for crystal growth, and Zn is used as a p-type impurity and Se is used as an n-type impurity.

In this device, the diffusion of Zn is suppressed by the diffusion preventing layers 105 and 109 doped with Se, the p inversion of the current blocking layers 106 and 108 is prevented, and the oscillation threshold is 50 m.
The value was as small as A, and no current leak outside the stripe was observed.

As shown in the above embodiment, the number of diffusion preventing layers may be one or two. Further, a crystal growth method used for manufacturing the element is appropriately selected and used, such as an MOCVD method, an LPE method, and an MBE method. In all the above-described examples, the same effect can be obtained even when the conductivity types of all the layers are reversed.

[0023]

As described above, according to the present invention, Al
In a GaAs-based or InGaAlP-based semiconductor laser device, the diffusion of Zn, Be, and Mg can be suppressed to be small, and good current blocking characteristics can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a SAS semiconductor laser showing first and fourth embodiments of the present invention.

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

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

FIG. 4 is a cross-sectional view of a conventional threshold-reduced SAS semiconductor laser.

FIG. 5 is a sectional view of a conventional SAS semiconductor laser.

FIG. 6 is a profile of Zn diffusion into a non-doped or Se or Te-doped AlGaAs layer.

FIG. 7 is a profile of Zn diffusion into an AlGaInP layer that is non-doped or doped with Se or Te.

[Explanation of symbols]

101, 201, 301, 401, 501 Substrate 102, 207, 302, 402, 502 Lower cladding layer 103, 208, 303, 403, 503 Active layer 104, 110, 209, 304, 307, 404, 4
08, 504, 506 Upper cladding layer 105, 109, 202, 206, 305 Diffusion prevention layer 106, 108, 203, 205, 306, 405, 4
07, 505 Current blocking layer 107, 204, 406 Mode confinement layer 111, 210, 308, 409, 507 Contact layer 112, 212, 310, 410, 509 p-side electrode 113, 211, 309, 411, 508 n-side electrode

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-253389 (JP, A) JP-A-1-251684 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01S 5/00-5/50 JICST file (JOIS)

Claims (4)

(57) [Claims] 1. An AlxGa1-xAs or (AlxGa1-x) 1-yInyP
Semiconductor laser device with a laminated structure of
And any one of Zn, Mg, and Be is doped as a p-type impurity.
The first semiconductor layer and a relatively Al mixed crystal doped with n-type impurities
A relatively non-doped or n-type impurity-doped relatively Al
A third semiconductor layer having a low crystal ratio or containing no Al
A semiconductor laser device characterized by the following . 2. An n-type impurity doped in the third semiconductor layer.
2. The material according to claim 1, wherein the material is Se or Te.
Semiconductor laser device. 3. The third semiconductor layer has an Al mixed crystal ratio x
Is 0 ≦ x ≦ 0.05, wherein 1 ≦ x ≦ 0.05
3. The semiconductor laser device according to 2. 4. The third semiconductor layer has a layer thickness d of 0.05
4. The device according to claim 1, wherein μm ≦ d ≦ 0.3 μm.
The semiconductor laser device according to any one of the above.