JP3139886B2 - Semiconductor laser device and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a semiconductor laser device and a method for manufacturing the same.

[0002]

2. Description of the Related Art In the above-mentioned semiconductor laser device, at the light emitting end face of a resonator, oxygen and the like in the atmosphere adhere to and bond to the crystal surface, and the surface level increases. Therefore, the band gap at the light emitting end face is narrower than inside the element, and the band gap at the light emitting end face of the active layer is also narrower than inside the element. Generally, the laser oscillation wavelength (energy) of a semiconductor laser device is determined by the band gap of the active layer. However, as described above, the band gap at the light emitting end face of the active layer is narrower than inside the device. Then, the laser light oscillated inside the element is absorbed by the light emitting end face. Therefore, heat is generated by the absorption of the laser light at the light emitting end face, and further, the band gap at the light emitting end face of the active layer is further narrowed by the heat generation, thereby causing a vicious cycle that the absorption of the laser light is further increased. Due to this vicious cycle, the crystal constituting the light-emitting end face eventually breaks and melts due to the high temperature, and the element is deteriorated. In addition, even when the crystal does not break, defects and dislocations in the crystal multiply and grow due to the temperature rise due to the heat generation.
It grows, and the deterioration of the element progresses. Such destruction of the crystal due to laser light absorption at the light emitting end face is a factor that impairs the reliability of the semiconductor laser device.

Conventionally, semiconductor laser devices having various structures have been proposed in order to prevent the device from being deteriorated due to the absorption of laser light at the light emitting end face. For example, Matsumoto et al. At the 51st Academic Lecture on Applied Physics in the fall of 1990: 28p-R-5 to 6) proposed a window-type structure in which an end face growth layer with little absorption of oscillating laser light was provided on the light emitting end face. A semiconductor laser device has been proposed. FIG. 4 shows a semiconductor laser device having the above window structure. The internal structure 40 of this semiconductor laser device is S. Yamamo
To et. al; Appl. Phys. Lett. 40 (1982) 372. VSIS (V-
channel substrate inner stripe) structure,
An end face growth layer 43 having a larger band gap than the active layer 41 is formed on the light emitting end face. In this figure, 45 indicates a p-side electrode, 46 indicates an n-side electrode, and 47 indicates a dielectric film.

For example, a VSIS having an oscillation wavelength of 780 nm
In the case of the type semiconductor laser device, the Al mixed crystal ratio x of the active layer 41
Is 0.14, whereas A as the end face growth layer 43
l mole ratio t can be used Ga _1-t Al _t As crystals of less than 0.14. In this case, the bandgap of the end face growth layer 43 is larger than that of the active layer 41, and the layer has less absorption of the oscillation laser light. For this reason, especially the characteristics at the time of high output are improved, and a semiconductor laser device excellent in long-term reliability can be realized.

The above window type semiconductor laser device is manufactured as follows. First, as shown in FIG.
A VSIS structure as the internal structure 40 is formed by a liquid phase epitaxial growth (LPE) method.

[0006] Next, as shown in FIG.
The wafer 50 on which the structure is formed is cleaved into bars 51. The cleavage plane 42 of the bar 51 becomes a cavity end face which is a light emission end face of the semiconductor laser device.

[0007] Thereafter, as shown in FIG.
1 on a carbon jig 53, and
It is installed on a susceptor 54 in a (organic metal vapor phase epitaxy) type growth apparatus. The growth of the end face growth layer 43 is performed by high-frequency heating the susceptor 54 while flowing, for example, AsH ₃ gas, TMA (trimethylaluminum), TMG (trimethylgallium), or the like as the source gas 55. The growth temperature at this time is set to about 800 ° C.

Since the entire surface of the bar 51 is a good crystal plane, the growth of the end face growth layer is performed on the entire surface as shown in FIG. In the grown end face growth layer, the portion 43a is a portion where the p-side electrode 46 is formed. If left, the device resistance of the semiconductor laser device increases. Therefore, after the growth is completed, the end face growth layer 43 on the light emission end face
A dielectric film 47 for suppressing oxidation is deposited thereon, and the unnecessary portion 43a is removed by etching using this as a mask as shown in FIG.

Thereafter, as shown in FIG. 5F, a p-side electrode 45 and an n-side electrode 46 are formed in a bar state, and the chip is divided into chips. Thus, a window-type semiconductor laser device is obtained.

[0010]

In the above-mentioned window type semiconductor laser device, since the end face growth layer 43 is formed, light absorption at the light emitting end face 42 is suppressed to improve the device characteristics at the time of high output. Can be. However, since the formation of the end face growth layer 43 is performed in a high-temperature atmosphere of about 800 ° C., the following problem occurs.

In order to control the conductivity type, Zn, Be, Mg, etc. are added to the crystal constituting the semiconductor laser element, and Te, Se, Si, etc. are added as impurities to the p-type, and trace amounts are added as impurities to the n-type. Have been. However, when these impurities are placed at a high temperature during the formation of the end face growth layer 43, they diffuse inside the semiconductor laser device, thereby moving the formed pn junction position or moving impurities between crystals having different compositions. To change the impurity concentration distribution inside the semiconductor laser device. As a result, the electrical and optical characteristics of the semiconductor laser device are deteriorated, and the reliability of the semiconductor laser device is adversely affected.

The present invention solves the above problems,
An object of the present invention is to provide a semiconductor laser device having high reliability by suppressing internal diffusion of an impurity added to a crystal constituting a semiconductor laser device.

[0013]

A semiconductor laser device according to the present invention is composed of a crystal containing Al, and has a larger band gap at the light emitting end face of a resonator including an active layer than the crystal constituting the active layer. In a semiconductor laser device having an end face growth layer made of a crystal, the end face growth layer is formed by growing at a growth temperature of 500 ° C. or less by metal organic chemical vapor deposition or molecular beam epitaxy. Thereby, the above object is achieved.

A method for manufacturing a semiconductor laser device according to the present invention
A method of manufacturing a semiconductor laser device, comprising: an end face growth layer made of a crystal having a band gap larger than that of a crystal forming an active layer formed on a light emitting end face of a resonator including an active layer, the end face growth layer being formed of a crystal including Al. The end face growth layer is grown at a growth temperature of 500 ° C. or less by a metalorganic vapor phase epitaxy method or a molecular beam epitaxy method, thereby achieving the above object.

[0015]

In the present invention, the end face growth layer is grown at a low temperature of 500.degree. C. or less by the metalorganic vapor phase epitaxial growth method or the molecular beam epitaxial growth method. Therefore, it is possible to suppress the impurity added to the crystal from being diffused inside.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

Example 1 FIG. 1A is a perspective view showing a semiconductor laser device of Example 1. FIG. This semiconductor laser device has a VSIS structure. A striped V-shaped groove 13 is formed in a p-type GaAs substrate 11 on which an n-type GaAs current confinement layer 12 is formed, and a p _- type Ga _1-y A is formed thereon.
_{l y As (0 <y ≦} 1) cladding layer 14, p-type Ga _1-x A
l _x As (0 ≦ x <1) active layer 3, n-type Ga _{1 -z} Al _z A
An s (0 <z ≦ 1) cladding layer 16 and an n-type GaAs contact layer 17 are sequentially laminated. The end face of the VSIS internal structure 1 is formed as a laser light emission end face 2 by cleavage. The light emitting end face 2, Ga _1-t Al having a high Al mixed crystal ratio t than Al content of the active layer 3 x t As (x
<T ≦ 1) The end face growth layer 4 is formed. For example, in the case of a semiconductor laser device having an oscillation wavelength of 780 nm, the Al mixed crystal ratio t can be set to t> 0.14. In this embodiment, t = 0.6 is set to have a sufficiently large band gap with respect to the active layer inside the device. The end face growth layer 3 is grown at a growth temperature of 500 ° C. or lower. Further, a dielectric film 8 is formed on the end face growth layer 4, and the substrate 11 side and the contact layer 17 are formed.
On the sides, a p-side electrode electrode 6 and an n-side electrode 7 are formed, respectively.

The manufacture of the semiconductor laser device can be performed, for example, as follows. First, as shown in FIG. 2A, the internal structure 1 of the semiconductor laser device is formed. An n-type GaAs current confinement layer 12 having a thickness of 0.8 μm is laminated on the p-GaAs substrate 11 by the LPE method, and a stripe-shaped V groove 13 having a width of 3 μm and a depth of 1.0 μm is formed by chemical etching. Thereafter, in the second growth step by the LPE method, the p-Ga _0.55 Al _0.45 As clad layer 14 having a thickness of 0.8 μm (the portion other than the V-groove 13) and the p-Ga _0.86 Al _0.14 As active layer having a thickness of 0.06 μm are formed. 3. An n-Ga _0.55 Al _0.45 As cladding layer 16 having a thickness of 1 μm and an n-GaAs contact layer 17 having a thickness of 2 μm are continuously laminated.

The wafer 20 on which the laminated structure has been formed as described above is cleaved to a cavity length to obtain a laser bar 21 as shown in FIG. 2B. The cleavage plane of this laser bar 21
It becomes the light emitting end face 2 of the semiconductor laser device.

Next, as shown in FIG. 2C, the MOCV
According to the D method, a Ga _{0.6 layer} having a thickness of 0.1 μm
An Al _0.4 As end face growth layer 4 is grown. The growth temperature at this time was set to 500 ° C. or lower, and the growth was performed with the V / III ratio set to 45. As described above, at a low growth temperature of 500 ° C. or lower, the diffusion of impurities added into the n-type or p-type crystal can be reduced.

The growth of the end face growth layer 4 is also performed on portions other than the light emitting end face 2 as shown in FIG. If the portion 4a is left in the grown end face growth layer, the device resistance of the semiconductor laser device is increased. A dielectric film 8 for suppressing oxidation is deposited on the end face growth layer 4 on the light emitting end face, and this is used as a mask in FIG.
As shown in (d), the unnecessary portion 4a is removed by etching.

Next, the p-side electrode 6 and the n-side electrode 7 are formed on the laser bar 21 in this state. AuZn, Au, Mo, and Au are sequentially deposited as a metal for the p-side electrode 6 and AuGe, Ni, Mo, and Au are sequentially deposited as a metal for the n-side electrode 7.
A good ohmic contact can be obtained by alloying the deposited metal and the crystal constituting the semiconductor laser element in a nitrogen atmosphere at 00 ° C. Thereafter, the laser bar 21 is divided into chips to obtain a window-type semiconductor laser device as shown in FIG.

In the above-described semiconductor laser device, since the growth of the end face growth layer 4 is performed at a low temperature of 500 ° C. or less, the internal diffusion of impurities added to the crystal constituting the semiconductor laser device can be suppressed. . Therefore, it is possible to prevent the deterioration of the semiconductor laser device characteristics after the formation of the end face growth layer 4.

In order to suppress the oxidation of the light emitting end face, a dielectric film 8 is deposited on the end face growth layer 4 and assembled into a heat dissipation package.
A long-term running test was performed under a constant light output driving condition of mW. As a result, as shown in FIG. 2E, an increase in the driving current IOP was suppressed as compared with the conventional semiconductor laser device, and the reliability was improved.

Embodiment 2 FIG. 1B is a perspective view showing a semiconductor laser device of Embodiment 2. In the semiconductor laser device of this embodiment, the light emitting end face 5 is formed by etching.

The manufacture of this semiconductor laser device is performed as follows. First, the VSIS internal structure 1 is formed in the same manner as in the first embodiment. Next, as shown in FIG.
The resist 20 covers the wafer 20 except for the portion where the light emitting end face 5 is to be formed by photolithography.

Thereafter, as shown in FIG.
By dry etching such as E (reactive ion beam etching), a crystal plane to be the light emitting end face 5 is formed.

Next, as shown in FIG.
The end face growth layer 4 is grown by MOCVD using the same conditions as described above, and the unnecessary growth portion 4a is removed.

The wafer on which the end face growth layer 4 is formed as described above is cleaved into laser bars 21, and a dielectric for suppressing oxidation is formed on the end face growth layer 4 of the light emitting end face 5 as shown in FIG. The film 8 is deposited, and the unnecessary portion 4a is removed by etching using the film 8 as a mask.

Next, the p-side electrode 6 and the n-side electrode 7 are formed on the laser bar 21 in this state in the same manner as in the first embodiment, and the laser bar 21 is divided into chips, as shown in FIG. Window semiconductor laser device.

Also in the semiconductor laser device of this embodiment, the growth of the end face growth layer 4 is performed at a low temperature of 500 ° C. or less as in the first embodiment. Deterioration can be prevented.

In the first and second embodiments, AlGaAs
Although an s-based semiconductor laser device has been described, other compounds and mixed crystal systems can be used.
The present invention can also be applied to an AlP-based semiconductor laser device.

Although the description has been given of the semiconductor laser device having the VSIS structure, the present invention can be applied to a semiconductor laser device having another structure. Further, for the sake of simplicity, a semiconductor laser device having a double heterostructure has been described.
(Separated Confinement Heterostructure) type and GR
The present invention can also be applied to a semiconductor laser device such as an IN (Graded Index) -SCH type. MO is used as a growth method of the end face growth layer.
Although the CVD method is used, a similar effect can be obtained by using the MBE method.

[0034]

As is clear from the above description, in the present invention, since the end face growth layer grown on the light emitting end face of the resonator is grown at a low temperature of 500 ° C. or less, the semiconductor laser device is constructed. Internal diffusion of impurities contained in the resulting crystal can be suppressed. Therefore, it is possible to suppress the deterioration of the characteristics of the semiconductor laser element and improve the reliability.

[Brief description of the drawings]

FIG. 1A is a perspective view illustrating a semiconductor laser device according to a first embodiment, and FIG. 1B is a perspective view illustrating a semiconductor laser device according to a second embodiment.

2 (a) to 2 (d) are diagrams showing a manufacturing process of the semiconductor laser device of Example 1; and FIG. 2 (e) is a view showing a running time, a driving current and a driving current in Example 1 and a conventional semiconductor laser device. 6 is a graph showing the relationship of.

FIGS. 3A to 3E are diagrams illustrating a manufacturing process of the semiconductor laser device according to the second embodiment.

FIG. 4 is a perspective view showing a conventional semiconductor laser device.

5 (a) to 5 (f) are views showing a manufacturing process of a conventional semiconductor laser device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Internal structure 2, 5 Light emission end face 3 Active layer 4 End face growth layer 6 P-side electrode 7 N-side electrode 8 Dielectric film 11 Substrate 12 Current constriction layer 13 Stripe-shaped V-groove 14, 16 Cladding layer 17 Contact layer 20 Wafer 21 Laser bar

────────────────────────────────────────────────── ─── Continuation of front page (72) Hiroshi Hayashi 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (56) References JP-A 1-227485 (JP, A) JP-A 1-227 166588 (JP, A) JP-A-3-106090 (JP, A) JP-A-64-81289 (JP, A) JP-A-1-138784 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01S 5/00-5/50

Claims (2)

(57) [Claims] 1. A semiconductor laser comprising an Al-containing crystal and an end face growth layer made of a crystal having a band gap larger than that of the crystal constituting the active layer on a light emitting end face of a resonator including an active layer. in the element, the end face growth layer, a semiconductor laser device by metal organic chemical vapor deposition or molecular beam epitaxy, Ru is formed to grow at 500 ° C. below the growth temperature. 2. A semiconductor laser comprising an Al-containing crystal and an end face growth layer made of a crystal having a band gap larger than that of the crystal constituting the active layer on a light emitting end face of a resonator including the active layer. in the manufacturing method for the device, the end face growth layer by metal organic chemical vapor deposition or molecular beam epitaxy, a method of manufacturing a semiconductor laser device Ru grown at 500 ° C. below the growth temperature.