JPH0856047A - Semiconductor device and its manufacture - Google Patents

Abstract

PURPOSE:To provide a high reliability semiconductor device having no defect that a dislocation defect is generated in an active layer by stress distribution generated from an insulating film deposited in the vicinity of a laser end surface, and dark line deterioration is generated. CONSTITUTION:On a substrate 1, the following are formed; an N-GaAs buffer layer 2, an N-AlGaAs clad layer 3, an AlGaAs guide layer 4, an AlGaAsSCH layer 5, an Inlays strain quantum well active layer 6, an AlGaAsSCH layer 7, an AlGaAs guide layer 8, a P-AlGaAs clad layer 9 and a P<+>-GaAs contact layer 10. In this semiconductor device, an AlGaAs current blocking layer 11 composed of a semiconductor layer is formed in a non-excited region.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-power semiconductor laser having a non-excitation region near the end face and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, various semiconductor lasers having a semiconductor layer laminated on a GaAs substrate have been proposed. According to such a semiconductor laser, GaAs / AlGaA
A laser in the 0.6 to 0.8 μm band having s, InGaP as an active layer is used for optical information recording and optical information recording / reproducing. Further, in recent years, a laser having a wavelength band of 0.8 to 1 μm or more with an InGaAs / GaAs strained quantum well layer as an active layer has been used as an excitation light source for a fiber amplifier. Although high output operation is required for these lasers, there is a problem that it is difficult to obtain a semiconductor laser having a sufficient life even in high output operation. Several studies have been conducted so far on the state of deterioration of semiconductor lasers. These are optical damage destruction C of the cavity end face.
They are roughly classified into those caused by OD (Catastrophic Optical Damage), surface alteration, growth of crystal dislocation defects, and damage to other ohmic electrodes and generation of point defects. In particular, in a semiconductor laser having a semiconductor layer laminated on a GaAs substrate, it has been pointed out that the COD at the end face of the cavity is an important deterioration state that determines the lifetime of the laser in high-power operation. This COD is because the vicinity of the end face of the resonator of the semiconductor laser is an absorption region for laser light. This originates in the decrease in the band gap due to the temperature rise due to the non-radiative recombination via the surface dislocation existing on the semiconductor crystal surface. This bandgap reduction is accompanied by feedback that the temperature further rises. For this reason, melting of the end face is induced and the light output decreases,
Irreversible destruction occurs.

In order to increase the critical light output of this COD, a so-called window structure has been adopted in which the resonator end face is made of a semiconductor material having a high band gap. In addition, in order to suppress the temperature rise due to non-radiative recombination, current injection near the end face is suppressed. The end face non-excited structure was taken. In order to realize this end face non-excitation structure, a method of suppressing current injection by covering the surface of the waveguide portion near the end face with an insulating film such as SiO ₂ has been used (FIG. 5). In FIG. 5, 1 is an n ⁺ -GaAs substrate, 2 is an n-GaAs buffer layer, 3 is an n-AlGaAs cladding layer, and 4 is AlGa.
As guide layer, 5 AlGaAs SCH layer, 6 InG
aAs strained quantum well active layer, 7 AlGaAs SCH layer,
8 is an AlGaAs guide layer, 9 is a p-AlGaAs cladding layer, 10 is a p ⁺ -GaAs cap layer, and 11 is Al.
GaAs current blocking layer, 12 is an insulating film, 13 is a p-electrode, and 14 is an n-electrode.

[0004]

Among the above-mentioned conventional high-power semiconductor lasers, in the case of the window structure, it has been proposed to form the window structure by impurity diffusion and regrowth. The window structure by diffusion of impurities utilizes the thermal diffusion of Zn, Si, etc. to make the crystal disorder near the active layer and lower the effective refractive index to make it transparent to the oscillation wavelength. The window structure by regrowth is a semiconductor material having a band gap larger than that of the active layer, for example, AlGaAs or InGaP having a large Al composition.
Can be realized by configuring the resonator end face with. However, in the high-power semiconductor lasers having a window structure to date, there is a concern that the laser epitaxial characteristics may be deteriorated because a high temperature treatment process is required for both impurity diffusion and regrowth. Further, in both cases, since the process steps are complicated, there is a drawback that it is difficult to obtain a laser having good characteristics with good reproducibility and yield.

Among the conventional high-power semiconductor lasers, in the case of the end face non-excitation structure, the surface of the waveguide portion near the end face is made of SiO 2.
_A method of suppressing current injection by covering with an insulating film such as ₂ has been proposed (FIG. 6). However, although the effect of increasing the critical light output of COD has been confirmed in the conventional facet non-excited structure, dislocation defects are generated in the active layer due to the stress distribution generated from the insulating film deposited only near the facet. However, it has a drawback that it causes dark line deterioration. This dislocation easily occurs near the edge of the insulating film where the stress changes greatly, and when a part of the waveguide is covered with an insulating film such as SiO ₂ as in the conventional end face non-excited structure, this insulating film There was deterioration due to the dark line defect that occurred near the edge. Therefore, it is an object of the present invention to propose a novel semiconductor device having a non-excited region in the vicinity of an end face and a method for manufacturing the same, which does not have the above-mentioned drawbacks.

[0006]

To achieve the above object, (1) The present invention is a semiconductor device having a non-excitation region near an end face, wherein a current blocking layer made of a semiconductor layer is provided in the non-excitation region. A semiconductor device is a feature of the invention. (2) The semiconductor device according to (1) above, wherein the current blocking layer in the non-excitation region is an AlGaAs layer or an InGaP layer is a feature of the present invention. (3) In a method of manufacturing a semiconductor device having a non-excited region near an end face, a step of forming each semiconductor layer and a current block layer in a semiconductor device on a substrate by one-time growth; A method of manufacturing a semiconductor device, which comprises a step of etching away the current blocking layer, is a feature of the present invention. In other words, the semiconductor device having the non-excited region near the end face according to the present invention is characterized in that the current block layer in the non-excited region is formed of the semiconductor layer. Conventionally, the current blocking layer in the non-excitation region is formed of an insulating layer such as SiO ₂ . The method of manufacturing a semiconductor device according to the present invention is characterized in that the semiconductor device is formed by growing the constituent layer and the current blocking layer once, and high temperature treatment such as impurity diffusion and regrowth is not performed.

[0007]

According to the method of manufacturing a semiconductor device having a non-excited region near the end face according to the present invention, the high temperature treatment process used for impurity diffusion and regrowth in the conventional window structure high power semiconductor laser is unnecessary. , Reproducibility due to deterioration of laser epitaxial characteristics and complicated process steps,
It can be easily realized without deteriorating the yield. In the semiconductor device having the non-excitation region near the end face according to the present invention, as in the case of the end face non-excitation structure of the conventional high-power semiconductor laser, the surface of the waveguide portion near the end face is covered with an insulating film such as SiO _2. Since it can be realized without covering with, the stress distribution generated from the insulating film deposited only in the vicinity of the end face causes dislocation defects in the active layer, and dark line deterioration is not caused. A high output semiconductor device can be provided.

[0008]

EXAMPLES Next, examples of the present invention will be described. (Embodiment 1) FIG. 1 is a sectional view in the cavity direction of a semiconductor laser having a non-excitation region on an end face according to the first embodiment of the present invention, and FIGS. 2 and 3 are a current injection region and non-excitation region, respectively. It is a figure which shows the structure of the cross section perpendicular | vertical to the resonator direction in an area | region. In the figure, 1 is an n ⁺ -GaAs substrate, 2
Is an n-GaAs buffer layer, 3 is an n-AlGaAs cladding layer, 4 and 8 are AlGaAs guide layers, 5 and 7 are AlGaAs SCH layers, 6 is an InGaAs strained quantum well active layer, 9 is a p-AlGaAs cladding layer, and 10 is p.
⁺ -GaAs contact layer, 11 is an AlGaAs current blocking layer, 12 is an insulating film, 13 is a p-electrode, and 14 is an n-electrode. 2 is a sectional view taken along the line AA ′ in FIG.
FIG. 3 is a sectional view taken along the line BB 'in FIG.

In order to realize this structure, an epitaxial crystal growth apparatus (MOCVD method: metal organic chemical vapor deposition apparatus or MBE method: molecular beam epitaxy method) was used to form an n ⁺ -GaAs substrate 1 on the substrate, as shown in FIG. , Sequentially n-G
aAs buffer layer 2, n-AlGaAs cladding layer 3,
AlGaAs guide layer 4, AlGaAs SCH layer 5, I
nGaAs strained quantum well active layer 6, AlGaAs SCH layer 7, AlGaAs guide layer 8, p-AlGaAs cladding layer 9, p ⁺ -GaAs contact layer 10, AlGaA
The s current blocking layer 11 is formed. In the MOVPE method,
Trimethylindium (TMI), triethylgallium (TEG), trimethylaluminum (TMA), arsine (AsH ₃ ) are used as raw materials for semiconductor thin film growth.
Selenium sulfide (H ₂ Se) was used as the n-type dopant, and diethyl zinc (DEZn) was used as the p-type dopant. The epitaxial growth temperature is about 700 ° C., the growth pressure is about 0.1 atm, and the carrier gas is hydrogen. In the MBE method, metallic gallium (Ga) and indium (I) are used as raw materials.
n), aluminum (Al), arsenic (As solid),
Silicon (Si) was used as the type dopant, and zinc (Zn) was used as the p-type dopant. The epitaxial growth temperature is about 650 ° C. and the growth pressure is about 10 ⁻⁵ Torr.

After growth, the AlGaAs current blocking layer 1
1, processing the contact layer 10 and the clad layer 9,
A ridge having a width of about 1.5 to 3 μm is formed. Therefore, resist patterning is performed by photolithography, and using this as a mask, wet or dry etching is performed.
Etch 10,2 layers. The depth is determined in consideration of the transverse mode, and the guide layer 8 may be etched in some cases.
Next, the eleventh layer on the ridge in the current injection region other than the non-excitation region near the cavity end face is etched. After forming the ridge,
Insulated by sputtering film 12 (SiO ₂ or the like) is formed on the entire surface, after the SiO ₂ of the current injection region of the ridge top and etched off, Cr / Au or Ti / Pi / Au
An equal p electrode 13 and an n electrode 14 such as AnGeNi are formed. After that, ohmic sintering is performed to form an electrode portion.

Example 2 The same laser as that of Example 1 can be realized when 11 current blocking layers are InGaP layers. The epitaxial growth and manufacturing process can be performed in the same procedure. In this case, etching 11 layers is 10
It can be realized by selective etching with layers.

[0012]

According to the semiconductor device having the non-excited region near the end face and the manufacturing method according to the present invention, no sudden deterioration of the optical output at high output is observed, and reversible thermal saturation characteristics are observed. Even in the long-term current test with electric current, the failure deterioration due to COD was solved. Further, since the high temperature treatment process used for the impurity diffusion and regrowth in the conventional window structure high power semiconductor laser is not necessary, the deterioration of the laser epitaxial characteristics, the reproducibility due to the complicated process steps, and the yield increase. It could be easily realized without deterioration.
According to the semiconductor device having the non-excited region near the end face according to the present invention, as in the case of the end face non-excited structure in the conventional high-power semiconductor laser, the surface of the waveguide portion near the end face is insulated with SiO ₂ or the like. Since it can be realized without covering with a film, dislocation defects are generated in the active layer due to the stress distribution generated from the insulating film deposited only near the end face, and dark line deterioration is not caused. A high output semiconductor device can be provided. In the above embodiment, InGaAs / Ga laminated on the GaAs substrate is used.
The present invention relates to a semiconductor laser having a wavelength band of 0.8 to 1 μm or more with an As strained quantum well layer as an active layer, but the same effect can be obtained by using GaAs / AlGa laminated on a GaAs substrate.
It is also effective in a semiconductor laser using As or InGaP as an active layer.

[Brief description of drawings]

FIG. 1 shows a cross section of a semiconductor device according to a first embodiment of the present invention in a cavity direction.

FIG. 2 is a view of A- of a semiconductor device according to a first embodiment of the present invention.
A sectional view taken along the line A'shows the structure of the current injection region.

FIG. 3 is a semiconductor device B- according to the first embodiment of the present invention.
A sectional view taken along the line B'shows the structure of the non-excitation region.

FIG. 4 is a sectional view showing an epitaxial structure of a semiconductor device according to a first embodiment of the present invention.

FIG. 5 shows a cross-sectional view of a conventional semiconductor device having a non-excitation region in a resonator direction.

[Explanation of symbols]

1 n ⁺ -GaAs substrate 2 n-GaAs buffer layer 3 n-AlGaAs clad layer 4 AlGaAs guide layer 5 AlGaAsSCH layer 6 InGaAs strained quantum well active layer 7 AlGaAsSCH layer 8 AlGaAs guide layer 9 p-AlGaAs clad layer 10 p ⁺ -GaAs Contact layer 11 AlGaAs current blocking layer 12 Insulating film 13 p electrode 14 n electrode

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Eiichi Kuramochi 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation

Claims (3)

[Claims] 1. A semiconductor device having a non-excited region near an end face, wherein a current block layer made of a semiconductor layer is provided in the non-excited region. 2. The device according to claim 1, wherein the current blocking layer in the non-excitation region is an AlGaAs layer or InGa.
A semiconductor device having a P layer. 3. A semiconductor device is formed on a substrate in a method of manufacturing a semiconductor device having a non-excitation region near an end face,
A method of manufacturing a semiconductor device, comprising: a step of forming each semiconductor layer and a current blocking layer by one-time growth; and a step of etching and removing the current blocking layer in a current injection region.