JP2001217505A - Semiconductor optical element, its manufacturing method, and selective growth method of aluminum based compound semiconductor layer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a semiconductor optical element which does not grow polycrystals when a compound semiconductor layer containing Al is selectively grown. SOLUTION: This manufacturing method of a semiconductor optical element is provided with a process wherein n-type current blocking layers containing Al are buried in both sides of a p-type current injection layer formed in a ridge type. When the current blocking layer is buried and grown, halogen compound gas containing carbon atoms (C) and halogen atoms is mixed in material gas of the current blocking layer growth. As a result, the current blocking layer doped with C is epitaxially grown.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor optical device and a method for manufacturing the same, and more particularly, to a semiconductor optical device having good characteristics and conditions for setting an epitaxial selective growth step in manufacturing a semiconductor optical device. The present invention relates to a method of manufacturing a semiconductor optical device having a high degree of freedom.

[0002]

2. Description of the Related Art A ridge-embedded semiconductor laser device in which both sides of a ridge-shaped current injection layer are filled with a current blocking layer is widely used as a light source in the field of optical communication. In particular,
GaAs is used as the current blocking layer, and the wavelength is 650.
AlGaInP / GaAs that emits laser light of nm
A system semiconductor laser device is a typical one.

Here, the configuration of a conventional ridge-embedded AlGaInP / GaAs semiconductor laser device will be described with reference to FIG. FIG. 9 shows a conventional ridge embedded type Al.
FIG. 1 is a cross-sectional view illustrating a configuration of a GaInP / GaAs semiconductor laser device (hereinafter, simply referred to as a semiconductor laser device).
As shown in FIG. 9, a conventional semiconductor laser device 10 has n
-1500 nm thick n-Al on the GaAs substrate 12
GaInP (Zn = 0.7) lower cladding layer 14, GaI
nP / AlGaInP multiple quantum well structure layer (MQW) 1
6. A 1500 nm-thick p-AlGaInP (Zn =
0.7) The upper cladding layer 18 and the p-
It has a laminated structure composed of the GaAs contact layer 20.

In the laminated structure, the upper part of the upper cladding layer 18 and the contact layer 20 are formed as stripe-shaped ridges, and both sides of the ridge are buried with a Si-doped n-GaAs layer 22 functioning as a current blocking layer. Thus, a current confinement structure is formed in which the current injection region of the first conductivity type is separated from the pn junction by the n-type current blocking layer. Although not shown, contact 2
A p-side electrode is formed on 0, and an n-side electrode is formed on the back surface of the GaAs substrate 12.

Next, a method of manufacturing the semiconductor laser device 10 will be described with reference to FIG. FIGS. 10A and 10B
FIG. 2 is a cross-sectional view of a substrate in each step when manufacturing a conventional semiconductor laser device 10. First, in the first epitaxial growth step, as shown in FIG.
A 1500 nm-thick n-AlGaInP lower cladding layer 14, a GaInP / AlGaInP multiple quantum well structure layer (MQW) 16 and a 1500 nm-thick p-AlGaI are sequentially formed on a GaAs substrate 12 by MOCVD or the like.
The nP upper cladding layer 18 and the n-GaAs contact layer 20 are epitaxially grown to form a laminated structure.

Next, a SiN film is formed on the contact layer 20 and then patterned to form a SiN film having a stripe pattern of 5 μm width as shown in FIG.
A stripe mask 24 is formed, and then, using the SiN stripe mask 24 as a mask, a contact layer 20 and an upper cladding layer 1 are formed using a sulfuric acid-based and hydrochloric acid-based etchant.
8 is etched to form a ridge 25.

Next, in a second epitaxial growth step, a Si-doped n-GaAs current blocking layer 22 is grown on the side surfaces of the ridge as shown in FIG. 9 by a selective growth method using the SiN stripe mask 24 as a mask. . Thereafter, a p-side electrode is formed on the contact layer 20,
An n-side electrode is formed on the back surface of the GaAs substrate 12, and further,
By cleaving the resonator structure to a desired length, the semiconductor laser device 10 can be formed.

[0008]

The GaAs current blocking layer used in the conventional semiconductor laser device has a band gap energy of GaInP.
/ AlGaInPMQW absorbs light of the emission wavelength from MQW because it is larger than the band gap energy of
There is a problem on the laser characteristics that the luminous efficiency is reduced. Therefore, instead of GaAs, Al
Attempts have been made to form a current blocking layer with a transparent material such as (Ga) InP.

When an Al (Ga) InP layer is selectively grown as a current blocking layer using a SiN mask, an Al (Ga) InP layer is formed using TMAl, TMIn, or the like as a source gas.
When the (Ga) InP layer is epitaxially grown, Al
(Ga) InP reacts with other components in the source gas with Al contained in the source gas serving as a nucleus to form a polycrystal (Polycrystal). , There is a problem of deposition on the SiN mask. When poly is formed on the SiN mask, when the SiN mask is removed by etching with hydrofluoric acid after the selective growth step, the poly remains because it is not etched by hydrofluoric acid, and the bonding between the poly and the SiN mask is strong. Therefore, SiN under the poly will also remain. As a result, the surface smoothness is impaired, which hinders subsequent epitaxial growth, and poly and SiN become foreign substances, which change the composition of the compound semiconductor layer and the like, which adversely affects the characteristics of the optical device. Therefore, conventional Al (Ga) InP
In the epitaxial growth step, the growth temperature is raised or the growth rate is lowered to prevent the generation of poly. Although the problem caused by the generation of poly has been described using a SiN mask as an example, this problem is not limited to the SiN mask, but is a universal problem when selective growth is performed using a mask such as a dielectric film.

However, when the growth temperature is increased, p-Al
Z implanted as an impurity in the upper cladding layer of GaInP
Since n is diffused into the MQW, the laser characteristics are lowered, and if the growth rate is lowered, it is difficult to improve the productivity.

Although different from the buried growth of the current blocking layer, when fabricating a semiconductor optical device, an AlG
In many cases, a compound semiconductor containing Al such as aAs or AlGaInAs is grown in the selected region. However, as in the above-described buried growth, Al acts as a nucleus and reacts with a component in the source gas to generate “poly”. Due to this phenomenon, various technical difficulties are faced. In the selective region growth method, a pair of growth prevention masks is formed on a region where a layer is not desired to be formed, and the compound semiconductor layer is epitaxially grown on a growth region selectively exposed from the growth prevention mask by the growth prevention mask effect. And a method for controlling the thickness and composition of the layer.

Accordingly, an object of the present invention is to provide a semiconductor optical device having good device characteristics and a method of manufacturing a semiconductor optical device which does not generate “poly” when a compound semiconductor layer containing Al is selectively grown. To provide.

[0013]

The inventor of the present invention has proposed Al (G
a) When selectively growing the InP layer as a current blocking layer, it is thought that the above-mentioned problem can be solved by changing the source gas, and the Al (Ga) InP current blocking layer is selected using various gases. An experiment to grow was performed. Experimental Example 1 In this experimental example, Al (Ga) InP
The current blocking layer was selectively grown. Results of the experiment, when mixing the halogen compound gas with CBr _4, carbon and halogen CCl ₄ such as a source gas, the etching effect against "poly" halogen atom halogen compound gas, even at low growth temperatures, "Poly" mentioned above
Have been found to be able to suppress the precipitation of. At the same time, C in the halogen compound gas is Al (Ga)
Since it enters into InP, it has been found that C doping is performed and n-type conductivity type control can be performed.

That is, the "poly" produced by the reaction of Al in the source gas supplied on the SiN mask with the Al by the etching action of the halogen atoms such as CBr ₄ and CCl ₄ is formed at the stage of the initial growth nucleus. , The deposition of “poly” is suppressed. At the same time, C is AlGaI
It has been found that the AlGaInP selectively grown layer can function as a current blocking layer by being taken into nP and acting as an n-type dopant.

In this experimental example, AlGaInAs
In the case where a ridge is buried with AlInAs when fabricating an / InP-based semiconductor laser device on an InP substrate, similarly, C-doped Al is used as a current blocking layer.
It was found that (Ga) InAs could be grown. Further, in manufacturing an AlGaAs / GaAs semiconductor laser device on a p-type GaAs substrate, an AlG
Similarly, when performing ridge embedding with aAs,
It was found that a C-doped p-AlGaAs layer could be selectively grown as a current blocking layer.

EXPERIMENTAL EXAMPLE 2 As described above, when a compound semiconductor layer containing Al is grown in a selected region by the selected region growing method, the deposition of "poly" is a problem similarly to the buried growth of the current blocking layer. Had become. As a result of the experiment, CBr ₄ and CCl ₄
It has been found that the method of mixing the compound gas of carbon and halogen with the source gas and performing epitaxial growth is effective even when applied to the selective region growth method, similarly to the above-described buried growth of the current blocking layer. .

In order to achieve the above-mentioned object, based on the above-mentioned findings, a semiconductor optical device according to the present invention comprises a ridge-shaped current injection layer of the first conductivity type and a ridge-shaped current injection layer. A semiconductor optical device comprising a current blocking layer of the second conductivity type containing Al, in which both sides of the layer are buried, wherein the current blocking layer is doped with an impurity containing at least C.

In the present invention, the term "semiconductor optical device" refers to a light emitting / receiving semiconductor device, an optical waveguide, an optical amplifier or the like having the configuration specified in the present invention. The current blocking layer containing Al is, for example, an AlGaInP layer or an AlGaAs layer in a GaAs-based semiconductor optical device, and an InP-based semiconductor optical device.
This is an AlGaInAs layer. In addition, the current blocking layer may be doped with at least one of Si, Se, and Zn in addition to C as an impurity. This makes it possible to realize a semiconductor element having good control of the conductivity type and carrier concentration and having a desired current blocking layer.

The method for fabricating a semiconductor optical device according to the present invention (hereinafter referred to as the first invention method) is characterized in that a ridge-shaped first conductivity type current injection layer is formed on both sides with Al containing both sides. In the method for fabricating a semiconductor optical device, the method further includes a step of burying a conductive type current blocking layer. When the current blocking layer is buried and grown, the source gas for growing the current blocking layer contains a carbon atom (C) and a halogen atom. It is characterized in that a current blocking layer doped with C is epitaxially grown by mixing a halogen compound gas.

In the first invention method, for example, when manufacturing a GaAs-based semiconductor optical device as a current blocking layer containing Al, an AlGaInP layer or an AlGaAs layer is buried and grown to manufacture an InP-based semiconductor optical device. In this case, an AlGaInAs layer is buried and grown. When the current blocking layer containing Al is buried and grown, Si, Se and Zn are added in addition to C as an impurity.
At least one of them is doped. This further facilitates control of the conductivity type.

Another method for fabricating a semiconductor optical device according to the present invention (hereinafter referred to as a second invention method) is a step of growing a compound semiconductor layer containing Al in a selected region using a selective growth mask made of a dielectric. A method of manufacturing a semiconductor optical device, comprising: mixing a halogen compound gas containing a carbon atom (C) and a halogen atom with a raw material gas for growing a compound semiconductor layer containing Al; Is grown epitaxially.

In the first and second invention methods, CC is used as the halogen compound gas containing carbon atoms and halogen atoms.
l _4, and CBr _4, it is effective to use at least one of.

In the case where a compound semiconductor layer containing Al is selectively grown in a selected region, the grown film thickness is relatively smaller than the thickness of the current blocking layer.
Although it is possible to suppress the growth of “poly” by reducing the / III ratio, by combining with the second invention method in which a small amount of CBr ₄ is supplied to the source gas, the precipitation of “poly” can be more reliably performed. In addition, the carrier concentration can be controlled by eliminating the doping amount of C in the epitaxial growth film sufficiently. This can be applied to, for example, the growth of an epitaxial selective region such as an active layer.

Further, when the second invention method is applied to the growth of the barrier layer by utilizing the C doping effect of the second invention method by growing while introducing CBr ₄ , the modulation-doped quantum well structure becomes It can be easily manufactured. In this case, in addition to improving the selective growth characteristics, C that is difficult to diffuse
Is possible, so that the effect as modulation doping can be effectively achieved.

As described above, AlGaInAs and AlGaIn are formed by the selective growth method using the SiN mask.
When an Al-based compound semiconductor layer such as P or AlGaAs is formed as a current blocking layer and a mesa structure is embedded,
Polycrystals are formed on the mask, causing problems such as a decrease in yield. Note that the selective growth method refers to a method in which at least a part of a substrate is covered with a mask for preventing growth and a compound semiconductor layer or the like is epitaxially grown in an exposed region.

As described above, conventionally, polycrystalline precipitation has been suppressed by changing the growth conditions such as growing at a low growth temperature or growing at a low growth rate.
It has been difficult to effectively suppress polycrystal formation. In addition, since the conditions are different from the optimum conditions for obtaining a good crystal film, device characteristics are deteriorated. For example, lowering the growth temperature is more effective in suppressing polycrystals, but when growing a film containing Al, the concentration of impurities such as oxygen increases and the optical and electrical characteristics deteriorate. There was a tendency.

Therefore, the present inventor has developed the first and second invention methods described above. Further research continued and found that, when selectively growing an Al-based compound semiconductor layer, by simultaneously supplying a gas having an etching characteristic to a film forming chamber, that is, a substrate, the deposition and formation of polycrystals can be suppressed. Was. The following experimental examples 3 and 4 are one of many experimental examples. Since a normal chlorine-based etching gas has a large effect on the apparatus and the environment, a bromine-based etching gas was used as the etching gas.

Experimental Example 3 In this experimental example, as an example of general selective growth, an AlInAs layer was grown on an InP substrate having a mask pattern. That is, as shown in FIG. 11, a 100 nm-thick nitrogen silicon (SiN) film 64 is formed on the InP substrate 62 by a plasma CVD method, and then patterned by photolithography and etching using hydrofluoric acid. , Mask size width is 80 μm and length is 600
A μm selective growth mask 64 was formed. As a raw material,
Metalorganic vapor phase epitaxy (MO) using trimethylindium (TMIn), trimethylaluminum (TMAl), and arsine (AsH ₃ ) at a growth temperature of 680 ° C., a growth pressure of 100 hPa, and a growth rate of 1.8 μm / hour.
500 nm thick on the pattern substrate by using the CVD method.
AlInAs layer 66 was grown.

First, as a comparative example, when an AlInAs layer was formed without supplying any etching gas to the film forming chamber, a large amount of polycrystal was deposited on the mask as shown in FIG. These polycrystals were difficult to remove by etching or the like, and hindered subsequent processes. As a result, ultimately, the yield of the device is reduced. FIG. 12 (a) and the next FIG. 12 (b)
Are the comparative examples and the following experimental examples of the present invention, respectively.
After the InAs layer was selectively grown, the object region (indicated by the broken line in FIG. 11) was taken with an optical microscope camera, and the dark region was the mask portion, and the upper and lower white portions were AlI.
It is an nAs layer. In FIG. 12A, black particles on the mask are polycrystalline.

Next, as an experimental example of the present invention, AlIn
Upon selective growth of the As layer, carbon tetrabromide (CBr ₄ ) was simultaneously supplied to the film formation chamber together with the raw material gas.
As shown in FIG. 12B, the generation amount of polycrystal on the mask could be reduced. Quantitatively, as shown in FIG. 13, when the supply amount of CBr ₄ is 1.6 μmol / min,
When the number of polycrystals precipitated per 1 mm ^{2 of} area (hereinafter referred to as the number of polycrystals) is about 100 × 10 ³ and 3.2 μmol / min, the number of polycrystals precipitated is almost 0 (zero). Became. When CBr ₄ was not supplied, the number of polycrystals precipitated was about 200 × 10 ³ . 3.2 μm of CBr ₄
FIG. 12 (b) shows a photograph transferred on the mask at the time of mol / min.
Indicates that no polycrystal was formed at all.

When CBr ₄ is supplied, the growth rate may decrease or the composition of the film to be formed may change in the normal growth region, that is, in the region exposed from the mask. At that time, if necessary, the raw material gas, especially TM
It was confirmed that the problem could be solved by adjusting the supply amount of a group III raw material such as Al or TMIn. The optimum range of the supply amount of CBr ₄ is determined by the composition of the AlInAs layer to be formed,
In particular, it depends on various factors such as the Al composition, the growth conditions such as the growth temperature and growth rate of the AlInAs layer, and the size of the mask and the surface condition of the mask. In this experimental example,
The same effect can be obtained by using another bromine-based etching gas, for example, methyl bromide (CH ₃ Br) instead of CBr ₄ as an etching material.

Experimental Example 4 This experimental example is an experiment relating to a butt joint (butt joint). The steps of the experiment will be described with reference to FIG. 14 (a) to 14 (c) show experimental example 4 respectively.
It is a typical perspective view of the board | substrate for every process. First, FIG.
(A) As shown in FIG.
A GaInAsP-based DH structure 74 having an As multiple quantum well structure 73 was formed. Subsequently, a silicon nitride (SiN) film having a thickness of 100 nm is formed by a plasma CVD method, and is patterned by photolithography and etching using hydrofluoric acid.
A mask 76 having a thickness of μm and a length of 800 μm was formed. Subsequently, as shown in FIG. 14B, using a mask 76,
The DH structure 74 was etched to a predetermined position, and an exposed surface 75 was formed on the InP substrate 72 at that position.

Next, the exposed surface 75 on the InP substrate 72
Next, as shown in FIG. 14C, an AlGaInAs multiple quantum well structure 78 and an InP film 79 were selectively grown. At the time of selective growth, only when growing an Al-based compound semiconductor layer containing Al, for example, an AlGaInAs layer,
CBr ₄ was supplied. The supply amount of CBr ₄ depends on the size of the mask and the like.
Minutes. Thereby, deposition of polycrystal on the mask was suppressed, and selective growth with high selectivity could be performed.

During the growth of the Al-based compound semiconductor layer, C
Since there is a concern that the supply of Br ₄ may affect the crystallinity and optical characteristics, the present experimental example examined such concerns. As a result, regarding the crystallinity of the AlGaInAsAl-based compound semiconductor layer, there is no problem in the surface morphology,
It was a mirror surface and no defects were observed, and the crystallinity was evaluated to be good. Regarding the optical characteristics, both the photoluminescence characteristics and the laser characteristics of the AlGaInAs-based multiple quantum well formed by supplying CBr ₄ are CBr.
It was equivalent to not supplying ₄ . Experimental Examples 3 and 4
From this, it was confirmed that by supplying CBr ₄ to the film formation chamber together with the source gas, it was possible to suppress the deposition of polycrystal and improve the selectivity of selective growth without deteriorating the quality of the crystal.

Based on the above findings, the A according to the present invention
In the selective growth method of the l-based compound semiconductor layer (hereinafter, referred to as a third invention method), when the Al-based compound semiconductor layer is selectively grown on a substrate using a source gas for forming the Al-based compound semiconductor layer, A bromine-based etching gas is supplied to the substrate in addition to the source gas for forming the Al-based compound semiconductor layer, and the
It is characterized by selectively growing a compound semiconductor layer.

The flow rate of the bromine-based etching gas varies depending on various factors such as the composition of the Al-based compound semiconductor layer, in particular, the composition of Al, growth conditions such as growth temperature and growth rate, and mask conditions such as size and surface condition. Therefore, it is necessary to determine in advance by experiments and the like. The mask used for selective growth by applying the third invention method may be a mask formed of a dielectric film, such as a silicon nitride film,
A mask formed of a silicon oxide film or the like can be used. In the third invention method, when the Al-based compound semiconductor layer is selectively grown, there is no restriction on the composition of the Al-based compound semiconductor layer.
nP layer, AlGaAs layer, AlInAs layer, and AlG
Any of the aInAs layers can be formed. The composition of the bromine-based etching gas is not limited. For example, CBr ₄ is used as the bromine-based etching gas.

The third invention method can be applied to any of buried growth, selective region growth, and butt-connect growth of an Al-based compound semiconductor layer.

[0038]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to the accompanying drawings based on embodiments. Embodiment of Semiconductor Optical Device This embodiment is an example of an embodiment in which the semiconductor optical device according to the present invention is applied to a semiconductor laser device, and FIG. 1 shows the configuration of the semiconductor optical device of this embodiment. It is sectional drawing.
In FIG. 1, the same components as those in FIG. 9 are denoted by the same reference numerals. The semiconductor laser device 30 of the present embodiment has the same configuration as the conventional semiconductor laser device 10 except for the configuration of the current blocking layer. That is, the semiconductor laser element 30 has n
-1500 nm thick n-Al on the GaAs substrate 12
GaInP (Zn = 0.7) lower cladding layer 14, GaI
nP / AlGaInP multiple quantum well structure layer (MQW) 1
6. A 1500 nm-thick p-AlGaInP (Zn =
0.7) The upper cladding layer 18 and the p-
It has a laminated structure composed of the GaAs contact layer 20.

In the laminated structure, the upper part of the upper cladding layer 18 and the contact layer 20 are formed as stripe-shaped ridges, and both sides of the ridge function as current blocking layers and have a carrier concentration of 1 × 10 ¹⁸ cm ⁻³ . C dope n
Embedded in the AlInP layer 32, the p-type current injection region is separated from the current blocking layer by pn junction separation, and a current confinement structure is formed. Although not shown, a p-side electrode is formed on the contact 20, and an n-side electrode is formed on the back surface of the GaAs substrate 12.

Embodiment 1 of the Method for Fabricating a Semiconductor Optical Device This embodiment is an example of the embodiment of the method for fabricating a semiconductor optical device according to the present invention. This is an example applied when manufacturing No. 30. With reference to FIG. 9, a manufacturing method of the present embodiment will be described. As shown in FIGS. 11A and 11B, a laminated structure is formed and then etched to form a ridge 25 in the same manner as in the conventional manufacturing method described above. Next, by using the SiN stripe mask 24 as a growth preventing mask for selective growth by MOCVD, as shown in FIG. 1, the C-doped n-AlInP current blocking layer 32 is formed.
Select regrow.

The growth conditions employed in this embodiment are as follows. Epitaxial growth temperature of AlInP layer: 600 ° C. Component of C raw material: CBr ₄ supply amount: 5 μmol / min Group III raw material gas: TMAl and TMIn supply amount: Total 20 μmol / min Growth rate: 3 μm / hour The supply amount of CBr ₄ is as follows. After considering the etching effect,
The ratio was determined so as to have a lattice matching ratio on a GaAs substrate.

The carrier concentration of the AlInP layer grown in this condition, a 2 × 10 ¹⁷ cm ^-3, for slightly lower as a current blocking layer, by supplying the SiH ₄ gas,
The carrier concentration was set to 1 × 10 ¹⁸ cm ⁻³ by doping Si at the same time. The AlInP layer of this embodiment has almost the same mobility as an epitaxially grown layer having a carrier concentration of 1 × 10 ¹⁸ cm ⁻³ by doping of only Si, which is usually performed. I couldn't see it.

When the AlInP layer was selectively grown by the method of this embodiment, no "poly" was deposited on the SiN mask having a width of 10 μm. Therefore, it can be evaluated that the method of the present embodiment has a clear effect as compared with the case where the amount of “poly” produced was very large when the conventional method in which CBr ₄ was not mixed was carried out.

Various experiments were conducted in connection with the method of the present embodiment, and the following findings were obtained. First, referring to FIG.
The relationship between the supply amount of Br _{4 and} the amount of “poly” generated will be described.
FIG. 2 is a graph showing the relationship between the amount of CBr ₄ supplied and the amount of “poly” generated. On the vertical axis of FIG. 2, the generation amount of “poly” is 0
Indicates that “poly” has not been generated on the mask for selective growth, and 1 indicates that “poly” has been generated on the entire surface of the mask for selective growth. In preparing FIG. 2, the effect of CBr ₄ was confirmed by changing the supply amount of CBr ₄ while maintaining the growth condition of the AlInP layer of the present embodiment. The amount of “poly” generated depends on the growth temperature of the AlInP layer, the supply amount of the group III source gas and the growth conditions such as the amount of Al composition, and the size of the selective growth mask. As shown in FIG. 2, the presence or absence of
Clear threshold for Br ₄ flow rate, 5 μmol / min
Exists. For example, under the growth conditions of the present embodiment, as shown in FIG. 2, the deposition of “poly” was almost completely suppressed when the supply amount of CBr ₄ was 5 μmol / min or more.

According to experiments, when the ratio of [Group III raw material gas] / [CBr ₄ ] is smaller than 2, the etching effect is larger than the growth of the AlInP layer itself. The ratio significantly decreases and the growth on the substrate may not even be confirmed, so that a [III group source gas] / [CBr ₄ ] ratio of less than 2 is inappropriate.
On the other hand, if the ratio of [Group III source gas] / [CBr ₄ ] is larger than 4, “poly” precipitates, which is not suitable. Therefore, when the growth temperature is 600 ° C. with AlInP,
The ratio of [Group III source gas] / [CBr ₄ ] is preferably in the range of 2 or more and 4 or less. However, when CCl ₄ is used instead of CBr ₄ , this range has a large upper and lower limit because the etching effect is increased. In the case where AlGaInP lattice-matched to GaAs is selectively grown instead of AlInP, the lower the Al composition, the lower the lower limit of the [III-group source gas] / [CBr ₄ ] ratio, and the higher the upper limit. It will be quite large. As a result, the range of the optimum value is widened.

Next, the correlation between the carrier concentration caused by C doping and the supply amount of CBr ₄ will be described with reference to FIG. FIG. 3 is a graph showing the relationship between the carrier concentration due to C doping and the supply amount of CBr ₄ . As shown in FIG. 3, the carrier concentration increases almost in proportion to the supply amount of CBr ₄ . However, when the supply amount of CBr ₄ increases,
The carrier concentration tends to be saturated, and the optical element characteristics may not be good. For this reason, it may be preferable to obtain a desired carrier concentration in combination with an n-type dopant such as Se.

In order to suppress the "poly" growth on the mask, the growth can be achieved by sufficiently lowering the selective growth rate of the AlInP layer. However, the current blocking layer which requires the selective growth of a thickness of 1 μm or more is required. In the case of the buried growth, the selective growth requires a long time and the productivity is lowered, so that it is unsuitable in an actual manufacturing process. However, in the present embodiment, the selective growth rate of the AlInP layer is 3 μm /
Because of the time and relatively fast growth rate, it can be said that there is no problem of productivity reduction.

In this embodiment, the growth temperature is set to 60.
Since the temperature is kept at 0 ° C., the diffusion of Zn in the upper cladding can also be suppressed. Although a low growth temperature is disadvantageous from the viewpoint of suppressing the deposition of “poly”, selective growth can be performed without any trouble by adding CBr ₄ . Therefore, in the present embodiment, since Zn diffusion can be suppressed, it is possible to increase the Zn concentration of the upper cladding layer when forming a stacked structure in the first epitaxial growth step. This has an advantage that the oscillation threshold value of the manufactured semiconductor laser element can be maintained satisfactorily and is directly linked to an improvement in temperature characteristics.

Referring to FIG. 4, the relationship between the burying growth temperature of the AlInP layer and the threshold current density will be described. FIG. 4 shows A
4 is a graph showing the relationship between the threshold current density of a semiconductor laser device and the carrier concentration of an upper cladding layer, using the buried growth temperature of the lInP layer as a parameter. The solid line graph (1) shows that the first epitaxial growth step was performed,
4 is a graph showing a relationship between a carrier concentration and a threshold current density before a filling step. The graphs indicated by a broken line and a dashed line are graphs after the embedding process is performed, respectively.
The broken line graph (2) is a graph showing the relationship between the threshold current density and the carrier concentration when the AlInP layer is regrown at the buried growth temperature of 700 ° C. by the conventional method without mixing CBr ₄ , Graph (3) is a graph showing the relationship between the threshold current density and the carrier concentration when the AlInP layer is regrown at a buried growth temperature of 600 ° C. by the method of the present embodiment.

As shown in FIG. 4, when the AlInP layer is regrown at a selective growth temperature of 700 ° C. without CBr ₄ ,
The carrier concentration of the upper cladding layer is 1.5 × 10 ¹⁸ cm ⁻³
Above the threshold value, the threshold current density greatly increases as compared with the solid line due to the diffusion of Zn due to the influence of heat generated during the burying growth. On the other hand, CBr ₄ was introduced and 60
When regrown at 0 ° C., the threshold current density hardly increases as compared with the solid line until the carrier concentration of the upper cladding layer becomes about 3 × 10 ¹⁸ cm ⁻³ .

Embodiment 2 of the method for fabricating a semiconductor optical device This embodiment is another example of the embodiment of the method for fabricating a semiconductor optical device according to the present invention. This is an example applied when manufacturing an element. 5 (a) to 5 (c) are diagrams for explaining the method of the present embodiment. FIG. 5 (a) is a plan view of a selective growth mask, and FIG. 5 (b) is a line A. -A '
5 (a) and FIG. 5 (c) are taken along line BB '.
FIG. 6 is a cross-sectional view of FIG. FIGS. 6A and 6B
Respectively represent the line A- in FIG. 5A after the selective growth process.
Sectional view of the substrate at A ', and line BB' after the selective growth step
FIG.

The method of this embodiment will be described below with reference to FIGS. First, FIG. 5A to FIG.
As shown in (c), a pattern having a mask width W of 50 μm and a mask gap G of 1 is formed on the n-InP substrate 42.
A pair of masks 44 made of a SiN film are formed in an arrangement of 0 μm. The region 46 where the line AA ′ crosses is where the substrate 42 is exposed from the mask 44 with the size of the mask gap G,
It is a growth area. A region 45 crossed by the line BB 'is a substrate region where the mask 44 does not exist, that is, a region where the mask does not affect.

Next, as shown in FIGS. 6A and 6B, the mask gap region 46 is formed by MOCVD.
A 50 nm-thick n-InP lower cladding layer 48 and a 100 nm-thick AlGaInAs (λg = 1000 nm)
Optical confinement layer 50, multiple quantum well structure layer (MQW) 5
2. 100 nm thick AlGaInAs (λg = 100
0 nm) The light confinement layer 54 and the p-
InP layers 56 are sequentially grown. . The n-InP lower cladding layer 48 has a carrier concentration of 1 × 10 ¹⁸ cm ⁻³ by Se doping. The MQW 52 has a well layer thickness of 5 nm, a well strain of + 1.0%, a barrier layer thickness of 10 nm, a barrier layer composition λg = 1000 nm, and six well layers. The p-InP layer 56 has a carrier concentration of 1 × 10 ¹⁸ cm ⁻³ by Zn doping. The growth conditions were a growth temperature of 650 ° C., and a growth rate of 1.2 μm / hour in a region not affected by the mask, that is, in a region 45. When growing the AlGaInAs layer, the AlG
In addition to the growth source gas of aInAs, CBr ₄ is 2 μm
ol / min.

The total thickness of the AlGaInAs light confinement layer and the MQW is different between the mask gap region 46 and the region 45 having no mask effect by the selective region growth method of the present embodiment. As shown in FIG. Then, the film thickness increases. As a result, the emission wavelength of the quantum well becomes longer in the region 46 as shown in FIG. 7 and 8
6 is a graph showing the total thickness of the AlGaAs light confinement layer and the MQW in the regions 46 and 45 along the line CC ′ in FIG. 5 and the emission wavelength (PL wavelength) of the MQW 52, respectively. By applying the selective region growth method of the present embodiment, a semiconductor device having the region 46 as a semiconductor laser element and the region 45 as an output waveguide is formed in the same manner as the selective region growth performed in the InGaAsP / InP system. By doing so, an optical device having a waveguide in the region 45 that hardly absorbs laser light emitted from the semiconductor element in the region 46 can be configured.

In this embodiment, when growing the AlGaInAs layer, CBr ₄ is simultaneously introduced at a supply rate of 2 μmol / min.
The amount of C doped in the nAs layer is small and does not affect the electrical characteristics. Moreover, selectivity of epitaxial growth is improved, generated when no CBr ₄ was slightly observed on the mask of the "poly" is, CBr ₄
In the embodiment of the present invention where is mixed, there was no case. Also, C
When the supply amount of Br ₄ is small, it becomes n-type by doping Se, and becomes p-type by doping Zn.
Since it becomes a mold, it is also possible to control the electrical characteristics of a layer containing Al such as AlGaInAs.

Further, modulation doping of the barrier layer is attempted.
Therefore, only when growing the barrier layer, CBr _Four20μ
mol / min, C was doped.
And the carrier concentration is 1 × 10¹⁸cm^-3Became. this
Can be used as a modulation degree dope by applying
It is possible to

Implementation of selective growth method for Al-based compound semiconductor layer
Embodiment This embodiment is an example of an embodiment according to the third invention method for selective growth of an Al-based compound semiconductor layer. FIG.
(A) to (c) are cross-sectional views for each step when the third invention method is applied to the buried growth of the mesa structure, and FIGS. 16 (a) and (b) respectively show the selective region growth. FIG. 1 is a sectional view of each step when the third invention method is applied, and FIG.
FIGS. 7 (a) to 7 (c) and FIGS. 18 (d) to 18 (f) are cross-sectional views for respective steps when the third invention method is applied to butt connection growth.

The burying growth is applied when a mesa structure or the like formed on a substrate is buried as shown in FIG. In the buried growth, first, as shown in FIG. 15A, GaInP / AlGaI is formed on an n-GaAs substrate 80.
AlG having nP multiple quantum well structure layer (MQW) 81
An aInP-based DH structure 82 is formed. Then, FIG.
As shown in (b), a mask 84 for selective growth is formed on the upper surface of the DH structure 82, and the upper part of the DH structure 82 is etched to form a mesa structure 86. Subsequently, FIG.
As shown in FIG. 7, the third invention method is applied using a mask 84 to form p-AlInP as current blocking layers 88/89.
A layer 88 / n-AlInP layer 89 is selectively grown on both sides of the mesa structure 86, and the current block layer 88/89 forms the mesa structure 8
Embed both sides of 6. Thereafter, a P-AlGaInP cladding layer and a P-GaAs contact layer are grown on the entire surface,
A semiconductor laser is manufactured by forming a p-side electrode and an n-side electrode on an upper surface and a lower surface of a substrate, respectively.

As shown in FIG. 16, the selective region growth is mainly applied when manufacturing an integrated optical device in which optical devices having different configurations are integrated on one substrate. In the example of the selective region growth, as shown in FIG.
A mask 92 for selective growth is formed on a GaAs substrate 90. Next, as shown in FIG. 16B, masks 9 are respectively formed on two sections of the area exposed from the mask 92.
And applying the third invention method using MQW93,95
The AlGaInP-based DH structures 94 and 96 are formed. When forming the DH structures 94 and 96, the third invention method is to use a compound semiconductor layer containing Al, for example, AlGaIn.
This is applied when forming a P layer. In the second embodiment of the method for fabricating a semiconductor optical device described above, the selective growth method of the Al-based compound semiconductor layer according to the third invention is applied to form an AlG
The selected region of the aInAs light confinement layer 50 is grown.

The butt-connect growth is a selective growth method applied in Experimental Example 4 described above, and is applied, for example, when manufacturing an integrated optical device such as a semiconductor laser device with an optical modulator. In the butt-connect growth method, as shown in FIG. 17, at least a part of one optical element, for example, an MQW 101 exhibiting a function of a semiconductor laser, and another at least a part of a layer, for example, a function of an optical modulator, are provided. MQW to be expressed
105 and connected to each other.

In the example of butt connection growth, FIG.
As shown in (a), M is formed on the InP substrate 100 on the substrate.
GaIn having QW101 (emission wavelength: 1550 nm)
A DH structure 102 of an AsP-based semiconductor laser is formed.
At this time, a diffraction grating is formed in advance and functions as a DFB-LD. Next, as shown in FIG.
A SiN mask 104 for selective growth is formed in a half section of the upper surface of the DH structure 102, and the exposed upper portion of the DH structure 102 is etched to expose the InP substrate 100. On this occasion,
A region left by the etching is an LD region. Subsequently, as shown in FIG. 17C, the DH structure 106 of the optical modulator having the MQW 105 (emission wavelength: 1500 nm) is formed on the exposed InP substrate 100. At this time, a region where the DH structure 106 is formed by selective growth is a modulator region. In forming the DH structure 106, the third invention method is applied when forming an Al-based compound semiconductor layer.

Next, the SiN mask 104 is removed, and an SiN mask 108 having a stripe pattern is formed as shown in FIG. Subsequently, FIG.
As shown in FIG.
The H structure 102 and the DH structure 106 are etched to the InP substrate 100 to form a mesa structure 109, and the InP substrate 100 is exposed. Next, as shown in FIG. 18F, both sides of the mesa structure 109 are buried with a Fe-InP layer 110 as a current blocking layer by a normal selective growth method using the SiN mask 108 as a mask for selective growth. Thereafter, by forming electrodes in the LD region and the modulator region, respectively, the semiconductor laser 11 with the optical modulator is formed.
1 can be produced.

[0063]

According to the present invention, since the current blocking layer is doped with an impurity containing at least C, it is possible to realize a semiconductor optical device having good device characteristics and a structure which can be manufactured economically. I have. According to the first and second invention methods, when the current blocking layer is buried and grown, a halogen compound gas containing a carbon atom (C) and a halogen atom is mixed into a raw material gas for growing the current blocking layer. When the doped current blocking layer is epitaxially grown, and when the Al-containing layer is grown in the selective region, a halogen compound gas containing a carbon atom (C) and a halogen atom is used as a source gas for growing the Al-containing layer. Is mixed, and the layer containing Al is epitaxially grown, so that the current blocking layer or the layer containing Al can be selectively grown at a low growth temperature and at a high growth rate.

According to the third invention, when the Al-based compound semiconductor layer is selectively grown on the substrate by using the Al-based compound semiconductor layer-forming material gas, the material for forming the Al-based compound semiconductor layer is used. By supplying a bromine-based etching gas to the substrate in addition to the gas to selectively grow the Al-based compound semiconductor layer on the substrate, it is possible to prevent polycrystals from being deposited on the selective growth mask and to improve the light yield with a high yield. An element can be manufactured.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of a semiconductor optical device according to an embodiment.

FIG. 2 is a graph showing a relationship between a supply amount of CBr ₄ and a “poly” generation amount.

FIG. 3 shows carrier concentration and CBr ₄ by doping of C.
It is a graph which shows the relationship of supply amount.

FIG. 4 is a graph showing the relationship between the threshold current density of the semiconductor laser device and the carrier concentration of the upper cladding layer, using the buried growth temperature of the AlInP layer as a parameter.

5 (a) to 5 (c) are views for explaining a method according to the second embodiment. FIG. 5 (a) is a plan view of a selective growth mask, and FIG. 5) is a cross-sectional view of FIG. 5A along line AA ', and FIG. 5C is a cross-sectional view of FIG. 5A along line BB'.

FIGS. 6A and 6B are cross-sectional views of a substrate taken along line AA ′ after the selective growth step and a line BB ′ after the selective growth step, respectively, of the second embodiment. FIG.

FIG. 7 shows regions 46 and 45 along the line CC ′ of FIG. 5;
4 is a graph showing the thickness of the AlGaAs light confinement layer of FIG.

FIG. 8 shows regions 46 and 45 along the line CC ′ of FIG. 5;
5 is a graph showing an emission wavelength (PL wavelength) of the quantum well 52 of FIG.

FIG. 9 shows a conventional ridge-buried type AlGaInP / Ga.
FIG. 3 is a cross-sectional view illustrating a configuration of an As-based semiconductor laser device.

FIGS. 10A and 10B are cross-sectional views of a substrate in each step in manufacturing a conventional semiconductor laser device.

FIG. 11 is a schematic diagram illustrating a sample of Experimental Example 3.

12 (a) and 12 (b) are a comparative example and an experimental example, respectively, and show an object area (FIG. 1) after selective growth.
1 (indicated by a broken line) is a copy of a photograph taken by an optical microscope camera.

FIG. 13 is a graph showing the relationship between the flow rate of CBr ₄ and the number of polycrystalline precipitates.

FIGS. 14A to 14C are schematic perspective views of a substrate in each step of Experimental Example 4;

FIGS. 15A to 15C are cross-sectional views for respective steps when the third invention method is applied to burying growth.

16 (a) and 16 (b) are cross-sectional views for respective steps when the third invention method is applied to selective region growth.

FIGS. 17 (a) to 17 (c) are cross-sectional views for respective steps when the third invention method is applied to butt-connect growth.

FIGS. 18 (d) to 18 (f) respectively show FIGS.
It is sectional drawing of every process at the time of applying the 3rd invention method to butt connection growth following 7 (c).

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Conventional semiconductor laser element 12 n-GaAs substrate 14 n-AlGaInP (Zn = 0.7) lower cladding layer 16 GaInP / AlGaInP multiple quantum well structure layer (MQW) 18 p-AlGaInP (Zn = 0.7) upper cladding Layer 20 p-GaAs contact layer 22 Si-doped n-GaAs layer 24 etching mask 25 ridge 30 semiconductor laser device of embodiment 32 C-doped n-AlInP layer 42 n-InP substrate 44 A pair of masks made of SiN film 46 growth region 45 Substrate region without mask / region not affected by mask 48 n-InP lower cladding layer 50 AlGaInAs (λg = 1000 nm) light confinement layer 52 Multiple quantum well 54 AlGaInAs (λg = 1000 nm) light confinement layer 56 p-InP layer 80 n-G As substrate 81 multiple quantum well structure layer 82 DH structure 84 mask 86 mesa structure 88, 89 current block layer 90 n-GaAs substrate 92 mask 93, 95 MQW 94, 96 DH structure 100 InP substrate 101, 105 MQW 102, 106 DH structure 104 SiN mask 108 SiN mask 109 Mesa structure 110 Fe-InP layer 111 Semiconductor laser with optical modulator

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Mitsumasa Ito 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd. (72) Inventor Akihiko Kasukawa 2-6-1 Marunouchi, Chiyoda-ku, Tokyo F-term in Furukawa Electric Co., Ltd. (reference) 4K030 AA02 AA03 BA02 BA08 BA11 BA25 BA51 BB02 CA04 DA04 FA10 LA14 5F045 AA04 AB09 AB12 AC08 AC19 AD10 AF04 BB12 CA12 DA55 DA58 DB02 5F073 AA21 AA22 AA74 AB21 BA01 CA07 CB02 DA05

Claims (13)

[Claims] A ridge-shaped current injection layer of a first conductivity type, and a current blocking layer of a second conductivity type containing Al and embedded on both sides of the ridge-shaped current injection layer. A semiconductor optical device, wherein the current blocking layer is doped with an impurity containing at least C. 2. The current blocking layer containing Al includes Ga
In an As-based semiconductor optical device, an AlGaInP layer or an AlG
aAs layer. In an InP-based semiconductor optical device,
2. The semiconductor optical device according to claim 1, wherein the semiconductor optical device is an InAs layer. 3. The semiconductor optical device according to claim 1, wherein the current blocking layer is doped with at least one of Si and Se in addition to C as an impurity. 4. A method for manufacturing a semiconductor optical device, comprising a step of embedding both sides of a first conductivity type current injection layer formed in a ridge shape with a second conductivity type current blocking layer containing Al. When the current blocking layer is buried and grown, a halogen compound gas containing a carbon atom (C) and a halogen atom is mixed into a source gas for growing the current blocking layer, and the current blocking layer doped with C is epitaxially grown. Of manufacturing a semiconductor optical device. 5. A current blocking layer containing Al,
When fabricating a GaAs-based semiconductor optical device, AlGaI
An nP layer or an AlGaAs layer is buried and grown, and InP
5. The method according to claim 4, wherein the AlGaInAs layer is buried and grown when the semiconductor optical device is manufactured. 6. When burying and growing a current blocking layer containing Al, in addition to C as an impurity, Si, S
6. The method according to claim 4, wherein at least one of e and Zn is doped. 7. A method for fabricating a semiconductor optical device, comprising a step of growing a compound semiconductor layer containing Al in a selected region using a selective growth mask made of a dielectric material, wherein a source gas for growing the compound semiconductor layer containing Al is provided. A compound semiconductor layer containing Al by epitaxially growing a compound semiconductor layer containing Al by mixing a halogen compound gas containing carbon atoms (C) and halogen atoms. 8. The semiconductor light according to claim ₄ , wherein at least one of CCl ₄ and CBr ₄ is used as the halogen compound gas containing carbon atoms and halogen atoms. Method for manufacturing element. 9. When selectively growing an Al-based compound semiconductor layer on a substrate using a source gas for forming an Al-based compound semiconductor layer, bromine-based etching is performed in addition to the source gas for forming an Al-based compound semiconductor layer. Gas is supplied to the substrate, and Al
A characterized by selectively growing a compound semiconductor layer
A selective growth method for an l-based compound semiconductor layer. 10. An Al-based compound semiconductor layer comprising AlG
aInP layer, AlGaAs layer, AlInAs layer, and A
10. The method for selectively growing an Al-based compound semiconductor layer according to claim 9, wherein one of the 1GaInAs layers is formed. CBr ₄ as a bromine-based etching gas.
The method for selectively growing an Al-based compound semiconductor layer according to claim 9, wherein: 12. One of claims 9 to 11
The selective growth method of the Al-based compound semiconductor layer described in the paragraph, performing one of the buried growth, the selective region growth, and the butt-connect growth of the Al-based compound semiconductor layer. Selective growth method. 13. A device having an Al-based compound semiconductor layer, wherein the Al-based compound semiconductor layer is formed by the method for selectively growing an Al-based compound semiconductor layer according to any one of claims 9 to 12. Device.