JPH11112099A - Manufacture of semiconductor optical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily manufacture a semiconductor optical element comprising an active layer of quantum dot configuration, which manifests intrinsic characteristics. SOLUTION: A through hole membrane 101 is provided on a substrate 501 comprising n-type GaAs as a main front surface (001), Pt is vapor-deposited with the through hole membrane 101 as a mask, and a mask pattern 502 of Pt is formed on the substrate 501. Then, the substrate 501 is etched with the mask pattern 502 as a mask, and a strain introducing layer 503a comprising a dot 503 is formed on the front surface of the substrate 501.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor optical device having an active layer having a quantum well structure.

[0002]

2. Description of the Related Art In an optical element, a functional part, for example, an active layer portion of a semiconductor laser or an optical modulator is changed from a bulk structure to a multiple quantum well structure (MQW) to reduce the oscillation threshold value. Element characteristics can be improved. Further, in the MQW structure, by intentionally shifting the lattice constant between the well layer and the barrier layer to about 0.5 to 1%,
Higher efficiency can be obtained by employing a strained MQW structure in which stress is embedded in W. Further, by further reducing the dimensions such as the quantum wire structure and the quantum dot structure, further improvement of the characteristics of the active layer is expected.

[0003] The quantum dot structure is expected to further improve the characteristics based on the quantum effect such as the carrier confinement effect and the increase in the density of states. Is being actively conducted. Regarding the formation of the above-mentioned quantum dot structure, a method of approaching from crystal growth such as self-organizing growth or selective growth using masking, or a method of reducing the dimension of a crystal having a quantum well structure by fine processing by etching technology Have been tried.

[0004]

However, a technology that surpasses an optical device having an MQW structure in which a quantum well layer is formed in a plane has not been developed at present. The main reasons why the optical element using the quantum dots formed by the above-described technique cannot obtain the original characteristics are fluctuations in the size of the formed quantum dots and irregularities in the arrangement. The present invention has been made in order to solve the above problems, and has as its object to enable easy manufacture of a semiconductor optical device having an active layer of a quantum dot configuration capable of exhibiting the original characteristics. I do.

[0005]

According to a method of manufacturing a semiconductor optical device of the present invention, a through-hole membrane having a plurality of through holes is arranged on a substrate made of a semiconductor, and a mask material is formed on the substrate using the through-hole membrane as a mask. A first step of forming a dot pattern made of a mask material on the substrate in accordance with the arrangement of the through holes by depositing
A second step of removing the through-hole membrane from above the substrate, a third step of etching the substrate using the dot pattern as a mask to form projections on the substrate surface, and forming a strain-introducing layer on the substrate surface, A fourth step of removing the first semiconductor layer, and growing a first semiconductor lattice-matched to the substrate such that the protrusions are almost buried, thereby forming a first barrier layer made of the first semiconductor on the strain introducing layer. A fifth step of crystallizing the second semiconductor having a lattice constant different from that of the first semiconductor to such an extent that the second semiconductor is not formed in a continuous film form, so that the quantum dots made of the second semiconductor are formed into a strain-introducing layer. A sixth step of forming on the first barrier layer in accordance with the position of the protrusion;
Crystal growth of the first semiconductor on the barrier layer of
And a seventh step of forming a second barrier layer made of the first semiconductor so that the quantum dots are almost buried. Since the semiconductor optical device is manufactured as described above, quantum dots are formed so as to match the positions of the through holes of the through-hole membrane. In addition, the method for manufacturing a semiconductor optical device of the present invention includes a first step of forming a strained film having a lattice constant different from that of a substrate on a substrate made of a semiconductor, and forming a through-hole membrane having a plurality of through holes on the strained film. Arranging and depositing a mask material on the strained film using the through-hole membrane as a mask, thereby forming a dot pattern made of the mask material on the strained film in accordance with the arrangement of the through holes;
A third step of removing the through-hole membrane from the upper part of the substrate, a fourth step of forming a distortion introducing layer on the substrate by etching the distortion film using the dot pattern as a mask to form projections on the substrate surface, and A fifth step of removing the pattern; and growing a first semiconductor lattice-matched to the substrate by crystal growth such that the protrusions are almost buried, thereby forming a first barrier layer made of the first semiconductor on the strain-introducing layer. The sixth step of forming and growing the second semiconductor having a lattice constant different from that of the first semiconductor to such an extent that the second semiconductor does not form a continuous film, thereby forming a projection of the strain-introducing layer on the first barrier layer. A seventh step of forming a quantum dot made of a second semiconductor in accordance with the position of
Crystal growth of the first semiconductor on the barrier layer of
And an eighth step of forming a second barrier layer made of the first semiconductor so that the quantum dots are almost buried. Since the semiconductor optical device is manufactured as described above, quantum dots are formed so as to match the positions of the through holes of the through-hole membrane. Further, according to the method of manufacturing a semiconductor optical device of the present invention, a first through-hole membrane having a plurality of through holes is disposed on a substrate made of a semiconductor, and the first through-hole membrane has a lattice constant different from that of the substrate on the substrate using the through-hole membrane as a mask. A first step of forming a dot pattern made of the first semiconductor on the substrate by depositing the semiconductor according to the arrangement of the through holes, a second step of removing the through-hole membrane from the upper part of the substrate, A third step of crystal-growing a second semiconductor lattice-matched to the crystal so that the dot pattern is substantially embedded, thereby forming a first barrier layer made of the second semiconductor on the strain-introducing layer; The third semiconductor having a different lattice constant from that of the first semiconductor is crystal-grown to such an extent that the third semiconductor is not formed in a continuous film form. The fourth step of forming quantum dots made of the third semiconductor in accordance with the position, and the crystal growth of the second semiconductor on the first barrier layer containing the quantum dots, so that the quantum dots are almost embedded. Second
And a fifth step of forming a second barrier layer made of a semiconductor. Since the semiconductor optical device is manufactured as described above, quantum dots are formed so as to match the positions of the through holes of the through-hole membrane.

Further, the method for fabricating a semiconductor optical device according to the present invention comprises a first step of forming an active layer composed of a quantum well layer sandwiched between upper and lower barrier layers on a substrate composed of a semiconductor. A second pattern in which a dot pattern made of a mask material is formed on the substrate in accordance with the arrangement of the through-holes by disposing the through-hole membrane having an active layer on the active layer and depositing a mask material on the substrate using the through-hole membrane as a mask; A third step of removing the through-hole membrane from above the substrate, a fourth step of selectively etching the active layer using the dot pattern as a mask to form a post made of the active layer, and a substrate surrounding the post. And a fifth step of forming a buried layer made of a high-resistance semiconductor thereon. Since the semiconductor optical device is manufactured as described above, quantum dots are formed from the quantum well layers separated by the formation of the posts,
It is formed so as to match the position of the through-hole of the through-hole membrane. In addition, the method of manufacturing a semiconductor optical device of the present invention includes disposing a through-hole membrane having a plurality of through-holes on a substrate made of a semiconductor, and selectively etching the substrate surface using the through-hole membrane as a mask. A first step of forming a concave portion on the surface according to the arrangement of the through holes of the through-hole membrane;
At least a second step of removing the through-hole membrane from the upper part of the substrate and a third step of forming a quantum dot or a multiple quantum dot structure in each of the recesses by growing a semiconductor layer so as to fill the recesses. did. Since the semiconductor optical device is manufactured as described above, a quantum dot or multiple quantum dot structure separated by the inside of the recess is formed, and is formed so as to match the position of the through hole of the through-hole membrane. The method of manufacturing a semiconductor optical device according to the present invention includes disposing a through-hole membrane having a plurality of through-holes on a substrate made of a semiconductor, and selectively etching the substrate surface using the through-hole membrane as a mask. A first step of forming a recess in accordance with the arrangement of through holes on the surface, and forming a quantum dot or a multiple quantum dot structure in each of the recesses by crystal-growing a semiconductor layer so as to fill the recess using a through-hole membrane as a mask; And a third step of removing the through-hole membrane from above the substrate. Since the semiconductor optical device is manufactured as described above, a quantum dot or multiple quantum dot structure separated by the inside of the recess is formed, and is formed so as to match the position of the through hole of the through-hole membrane.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. First Embodiment First, a method for manufacturing a semiconductor optical device according to a first embodiment of the present invention will be described. First, the outline will be described. At predetermined intervals, pores (through holes) having desired dimensions are provided.
By using as a mask the through-hole membrane on which was formed, fine quantum dots periodically arranged in the order of nm were formed, and a semiconductor optical device using this was manufactured.

FIG. 1 shows the through-hole membrane 10.
1 is a perspective view showing a fine hole (through hole) 102 having a diameter φ.
Are regularly formed at intervals Λ. In addition, the pore 10
2 is arranged so as to form an equilateral triangle when the three nearest vertices in plan view are vertices. The method of manufacturing the through-hole membrane 101 will be briefly described. First, as shown in FIG.
200 having aluminum and aluminum substrate 203 made of aluminum whose surface is mirror-finished by electrolytic polishing or the like
Prepare Here, the protrusions 201 are regularly arranged at an interval Λ. Then, as shown in FIG. 3B, the surface of the substrate 200 on which the protrusion 201 is formed is pressed against the aluminum substrate 203, and a fine recess 204 is formed in a portion corresponding to the protrusion 201 on the surface of the aluminum substrate 203. That is, the substrate 200
Is transferred to the surface of the aluminum substrate 203. This pressing may be performed by pressing the surface of the substrate 200 on which the projections 201 are formed against the surface of the aluminum substrate 203 and applying a pressure of, for example, 1 ton / cm ² from the back surfaces of both substrates using a hydraulic press or the like.

The substrate 200 is preferably made of a material having strength and hardness so that the substrate 200 itself and the projections 201 are not broken or deformed in transferring the pattern by pressing. For example, if a silicon substrate or the like is used, the projections can be easily formed. Considering that this substrate is used repeatedly, it is more preferable to use diamond, silicon carbide (SiC) or tantalum having higher strength as the substrate.

Next, the aluminum substrate 203 is anodized in an acidic electrolyte solution, thereby
That is, aluminum is oxidized. By this anodic oxidation, an oxide layer 203a changed to alumina is formed on the surface of the aluminum substrate 203 as shown in FIG.
At this time, the aluminum substrate 2 on which the depression 204 is not formed
03 surface is particularly oxidized, and alumina grows in that region. As a result, as shown in FIG. 3C, a hole 204a is formed in the formed oxide layer 203a at the position of the depression 204 formed in the surface of the aluminum substrate 203. Here, in this anodic oxidation, the voltage condition is controlled as shown in FIG. 4 according to the hole diameter (φ) and the arrangement dimension (Λ) of the pores to be formed. For example, φ = 20 nm,
If Λ = about 50 nm, the voltage may be about 20 V. And by changing the voltage,
The hole diameter can be changed according to the array size. Regarding the hole diameter, by post-treatment using phosphoric acid, etc.
It is possible to increase the size to about 90% of the array size.

Then, by performing the above-described anodic oxidation for an appropriate time, the oxide layer 203a is grown to a desired thickness and the hole 204a is grown to a desired depth. Then, the aluminum portion of the aluminum substrate 203 under the oxide layer 203a is selectively removed by etching, and the oxide layer 203a is also slightly etched to complete the through-hole membrane 101 as shown in FIG. . Here, in the selective etching of aluminum, a saturated aqueous solution of HgCl ₂ or a saturated methanol solution of Br ₂ may be used as an etchant. In etching the oxide layer 203a, phosphoric acid or the like may be used. The thickness (h) of the through-hole membrane is determined by the anodic oxidation time.
It can be formed from a thin film of about 5 μm to a thick film of several tens μm. The size of the through-hole membrane is several meters.
It can be formed up to the order of m square.

A method for manufacturing the semiconductor optical device according to the first embodiment using the through-hole membrane 101 (FIG. 1) manufactured as described above will be described below. In the following, Λ = 50 nm, φ = 2
0 nm and h = 2 μm. First, as shown in FIG. 5A, the main surface of the through-hole membrane 101 is (00).
1) is arranged on a substrate 501 made of n-type GaAs, and as shown in FIG.
01 is used as a mask to deposit Pt on the substrate 5.
First, a mask pattern 502 made of Pt is formed on the mask pattern 01. Here, after forming the mask pattern 502, the through-hole membrane 101 is removed from the substrate 501. The material of this mask pattern is P
The material is not limited to t, and other metals that can be deposited, such as Au, Ni, Al, and Ta, or silicon oxide, silicon nitride, or the like may be used. In other words, any material can be used as the mask pattern, as long as it has a high selectivity in etching with the underlying compound semiconductor and does not hinder the subsequent steps.

Next, as shown in FIG. 5C, the substrate 501 is etched using the mask pattern 502 as a mask, thereby forming dots 503 on the surface of the substrate 501.
Is formed. Here, this etching may be wet etching with acid or the like, or dry etching such as Ar ion milling or etching with reactive ions. Next, the mask pattern 502 is removed by a plasma oxidation treatment or an appropriate acid treatment (wet), and a natural oxide film on the substrate surface is removed by an acid treatment or the like to clean the substrate surface. As a result, FIG.
As shown in (1), a state is obtained in which a strain introducing layer 503a in which dots 503 having a height of about 10 nm are regularly arranged at intervals of 50 nm is formed on the surface of the substrate 501.

Next, as shown in FIG. 5E, the substrate temperature is set to 500 ° C. by molecular beam epitaxy (MBE).
In this case, GaAs is crystal-grown on the substrate 501 including the strain introducing layer 503a.
4 is formed. Here, the thickness of this grown film is 15-20.
nm. As described above, when the GaAs (lower barrier layer 504) (the same material) that is lattice-matched to the substrate is crystal-grown to a thickness of about three times the projection height of the lower dot 503 of about 10 nm, the step of the dot 503 is eliminated. Is not completely flattened. Therefore, the dot 50
The stress (strain) remains on the surface of the lower barrier layer 504 located above the third barrier layer 504. Then, on the lower barrier layer 504 in which the stress remains, the conditions are changed in the same crystal growth apparatus, such as changing the source gas, and then InAs is grown by an amount equivalent to two monolayers. The quantum well layer 50 composed of quantum dots 505 is formed on the surface of the lower barrier layer 504 in accordance with the arrangement of the dots 503.
5a is formed.

In general, in the crystal growth of a lattice-mismatched system, when a crystal having a lattice constant different from that of a substrate is to be epitaxially grown, the grown crystal is aggregated into a three-dimensional island at an early stage of the growth. It is in a state. That is, when a crystal having a lattice constant different from that of the substrate is epitaxially grown to such an extent that it is not formed into a continuous film, the grown crystal is in a three-dimensional island-like state. The shape and dimensions of the island are determined by the crystal growth conditions. If a strain is present on the substrate surface, the island is preferentially formed at the position of the strain. Therefore, in the state shown in FIG.
Due to the presence of “a”, strains regularly arranged at 50 nm intervals exist on the surface of the lower barrier layer 504. Then, when InAs having a lattice mismatch of about 7% with respect to the substrate 501 is grown on the crystal by about 2 monolayers, the quantum dots 505 made of InAs are formed in accordance with the position of the strain. .

The quantum dots 505 have a thickness of 50 nm.
If the intermediate barrier layer 504a is formed by crystal-growing GaAs so as to embed the quantum dots 505 on the quantum well layer 505a formed regularly at intervals, the quantum dots 505 are also formed on the surface of the intermediate barrier layer 504a. There is a state where the strain exists according to the position. Therefore,
On top of this, in the same crystal growth apparatus, InA
If s is made to grow by about two monolayers, then FIG.
As shown in (5), quantum dots 505 are formed on the intermediate barrier layer 504a in accordance with the position of the strain. By repeating the above for a desired number of times, FIG.
As shown in (g), a multiple quantum dot structure 506 is formed.

Here, as shown in FIG. 5 (g), after forming a protective layer 507 on the multiple quantum dot structure 506, it is taken out from the crystal growth apparatus and the multiple quantum dot structure 506 is evaluated by a photoluminescence method or the like. Then, light emission with a very narrow spectral width reflected on the dot structure is observed. Then, after the evaluation, the protective layer 507 is selectively removed, and a cladding layer 508 made of P-type GaAs is formed on the multiple quantum dot structure 506 as shown in FIG. Ohmic contact layer 50
By forming No. 9, the basic structure of the semiconductor optical device in the first embodiment is completed. Note that the above evaluation is not necessarily a necessary step, and this step is omitted, and the cladding layer 508 and the ohmic contact layer 509 are successively formed on the multiple quantum dot structure 506 without forming the protective layer 507. You may.

As described above, according to the first embodiment, the quantum dots can be formed in accordance with the positions of the pores of the through-hole membrane, so that a quantum dot structure composed of quantum dots accurately arranged is provided. A semiconductor optical device can be obtained. For example, a semiconductor laser having a multiple quantum dot structure in which six layers in which quantum dots having a diameter of 20 nm are regularly arranged with a period of 100 nm being stacked, and a resonator town oscillating at 1.55 μm and having a cavity of 300 μm can be easily formed. It becomes possible. This semiconductor laser can have an oscillation threshold value of 1 mA or less.

Embodiment 2 Hereinafter, a method for manufacturing a semiconductor optical device according to a second embodiment of the present invention will be described. Also in the second embodiment, the through-hole membrane 101 shown in FIG. 1 is used as in the first embodiment. Hereinafter, a method for manufacturing the semiconductor optical device according to the second embodiment will be described. First, as shown in FIG.
01) on a substrate 701 made of n-type GaAs.
The layer 701a is formed to a thickness of 10 nm, and the through-hole membrane 101 is disposed thereon. Then, FIG.
As shown in FIG. 7, Pt is deposited using the through-hole membrane 101 as a mask, thereby forming the InAs layer 70.
A mask pattern 702 made of Pt is formed on 1a.

Next, as shown in FIG. 7C, this time, the mask pattern 702 is used as a mask to form the InAs layer 701a.
Is etched, whereby the surface of the substrate 701 becomes In
A dot 703 made of As is formed. Here, this etching is the same as in the first embodiment, and may be wet etching using an acid or the like, or may be dry etching such as Ar ion milling or etching using reactive ions. . Next, the mask pattern 702 is removed by a plasma oxidation treatment or an appropriate acid treatment (wet), and a natural oxide film on the substrate surface is removed by an acid treatment or the like, thereby cleaning the substrate surface. As a result, as shown in FIG. 7D, the surface of the substrate 701 has an In height of about 10 nm.
As a result, a strain introducing layer 703a in which dots 703 made of As are regularly arranged at intervals of 50 nm is obtained.

Next, as shown in FIG. 8E, GaAs is crystal-grown on the substrate 701 including the strain-introducing layer 703a at a substrate temperature of about 500 ° C. by MBE. A barrier layer 704 is formed. Here, the thickness of the grown film is set to about 15 to 20 nm. By the way, as described above, InAs is Ga
It has a lattice mismatch of about 7% with respect to As. For this reason, when GaAs (lower barrier layer 704) is crystal-grown to a thickness up to about three times the projection height of the lower layer dot 703 of 10 nm, the lower barrier layer 704 is located on the dot 703 having a different lattice constant on the surface. The region is in a state where stress (strain) remains. Then, conditions are changed on the lower barrier layer 704 in a state where the stress remains, for example, by changing the source gas in the same crystal growth apparatus.
As is grown for two monolayers. Thus, as in the first embodiment, the quantum dots 70 are formed on the surface of the lower barrier layer 704 in accordance with the arrangement of the dots 703 in the lower layer.
5 are regularly arranged at intervals of 50 nm.

Then, an intermediate barrier layer 704a made of GaAs is formed on the quantum well layer 705a made of the quantum dots 705 so as to embed the quantum dots 705, and subsequently, similarly in the same crystal growth apparatus. I
By repeating the crystal growth of nAs for about two monolayers, a multiple quantum dot structure 706 is formed as shown in FIG. Here, as shown in FIG. 8 (f), after forming the protective layer 707 on the multiple quantum dot structure 706, take out from the crystal growth apparatus, and evaluate the multiple quantum dot structure 706 by a photoluminescence method or the like. Light emission with a very narrow spectrum width reflected in the dot structure is observed.

Next, after the evaluation, the protective layer 707 is selectively removed, and a cladding layer 708 made of P-type GaAs is formed on the multiple quantum dot structure 706 as shown in FIG. And the ohmic contact layer 70
By forming No. 9, the basic structure of the semiconductor optical device in the first embodiment is completed. Note that the above evaluation is not necessarily a necessary step, and this step is omitted, and the cladding layer 708 and the ohmic contact layer 709 are successively formed on the multiple quantum dot structure 706 without forming the protective layer 707. You may. As described above, also in the second embodiment, since the quantum dots can be formed in accordance with the positions of the pores of the through-hole membrane, a semiconductor optical device having a quantum dot structure composed of quantum dots arranged accurately can be used. Obtainable.

In the second embodiment, dots made of materials having different lattice constants are formed by lithography and selective etching as a strain-introducing layer for forming quantum dots in a regular arrangement. It is not limited to this. By using the through-hole membrane 101 shown in FIG. 1 as a mask, for example, InAs is crystal-grown on the GaAs substrate surface,
A strain introduction layer composed of InAs dots having different lattice constants may be formed on the As substrate surface.

In the crystal growth of InAs, for example, M
A crystal growth technique such as BE or metal organic vapor phase epitaxy (MOVPE) may be used. Then, by using these crystal growth techniques and supplying atoms, molecules or reaction gases serving as In and Ga sources through the pores 102 of the through-hole membrane 101, dots made of InAs can be formed. This crystal growth technique is the same in the InAs crystal growth in the first and second embodiments.

If the formation of the strain-introducing layer is performed only by crystal growth using the through-hole membrane 101, the following steps can be taken out from the same crystal growth apparatus as shown below. Since they can be continuously performed without any change, the crystallinity can be improved. For example, after forming a strain-introducing layer using a through-hole membrane, first, from the reaction chamber in which the crystal was grown, a load-lock chamber for exchanging a substrate connected to the reaction chamber in the same vacuum atmosphere. Then, the substrate and the through-hole membrane are put on standby. Next, the through-hole membrane is removed from the substrate surface in the load lock chamber.
Then, only the substrate is returned to the reaction chamber, and the load lock chamber and the reaction chamber are separated from each other. Then, crystal growth of the lower barrier layer is performed in the reaction chamber.

That is, in the first and second embodiments, the lithography and the selective etching are performed by taking out the crystal growth apparatus once to form the strain-introduced layer. Therefore, after the formation of the strain-introducing layer, the surface of the substrate including the strain-introducing layer is exposed to the atmosphere, and growth of the native oxide film, contamination, and the like cannot be avoided, and a decrease in crystallinity cannot be avoided. On the other hand, as described above, if the steps from the formation of the strain-introducing layer to the formation of the multiple quantum dot structure are performed in the same crystal growth apparatus, the above-described contamination and the like will not occur, and the crystallinity will not increase. Can be improved. In the above description, the combination of GaAs and InAs has been described. However, the present invention is not limited to this.
And InP, or In _0.5 Ga _0.5 As and GaAs
It goes without saying that a combination of s and a combination of GaAs, SiGe and Si may be used.

Embodiment 3 Hereinafter, a method for manufacturing a semiconductor optical device according to a third embodiment of the present invention will be described. Also in the third embodiment, the through-hole membrane 101 shown in FIG. 1 is used as in the first and second embodiments. Hereinafter, a method of manufacturing the semiconductor optical device according to the third embodiment will be described. First, as shown in FIG.
On a substrate 901 made of P, 1.55 μm InG
The semiconductor layer 902 is formed by growing the aAsP crystal to a thickness of 100 nm, and the through-hole membrane 101 is disposed thereon. Then, as shown in FIG. 10B, a mask pattern 903 made of Pt is formed on the semiconductor layer 902 by depositing Pt using the through-hole membrane 101 as a mask. The material of the mask pattern is not limited to Pt,
Other metals that can be deposited, such as Au, Ni, Al, Ta,
Silicon oxide, silicon nitride, or the like may be used.

Next, as shown in FIG. 10C, a part of the semiconductor layer 902 and the substrate
The post 902a is formed by etching with strong vertical anisotropy using 03 as a mask.
For this etching, for example, a reactive ion beam etching apparatus using a bromine-based gas may be used. This dry etching has features that it has vertical anisotropy, has low damage, and can form a uniform depth. This post 902a has
It becomes a quantum post having a diameter of about nm and a height of about 100 nm. FIG. 10D shows the mask pattern 90.
FIG. 9 is a perspective view showing a state in which a post 902a is formed on a substrate 901 using No. 3 as a mask.

Next, after the mask pattern 903 is removed by plasma oxidation or an appropriate acid treatment (wet treatment), as shown in FIG. 10E, a post 902a is formed using a liquid phase epitaxial growth apparatus. Is grown on the substrate 901 to form a buried layer 904. Further, as shown in FIG. 10 (f), a 1.3 μm composition InGaAs is formed by a metal organic chemical vapor deposition method or the like.
By forming an optical guide layer 905 made of sP, an upper cladding layer 906 made of P-type InP, and an ohmic contact layer 907 made of P-type InAsP, the basic structure of the semiconductor optical device according to the third embodiment is improved. It is completed.

In the third embodiment, since the posts are formed of the quantum well layers sandwiched between the upper and lower barrier layers, a fine quantum well structure is formed for each post. That is, a quantum dot structure is formed for each post. Then, since the posts are formed in accordance with the positions of the pores of the through-hole membrane, the quantum dots for each post constituting the quantum dot structure are also accurately arranged and formed.

Embodiment 4 Hereinafter, a method of manufacturing a semiconductor optical device according to a fourth embodiment of the present invention will be described. Also in the fourth embodiment, the through-hole membrane 101 shown in FIG. 1 is used as in the first to third embodiments. Hereinafter, a method of manufacturing the semiconductor optical device according to the fourth embodiment will be described. First, as shown in FIG.
A multiple quantum well structure 11 is formed on a substrate 1101 made of nP.
02 and the light guide layer 1103 are formed, and the through-hole membrane 101 is disposed thereon. This quantum well structure 1102 is composed of six layers of InGaP / InGaAsP and oscillates at 1.55 μm. The light guide layer 1103 is made of InGaAsP having a composition of 1.3 μm.

Then, as shown in FIG. 11B, a mask pattern 1104 made of Pt is formed on the light guide layer 1103 by depositing Pt using the through-hole membrane 101 as a mask. The material of the mask pattern is not limited to Pt, but may be At.
Other refractory metals that can be deposited, such as u, Ni, Al, Ta, or silicon oxide, silicon nitride, or the like may be used.

Next, as shown in FIG. 11C, the light guide layer 1103, the multiple quantum well structure 1102 and the substrate 1
A part of the substrate 101 is etched by etching with strong vertical anisotropy using the mask pattern 1104 as a mask to form a post 1105. Next, the mask pattern 1104 is removed by performing plasma oxidation or an appropriate acid treatment (wet treatment), and then, as shown in FIG.
05 is just filled, semi-insulating P-type InP
Crystals are grown on the substrate 1101, which forms the buried layer 1107. Further, as shown in FIG. 11 (e), a P-type I
By forming an upper cladding layer 1108 made of nP and an ohmic contact layer 1109 made of P-type InAsP, the basic structure of the semiconductor optical device according to the fourth embodiment is completed. In the fourth embodiment, a state in which a multiple quantum dot structure including a multiple quantum well structure processed into a cylindrical shape is obtained.

In the above description, the post 1105 is formed after forming the light guide layer 1103 first. However, the light guide layer 1103 is formed after the post is formed and buried with the high resistance layer. It may be. The height of the post can be controlled by the dry etching time using the mask pattern 1104 as a mask. Here, in the liquid phase epitaxial growth in which the high resistance layer is embedded, it is necessary to prevent the high resistance layer from growing on the post. For this purpose, the height of the post needs to be 0.5 μm or less. As described above, in the fourth embodiment, a fine multiple quantum well structure is formed for each post. That is, a multiple quantum dot structure is formed for each post. Since the posts are formed in accordance with the positions of the pores of the through-hole membrane, the quantum dots for each post constituting the multiple quantum dot structure are also accurately arranged and formed.

Embodiment 5 Hereinafter, a method for manufacturing a semiconductor optical device according to a fifth embodiment of the present invention will be described. Also in the fifth embodiment, the through-hole membrane 101 shown in FIG. 1 is used as in the first to fourth embodiments. Hereinafter, a method of manufacturing the semiconductor optical device according to the fifth embodiment will be described. First, as shown in FIG.
A multiple quantum well structure 12 is formed on a substrate 1201 made of nP.
02 and the light guide layer 1203 are formed, and the through-hole membrane 101 is disposed thereon. This quantum well structure 1202 is composed of six layers of InGaP / InGaAsP and oscillates at 1.55 μm. The light guide layer 1203 is made of 1.3 μm InGaAsP. These are the same as in the fourth embodiment.

In the fifth embodiment, first, an oxide such as silicon oxide is vapor-deposited using the through-hole membrane 101 as a mask, and then Pt is vapor-deposited. As a result, as shown in FIG. 12B, a lower mask pattern 1204a made of silicon oxide and an upper mask pattern 1204b made of Pt are formed on the light guide layer 1203. Next, as shown in FIG. 12C, the light guide layer 1203, the multiple quantum well structure 1202, and a part of the substrate 1201 are removed from the upper mask pattern 120.
The post 1205 is formed by etching with strong vertical anisotropy using the mask 4b as a mask.

Next, only the upper mask pattern 1204b is removed by performing plasma oxidation or an appropriate acid treatment (wet treatment). And then, FIG.
As shown in (d), a semi-insulating P is used by using a liquid phase epitaxial growth apparatus with the lower mask pattern 1204a formed on the post 1205 so that the post 1205 and a part of the lower mask pattern 1204a are filled. A shaped InP crystal is grown on the substrate 1201, thereby forming a buried layer 1207. Here, the lower mask pattern 1204a serves as a selective growth mask.

Next, the lower layer mask pattern 1204
a was removed by wet treatment with hydrofluoric acid, and FIG.
As shown in (e), by metal organic chemical vapor deposition or the like,
By forming the upper cladding layer 1208 made of P-type InP and the ohmic contact layer 1209 made of P-type InAsP, the basic structure of the semiconductor optical device according to the fifth embodiment is completed. Also in the fifth embodiment, a state in which a multiple quantum dot structure composed of a columnar multiple quantum well structure is formed is obtained, and a semiconductor optical device using the same can be obtained.

Further, according to the fifth embodiment, since the buried layer is formed with the selective growth mask arranged on the post, it is possible to form the buried layer above the height of the post. Become. That is, according to the fifth embodiment, there is no need to limit the height of the post. In the above description, a mask for pattern formation and a selective growth mask are prepared, respectively, but one of them may be shared. For example, if nickel oxide is used as the material for the mask pattern, the etching selectivity can be maintained even during the selective etching for forming the post, and it can be used as a selective growth mask.

Embodiment 6 Hereinafter, a method for manufacturing a semiconductor optical device according to a sixth embodiment of the present invention will be described. Also in the sixth embodiment, the through-hole membrane 101 shown in FIG. 1 is used as in the first to fifth embodiments. Hereinafter, a method of manufacturing the semiconductor optical device according to the sixth embodiment will be described. First, as shown in FIG.
The through-hole membrane 101 is arranged on a substrate 1301 made of nP.

In the sixth embodiment, the through-hole membrane 101 is used as a mask and the substrate 1301
Is selectively etched, and as shown in FIG.
A fine hole 1302 having a depth of about 100 nm is formed on the surface of the substrate 1301. For this etching, for example, an ECR plasma etching apparatus using a bromine-based gas may be used. This dry etching has features that it has vertical anisotropy, has low damage, and can form a uniform depth.

Next, after removing the through-hole membrane 101 and treating the surface of the substrate 1301 with an acid such as sulfuric acid, InGaAsP is crystal-grown using a liquid phase growth method so that the holes 1302 are just filled. In addition, In
Instead of GaAsP, an InGaAs / InGaAsP multiple quantum well may be grown. As a result, as shown in FIG. 13C, a quantum dot layer 1303a composed of quantum dots 1303 is formed on the substrate 1301. Then, as shown in FIG. 13E, the light guide layer 1304 made of InGaAsP and the upper cladding layer 1 made of P-type InP are formed by metal organic chemical vapor deposition or the like.
By forming an ohmic contact layer 1306 made of P-type InAsP, the basic structure of the semiconductor optical device according to the sixth embodiment is completed.

In the sixth embodiment, a quantum dot structure having a diameter of several tens of nanometers and having quantum dots having a height equal to the depth of the holes 1302 can be realized. Further, if a multiple quantum well structure is crystal-grown in the hole 1302, a multiple quantum dot structure in which quantum dots having a diameter of several tens of nm are regularly arranged can be realized, and a semiconductor optical device using the same can be obtained.
The height of the quantum dots can be arbitrarily controlled by the depth of the hole 1302.

Seventh Embodiment A method for manufacturing a semiconductor optical device according to a seventh embodiment of the present invention will be described below. Also in the seventh embodiment, the through-hole membrane 101 shown in FIG. 1 is used as in the first to sixth embodiments. Hereinafter, a method of manufacturing the semiconductor optical device according to the seventh embodiment will be described. First, as shown in FIG.
The through-hole membrane 101 is arranged on a substrate 1401 made of nP.

Next, as in the sixth embodiment, the through-hole membrane 101 is used as a mask and the substrate 14
01 is selectively etched to form fine holes 1402 having a depth of about 100 nm on the surface of the substrate 1401 as shown in FIG. Next, in the seventh embodiment, as shown in FIG. 14C, the through-hole membrane 101 is used as a mask while the substrate 14 is used as a mask.
01 selectively on InGaAsP or InGaAs
/ InGaAsP quantum well crystal growth. This crystal growth may be performed, for example, by the MOVPE method. As a result, as shown in FIG. 14C, a quantum dot layer 1403a including quantum dots 1403 is formed on the substrate 1401.

Next, the through-hole membrane 101 is removed, and as shown in FIG. 14D, the light guide layer 1404 made of InGaAsP is formed by MOVPE or the like.
By forming the upper cladding layer 1405 made of P-type InP and the ohmic contact layer 1406 made of P-type InAsP, the basic structure of the semiconductor optical device according to the seventh embodiment can be changed as in the sixth embodiment. It is completed. And also in this Embodiment 7,
It is possible to realize a quantum dot structure in which quantum dots having a diameter of several tens nm and the height of the depth of the hole 1402 are regularly arranged. Further, if a multiple quantum well structure is crystal-grown in the hole 1402, a multiple quantum dot structure in which multiple quantum dots having a diameter of several tens of nm are regularly arranged can be realized. The height of the quantum dots can be arbitrarily controlled by the depth of the hole 1402.

As described above, according to the present invention, a quantum dot structure composed of regularly arranged quantum dots,
In addition, a multiple quantum dot structure in which they are formed in multiple layers via a barrier layer can be easily formed. Then, a quantum dot structure or a multiple quantum dot structure is used as an active layer,
A semiconductor optical device such as a semiconductor laser as shown in FIG.

That is, for example, in the basic structure (FIG. 6) shown in the first embodiment, first, a stripe-shaped mask pattern is formed on the ohmic contact layer 509, and this is used as a mask to select a part of the substrate 501. Ridge 15 as shown in FIG.
01 is formed. Next, buried layers 1502 are formed by growing semi-insulating GaAs on both sides of the ridge 1501 so as to fill the ridge 1501. Then, if a p-side electrode 1503 is formed on the upper surface and an n-side electrode 1504 is formed on the lower surface, a semiconductor laser can be formed. This semiconductor laser oscillates from a multiple quantum dot structure 506 which becomes an active layer and is buried in a buried layer 1502 shown in FIG.

FIG. 16 is a characteristic diagram showing light emission characteristics of the semiconductor laser when current is injected. FIG. 16A shows a result when the multiple quantum dot structure obtained in the first embodiment is used as an active layer.
(B) shows the result when the multiple quantum dot structure obtained in the fourth embodiment is used as an active layer. (C) shows the result when the multiple quantum dot structure obtained in the third embodiment is used as an active layer. (D) shows the result when the conventional multiple quantum well structure is used as the active layer. As is clear from FIG. 16, according to the present invention, it is found that the oscillation threshold value is lower than in the case where the conventional multiple quantum well structure is used as the active layer. In the above description, the case where the present invention is applied to a semiconductor laser has been described.
It goes without saying that the present invention can be applied to an optical modulator, an optical receiver, and the like. Also in this case, the structures of the quantum dot structure and the multiple quantum dot structure are the same.

[0051]

As described above, according to the present invention, first, a semiconductor optical device is manufactured by providing the following steps. That is, by disposing a through-hole membrane having a plurality of through-holes on a substrate made of a semiconductor and depositing a mask material on the substrate using the through-hole membrane as a mask, a dot pattern made of a mask material is formed on the substrate through the through-hole. A second step of removing the through-hole membrane from the upper part of the substrate, and a step of etching the substrate using the dot pattern as a mask to form projections on the substrate surface, thereby distorting the substrate surface. A third step of forming an introduction layer, a fourth step of removing a dot pattern, and crystal growth of a first semiconductor lattice-matched to the substrate such that the projections are almost buried. A fifth step of forming a first barrier layer made of a first semiconductor in
By growing a second semiconductor having a different lattice constant from that of the first semiconductor so as not to form a continuous film, the second semiconductor is formed on the first barrier layer in accordance with the position of the protrusion of the strain introducing layer. A sixth step of forming a quantum dot made of a semiconductor, and a step of growing the first semiconductor on a first barrier layer containing the quantum dot by crystal growing the first semiconductor so that the quantum dot is almost embedded. And a seventh step of forming a second barrier layer. Since the semiconductor optical device is manufactured as described above, quantum dots are formed so as to match the positions of the through holes of the through-hole membrane. Therefore, if the opening diameter and the arrangement of the through-holes of the through-hole membrane are formed with high precision in the order of nm, the quantum dots can be formed with high precision. An optical element can be easily manufactured.

Second, in the present invention, a semiconductor optical device is manufactured by providing the following steps. That is, a first step of forming a strained film having a lattice constant different from that of a substrate on a substrate made of a semiconductor, and disposing a through-hole membrane having a plurality of through holes on the strained film, and using the through-hole membrane as a mask, A second step of forming a dot pattern made of the mask material on the strained film in accordance with the arrangement of the through holes by depositing a mask material thereon, and a third step of removing the through-hole membrane from the upper portion of the substrate; A fourth step of forming a distortion-introducing layer on the substrate by forming a projection on the substrate surface by etching the distortion film using the dot pattern as a mask, a fifth step of removing the dot pattern, and lattice matching with the substrate A first barrier layer made of the first semiconductor is grown on the strain-introducing layer. The sixth step of forming and growing the second semiconductor having a lattice constant different from that of the first semiconductor to such an extent that the second semiconductor does not form a continuous film, thereby forming a projection of the strain-introducing layer on the first barrier layer. And the seventh step of forming a quantum dot made of the second semiconductor in accordance with the position of the first semiconductor, and the crystal growth of the first semiconductor on the first barrier layer containing the quantum dot, whereby the quantum dot is almost embedded. Thus, at least the eighth step of forming the second barrier layer made of the first semiconductor is provided. Since the semiconductor optical device is manufactured as described above, quantum dots are formed so as to match the positions of the through holes of the through-hole membrane. Therefore, similarly to the above-described method, if the opening diameter and the arrangement of the through-holes of the through-hole membrane are formed with high accuracy in the order of nm, the quantum dots can be formed with high accuracy, and the quantum dots that can exhibit the original characteristics can be obtained. A semiconductor optical device having an active layer having a configuration can be easily manufactured.

Thirdly, in the present invention, a semiconductor optical device is manufactured by providing the following steps. That is, a through-hole membrane having a plurality of through holes is arranged on a substrate made of a semiconductor, and a first semiconductor having a lattice constant different from that of the substrate is deposited on the substrate using the through-hole membrane as a mask. A first step of forming a dot pattern made of the first semiconductor in accordance with the arrangement of the through-holes, a second step of removing the through-hole membrane from the upper portion of the substrate, and a step of forming the second semiconductor lattice-matched to the substrate by the dot pattern. And a third step of forming a first barrier layer made of a second semiconductor on the strain-introducing layer, and a third step having a different lattice constant from the second semiconductor. Is grown to such an extent that it does not form a continuous film, so that the third semiconductor is formed on the second barrier layer in accordance with the position of the protrusion of the strain introducing layer. A fourth step of forming a Ranaru quantum dots, the second to the first barrier layer including quantum dots
A fifth step of forming a second barrier layer made of the second semiconductor so that the quantum dots are almost buried by crystal-growing the semiconductor. Since the semiconductor optical device is manufactured as described above, also in this method, quantum dots are formed so as to match the positions of the through holes of the through-hole membrane. Also, if the opening diameter and the arrangement of the through-holes of the through-hole membrane are formed with high precision in the order of nanometers, quantum dots can be formed with high precision. A semiconductor optical device having the same can be easily manufactured.

In the present invention, fourthly, a semiconductor optical device is manufactured by providing the following steps. That is, a first step of forming an active layer consisting of a quantum well layer sandwiched between upper and lower barrier layers on a substrate made of a semiconductor, and a through-hole membrane having a plurality of through holes are arranged on the active layer. A second step of forming a dot pattern made of the mask material on the substrate in accordance with the arrangement of the through holes by depositing a mask material on the substrate using the membrane as a mask, and a third step of removing the through-hole membrane from the upper portion of the substrate. A fourth step of selectively etching the active layer using the dot pattern as a mask to form a post made of the active layer, and a fourth step of forming a buried layer made of a high-resistance semiconductor on the substrate around the post. And at least 5 steps.

Since the semiconductor optical device is manufactured as described above, the quantum dots are formed from the quantum well layers separated by the formation of the posts, and are formed so as to match the positions of the through holes of the through-hole membrane. Is done. Then, a quantum well layer sandwiched between the upper and lower barrier layers is formed for each post, so that a minute quantum well structure, that is, a quantum dot structure is formed so as to match the position of the through hole of the through-hole membrane. Will be done. Therefore, also in this method, if the opening diameter and the arrangement of the through-holes of the through-hole membrane are formed with high precision in the order of nanometers, the quantum dots can be formed with high precision. A semiconductor optical device having an active layer having a quantum dot structure can be easily manufactured.

Fifth, in the present invention, a through-hole membrane having a plurality of through holes is disposed on a substrate made of a semiconductor, and the substrate surface is selectively etched using the through-hole membrane as a mask. Forming a concave portion on the surface of the substrate in accordance with the arrangement of the through holes, and forming a quantum dot or a multiple quantum dot structure in each concave portion by crystal-growing a semiconductor layer so as to fill the concave portion. did. Since the semiconductor optical device is manufactured as described above, a quantum dot or multiple quantum dot structure separated by the inside of the recess is formed, and is formed so as to match the position of the through hole of the through-hole membrane. Therefore, also in this method, if the opening diameter and the arrangement of the through holes of the through-hole membrane are formed with high accuracy in the order of nm,
Since quantum dots can be formed with high precision, a semiconductor device having a quantum dot and an active layer having a multiple quantum dot structure that can exhibit original characteristics can be easily manufactured.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a configuration of a through-hole membrane.

FIG. 2 is an explanatory view showing a method for producing the through-hole membrane of FIG.

FIG. 3 is an explanatory view following FIG. 2 and showing a method for producing the through-hole membrane of FIG. 1;

FIG. 4 is a characteristic diagram showing voltage conditions in anodic oxidation in production of a through-hole membrane.

FIG. 5 is an explanatory diagram illustrating a method for manufacturing the semiconductor optical device according to the first embodiment of the present invention.

FIG. 6 is an explanatory view following FIG. 5 illustrating the method for manufacturing the semiconductor optical device according to the first embodiment of the present invention.

FIG. 7 is an explanatory view illustrating a method for manufacturing a semiconductor optical device according to a second embodiment of the present invention.

FIG. 8 is an explanatory view following FIG. 7 showing a method for manufacturing a semiconductor optical device according to the second embodiment of the present invention.

FIG. 9 is an explanatory diagram illustrating a method for manufacturing a semiconductor optical device according to a third embodiment of the present invention.

FIG. 10 is an explanatory view following FIG. 9 illustrating the method for manufacturing the semiconductor optical device in the third embodiment of the present invention.

FIG. 11 is an explanatory diagram illustrating a method for manufacturing a semiconductor optical device according to a fourth embodiment of the present invention.

FIG. 12 is an explanatory diagram illustrating a method for manufacturing a semiconductor optical device according to a fifth embodiment of the present invention.

FIG. 13 is an explanatory view illustrating a method for manufacturing a semiconductor optical device according to a fifth embodiment of the present invention.

FIG. 14 is an explanatory diagram illustrating a method for manufacturing a semiconductor optical device according to a fifth embodiment of the present invention.

FIG. 15 is a perspective view showing a schematic configuration of a semiconductor optical device according to the present invention.

FIG. 16 is a characteristic diagram showing oscillation characteristics of the semiconductor optical device according to the present invention.

[Explanation of symbols]

101: through-hole membrane, 102: pore, 50
1 ... substrate, 502 ... mask pattern, 503 ... dots,
503a: strain introduction layer, 504: lower barrier layer, 504
a: Intermediate barrier layer, 505: quantum dot, 505a: quantum well layer, 506: multiple quantum dot structure, 507: protective layer, 508: cladding layer, 509: ohmic contact layer.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshimasa Amano 3-19-2 Nishi Shinjuku, Shinjuku-ku, Tokyo Japan Telegraph and Telephone Corporation (72) Inventor Hideki Masuda 2-1-3-2 Bessho, Hachioji-shi, Tokyo 510

Claims (11)

[Claims] 1. A dot pattern comprising a mask material, wherein a through-hole membrane having a plurality of through holes is arranged on a substrate made of a semiconductor, and a mask material is deposited on the substrate using the through-hole membrane as a mask. A first step of forming the through hole on the substrate in accordance with the arrangement of the through holes; a second step of removing the through hole membrane from above the substrate; and etching the substrate using the dot pattern as a mask. A third step of forming a strain-introducing layer on the substrate surface by forming a projection on the substrate surface, a fourth step of removing the dot pattern, and projecting the first semiconductor lattice-matched to the substrate by the projection Is grown so as to be substantially buried, whereby a first barrier layer made of the first semiconductor is formed on the strain-introducing layer. Forming a quantum dot made of the second semiconductor by growing a second semiconductor having a lattice constant different from that of the first semiconductor so as not to form a continuous film. A sixth step of forming the first semiconductor on the first barrier layer in accordance with the position of the protrusion of the strain introducing layer, and crystal-growing the first semiconductor on the first barrier layer including the quantum dots. And a seventh step of forming a second barrier layer made of the first semiconductor so that the quantum dots are almost buried. A first step of forming a strained film having a lattice constant different from that of the substrate on a substrate made of a semiconductor; a through-hole membrane having a plurality of through-holes disposed on the strained film; A second step of forming a dot pattern made of the mask material on the strained film in accordance with the arrangement of the through holes by depositing a mask material on the strained film using the membrane as a mask; A third step of removing from the upper part of the substrate, and a fourth step of forming a distortion introducing layer on the substrate by etching the distortion film using the dot pattern as a mask to form projections on the substrate surface. A fifth step of removing the dot pattern; and bonding a first semiconductor lattice-matched to the substrate such that the protrusion is substantially embedded. A sixth step of growing and thereby forming a first barrier layer made of the first semiconductor on the strain-introducing layer; and connecting a second semiconductor having a different lattice constant from the first semiconductor. A seventh step of forming the quantum dots made of the second semiconductor on the first barrier layer in accordance with the positions of the protrusions of the strain-introducing layer by growing the crystals to such an extent that they do not form a film; Forming a second barrier layer made of the first semiconductor so that the quantum dots are almost embedded by crystal-growing the first semiconductor on the first barrier layer containing the quantum dots; 8. A method for manufacturing a semiconductor optical device, comprising at least the steps of: 3. A through-hole membrane having a plurality of through holes is disposed on a substrate made of a semiconductor, and a first semiconductor having a lattice constant different from that of the substrate is deposited on the substrate using the through-hole membrane as a mask. A first step of forming a dot pattern made of the first semiconductor on the substrate in accordance with the arrangement of the through holes; a second step of removing the through-hole membrane from above the substrate; A third step of crystal-growing a second semiconductor lattice-matched to the substrate such that the dot pattern is substantially embedded therein, thereby forming a first barrier layer made of the second semiconductor on the strain-introducing layer; And growing the third semiconductor having a different lattice constant from the second semiconductor to such an extent that the third semiconductor is not formed into a continuous film. A fourth step of forming a quantum dot made of a semiconductor on the second barrier layer in accordance with the position of the protrusion of the strain-introducing layer; and forming the second dot on the first barrier layer containing the quantum dot. A fifth step of forming a second barrier layer made of the second semiconductor so that the quantum dots are substantially buried by crystal-growing the semiconductor according to the first aspect of the present invention. Method of manufacturing. 4. A first step of forming, on a substrate made of a semiconductor, an active layer comprising a quantum well layer sandwiched between upper and lower barrier layers, and disposing a through-hole membrane having a plurality of through holes on the active layer. Depositing a mask material on the substrate using the through-hole membrane as a mask, thereby forming a dot pattern made of the mask material on the substrate in accordance with the arrangement of the through holes; A third step of removing the through-hole membrane from above the substrate, a fourth step of selectively etching the active layer using the dot pattern as a mask to form a post made of the active layer, A fifth step of forming a buried layer made of a high-resistance semiconductor on the substrate. Method. 5. The method for manufacturing a semiconductor optical device according to claim 4, wherein the dot pattern is removed before the fifth step. 6. The method for manufacturing a semiconductor optical device according to claim 4, wherein in the first step, a plurality of pairs of the quantum well layer and a barrier layer disposed thereon are formed. A method for manufacturing a semiconductor optical device, comprising forming an active layer. 7. The method of manufacturing a semiconductor optical device according to claim 4, wherein an optical guide layer is formed on the active layer before the second step. Of manufacturing a semiconductor optical device. 8. A through-hole membrane having a plurality of through-holes is arranged on a substrate made of a semiconductor, and the substrate surface is selectively etched using the through-hole membrane as a mask to match the arrangement of the through-holes. A first step of forming a recess in the surface of the substrate, a second step of removing the through-hole membrane from above the substrate, and crystal growth of a semiconductor layer so as to fill the recess. A method for manufacturing a semiconductor optical device, comprising at least a third step of forming dots. 9. A through-hole membrane having a plurality of through-holes disposed on a substrate made of a semiconductor, and selectively etching the surface of the substrate using the through-hole membrane as a mask, thereby forming the through-hole on the substrate surface. A second step of forming quantum dots in each of the concave portions by crystal-growing a semiconductor layer so as to fill the concave portions using the through-hole membrane as a mask; and And a third step of removing the through-hole membrane from above the substrate. 10. A through-hole membrane having a plurality of through-holes is arranged on a substrate made of a semiconductor, and the substrate surface is selectively etched using the through-hole membrane as a mask to match the arrangement of the through-holes. A first step of forming a recess in the surface of the substrate, a second step of removing the through-hole membrane from above the substrate, and a first semiconductor layer serving as a barrier layer and a quantum well so as to fill the recess. A third step of forming a multiple quantum dot structure in each of the concave portions by alternately growing a second semiconductor layer to be a crystal, thereby forming a semiconductor optical device. 11. A through-hole membrane having a plurality of through-holes is disposed on a substrate made of a semiconductor, and the surface of the substrate is selectively etched using the through-hole membrane as a mask to match the arrangement of the through-holes. A first semiconductor layer serving as a barrier layer and a second semiconductor layer serving as a quantum well layer so as to fill the recess using the through-hole membrane as a mask. A second step of forming a multiple quantum dot structure in each of the concave portions by alternately growing crystals, and a third step of removing the through-hole membrane from above the substrate. A method for manufacturing a semiconductor optical device.