JP2000162459A - Photonic crystal and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photonic crystal easily manufactured and used, for example, for a reflection mirror and an optical waveguide of a semiconductor laser, and to provide a manufacturing method therefor. SOLUTION: After a GaAs buffer layer 11 of a semiconductor layer is formed on a GaAs semiconductor substrate 10 of a single crystal substarte using an MOCVD method, the layer 11 is oxidized periodically with a prescribed distance one another using an atomic force microscope(AFM) fine working method to form fine oxide masks 11a. Thin film material layers 12, 13, 14 are not formed on portions with the oxide masks 11a formed by forming thin film material layers, each of which includes a clad layer 12, a core layer 13 and a clad layer 14, for forming, optical wave guides on the buffer layer 11 with the oxide masks 11a formed using the MOCVD method, and, on the other hand, the thin film material layers 12, 13, 14 are formed in portions with no oxide mask 11a formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photonic crystal for use in, for example, a reflection mirror or an optical waveguide of a semiconductor laser, and a method of manufacturing the same.

[0002]

2. Description of the Related Art A photonic crystal is a two-dimensional or three-dimensional cycle formed by alternately repeating two or more kinds of dielectrics or air and semiconductors or metals at a half wavelength cycle of light. It is a crystal having a structure. In such a structure, the behavior of light is determined by a dispersion characteristic called a photonic band. Further, a forbidden band called a photonic gap that does not allow the existence of light can be generated.

If such a photonic crystal can be realized, a reflection mirror of a semiconductor laser and an optical waveguide structure can be realized.

[0004]

However, the photonic crystal is disclosed in the prior art document 1 "Eli Yablonovitch,"
nhibited Spontaneous Emission in Solid-State Physi
cs and Electronics ”, Physical Review Letters, Vol.5
8, No. 20, pp. 2059-2062, May 18, 1987, has been a topic in the field of physics,
Little engineering application has been made. This is because submicron microfabrication is difficult and the effects of processing damage are so great that the effects cannot be discussed.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to make the manufacturing method simpler than that of the prior art. For example, a photonic crystal for use in a reflecting mirror or an optical waveguide of a semiconductor laser and the manufacturing thereof It is to provide a method.

[0006]

According to a first aspect of the present invention, in a photonic crystal according to the present invention, after a semiconductor layer is formed on a single crystal substrate, the semiconductor layers are separated from each other by a predetermined fine processing method. A fine oxide mask is formed by periodically oxidizing at intervals, and a predetermined thin film material layer is formed using a predetermined crystal growth method on the semiconductor layer on which the periodic oxide mask is formed. Thereby, the thin film material layer is not formed on the portion where the oxide mask is formed, but the thin film material layer is formed on the portion where the oxide mask is not formed.

The photonic crystal according to claim 2 is the photonic crystal according to claim 1, wherein the single crystal substrate is a GaAs semiconductor substrate, an InP semiconductor substrate,
It is a SiC substrate or a Si substrate.

Further, the photonic crystal according to claim 3 is the photonic crystal according to claim 1 or 2,
The fine processing method is an atomic force microscope (AFM) fine processing method or a scanning tunneling microscope (STM) fine processing method.

According to a fourth aspect of the present invention, there is provided a method for manufacturing a photonic crystal, comprising: forming a semiconductor layer on a single crystal substrate; and forming the semiconductor layer at a predetermined distance from each other by using a predetermined fine processing method. Forming a fine oxide mask by opening and periodically oxidizing, and forming a predetermined thin film material layer using a predetermined crystal growth method on the semiconductor layer on which the periodic oxide mask has been formed. Forming the thin film material layer in a portion where the oxide mask is not formed, and forming the thin film material layer in a portion where the oxide mask is not formed. .

According to a fifth aspect of the present invention, in the method for manufacturing a photonic crystal according to the fourth aspect, the single crystal substrate is a GaAs semiconductor substrate.
It is an InP semiconductor substrate, a SiC substrate, or a Si substrate.

Further, the method for manufacturing a photonic crystal according to claim 6 is the method for manufacturing a photonic crystal according to claim 4 or 5, wherein the fine processing method is an atomic force microscope (AFM) fine processing method. Scanning tunnel microscope (S
(TM) a fine processing method.

[0012]

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

FIG. 1 is a partially cutaway perspective view showing a structure of an optical waveguide formed of a photonic crystal according to an embodiment of the present invention. FIGS. 2 to 4 are views of the photonic crystal of FIG. It is sectional drawing which shows the manufacturing process of an optical waveguide. As shown in FIG. 2 to FIG. 4, an optical waveguide formed by the photonic crystal of this embodiment is formed on a GaAs semiconductor substrate 10 which is a single crystal substrate by a MOCVD method.
After forming the aAs buffer layer 11, a fine oxide mask 11a is formed by periodically oxidizing the buffer layer 11 at predetermined intervals using an atomic force microscope (AFM) fine processing method. MOCVD is performed on the buffer layer 11 on which the periodic oxide mask 11a is formed.
Layer 1 for forming an optical waveguide by using the
2. By forming the thin film material layer including the core layer 13 and the cladding layer 14, the thin film material layers 12, 13, and 14 are not formed in the portion where the oxide mask 11a is formed, while the oxide mask 11a is formed. It is characterized in that the thin film material layers 12, 13, and 14 are formed in portions where they are not formed.

A semiconductor laser, which is a light emitting source, is formed on a single crystal semiconductor substrate by metal organic chemical vapor deposition (hereinafter referred to as MOC).
It is called VD method. ), A single crystal having various functions is formed (single crystal growth) using a molecular beam growth method (hereinafter, referred to as MBE method) or an organometallic molecular beam growth method (hereinafter, referred to as MOMBE method). It is made. This utilizes the fact that a thin film formed on the substrate reflects the crystallinity of the substrate and grows under a certain condition because the substrate is a single crystal material. On the other hand, in the present embodiment, by covering the substrate with another material, it is possible to partially suppress the growth and perform so-called selective growth.
It becomes possible to produce a photonic crystal by producing a fine single crystal. In this photonic crystal, light (light wave) can be present (guided) only in a portion having a photonic band. That is, the photonic band structure formed simultaneously with the production of the light emitting element enables the production of the reflector and the optical waveguide of the laser element.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As an example, a method for manufacturing an optical waveguide made of a photonic crystal according to the present embodiment will be described below with reference to FIGS. Here, as a single crystal semiconductor substrate, GaAs whose front surface has a plane orientation (1, 0, 0)
An s semiconductor substrate 10 was used. First, the front surface of the semiconductor substrate 10 having a thickness of 400 μm was washed with an organic solvent and an acidic solution, and then, as shown in FIG. 2, crystal growth required for manufacturing a light emitting element was performed by MOCVD. Here, the crystal growth method is not limited to the MOCVD method, but may be an MBE method, a vapor phase epitaxial method (hereinafter, referred to as VPE method), a liquid phase epitaxial method (hereinafter, referred to as LPE method), or the like.

Referring to FIG. 2, an atomic force microscope (A) is used to perform good crystal growth on a semiconductor substrate 10.
FM) A 200-nm-thick GaAs buffer layer 11, which is a semiconductor layer for forming the oxide mask 11a, was grown by a fine processing method (or also referred to as an AFM lithography method).

Next, a fine 8 nm-thick film made of Ga _x O _y or As _{x '} O _{y '} is formed on the portion where the photonic crystal is to be formed by using a known atomic force microscope (AFM) fine processing method. The distance between the centers of the adjacent oxide masks 11a is の of the light guided by the waveguide.
It was formed to have a wavelength. This forming method is, for example,
Prior Art Document 2 “M. Ishii et al,” Control of Curren
t in 2DEG Channel byOxide Wire Formed Using AFM ”,
Japan Journal of Physics, Vol.34, pp.1329-1331, Part
1, No. 2B, February 1995 ", as shown in FIG. 5, the tip of the cantilever 20 of the AFM is brought into contact with the buffer layer 11 which is a semiconductor layer, and the gap between the cantilever 20 and the semiconductor substrate 10 is formed. While applying a predetermined DC electric field from the variable voltage DC power supply 30 to the
By moving in the direction of 0, an anodizing reaction is caused by a reaction between the current flowing into the semiconductor substrate 10 and water vapor in the air, and the GaAs oxide mask 11 is formed.
This is a method for forming a. The prepared oxide mask 11a
Is described in, for example, prior art document 3 “Yasufumi Fujiwar
a et al, ”Fabrication of Two-Dimensional InP Photo
nic Band-Gap Crystals by Reactive Ion Etching with
Inductively Coupled Plasma ”Japan Journal of Phys
ics, Vol.36, pp.7763-7768, Part1, No.12B, December 1997 ''
Is disclosed.

In the oxidation treatment using the AFM microfabrication method, the cantilever 20 of an atomic force microscope (AFM) is used as an ultra-fine electrode for causing a chemical reaction to form a nanoscale fine oxide fine line. it can. Here, when a positive DC bias voltage is applied to the cantilever of the AFM and a negative DC bias voltage is applied to the substrate, a tunnel current flows between the cantilever 20 and the surface of the semiconductor substrate 10 to which moisture in the air has been adsorbed. Faraday current flows through water, causing an oxidation reaction. By utilizing this reaction, the substrate just under the probe can be oxidized to form a fine oxide thin line. Since the fine oxide wires function as an energy barrier for electrons, an electronic device can be formed. In the present embodiment, the oxidized portion changes to a material (oxide mask 11a) having a different refractive index from that of the base GaAs, so that the oxide mask 11a is two-dimensionally and periodically separated by a predetermined interval. Can be formed. In the present embodiment, the planar shape of the oxide mask 11a is circular, but the present invention is not limited to this, and may be a polygonal shape such as a hexagonal shape.

After the formation of the oxide mask 11a, the following thin film material layers 12, 13, and
14 were grown. As shown in FIG. 4, first, in order to confine light to the semiconductor substrate 10, that is, on the upper side in the thickness direction of the semiconductor substrate 10, the thickness 500
A cladding layer 12 of Al _0.5 Ga _0.5 As with a thickness of nm was grown. Next, as the core of the waveguide, a thickness of 300 n
After the core layer 13 made of AlAs of m is formed, an A layer having a thickness of 500 nm is formed in order to confine an optical signal in a vertical direction in the drawing, which is a direction perpendicular to the substrate surface of the semiconductor substrate 10.
A cladding layer 14 of l _0.5 Ga _0.5 As was grown.
Here, prior art document 4 “K. Shiralagi et al,” GaAs M
ESFET Fabrication Without Using Photoresist ”, IEEE
Electron Device Letters, Vol.19, No.2, February 1998 ''
As described in the above, crystal growth is not performed on the oxide mask 11a which is a GaAs oxide, and crystal growth is selectively performed only on a portion where the oxide mask 11a is not provided.
Through the above manufacturing steps, as shown in FIG. 4, an optical waveguide to be air or a dielectric is formed at the portion where the oxide mask 11a is formed. That is, at a half wavelength period of light,
A photonic crystal having a two-dimensional periodic structure formed by alternately repeating two or more kinds of dielectrics or air and a semiconductor can be formed.

As described above, according to the present embodiment, the MOGaAs is formed on the GaAs semiconductor substrate 10 which is a single crystal substrate.
GaAs buffer layer 11 as a semiconductor layer by CVD
Is formed, the buffer layer 11 is periodically oxidized at a predetermined interval from each other by using an atomic force microscope (AFM) fine processing method, thereby forming a fine oxide mask 11a.
And a thin film material layer including a cladding layer 12, a core layer 13, and a cladding layer 14 for forming an optical waveguide by MOCVD on the buffer layer 11 on which the periodic oxide mask 11a is formed. Is formed, the thin film material layer 1 is formed at the portion where the oxide mask 11a is formed.
The oxide mask 11a is not formed while no 2, 13, 14 are formed.
Are not formed in the thin film material layers 12, 1
3 and 14 are formed.

Therefore, it is possible to manufacture a submicron structure, which has been difficult in the past, without damage, and a high-quality photonic crystal can be formed. In addition, by incorporating a process using an atomic force microscope (AFM) microfabrication method into a manufacturing process of a semiconductor laser or a semiconductor photodetector used in an optical communication field, a photonic crystal can be formed at the same time. It is possible to simultaneously manufacture a laser reflection mirror and a waveguide of an optical circuit in which optical components are integrated. As a result, integration of the optical integrated circuit is further facilitated, and component costs and assembly costs can be significantly reduced.

<Modification> In the above embodiment, GaAs
Although the present invention is not limited to this, the present invention is not limited to this. For example, an InP semiconductor substrate, a SiC substrate,
An i-substrate may be used.

In the above embodiment, the atomic force microscope (A
Although the photonic crystal is formed by using the FM) microfabrication method, the present invention is not limited to this, and the scanning tunneling microscope (STM) may be formed using a probe of a scanning tunneling microscope (STM).
TM) The photonic crystal may be formed by using a fine processing method.

[0024]

As described in detail above, according to the photonic crystal and the method for manufacturing the same according to the present invention, after forming a semiconductor layer on a single crystal substrate, the semiconductor layer is formed by a predetermined fine processing method. A fine oxide mask is formed by periodically oxidizing at a predetermined interval from each other, and a predetermined thin film material is formed on the semiconductor layer on which the periodic oxide mask is formed by using a predetermined crystal growth method. By forming the layer, the thin film material layer is not formed on the portion where the oxide mask is formed, while the thin film material layer is formed on the portion where the oxide mask is not formed.

Therefore, according to the present invention, a submicron structure, which has been conventionally difficult, can be manufactured without damage, and a high-quality photonic crystal can be formed. In addition, an atomic force microscope (AF) is used in the manufacturing process of semiconductor lasers and semiconductor photodetectors used in the optical communication field.
M) A photonic crystal can be formed at the same time by incorporating a process using a microfabrication method such as a microfabrication method. Therefore, a reflecting mirror of a semiconductor laser and a waveguide of an optical circuit in which optical components are integrated are simultaneously produced. It is possible to do. This makes it easier to integrate the optical integrated circuit,
Parts costs and assembly costs can be greatly reduced.

[Brief description of the drawings]

FIG. 1 is a partially cutaway perspective view showing a structure of an optical waveguide made of a photonic crystal according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a first step of a step of manufacturing the optical waveguide of the photonic crystal in FIG.

FIG. 3 is a cross-sectional view showing a second step in the manufacturing steps of the optical waveguide of the photonic crystal in FIG. 1;

FIG. 4 is a cross-sectional view showing a third step of the step of manufacturing the optical waveguide of the photonic crystal in FIG. 1;

5 is a perspective view showing a method of manufacturing an oxide mask 11a using an atomic force microscope (AFM) fine processing method in a second step of FIG. 3;

DESCRIPTION OF SYMBOLS 10: semiconductor substrate, 11: buffer layer, 11a: oxide mask, 12: clad layer, 13: core layer, 14: clad layer, 20: cantilever, 30: variable voltage DC power supply.

Continuing on the front page (72) Inventor Chiaki Domoto 5 Sanraya, Daiya, Seika-cho, Soraku-cho, Kyoto Pref. ATIR Co., Ltd. Environmentally Friendly Communication Laboratory (72) Inventor Kazumi Wada Lexington, MA 02173 United States 02173 No. 26, Winchester Drive (72) Inventor Seiji Sakata 5th Sanraya, Inaya, Seika-cho, Soraku-gun, Kyoto Pref. ATI Research Institute for Environmentally Friendly Communication (72) Inventor Norifumi Egami Kyoto 5F, Sanraya, Seiya-cho, Seika-cho, Soraku-gun, F-term (reference) 2A047 PA06 PA24 QA02 TA05 5F073 CA04 DA05 DA35

Claims (6)

[Claims] After forming a semiconductor layer on a single crystal substrate,
Forming a fine oxide mask by periodically oxidizing the semiconductor layer at a predetermined interval from each other using a predetermined fine processing method, on the semiconductor layer on which the periodic oxide mask is formed, By forming a predetermined thin film material layer using a predetermined crystal growth method, the thin film material layer is not formed on the portion where the oxide mask is formed, while the thin film material layer is not formed on the portion where the oxide mask is not formed. A photonic crystal formed by forming a thin film material layer. 2. The photonic crystal according to claim 1, wherein the single crystal substrate is a GaAs semiconductor substrate, an InP semiconductor substrate, a SiC substrate, or a Si substrate. 3. The photonic crystal according to claim 1, wherein the fine processing method is an atomic force microscope (AFM) fine processing method or a scanning tunneling microscope (STM) fine processing method. Photonic crystal. 4. A fine oxide mask is formed by forming a semiconductor layer on a single crystal substrate and periodically oxidizing the semiconductor layers at predetermined intervals with a predetermined fine processing method. And forming a predetermined thin film material layer on the semiconductor layer on which the periodic oxide mask is formed by using a predetermined crystal growth method. Forming a thin film material layer at a portion where an oxide mask is not formed, while not forming a thin film material layer. 5. The method for manufacturing a photonic crystal according to claim 4, wherein the single crystal substrate is a GaAs semiconductor substrate, an InP semiconductor substrate, a SiC substrate, or a Si substrate. . 6. The method for manufacturing a photonic crystal according to claim 4, wherein the fine processing method is an atomic force microscope (AFM) fine processing method or a scanning tunneling microscope (STM) fine processing method. A method for producing a photonic crystal, comprising: