JP2005347662A - Semiconductor quantum dot structure and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture a semiconductor quantum dot which has a further wide producible emission wavelength range, has little defect, is excellent in optical property and has little manufacturing limit with good uniformity and reproducibility. <P>SOLUTION: In a structure wherein a semiconductor quantum dot 105 is formed on a semiconductor substrate 101, the semiconductor quantum dot 105 is laminated with at least one thin film semiconductor layer 106 consisting of a semiconductor material which is different from a semiconductor material constituting the semiconductor substrate 101 in composition or constituent element. At least one thin film semiconductor layer 106, or both at least one thin film semiconductor layer 106 and the semiconductor quantum dot 105 are impregnated with bismuth. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a semiconductor quantum dot structure and a manufacturing method thereof.

Many semiconductor quantum dots with conventional structures utilize the phenomenon of self-formation of quantum dots that occurs when a semiconductor layer with a lattice constant different from that of the substrate by a certain value is grown on a semiconductor substrate under specific conditions. Therefore, there is a problem that it is difficult to control the size and density of the semiconductor quantum dots and the distortion when the dots are embedded in another semiconductor layer as intended.
For example, in the case of creating InAs quantum dots on a GaAs substrate, for example, when the size of the quantum dots is increased to increase the emission wavelength, the density of dots in the plane decreases, and the dot density However, there is a restriction that the size of the quantum dot becomes small when trying to increase it.

Further, when the InAs quantum dots are embedded with GaAs, a large compressive strain remains in the InAs quantum dots, so that the emission wavelength is significantly shorter than that due to the band gap inherent in InAs.
In order to solve the above problems, various semiconductor quantum dot structures and manufacturing methods have been conventionally devised. For example, in the case where InAs quantum dots are again formed on a GaAs substrate, the InAs quantum dots may be formed on or above the InAs quantum dots. A method of laminating an InGaAs layer having a compressive strain and reducing the residual strain in the InAs quantum dots by elastically reducing it, or a layer of a GaAsN layer having an extension strain instead of an InGaAs layer having a compressive strain is the same. A method for obtaining an effect is used.

In addition, as a method of increasing the size of the dots without reducing the in-plane density, a phase separation phenomenon that occurs under certain conditions when the InGaAs layer is stacked is used to surround the InAs quantum dots. A method of selectively growing InGaAs with a high In composition to increase the effective dot volume is also used in part (see Non-Patent Document 1, for example).
However, the semiconductor quantum dots obtained by the conventional structure and manufacturing method as described above have problems that the reproducibility and in-plane uniformity in production are not sufficient, and further, the formation of quantum dots and other semiconductor layers In the buried growth, growth at a lower temperature than usual is required. As a result, defects that become non-luminescent centers are easily introduced, and it is difficult to obtain sufficient optical characteristics.

In particular, in the organic metal compound vapor phase epitaxial growth method (MOVPE method) often used for the production of epitaxial wafers for semiconductor lasers and the like, it is necessary to thermally decompose the growth raw material, so that a high-quality semiconductor layer can be obtained under low temperature growth conditions. It was difficult.
On the other hand, attempts have been made to obtain crystals with good flatness by supplying materials such as bismuth, antimony, and thallium during the growth of semiconductor thin films and using them as surface modifiers (called surfactants). 1 (see Non-Patent Document 2), however, there was no example in which these raw materials were used for promoting phase separation as described above.
Patent Publication No. 3239821, “Method for producing strained semiconductor crystal” MV. Maximov et al., “GaAs-Based 1.3μm InGaAs Quantum Dot Lasers: A status Report” Journal of Electronic Materials, Vol. 29 p.476, 2000. S. Tixier et al., “Surfactant enhanced growth of GaNAs and InGaNAs using bismuth” Journal of Crystal Growth, VoL.251, p.449, 2003.

  The present invention was made to solve the limitations or disadvantages of the semiconductor quantum dots by the conventional structure and manufacturing method as described above, and has a wider range of light emission wavelengths that can be manufactured, and has fewer defects and excellent optical properties. The purpose is to produce semiconductor quantum dots with few restrictions on production with good uniformity and reproducibility.

  The semiconductor quantum dot structure according to claim 1 of the present invention for solving the above-mentioned problems is a structure in which semiconductor quantum dots are formed on a semiconductor substrate, wherein the semiconductor quantum dots are composed of a semiconductor material constituting the semiconductor substrate, or It is laminated with at least one semiconductor thin film layer made of a semiconductor material having different constituent elements, and bismuth is formed in at least one layer of the semiconductor thin film layer, or in at least one layer of the semiconductor thin film layer and the semiconductor quantum dot. It is characterized by being added.

  The semiconductor quantum dot structure according to claim 2 of the present invention for solving the above-mentioned problems is the semiconductor quantum dot structure according to claim 1, wherein the semiconductor substrate, the semiconductor quantum dot and the semiconductor thin film layer are III-V compound semiconductors. Or a III-V compound semiconductor mixed crystal.

  The semiconductor quantum dot structure according to claim 3 of the present invention for solving the above-described problems is the semiconductor quantum dot structure according to claim 2, wherein the semiconductor substrate is GaAs or InGaAs, and the semiconductor quantum dots are InAs, InAsSb. InGaAs, InGaAsP or InGaAsSb, and the semiconductor thin film layer is InGaAs, InGaAsP or InGaAsSb.

The semiconductor quantum dot structure according to claim 4 of the present invention that solves the above problem is the semiconductor quantum dot structure according to claim 2, wherein the semiconductor substrate is InP, and
The semiconductor quantum dot is InAs, InAsSb, InGaAs, InGaAsP or InGaAsSb, and the semiconductor thin film layer is InGaAs, InGaAsP or InGaAsSb.

  The semiconductor quantum dot structure according to claim 5 of the present invention for solving the above-mentioned problems is the semiconductor quantum dot structure according to claim 2, wherein the semiconductor substrate is GaAs or InGaAs, and the semiconductor quantum dots are InNAs, GaInNAs. InNAsSb or GaInNAsSb, and the semiconductor thin film layer is InGaAs, InGaAsP, InGaAsSb, GaNAs, InNAs, GaInNAs, InNAsSb, or GaInNAsSb.

  The semiconductor quantum dot structure according to claim 6 of the present invention for solving the above-mentioned problems is the semiconductor quantum dot structure according to claim 2, wherein the semiconductor substrate is InP, and the semiconductor quantum dots are InNAs, GaInNAs, InNAsSb. Alternatively, it is GaInNAsSb, and the semiconductor thin film layer is InGaAs, InGaAsP, InGaAsSb, GaNAs, InNAs, GaInNAs, InNAsSb, or GaInNAsSb.

  The method of manufacturing a semiconductor quantum dot structure according to claim 7 of the present invention for solving the above-described problem is the method of manufacturing a semiconductor quantum dot structure according to claim 1, 2, 3, 4, 5 or 6, wherein the semiconductor thin film The growth temperature of the layer is 500 ° C. or less, and bismuth is supplied during growth of at least one of the semiconductor thin film layers or growth of at least one of the semiconductor thin film layers and the semiconductor quantum dots. And

  The method for producing a semiconductor quantum dot structure according to claim 8 of the present invention for solving the above-described problem is the method for producing a semiconductor quantum dot structure according to claim 7, wherein trimethylbismuth is used as the bismuth material and gallium is used as the gallium material. Triisopropyl gallium is used.

When the semiconductor quantum dot structure according to the present invention is used as the active layer of the semiconductor light source, the wavelength range of the light output that can be emitted can be greatly widened compared to the case of using the prior art, and the light emission efficiency and temperature characteristics are also improved. It can be greatly improved.
In addition, when the semiconductor quantum dot structure according to the present invention is used as the active layer of the semiconductor optical amplifier, the wavelength band that can be amplified is wide, the saturation light output is large, and the high-speed response characteristic is obtained as compared with the case of using the prior art. It is possible to obtain the combined characteristics.
Further, when the method for producing a semiconductor quantum dot structure according to the present invention is used, the semiconductor quantum dot structure according to the present invention can be provided with good reproducibility and yield.

(1) In the semiconductor quantum dot structure according to the present invention, the semiconductor quantum dot is laminated with at least one semiconductor thin film layer made of a semiconductor material having a composition or a constituent element different from that of the semiconductor material constituting the semiconductor substrate. Bismuth is added to at least one of the semiconductor thin film layers, or to at least one of the semiconductor thin film layers and the semiconductor quantum dots.
Here, the effects obtained by adding bismuth are roughly divided into three types.

The first effect is that the addition of bismuth has few defects that become non-luminescent centers, and the semiconductor quantum dots having excellent optical properties and the semiconductor thin film layer can be obtained even under low temperature growth conditions. Second, the addition of bismuth. As a result of promoting the phase separation phenomenon during the growth of the semiconductor thin film layer, a semiconductor quantum dot that is larger, that is, emits light at a longer wave, is configured with good uniformity. Third, the addition of bismuth makes the semiconductor quantum dot The band gap of the material constituting the material is reduced, and a semiconductor quantum dot structure in which the light emission becomes longer wave is obtained.
As a result, the semiconductor quantum dot structure according to the present invention is characterized by excellent optical characteristics, a high degree of freedom regarding the emission wavelength, and a high uniformity within the wafer surface.

(2) In the method of manufacturing a semiconductor quantum dot structure according to the present invention, the growth temperature is set to 500 ° C. or less during the growth of the semiconductor thin film layer in which the semiconductor quantum dots are embedded, and bismuth is supplied during the growth of the semiconductor thin film layer. It is characterized in that self-generated phase separation in the semiconductor thin film structure can be promoted without deteriorating optical characteristics.
Here, the reason why the growth temperature is set to 500 ° C. or lower is that when the semiconductor quantum dots are embedded at a temperature exceeding 500 ° C., the quantum dots are deformed and the optical characteristics are deteriorated, and the above-mentioned phase is thermodynamically. This is because separation hardly occurs and control for obtaining a desired emission wavelength becomes difficult.

In addition, in the growth of a semiconductor layer by the MOVPE method, which is conventionally difficult to grow at a low temperature, in the present invention, trimethylbismuth is used as a bismuth raw material, and trimethylgallium and triethylyl having a decomposition temperature higher than that of a raw material such as trimethylindium. By using triisopropyl gallium instead of a gallium raw material such as gallium, it is possible to grow a high-quality semiconductor layer even under low temperature growth conditions.
As a result, in the method of manufacturing a semiconductor quantum dot structure according to the present invention, compared with the method of enlarging the dot volume using the phase separation phenomenon according to the conventional invention, the optical characteristics are superior and the degree of freedom with respect to the emission wavelength is large. It is possible to provide a semiconductor quantum dot structure with high in-plane uniformity with good reproducibility and yield even when the MOVPE method is used.

The reason why the above action can be obtained by supplying bismuth is not clear at present, but the supply of bismuth decreases the surface energy on the growth layer surface and increases the diffusion distance on the crystal surface of the growth material. Although the effect, that is, the effect obtained as a result is completely opposite to the conventional proposal, it is considered to be a kind of surfactant effect.
However, since the manufacturing method of the semiconductor quantum dot structure according to the present invention uses low-temperature growth conditions, the supplied bismuth is not a pure surfactant, and a part of the bismuth is taken into the crystal to narrow the band gap. It is characterized by having an action.
[Action]

The semiconductor quantum dot structure according to the present invention is more excellent in characteristics such as light emission efficiency than the semiconductor quantum dot structure according to the prior art, and acts as an active layer of a semiconductor light source having a higher degree of freedom regarding the emission wavelength.
Also, the method for producing a semiconductor quantum dot structure according to the present invention makes it possible to provide the semiconductor quantum dot structure according to the present invention with good reproducibility and yield.

An embodiment relating to claims 1, 2 and 3 of the invention is represented in FIG.
In the figure, 101 is a substrate (GaAs), 102 is a cladding layer (AlGaAs, film thickness 1.5 μm), 103 is an optical confinement layer (AlGaAs, film thickness 200 nm), 104 is a barrier layer (GaAs, film thickness 50 nm), 105 Is a quantum dot (In (Ga) As: Bi), 106 is a thin film layer (InGaAs: Bi, film thickness 10 nm), and 107 is a contact layer (GaAs, film thickness 300 nm).
Further, among the quantum dots 105, 105a is a region made of self-formed InAs: Bi, and 105b is made of InGaAs: Bi selectively grown on the dots of 105a by phase separation during the growth of the thin film layer 106. It is an area.

Here, since the In composition of the selectively grown region (InGaAs: Bi) 105b is much higher than the average In composition of the thin film layer 106, the composite of the region 105a and the region 105b is formed in this embodiment. The quantum dot 105 acts as an effective quantum dot 105, and the light emission wavelength becomes longer as the volume of the quantum dot 105 increases.
In addition, since bismuth is added to the quantum dots 105 composed of the regions 105a and 105b, the emission wavelength of the quantum dots can be further increased.

That is, the following three types of effects can be obtained by adding bismuth.
The first effect is that the addition of bismuth has few defects serving as non-luminescent centers, and the semiconductor quantum dots having excellent optical characteristics and the semiconductor thin film layer can be obtained even under low temperature growth conditions.
The second effect is that the addition of bismuth promotes the phase separation phenomenon during the growth of the semiconductor thin film layer, and as a result, the semiconductor quantum dots that are larger, that is, emit light at longer waves, are configured with good uniformity. .
The third effect is that by adding bismuth, the band gap of the material constituting the semiconductor quantum dot is reduced, and a semiconductor quantum dot structure in which the light emission becomes longer wave is obtained.
As a result, the semiconductor quantum dot structure according to the present embodiment is characterized by excellent optical characteristics, a large degree of freedom with respect to the emission wavelength, and a high uniformity within the wafer surface.

Here, in the present embodiment, the thin film layer 106 is above and below the quantum dot 105, but even if the thin film layer 106 is only above the quantum dot 105, the effect of the present invention can be obtained similarly.
As a result of producing the semiconductor quantum dot structure according to this example using various growth conditions and producing a laser diode element, an element having an emission wavelength of 1 to 1.5 μm was obtained.
In addition, when creating the same structure, the growth conditions are intentionally determined so that the size of the quantum dots is distributed, and as a result of creating a semiconductor optical amplifier with the obtained structure, a wide band with an amplification band of 1 to 1.5 μm, A highly saturated output device was obtained.

  Note that InGaAs instead of GaAs is used as the substrate 101, InAs, InAsSb, InGaAsP or InGaAsSb is used as the quantum dot 105, and InGaAsP or InGaAsSb is used as the thin film layer 106 instead of InGaAs. Needless to say.

An embodiment relating to claims 1, 2 and 4 of the invention is represented in FIG.
In the figure, 201 is a substrate (InP), 202 is a cladding layer (InP, thickness 1.5 μm), 203 is an optical confinement layer (InGaAsP, thickness 200 nm), and 204 is a barrier layer (InGaA).
sP, film thickness 50 nm), 205 is a quantum dot (In (Ga) As: Bi), 206 is a thin film layer (InGaAs: Bi, film thickness 10 nm), and 207 is a contact layer (InGaAs, film thickness 300 nm).
Further, among the quantum dots 205, 205a is a region made of self-formed InAs: Bi, and 205b is made of InGaAs: Bi selectively grown on the dots in the region 205a by phase separation during the growth of the thin film layer 206. It is an area.

Here, since the In composition of the selectively grown region (InGaAs: Bi) 205b is significantly higher than the average In composition of the thin film layer 206, in this embodiment, the composite of the region 205a and the region 205b is used. The body acts as an effective quantum dot 205, and the emission wavelength of the quantum dot 205 is increased by increasing the volume of the quantum dot 205.
In addition, since bismuth is added to the quantum dots 205 composed of the regions 205a and 205b, the emission wavelength of the quantum dots can be further increased.
That is, by adding bismuth, also in this embodiment, as described in Embodiment 1, three kinds of effects are exhibited.

Here, in this embodiment, the thin film layer 206 is above and below the quantum dot 205, but the effect of the present invention can be similarly obtained even if the thin film layer 206 is only above the quantum dot 205.
The semiconductor quantum dot structure according to the present example was prepared using various growth conditions, and a laser diode element was produced. As a result, an element having an emission wavelength of 1.3 to 2.2 μm was obtained.
Moreover, when creating the same structure, the growth conditions are intentionally determined so that the size of the quantum dots is distributed, and as a result of creating a semiconductor optical amplifier with the obtained structure, an amplification band of 1.3 to 2.2 μm, A broadband, high-saturation output device was obtained.

  Needless to say, InAs, InAsSb, InGaAsP or InGaAsSb is used as the quantum dot 205 instead of InGaAs, and InGaAsP or InGaAsSb is used as the thin film layer 206 instead of InGaAs.

An embodiment relating to claims 1, 2 and 5 of the present invention is shown in FIG.
In the figure, 301 is a substrate (GaAs), 302 is a cladding layer (AlGaAs, film thickness 1.5 μm), 303 is an optical confinement layer (AlGaAs, film thickness 200 nm), 304 is a barrier layer (GaAs, film thickness 50 nm), 305 Is a quantum dot (In (Ga) NAs: Bi), 306 is a thin film layer (GaInNAs: Bi, film thickness 10 nm), and 307 is a contact layer (GaAs, film thickness 300 nm).
Further, in the quantum dots 305, 305a is a region made of self-formed InAs: Bi, and 305b is made of InGaNAs: Bi selectively grown on the dots in the region 305a by phase separation during the growth of the thin film layer 306. It is an area.

Here, since the In composition of the selectively grown region (InGaNAs: Bi) 305b is significantly higher than the average In composition of the thin film layer 306, in this embodiment, the composite of the region 305a and the region 305b is used. The body acts as an effective quantum dot 305, and the light emission wavelength becomes longer as the volume of the quantum dot 305 increases.
In addition, since bismuth is added to the quantum dot 305 constituted by the region 305a and the region 305b, the emission wavelength of the quantum dot can be further increased.
That is, by adding bismuth, also in this embodiment, as described in Embodiment 1, three kinds of effects are exhibited.

Here, in this embodiment, the thin film layer 306 is above and below the quantum dot 305, but even if the thin film layer 306 is only above the quantum dot 305, the effect of the present invention is obtained similarly.
The semiconductor quantum dot structure according to this example was created using various growth conditions, and laser diode elements were produced. As a result, an element having an emission wavelength of 1 to 1.7 μm was obtained.
In addition, when the same structure is created, growth conditions are intentionally determined so that the size of the quantum dots is distributed, and a semiconductor optical amplifier is created using the obtained structure. As a result, a wideband with an amplification band of 1 to 1.7 μm, A highly saturated output device was obtained.

  Note that InGaAs is used instead of GaAs as the substrate 301, InNAs, InNAsSb or GaInNAsSb is used as the quantum dot 305 instead of GaInNAs, and InGaAs, InGaAsP, InGaAsSb, GaNAs, instead of GaInNAs as the thin film layer 306, It goes without saying that InNAs, InNAsSb or GaInNAsSb is used.

An embodiment relating to claims 1, 2 and 6 of the present invention is shown in FIG.
In the figure, 401 is a substrate (InP), 402 is a cladding layer (InP, film thickness 1.5 μm), 403 is an optical confinement layer (InGaAsP, film thickness 200 nm), and 404 is a barrier layer (InGaA).
sP, film thickness 50 nm), 405 are quantum dots (In (Ga) NAs: Bi), 406 is a thin film layer (GaInNAs: Bi, film thickness 10 nm), and 407 is a contact layer (InGaAs, film thickness 300 nm).
Further, in the quantum dots 405, 405a is a region made of self-formed InNAs: Bi, and 405b is made of InGaNAs: Bi selectively grown on the dots in the region 405a by phase separation during the growth of the thin film layer 406. It is an area.

Here, since the In composition in the selectively grown region (InGaNAs: Bi) 405b is significantly higher than the average In composition of the thin film layer 406, in this embodiment, the composite of the region 405a and the region 405b is used. The body acts as an effective quantum dot 405, and the light emission wavelength is lengthened by increasing the volume of the quantum dot 405.
In addition, since bismuth is added to the quantum dot 405 composed of the region 405a and the region 405b, the quantum dot emission wavelength can be further increased.
That is, by adding bismuth, also in this embodiment, as described in Embodiment 1, three kinds of effects are exhibited.

Here, in this embodiment, the thin film layer 406 is above and below the quantum dot 405, but even if the thin film layer 406 is only above the quantum dot 405, the effect of the present invention can be obtained similarly.
Moreover, as a result of producing the semiconductor quantum dot structure according to this example using various growth conditions and producing a laser diode element, an element having an emission wavelength of 1.3 to 2.6 μm was obtained.
In addition, when creating the same structure, the growth conditions are intentionally determined so that the size of the quantum dots is distributed, and as a result of creating a semiconductor optical amplifier with the obtained structure, an amplification band of 1.3 to 2.6 μm, A broadband, high-saturation output device was obtained.

  It should be noted that InNAs, InNAsSb or GaInNAsSb is used as the quantum dot 405 instead of GaInNAs, and InGaAs, InGaAsP, InGaAsSb, GaNAs, InNAs, InNAsSb or GaInNAsSb is used as the thin film layer 406 instead of GaInNAs. .

Examples relating to Claims 7 and 8 of the present invention will be described below by taking as an example the case of manufacturing the structure of Example 1.
The MOVPE method was used for the growth of the semiconductor quantum dot structure.
First, a substrate (GaAs) 101 is introduced into the apparatus, and a cladding layer (AlGaAs) 102, an optical confinement layer (AlGaAs) 103, and a barrier layer (GaAs) 104 are grown by a normal growth procedure.
Next, after stopping the growth and lowering the substrate temperature to 450 ° C., quantum dots (In (Ga) As)
: Bi) 105 and a thin film layer (InGaAs: Bi) 106 were grown using trimethylindium, triisopropylgallium, trimethylbismuth, and tertiary butylarsine as raw materials.
Trimethylbismuth is supplied when the quantum dots 105 and the thin film layer 106 are grown. However, trimethylbismuth is supplied when at least one of the thin film layers 106 is grown or when both the thin film layer 106 and the quantum dots 105 are grown. You can also.

Here, by using triisopropyl gallium as a gallium material in the growth of the thin film layer 106, sufficient thermal decomposition was obtained even at a low temperature of 450 ° C., and crystallinity during low temperature growth by supplying a bismuth raw material. Crystals with good optical properties were obtained due to the effect of preventing deterioration.
Furthermore, the phase separation is promoted by supplying the bismuth raw material at a temperature of 450 ° C. at which the InGaAs mixed crystal is thermodynamically susceptible to phase separation, and a composite of quantum dots (In (Ga) As: Bi) 105 As a result, a region 105b made of InGaAs: Bi having a high In composition was formed with good reproducibility around the region (InAs: Bi) 105a.

  Next, after the growth is interrupted again and the substrate temperature is raised, a barrier layer (GaAs) 104, an optical confinement layer (AlGaAs) 103, a cladding layer (AlGaAs) 102, and a contact layer (GaAs) 107 are grown. The structure was obtained.

In the above embodiment, the growth temperature of the thin film layer 106 is set to 450 ° C. However, even when the growth temperature is 500 ° C. or less, the same effect as described above can be expected.
That is, in comparison with the case where the growth temperature is 500 ° C. or lower, when the semiconductor quantum dots are embedded at a temperature exceeding 500 ° C., the quantum dots are deformed and the optical characteristics are deteriorated, and the thermodynamically This is because the phase separation is less likely to occur, and control for obtaining a desired emission wavelength is difficult.

In this embodiment, trimethyl bismuth is used as a raw material for bismuth in the growth of a semiconductor layer by the MOVPE method, which has conventionally been difficult to grow at a low temperature, and trimethylgallium and triethylyl having a decomposition temperature higher than that of a raw material such as trimethylindium. By using triisopropyl gallium instead of a gallium raw material such as gallium, it is possible to grow a high-quality semiconductor layer even under low temperature growth conditions.
As a result, in the method of manufacturing a semiconductor quantum dot structure according to the present invention, compared with the method of enlarging the dot volume using the phase separation phenomenon according to the conventional invention, the optical characteristics are superior and the degree of freedom with respect to the emission wavelength is large. It is possible to provide a semiconductor quantum dot structure with high in-plane uniformity with good reproducibility and yield even when the MOVPE method is used.

The reason why the above action can be obtained by supplying bismuth is not clear at present, but the supply of bismuth reduces the surface energy on the surface of the growth layer and increases the diffusion distance of the growth raw material on the crystal surface. Although this effect, that is, the effect obtained as a result is completely opposite to that of the conventional proposal, it is considered to be a kind of surfactant effect.
However, since the manufacturing method of the semiconductor quantum dot structure according to the present invention uses low-temperature growth conditions, the supplied bismuth is not a pure surfactant, and a part of the bismuth is taken into the crystal to narrow the band gap. It is characterized by having an action.

  The raw materials used for the growth of each layer and the growth temperature are shown in the following table.

The material names abbreviated in the table are as follows.
TMA: Trimethylaluminum TMG: Trimethylgallium AsH3: Arsine TMI: Trimethylindium TIPG: Triisopropylgallium TMBi: Trimethylbismuth TBAs: Tertiary butylarsine

  As described above, the present invention relates to a semiconductor quantum dot structure used for an active layer such as a laser diode or a semiconductor optical amplifier. The active layer includes a quantum dot and a thin film semiconductor formed thereon, and at least the thin film semiconductor layer. It is characterized in that bismuth is added to one layer. In particular, since the quantum dot structure has a higher degree of freedom and the quality of the quantum dots is higher than in the past, it is possible to realize a semiconductor light source having a wide selection range of emission wavelengths and better emission efficiency and temperature characteristics.

  The semiconductor quantum dot according to the present invention can be widely used as an active layer of a semiconductor light source for a semiconductor communication optical amplifier or an optical measurement device.

FIG. 1A is a cross-sectional view showing an embodiment relating to claims 1, 2 and 3 of the present invention, and FIG. . 2A is a cross-sectional view showing an embodiment relating to claims 1, 2 and 4 of the present invention, and FIG. 2B is an enlarged view of a range B surrounded by a one-dot chain line in FIG. . 3A is a cross-sectional view showing an embodiment relating to claims 1, 2 and 5 of the present invention, and FIG. 3B is an enlarged view of a range B surrounded by a one-dot chain line in FIG. . 4A is a cross-sectional view showing an embodiment relating to claims 1, 2 and 6 of the present invention, and FIG. 4B is an enlarged view of a range B surrounded by a one-dot chain line in FIG. .

Explanation of symbols

101 GaAs substrate 102 AlGaAs cladding layer 103 AlGaAs optical confinement layer 104 GaAs barrier layer 105 In (Ga) As: Bi quantum dot 106 InGaAs: Bi thin film layer 107 GaAs contact layer 105a Self-formed region of InAs: Bi 105b Thin film layer 106 InGaAs: Bi region 201 InP substrate 202 InP clad layer 203 InGaAsP light confinement layer 204 InGaAsP barrier layer 205 In (Ga) As: Bi quantum dots selectively grown on the dots in the region 105a by phase separation during growth 206 InGaAs: Bi thin film layer 207 InGaAs contact layer 301 GaAs substrate 302 AlGaAs cladding layer 205a Self-formed region of InAs: Bi 205b Thin film layer 2 Region 303 made of InGaAs: Bi selectively grown on the dots in the region 205a by phase separation during the growth of layer 6 AlGaAs optical confinement layer 304 GaAs barrier layer 305 In (Ga) NAs: Bi quantum dot 306 GaInNAs: Bi thin film layer 307 GaAs contact layer 305a Self-formed InAs: Bi region 305b InGaN As: Bi region 401 grown selectively on the dots in region 305a by phase separation during the growth of thin film layer 306 InP substrate 402 InP cladding layer 403 InGaAsP optical confinement layer 404 InGaAsP barrier layer 405 In (Ga) NAs: Bi quantum dot 406 GaInNAs: Bi thin film layer 407 InGaAs contact layer 405a Self-formed region 40 of InNAs: Bi 5b InGaNAs: Bi region selectively grown on the dots in the region 405a by phase separation during the growth of the thin film layer 406

Claims (8)

In a structure in which semiconductor quantum dots are formed on a semiconductor substrate, the semiconductor quantum dots are laminated with at least one semiconductor thin film layer made of a semiconductor material having a composition or a constituent element different from that of a semiconductor material constituting the semiconductor substrate. And bismuth is added to at least one of the semiconductor thin film layers, or to at least one of the semiconductor thin film layers and both of the semiconductor quantum dots. 2. The semiconductor quantum dot structure according to claim 1, wherein the semiconductor substrate, the semiconductor quantum dot, and the semiconductor thin film layer are a III-V compound semiconductor or a III-V compound semiconductor mixed crystal. Dot structure. 3. The semiconductor quantum dot structure according to claim 2, wherein the semiconductor substrate is GaAs or InGaAs, the semiconductor quantum dot is InAs, InAsSb, InGaAs, InGaAsP or InGaAsSb, and the semiconductor thin film layer is InGaAs, InGaAsP. Alternatively, the semiconductor quantum dot structure is InGaAsSb. 3. The semiconductor quantum dot structure according to claim 2, wherein said semiconductor substrate is InP, said semiconductor quantum dot is InAs, InAsSb, InGaAs, InGaAsP or InGaAsSb, and said semiconductor thin film layer is InGaAs, InGaAsP or InGaAsSb. The semiconductor quantum dot structure characterized by being. 3. The semiconductor quantum dot structure according to claim 2, wherein said semiconductor substrate is GaAs or InGaAs, said semiconductor quantum dot is InNAs, GaInNAs, InNAsSb or GaInNAsSb, and said semiconductor thin film layer is InGaAs, InGaAsP, InGaAsSb. , GANAs, InNAs, GaInNAs, InNAsSb or GaInNAsSb. 3. The semiconductor quantum dot structure according to claim 2, wherein said semiconductor substrate is InP, said semiconductor quantum dot is InNAs, GaInNAs, InNAsSb or GaInNAsSb, and said semiconductor thin film layer is InGaAs, InGaAsP, InGaAsSb, GaNAs. , InNAs, GaInNAs, InNAsSb or GaInNAsSb. The method of manufacturing a semiconductor quantum dot structure according to claim 1, 2, 3, 4, 5, or 6, wherein a growth temperature of the semiconductor thin film layer is 500 ° C. or less, and at least one layer of the semiconductor thin film layer is formed. A method for producing a semiconductor quantum dot structure, comprising supplying bismuth during growth or growth of at least one of the semiconductor thin film layers and the semiconductor quantum dot. 8. The method of manufacturing a semiconductor quantum dot structure according to claim 7, wherein trimethyl bismuth is used as the bismuth raw material and triisopropyl gallium is used as the gallium raw material.

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