JP2009016562A - Semiconductor quantum dot element, method of forming semiconductor quantum dot element, and semiconductor laser using semiconductor quantum dot element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a plurality of semiconductor quantum dots having heights equivalent to one another on a compound semiconductor substrate in order to control a band gap of the semiconductor quantum dots in a wide range. <P>SOLUTION: A semiconductor quantum dot element 1 includes the compound semiconductor substrate 2, the plurality of semiconductor quantum dots 3 formed on the compound semiconductor substrate 2, and is characterized in that the plurality of semiconductor quantum dots 3 are formed to gradually reduce the diameters thereof toward a peripheral side from the center of the compound semiconductor substrate 2 and to set the heights thereof nearly constant. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a semiconductor quantum dot device, a method for forming a semiconductor quantum dot device, and a semiconductor laser using the semiconductor quantum dot device.

  In recent years, quantum dots have been developed with a focus on quantum dot lasers. In the quantum dot, electrons are confined in a three-dimensionally narrow potential energy, so that the energy level of the electrons is discretized and the density of states becomes a delta function. It has been reported that when quantum dots are used in the active layer of a semiconductor laser, the chirp is reduced during signal modulation and the dependence on temperature is reduced. Quantum dots are expected to develop in various application fields such as high-efficiency displays and single-photon generators, as well as optical communication fields such as optical amplifiers, photodetectors, and nonlinear optical elements.

  InAs quantum dots have recently been attracting attention in the field of optical communication because they emit light up to 1.5 μm band on a GaAs substrate and can be made longer. As a method for manufacturing a semiconductor quantum dot, a self-forming technique using a Strance-Krastanov (SK) growth mode manufactured using a lattice mismatch material can be cited as a simple method (Patent Document 1). In addition, when applying quantum dots to devices, it is important to control the size, density, and position of the dots from the viewpoints of higher efficiency and larger area. Currently, methods for controlling the size, density, and position of semiconductor quantum dots include a method using a micro phase separation film of a block copolymer (Non-Patent Document 1), a method using electron beam lithography (Non-Patent Document 2), and the like. is there.

  Semiconductor quantum dots using the SK growth mode are manufactured by simultaneously supplying a group III element such as In and Ga and a group V element such as As and N to a compound semiconductor substrate such as GaAs and GaN. Done. At the beginning of growth, since InAs or GaN does not exceed the elastic limit due to lattice mismatch, growth is performed two-dimensionally, and an InAs or GaN wetting layer is grown. When the growth is further continued, InAs or GaN quantum dots grow on the surface of the wetting layer on the order of nanometers when the thickness of InAs or GaN exceeds the elastic limit.

A method for producing semiconductor quantum dots using a block copolymer microphase separation membrane will be briefly described. First, an intermediate layer made of an insulator such as SiO ₂ or SiN is formed on a compound semiconductor substrate such as GaAs or GaN using a CVD (chemical vapor deposition) or spin coating technique to a thickness of several tens of nm. Accumulate. And the block polymer layer which is the solution which melt | dissolved PS (polystyrene) -PMMA (polymethylmethacrylate) on it is formed by spin coating.

  Next, by annealing the block polymer layer, the block polymer layer changes into a block copolymer layer in which a plurality of PMMA fine particles are phase-separated in the PS matrix. When the formed block copolymer layer is etched using oxygen gas, a plurality of PMMA fine particles inside the PS are selectively etched, so that the block copolymer layer has a plurality of hole patterns having the same size as the PMMA fine particles. It becomes the PS porous layer which has. By using the porous layer thus obtained as an etching mask and etching the intermediate layer with fluoride gas, a plurality of hole patterns of several tens of nm are formed in the intermediate layer.

  Through the above steps, a compound semiconductor substrate having an intermediate layer having a plurality of hole patterns of the same size as the PMMA fine particles on the upper surface is manufactured. When semiconductor quantum dots are grown using this compound semiconductor substrate in the same manner as in the SK growth mode described above, the semiconductor quantum dots are selectively grown inside the holes. Thereafter, the remaining intermediate layer is removed, and the periphery of the grown semiconductor quantum dots is filled with a semiconductor such as GaAs, and applied to a semiconductor quantum dot laser or the like.

JP 2006-269886 A Applied Physics Letter, 2000, volume 76, p. 1689 Journal of Crystal Growth, 2004, volume 261, p. 444

  However, when semiconductor quantum dots are grown on a compound semiconductor substrate using the SK growth mode, the semiconductor quantum dots are formed at a high density on the compound semiconductor substrate. Due to temperature distribution, flow rate distribution of the raw material of the semiconductor quantum dots, etc., the sizes of the semiconductor quantum dots, that is, their diameters and heights are formed to be considerably nonuniform. Normally, it is difficult to uniformly grow both the diameter and height of a semiconductor quantum dot, and more difficult techniques are required to grow a semiconductor quantum dot having a uniform diameter and height on the entire compound semiconductor substrate. .

  Even in a method using a block copolymer microphase separation film or a method using electron beam lithography, the size of the semiconductor quantum dots that can be controlled is only the diameter, and the height cannot be controlled by this method. For this reason, a new technique is required to make the height of the semiconductor quantum dots uniform.

  In particular, when semiconductor quantum dots are applied to light emitting elements and optical switches, it is important to control the band gap. The semiconductor quantum dots formed by the conventional forming method have a diameter 3 to 5 times larger than the height, and may be 10 times or more depending on the material of the semiconductor quantum dots. For this reason, the band gap of the semiconductor quantum dot is controlled by the height rather than the diameter, and the diameter does not have a great influence on the band gap. Therefore, when semiconductor quantum dots are used for an element, it is an important technique to align the heights of semiconductor quantum dots in a wide range of regions.

  The present invention has been made in view of the above, and a semiconductor quantum dot device capable of controlling the band gap over a wide range by making the height of a plurality of semiconductor quantum dots formed on a compound semiconductor substrate uniform. It is an object to provide a method for forming a semiconductor quantum dot device and a semiconductor laser using the semiconductor quantum dot device.

  In order to solve the above-described problems and achieve the object, the present invention includes a compound semiconductor substrate and a plurality of semiconductor quantum dots formed on the compound semiconductor substrate, and the plurality of semiconductor quantum dots includes: The diameter is gradually reduced from the center of the compound semiconductor substrate toward the peripheral side, and the height is substantially constant.

  The present invention also provides an intermediate layer forming step of forming an intermediate layer on the compound semiconductor substrate, and a plurality of fine layers on the intermediate layer that gradually decrease in diameter from the center of the compound semiconductor substrate toward the peripheral side. A mask layer manufacturing step of manufacturing a mask layer having a hole pattern, and using the mask layer as a mask, the intermediate layer is etched by dry etching to expose a portion of the compound semiconductor substrate corresponding to the plurality of fine hole patterns And a self-forming step of selectively self-forming a plurality of semiconductor quantum dots on a portion of the compound semiconductor substrate exposed by the etching step.

  According to the present invention, since the height of the plurality of semiconductor quantum dots formed on the compound semiconductor substrate can be controlled uniformly, the band gap of the semiconductor quantum dot device can be controlled over a wide range.

  Exemplary embodiments of a semiconductor quantum dot device, a method for forming a semiconductor quantum dot device, and a semiconductor laser using the semiconductor quantum dot device will be described below in detail with reference to the accompanying drawings. In the drawings shown below, for convenience of explanation, the scales of the members of the drawings may be described differently.

(First embodiment)
A first embodiment will be described with reference to the accompanying drawings. FIG. 1 is a top view of the semiconductor quantum dot device according to the first embodiment, and FIG. 2 is a cross-sectional view taken along line AA in FIG. The semiconductor quantum dot device 1 has a structure in which a plurality of semiconductor quantum dots 3 are formed at regular intervals on a compound semiconductor substrate 2. The diameter D 1 of the semiconductor quantum dot 3 formed at the center of the compound semiconductor substrate 2 is the largest among the semiconductor quantum dots 3. The diameter of the semiconductor quantum dot 3 gradually decreases from the center of the compound semiconductor substrate 2 toward the peripheral side, and the diameter D2 of the semiconductor quantum dot 3 formed on the peripheral edge of the compound semiconductor substrate 2 is the semiconductor quantum dot. The smallest among the three. Further, the height H of the semiconductor quantum dots 3 is substantially constant regardless of the position of the compound semiconductor substrate 2.

  The reason why the semiconductor quantum dot device is formed as described above will be described in comparison with a conventional semiconductor quantum dot device. FIG. 3 is a top view of a conventional semiconductor quantum dot device manufactured using a microphase separation film of a conventional block copolymer, and FIG. 4 is a cross-sectional view taken along line AA in FIG. In the conventional semiconductor quantum dot device 4, the diameter d of the conventional semiconductor quantum dot 5 formed on the compound semiconductor substrate 2 is constant regardless of the position of the compound semiconductor substrate 2. On the other hand, the height h1 of the conventional semiconductor quantum dot 5 formed at the center of the compound semiconductor substrate 2 is the highest among the conventional semiconductor quantum dots 5. Then, the height of the conventional semiconductor quantum dots 5 gradually decreases from the center of the compound semiconductor substrate 2 toward the peripheral side, and the height h2 of the conventional semiconductor quantum dots 5 formed on the peripheral portion thereof is It is the lowest among the semiconductor quantum dots 5.

  As described above, the semiconductor quantum dots formed by the conventional forming method have a diameter 3 to 5 times larger than the height, and may be 10 times or more depending on the material of the semiconductor quantum dots. This relationship does not change even in the semiconductor quantum dots according to the present embodiment. Accordingly, the semiconductor quantum dots in FIGS. 1 to 4 are drawn with a height larger than the diameter, but actually, the diameter is 3 to 5 times larger than the height. Depending on the material of the dot, it may be 10 times or more. For this reason, the diameter of a semiconductor quantum dot does not have big influence on a band gap, and a band gap is controlled by height rather than a diameter.

  Accordingly, the semiconductor quantum dot device according to the present embodiment is formed so that the height of the semiconductor quantum dot is almost constant over the entire surface of the compound semiconductor substrate, and therefore, compared with the semiconductor quantum dot device formed by the conventional formation method. The band gap of the semiconductor quantum dots can be controlled over a wide range. As a result, when the semiconductor quantum dot device according to this embodiment is used for a semiconductor laser, a highly efficient semiconductor laser can be manufactured.

(Method of forming semiconductor quantum dot device)
Next, a method for forming a semiconductor quantum dot device according to the present embodiment will be described. 5-1 to 5-9 are cross-sectional process diagrams of the semiconductor quantum dot device according to the first embodiment, and correspond to a cross-sectional view taken along the line AA of FIG.

  First, the compound semiconductor substrate 2 is prepared as shown in FIG. For the compound semiconductor substrate 2, a semiconductor containing a group III-V element is used. Specifically, GaAs or AlN is preferable, but any of InGaAs, InP, AlGaAs, GaN, AlGaN, or InGaN is used. can do.

Then, as shown in FIG. 5B, the intermediate layer 6 is formed on the compound semiconductor substrate 2. The intermediate layer 6, AlGaAs, SiN, or semiconductor such as AlGaN or, using a metal oxide such as SiO _2, using the CVD of (chemical vapor deposition), spin coating techniques, a thickness of several tens nm Accumulate.

  Next, as illustrated in FIG. 5C, the block polymer layer 7 is formed on the intermediate layer 6. The block polymer layer 7 is formed by using a solution in which PS-PMMA is dissolved and using a spin coating technique. The ratio PS / PMMA of the molecular weight of PS to PMMA in the block polymer layer 7 is about 4 to 5.2.

  Next, the multilayer film composed of the compound semiconductor substrate 2, the intermediate layer 6, and the block polymer layer 7 is annealed (heat treatment). In this case, the annealing treatment time is set to 8 hours, the annealing treatment temperature is set to 100 degrees for the central portion of the compound semiconductor substrate 2 and 70 degrees for the peripheral portion, and the processing temperature is set from the center to the peripheral side. Set to gradually go down as you head. By this annealing, the block polymer layer 7 changes to a block copolymer layer 10 in which a plurality of PMMA fine particles 9 are phase-separated in a PS matrix 8 as shown in FIG. 5-4.

  Here, the diameter of the PMMA fine particles 9 formed at the center of the block copolymer layer 10 (compound semiconductor substrate 2) is the largest among the PMMA fine particles 9. The diameter of the PMMA fine particles 9 gradually decreases from the center of the block copolymer layer 10 (compound semiconductor substrate 2) toward the peripheral side, and the diameter of the PMMA fine particles 9 formed on the peripheral portion is equal to that of the PMMA fine particles 9. It is the smallest among them.

  This is because the PMMA fine particles 9 are deposited in the block copolymer layer 10 by varying the size of the PMMA fine particles 9 by annealing with a temperature difference between the central portion and the peripheral portion of the compound semiconductor substrate 2. In the portion where the temperature is high, the size of the PMMA fine particles 9 deposited in the block copolymer layer 10 is large, and in the portion where the temperature is low, the size of the PMMA fine particles 9 precipitated in the block copolymer layer 10 is small. Thus, by changing the temperature of the heat applied to the block polymer layer 7, the size of the PMMA fine particles 9 to be phase-separated can be changed.

  Next, a part of the block copolymer layer 10 is removed by etching. Although oxygen gas is used for this etching, the etching rate of PS is lower than that of PMMA, so that PMMA fine particles 9 are selectively etched. As a result, the block copolymer layer 10 becomes a PS porous layer 12 formed only of PS having a hole pattern 11 of the same size (several tens of nm) as the PMMA fine particles 9 at the places where the PMMA fine particles 9 existed. . 5-5 is a cross-sectional view after a part of the block copolymer layer 10 is removed by etching to become the PS porous layer 12.

  Next, the intermediate layer 6 is etched using the PS porous layer 12 as an etching mask. Fluoride gas is used for this etching, and as a result of the etching, a plurality of hole patterns 13 of several tens of nm are formed in the intermediate layer 6. Then, as shown in FIG. 5-6, a part of the upper surface of the compound semiconductor substrate 2 is exposed by the hole pattern 13.

  Next, as shown in FIGS. 5-7, semiconductor quantum dots 3 are formed on the exposed portion of the compound semiconductor substrate 2. The semiconductor quantum dots 3 are selectively grown by using a technique of MBE (molecular beam epitaxy) or MOCVD (metal organic chemical vapor deposition). The semiconductor quantum dot 3 uses a semiconductor containing a group III-V element. For example, InAs, InGaAs, or GaN is used, but any of InP, InN, AlGaAs, AlGaN, or InGaN can be used. it can.

  The semiconductor quantum dots 3 formed in this step have the same diameter as the size of the hole pattern 13 and gradually become smaller from the center of the compound semiconductor substrate 2 toward the peripheral side. Further, the height is almost constant regardless of the position of the compound semiconductor substrate 2. The reason for this will be explained.

  Usually, at the time of forming the semiconductor quantum dots 3, the central portion of the compound semiconductor substrate 2 is more than the peripheral portion thereof because of the temperature distribution of the compound semiconductor substrate 2, the flow rate distribution of the raw material of the semiconductor quantum dots 3, and the like. A large amount of raw material for the dots 3 is deposited. Therefore, as in the conventional example, if all the hole patterns 13 formed on the compound semiconductor substrate 2 have the same size, the height of the conventional semiconductor quantum dots 5 formed at the center of the compound semiconductor substrate 2 is increased. The height of the conventional semiconductor quantum dots 5 formed at the peripheral edge is lowered.

  In contrast, in the present embodiment, the size of the hole pattern 13 in the central portion where the deposition amount of the semiconductor quantum dots 3 is large is increased, and the size of the hole pattern 13 in the peripheral portion where the deposition amount of the material is small is decreased. This makes it possible to make the height of the semiconductor quantum dots 3 substantially constant over the entire compound semiconductor substrate 2.

  For example, when a conventional semiconductor quantum dot 5 made of GaN is grown by a conventional formation method, the diameter distribution of the conventional semiconductor quantum dot 5 is about 19.9 nm from the central part to the peripheral part of the compound semiconductor substrate 2. The height distribution is about 1.1 nm to 0.7 nm. On the other hand, when the semiconductor quantum dots 3 made of GaN are grown under the same conditions by the formation method according to the present embodiment, the diameter distribution of the semiconductor quantum dots 3 extends from the central part to the peripheral part of the compound semiconductor substrate 2. About 19.9 nm to 10 nm, and its height distribution is almost constant at about 1.1 nm. At this time, the diameter of the PMMA fine particles 9 is about 19.9 nm at the central portion of the compound semiconductor substrate 2 and about 10 nm at the peripheral portion, which is the same as the diameter of the grown semiconductor quantum dots 3.

  Further, when the conventional semiconductor quantum dots 5 made of InAs are grown by the conventional formation method, the diameter distribution of the conventional semiconductor quantum dots 5 from the center to the peripheral edge of the compound semiconductor substrate 2 is about 40 nm to 31 nm. The height distribution is about 10 nm to 7 nm. On the other hand, when the semiconductor quantum dots 3 made of InAs are grown under the same conditions by the formation method according to the present embodiment, the diameter distribution of the semiconductor quantum dots 3 extends from the central part to the peripheral part of the compound semiconductor substrate 2. , About 40 nm to 20 nm, and the height distribution is almost constant at about 10 nm. At this time, the diameter of the PMMA fine particles 9 is about 40 nm at the center of the compound semiconductor substrate 2 and about 20 nm at the peripheral portion, which is the same as the diameter of the grown semiconductor quantum dots 3.

  After the semiconductor quantum dots 3 are formed, the semiconductor quantum dot device 1 is completed by removing all of the intermediate layer 6 by dry etching or wet etching, as shown in FIGS. 5-8 corresponds to the states of FIGS. 1 and 2.

  Thereafter, as shown in FIG. 5-9, when the periphery of the semiconductor quantum dot 3 is embedded with a semiconductor 14 of a different type from the semiconductor quantum dot 3, the layer composed of the semiconductor quantum dot 3 and the semiconductor 14 becomes a semiconductor quantum dot. It becomes the active layer 15 and can be applied to a semiconductor quantum dot laser or the like. For example, GaAs or AlN is used as the semiconductor 14, but any of InGaAs, InP, AlGaAs, GaN, AlGaN, or InGaN can be used.

  In the present embodiment, the processing temperature in the step of annealing the multilayer film composed of the compound semiconductor substrate 2, the intermediate layer 6 and the block polymer layer 7 to change the block polymer layer 7 to the block copolymer layer 10 is as follows. 2 is set so that the temperature from the central part to the peripheral part gradually changes from 100 degrees to 70 degrees. If this treatment temperature is low, the PMMA fine particles 9 do not phase-separate. Conversely, if the treatment temperature is high, the shape of the PMMA fine particles 9 is lost, so that the temperature at the center is 1.1 to It is desirable to change within a range of 1.5 times.

  Thus, according to the semiconductor quantum dot device according to the first embodiment, a plurality of semiconductor quantum dots formed on the compound semiconductor substrate by controlling the size of the hole pattern of the intermediate layer for forming the semiconductor quantum dots. Since the height of the semiconductor quantum dots can be controlled uniformly, the band gap of the semiconductor quantum dots can be controlled over a wide range.

(Second Embodiment)
Next, a second embodiment will be described with reference to the accompanying drawings. In the present embodiment, the semiconductor quantum dot device according to the first embodiment is applied to a semiconductor laser. FIG. 6 is a cross-sectional view of a semiconductor laser using the semiconductor quantum dot device according to the first embodiment.

The semiconductor laser 20 includes an AuGe / Ni / Au electrode 30, an n-type GaAs substrate 40, an n-type GaAs growth layer 50, an n-type Al _0.3 Ga _0.7 As growth layer 60, a GaAs growth layer 70, and an InAs quantum dot device. The active layer 80, the GaAs growth layer 90, the p-type Al _0.3 Ga _0.7 As growth layer 100, the p-type GaAs growth layer 110, SiO ₂ 120, polyimide 130, and the Ti / Pt / Au electrode 140.

  Here, the GaAs growth layer 70 corresponds to the compound semiconductor substrate 2 in the first embodiment, and the InAs quantum dot element active layer 80 corresponds to the semiconductor quantum dot active layer 15 in the first embodiment. The InAs quantum dot device active layer 80 has the same structure as the semiconductor quantum dot 81 formed of InAs having the same structure as the semiconductor quantum dot 3 in the first embodiment and the semiconductor 14 in the first embodiment. And a semiconductor 82 made of GaAs or AlN. Therefore, the portion constituted by the GaAs growth layer 70 and the InAs quantum dot device active layer 80 corresponds to the portion constituted by the semiconductor quantum dot device 1 and the semiconductor 14 in the first embodiment. It is manufactured by the same method as the embodiment mode.

The semiconductor laser 20 is manufactured as follows. First, an n-type GaAs growth layer 50 having a thickness of 500 nm, an n-type Al _0.3 Ga _0.7 As growth layer 60 having a thickness of 1500 nm, and a 150 nm thickness is formed on the cleaned n-type GaAs substrate 40. The GaAs growth layer 70 is sequentially stacked by the MOCVD method. Here, the doping concentrations of the n-type GaAs growth layer 50 and the n-type Al _0.3 Ga _0.7 As growth layer 60 are 2 × 10 ¹⁸ cm ⁻³ and 1 × 10 ¹⁹ cm ⁻³ , respectively. .

  Next, the InAs quantum dot device active layer 80 is stacked on the GaAs growth layer 70 by the same method as the semiconductor quantum dot device active layer 15 in the first embodiment.

Furthermore, on the InAs quantum dot device active layer 80, a GaAs growth layer 90 having a thickness of 150 nm, a p-type Al _0.3 Ga _0.7 As growth layer 100 having a thickness of 2000 nm, and a p-type GaAs growth having a thickness of 100 nm. The layers 110 are sequentially stacked by the MOCVD method. Here, the doping concentrations of the p-type Al _0.3 Ga _0.7 As growth layer 100 and the p-type GaAs growth layer 110 are both 5 × 10 ¹⁸ cm ⁻³ .

After the above steps, the p-type Al _0.3 Ga _0.7 As growth layer 100 and the p-type GaAs growth layer 110 are scraped to create a ridge with a width of 3 to 40 μm. Further, the steps of applying SiO ₂ 120 and polyimide 130 and patterning the stripes are performed. Thereafter, Ti / Pt / Au electrode 140 is deposited and heated to be alloyed. The surface opposite to the Ti / Pt / Au electrode 140 is polished and then alloyed by vapor deposition and heating of the AuGe / Ni / Au electrode 30. Finally, the completed device is cracked in the direction perpendicular to the stripe direction to create a resonator, and the semiconductor laser 20 is manufactured.

  The semiconductor laser according to the present embodiment has a device structure in which the semiconductor quantum dots are embedded with a semiconductor layer such as GaAs or AlN, thereby forming a highly efficient inversion distribution with highly uniform quantum dots in the surface, and uniform Light emission and laser oscillation at a low threshold are possible.

  As described above, according to the semiconductor laser according to the second embodiment, the band gap of the semiconductor quantum dots of the semiconductor quantum dot active layer can be controlled over a wide range, so that the light emission efficiency can be increased. .

  In the second embodiment, the semiconductor quantum dot device according to the first embodiment is applied to the semiconductor laser. Similarly, the efficiency can be increased by controlling the band gap of the semiconductor quantum dot. You may apply to an optical switch, an optical amplifier, or a photodetector.

  The present invention is effective for any semiconductor quantum dot device that is required to control the band gap of the semiconductor quantum dots of the semiconductor quantum dot device over a wide range.

It is a top view of the semiconductor quantum dot device concerning a 1st embodiment. It is AA arrow sectional drawing of FIG. It is a top view of the conventional semiconductor quantum dot element produced using the micro phase separation film of the conventional block copolymer. It is AA arrow sectional drawing of FIG. It is sectional drawing of the semiconductor quantum dot element concerning 1st Embodiment. It is sectional drawing of the semiconductor quantum dot element concerning 1st Embodiment. It is sectional drawing of the semiconductor quantum dot element concerning 1st Embodiment. It is sectional drawing of the semiconductor quantum dot element concerning 1st Embodiment. It is sectional drawing of the semiconductor quantum dot element concerning 1st Embodiment. It is sectional drawing of the semiconductor quantum dot element concerning 1st Embodiment. It is sectional drawing of the semiconductor quantum dot element concerning 1st Embodiment. It is sectional drawing of the semiconductor quantum dot element concerning 1st Embodiment. It is sectional drawing of the semiconductor quantum dot element concerning 1st Embodiment. It is sectional drawing of the semiconductor laser using the semiconductor quantum dot element concerning 1st Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Semiconductor quantum dot element 2 Compound semiconductor substrate 3, 81 Semiconductor quantum dot 4 Conventional semiconductor quantum dot element 5 Conventional semiconductor quantum dot 6 Intermediate layer 7 Block polymer layer 8 PS matrix 9 PMMA microparticle 10 Block copolymer layer 11, 13 Hole pattern 12 PS porous layers 14, 82 Semiconductor 15 Semiconductor quantum dot active layer 20 Semiconductor laser 30 AuGe / Ni / Au electrode 40 n-type GaAs substrate 50 n-type GaAs growth layer 60 n-type Al _0.3 Ga _0.7 As growth layer 70, 90 GaAs growth layer 80 InAs quantum dot device active layer 100 p-type Al _0.3 Ga _0.7 As growth layer 110 p-type GaAs growth layer 120 SiO ₂
130 Polyimide 140 Ti / Pt / Au electrode

Claims (14)

A compound semiconductor substrate;
A plurality of semiconductor quantum dots formed on the compound semiconductor substrate,
The plurality of semiconductor quantum dots are formed such that the diameter gradually decreases from the center of the compound semiconductor substrate toward the peripheral side, and the height is substantially constant.
A semiconductor quantum dot device. The plurality of semiconductor quantum dots are formed on the compound semiconductor substrate at substantially constant intervals;
The semiconductor quantum dot device according to claim 1. Further, a semiconductor of a different type from the plurality of semiconductor quantum dots is embedded around the plurality of semiconductor quantum dots,
The semiconductor quantum dot device according to claim 1 or 2. The compound semiconductor substrate is one of GaAs, InGaAs, InP, AlGaAs, GaN, AlN, AlGaN, or InGaN;
The semiconductor quantum dot device according to any one of claims 1 to 3. The semiconductor quantum dot is any one of InAs, InGaAs, InP, InN, AlGaAs, GaN, AlGaN, or InGaN.
The semiconductor quantum dot device according to any one of claims 1 to 4, wherein: An intermediate layer forming step of forming an intermediate layer on the compound semiconductor substrate;
On the intermediate layer, a mask layer manufacturing step of manufacturing a mask layer having a plurality of fine hole patterns whose diameter gradually decreases from the center of the compound semiconductor substrate toward the peripheral side;
Etching the intermediate layer by dry etching using the mask layer as a mask to expose a portion of the compound semiconductor substrate corresponding to the plurality of fine hole patterns;
A self-forming step of selectively self-forming a plurality of semiconductor quantum dots on the compound semiconductor substrate in a portion exposed by the etching step,
A method for forming a semiconductor quantum dot device. The mask manufacturing process includes
On the intermediate layer, an application step of applying a mask layer made of a block polymer synthesized using polystyrene and polymethyl methacrylate;
A phase separation step in which the mask layer is heated, and the polystyrene is layered and the polymethyl methacrylate is finely divided;
Using the temperature distribution during heating in the phase separation step, a diameter changing step for changing the diameter of the polymethyl methacrylate to be phase-separated at a constant rate;
Etching the mask layer by dry etching to form the plurality of fine hole patterns, and a hole pattern forming step,
A method for forming a semiconductor quantum dot device according to claim 6. The temperature at which the mask layer is heated in the phase separation step is centered from the peripheral side of the compound semiconductor substrate so that the central portion is 1.1 to 1.5 times the peripheral portion of the compound semiconductor substrate. Gradually changing
A method for forming a semiconductor quantum dot device according to claim 7. The diameter of the polymethyl methacrylate fine particles to be phase-separated in the phase separation step is 1.1 to 1.5 times the central portion of the peripheral portion of the compound semiconductor substrate, and from the peripheral side of the compound semiconductor substrate. Gradually changing towards the center,
The method of forming a semiconductor quantum dot device according to claim 8. The fine hole patterns of the mask layer produced in the mask layer production step are provided on the intermediate layer at substantially constant intervals;
The method for forming a semiconductor quantum dot device according to any one of claims 6 to 9. Further comprising an intermediate layer removing step of removing the intermediate layer on the compound semiconductor substrate after the self-forming step;
The method of forming a semiconductor quantum dot device according to any one of claims 6 to 10. A semiconductor embedding step of embedding a semiconductor of a type different from the plurality of semiconductor quantum dots around the plurality of semiconductor quantum dots after the intermediate layer removing step;
The method of forming a semiconductor quantum dot device according to claim 11. The intermediate layer is formed of a semiconductor such as AlGaAs, SiN, or AlGaN, or a metal oxide such as SiO ₂ ;
The method of forming a semiconductor quantum dot device according to any one of claims 6 to 12.   A semiconductor laser using the semiconductor quantum dot device according to claim 1.

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