JP6054834B2 - Fabrication method of nanowire - Google Patents

Description

  The present invention relates to a method for producing a nanowire in which a metal nanoparticle is produced by metalorganic vapor phase epitaxy using an organic metal as a raw material.

  Application of nanowires made of group III-V semiconductors having a diameter of nanometer scale to optical devices, transistors, and the like has been studied. This nanowire can be produced in a bottom-up manner by crystal growth by metalorganic vapor phase epitaxy using fine particles of a catalytic metal. This nanowire production method is a technique that can efficiently produce nanowires by reducing the amount of raw materials used. However, stacking defects are likely to occur, and growth is performed at a low temperature.

  In contrast, when HCl gas is introduced as an etching gas during growth, nanowires can be grown at a higher temperature than when etching gas is not introduced, and contamination of impurities such as carbon is reduced. Has also been reported to be difficult to enter (see Non-Patent Document 1). It has been reported that the introduction of HCl gas suppresses the growth of the nanowire in the radial direction and improves the light emission characteristics of the light emitting element using the InP nanowire (see Non-Patent Document 1 and Non-Patent Document 2).

Thuy T T Vu1 et al., "High optical quality single crystal phase wurtzite and zincblende InP nanowires", Nanotechnology, vol, 24, 115705 (6pp), 2013. Magnus T. Borgstrom1 et al., "In Situ Etching for Total Control Over Axial and Radial Nanowire Growth", Nano Res, vol.3, pp.264-270, 2010. Koichi Naniwae et al., "Alloy composition control of InGaAs / InP grown by Cl-assisted MOVPE with tertiarybutylchloride", Journal of Crystal Growth, vol.248, pp.400-404, 2003.

However, the above-described technique can form high-quality nanowires, but HCl and PH ₃ are used, and since these gases are stored at a high pressure, they are not easy to handle and are not easy to manufacture. There was a problem.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to make it possible to more easily form high-quality nanowires.

The nanowire manufacturing method according to the present invention includes a fine particle arranging step of arranging fine particles of a catalytic metal on a substrate, a source gas composed of an organic metal on the substrate on which the fine particles are arranged, and using the fine particles as a catalyst. And a nanowire growth process for growing nanowires crystallized from the source gas. In the nanowire growth process, (CH ₃ ) ₃ CCl gas is supplied in addition to the source gas.

  In the nanowire production method, the nanowire growth step includes supplying a source gas having a composition different from that of the first nanowire growth step of supplying a predetermined source gas and growing the first nanowire using fine particles as a catalyst. And a second nanowire growth step of growing the second nanowire continuously with the first nanowire using the fine particles as a catalyst.

In the nanowire manufacturing method, (CH ₃ ) ₃ CCl gas is supplied in the first nanowire growth step and the second nanowire growth step.

In the above method for manufacturing a nanowire, a first nanowire growth process without supplying the (CH _{3) 3} CCl gas, in the second nanowire growth step of supplying a (CH _{3) 3} CCl gas.

  In the nanowire manufacturing method, the nanowire growth step includes a first conductivity type nanowire growth step of supplying a first impurity source material that becomes a first conductivity type impurity together with a source gas, and growing the first conductivity type nanowire using fine particles as a catalyst. And an i-type nanowire growth step for growing an i-type nanowire in which impurities are not continuously introduced into the first conductivity type nanowire using fine particles as a catalyst, and a second conductivity type impurity together with the source gas. And a second conductivity type nanowire growth step of growing the second conductivity type nanowire continuously with the i-type nanowire using fine particles as a catalyst.

  As described above, according to the present invention, it is possible to obtain an excellent effect that high-quality nanowires can be formed more easily.

FIG. 1 is a flowchart for explaining a nanowire manufacturing method according to Embodiment 1 of the present invention. FIG. 2 is a photograph showing a state where the produced nanowire is observed with a scanning electron microscope. FIG. 3 is a configuration diagram showing a configuration of a nanowire manufactured by the nanowire manufacturing method according to Embodiment 2 of the present invention. FIG. 4 is a configuration diagram showing a configuration of a nanowire manufactured by the nanowire manufacturing method according to Embodiment 3 of the present invention. FIG. 5 is a configuration diagram showing a configuration of a nanowire manufactured by the nanowire manufacturing method according to Embodiment 4 of the present invention. FIG. 6 is a perspective view showing a configuration of a light-emitting element using nanowires manufactured by the nanowire manufacturing method according to Embodiment 4 of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[Embodiment 1]
First, Embodiment 1 of the present invention will be described with reference to FIG. FIG. 1 is a flowchart for explaining a nanowire manufacturing method according to Embodiment 1 of the present invention. In this nanowire manufacturing method, first, in step S101, catalyst metal fine particles are arranged on a substrate (fine particle arrangement step). For example, fine particles having a diameter of about 10 nm made of Au may be disposed on an InP substrate whose main surface has a (111) B plane orientation.

Next, in step S102, a raw material gas composed of an organic metal is supplied onto the substrate on which fine particles are arranged as described above, and nanowires crystallized from the raw material gas are grown using the fine particles as a catalyst (nanowire growth step). ). For example, by supplying trimethylindium and tertiary butylphosphine as source gases under a predetermined growth temperature condition, an InP nanowire that is a group III-V compound semiconductor composed of In and P can be formed. At this time, in the present invention, a gas of (CH ₃ ) ₃ CCl is supplied in addition to the raw material gas. Hereinafter, (CH ₃ ) ₃ CCl is referred to as TBCl (tertiary butyl chloride).

Thus, by supplying TBCl to the growth atmosphere in addition to the source gas, the growth in the radial direction perpendicular to the extending direction of the nanowire (axial direction) is controlled (suppressed), and nanowires having a uniform diameter in the axial direction are formed. It becomes possible to form. The above-described nanowire growth is performed by VLS (va) using a metal fine particle catalyst by an organic metal vapor deposition method (MOCVD method) using an organic compound having a saturated vapor pressure at a low pressure (normal pressure or lower) as a material. p- or-liquid-solid) growth. According to this manufacturing method, a gas that is stored at a high pressure using a cylinder or the like and is not easy to handle, such as HCl and PH ₃ , is not used. Therefore, according to Embodiment 1, high quality nanowires can be easily formed in a safer environment.

  By the way, in the compound semiconductor thin film formation technique by the metal organic chemical vapor deposition method, it is reported that the growth rate and composition of the growing thin film are changed by this etching effect by using TBCl which is an organic chlorine compound. (See Non-Patent Document 3). In this report, crystals comparable to those not using TBCl are obtained. However, this technique is not the growth of nanowires using catalytic metal particles. In the nanowire growth technology, there has been no example of a growth method in which the same etching gas as that in the thin film formation technology is supplied during growth, and it has been unclear whether the same effect can be achieved in the nanowire.

  Hereinafter, the actually produced nanowire will be described with reference to FIG. FIG. 2 is a photograph showing a state where the produced nanowire is observed with a scanning electron microscope.

First, (a) and (a ′) in FIG. 2 show nanowires made of InP. In the manufacture of InP nanowires, first, an InP substrate having a main surface with a (111) B orientation was used. A plurality of Au fine particles having a diameter of 10 nm were arranged on the In substrate. In this state, the growth temperature was set to 375 ° C., and growth was performed by supplying TMsc (trimethylindium) 7 sccm and TBP (tertiary butylphosphine) 36 sccm into the growth chamber for 30 minutes. Here, (a ′) in FIG. 2 shows a case where growth is performed by supplying a TBCl gas at a flow rate of 0.8 sccm in addition to the source gas. Note that sccm is a unit of flow rate, and indicates that a fluid at 0 ° C. and 1013 hPa flows 1 cm ³ per minute.

  Next, FIGS. 2B and 2B show nanowires made of InAsP. In the manufacture of InAsP nanowires, first, a plurality of Au fine particles having a diameter of 10 nm were arranged on an In substrate as described above. In this state, the growth temperature was set to 330 ° C., and growth was performed by supplying TMIn 7 sccm, TBP 36 sccm, and TBAs (tertiary butylarsine) 4 sccm for 20 minutes. Here, (b ′) in FIG. 2 shows a case where growth is performed by supplying a TBCl gas at a flow rate of 6.4 sccm in addition to the source gas.

  Next, FIGS. 2C and 2C show nanowires made of GaInAs. In the manufacture of GaInAs nanowires, first, a plurality of Au fine particles having a diameter of 10 nm were arranged on an In substrate as described above. In this state, the growth temperature was set to 330 ° C., and TMIn 11 sccm, TEGa (triethyl gallium) 15 sccm, and TBAs 1 sccm were supplied for 40 minutes. Here, (C ′) in FIG. 2 shows a case where growth is performed by supplying a TBCl gas at a flow rate of 9.6 sccm in addition to the source gas.

  Since the growth temperature is relatively high, as shown in FIGS. 2A, 2B, and 2C, the substrate side becomes thicker due to the growth in the radial direction perpendicular to the axial direction under the condition where TBCl is not supplied. It has a tapered structure in which the tip side away from the substrate is narrowed. On the other hand, under the condition where TBCl is supplied, since the diffusion of the reactive species on the growth surface is promoted by the effect of etching of Cl supplied from TBCl, the growth in the radial direction becomes extremely slow. Further, since the reactive species diffusing in the side wall are taken up by the Au fine particle catalyst at the tip, the growth in the axial direction is promoted. As a result, a nanowire structure with better straightness can be formed with little change in composition and little change in diameter.

[Embodiment 2]
Next, a second embodiment of the present invention will be described. In the nanowire forming method according to the second embodiment, first, catalyst metal fine particles are arranged on a substrate in a first step (fine particle arrangement step). For example, a plurality of fine particles of about 10 nm in diameter made of Au are arranged on an InP substrate whose main surface has a (111) B plane orientation. For example, a dispersion liquid (colloid solution) in which Au fine particles are dispersed may be applied, and then the dispersion medium may be removed.

  Next, in the second step, as described above, a raw material gas composed of an organic metal is supplied onto a substrate on which fine particles are arranged, and nanowires crystallized from the raw material gas using the fine particles as a catalyst are grown (nanowire growth). Process).

Here, in the second embodiment, in the step of growing nanowires, first, a predetermined raw material gas is supplied to grow first nanowires using fine particles as a catalyst (first nanowire growth step). For example, TMIn 1 × 10 ⁻⁶ mol / min and TBP 1.2 × 10 ⁻³ mol / min are supplied into the growth chamber of the MOCVD apparatus, and at the same time, TBCl 3 × 10 ⁻⁶ mol / min is supplied into the growth chamber. Then, an InP nanowire is grown as the first nanowire for 15 minutes.

Next, a raw material gas having a composition different from that of the growth of the first nanowire is supplied, and the second nanowire is grown continuously from the first nanowire using the fine particles as a catalyst (second nanowire growth step). For example, TMIn 1 × 10 ⁻⁶ mol / min and TBAs 1.2 × 10 ⁻³ mol / min are supplied into the growth chamber of the MOCVD apparatus, and at the same time, TBCl 1 × 10 ⁻⁵ mol / min is supplied into the growth chamber. Then, an InAs nanowire is grown for 1 minute as the second nanowire.

Subsequently, TMIn 1 × 10 ⁻⁶ mol / min and TBP 1.2 × 10 ⁻³ mol / min are again supplied into the growth chamber of the MOCVD apparatus, and at the same time, TBCl 3 × 10 ⁻⁶ mol / min is supplied into the growth chamber. The InP nanowire is grown for 1 minute as the first nanowire. Subsequently, TMIn 1 × 10 ⁻⁶ mol / min and TBAs 1.2 × 10 ⁻³ mol / min are supplied into the growth chamber of the MOCVD apparatus, and at the same time, TBCl 1 × 10 ⁻⁵ mol / min is supplied into the growth chamber. Then, an InAs nanowire is grown as a second nanowire for 1 minute.

Subsequently, TMIn 1 × 10 ⁻⁶ mol / min and TBP 1.2 × 10 ⁻³ mol / min are supplied into the growth chamber of the MOCVD apparatus, and at the same time, TBCl 3 × 10 ⁻⁶ mol / min is supplied into the growth chamber. Then, an InP nanowire is grown for 1 minute as the first nanowire. Subsequently, TMIn 1 × 10 ⁻⁶ mol / min and TBAs 1.2 × 10 ⁻³ mol / min are supplied into the growth chamber of the MOCVD apparatus, and at the same time, TBCl 1 × 10 ⁻⁵ mol / min is supplied into the growth chamber. Then, an InAs nanowire is grown as a second nanowire for 1 minute.

Thereafter, TMIn 1 × 10 ⁻⁶ mol / min and TBP 1.2 × 10 ⁻³ mol / min are supplied into the growth chamber of the MOCVD apparatus, and at the same time, TBCl 3 × 10 ⁻⁶ mol / min is supplied into the growth chamber. Then, an InP nanowire is grown as the first nanowire for 10 minutes. The growth temperature condition in each growth described above is 370 ° C.

  3, the InP nanowire 303, the InAs nanowire 304, the InP nanowire 305, the InAs nanowire 304, the InP nanowire 305, the InAs nanowire 304, using the Au fine particle 302 as a catalyst on the InP substrate 301, as shown in FIG. A heterowire nanowire in which InP nanowires 306 are grown and laminated is obtained.

  In addition, with the above process conditions, the InP nanowire 303 and the InP nanowire 306 are formed relatively long, and the InAs nanowire 304, the InP nanowire 305, the InAs nanowire 304, the InP nanowire 305, and the InAs nanowire 304 have a quantum effect. It is formed short enough to be expressed. As a result, the InAs nanowire 304 can function as a quantum dot, and a quantum dot structure can be incorporated in the nanowire.

Also in the second embodiment, since TBCl is supplied to the growth atmosphere in addition to the source gas, the growth in the radial direction perpendicular to the nanowire extending direction (axial direction) is controlled (suppressed), and the diameter is increased in the axial direction. Uniform nanowires can be formed. According to this manufacturing method, a gas that is stored at a high pressure using a cylinder or the like and is not easy to handle, such as HCl, PH ₃ , and AsH ₃ , is not used. Therefore, also in Embodiment 2, high quality nanowires can be formed more easily.

  In Embodiment 2, since TBCl is supplied simultaneously with the source gas, InP is not stacked around the InAs nanowire growth layer, and InAs is not stacked around the InP nanowire growth layer. Structured nanowires can be formed.

[Embodiment 3]
Next, a third embodiment of the present invention will be described. In the nanowire forming method according to the third embodiment, first, catalyst metal fine particles are arranged on a substrate in a first step (fine particle arranging step). For example, a plurality of fine particles made of Au are arranged on a GaAs substrate whose main surface has a (111) B plane orientation. For example, an Au layer is formed on the substrate by vapor deposition or the like, and the formed Au layer is patterned by a well-known lithography technique to form an array pattern in which circular patterns having a diameter of 20 μm are arrayed. Thereafter, the substrate may be heated so that a plurality of Au fine particles are arranged on the substrate.

  Next, in the second step, as described above, a raw material gas composed of an organic metal is supplied onto a substrate on which fine particles are arranged, and nanowires crystallized from the raw material gas using the fine particles as a catalyst are grown (nanowire growth). Process).

Here, in the third embodiment, in the step of growing nanowires, first, a predetermined raw material gas is supplied to grow first nanowires using fine particles as a catalyst (first nanowire growth step). For example, TMIn 1 × 10 ⁻⁶ mol / min, TEGa 1 × 10 ⁻⁶ mol / min, TBAs ⁵ × 10 ⁻⁵ mol / min are supplied into the growth chamber of the MOCVD apparatus, and the growth temperature is 340 ° C., and GaInAs is used as the first nanowire. The nanowire is grown for 15 minutes. Here, TBCl is not supplied.

Next, a raw material gas having a composition different from that of the growth of the first nanowire is supplied, and the second nanowire is continuously grown on the first nanowire using the fine particles as a catalyst (second nanowire growth step). For example, TMIn 1 × 10 ⁻⁶ mol / min and TBP 1.2 × 10 ⁻³ mol / min are supplied, and an InP nanowire is grown as a second nanowire for 20 minutes at a growth temperature of 420 ° C. In this step, TBCl 3 × 10 ⁻⁶ mol / min is supplied (introduced) into the growth chamber in the final 2 minutes of growth.

  In the above-described growth of InP, GaInAs nanowires 403 grown using Au fine particles 402 as a catalyst are formed on a substrate 401 as shown in FIG. InP nanowires 404 are grown on the sides of the GaInAs nanowires 403. However, since TBCl is supplied from the middle, the InP layer grown on the side of the GaInAs nanowire 403 is etched, and the side of the GaInAs nanowire 403 is exposed as shown in FIG. 4B. As a result, a state in which InP nanowires 405 are continuously formed on the GaInAs nanowires 403 is obtained. The supply of TBCl may be performed after the growth of the InP nanowire is completed.

[Embodiment 4]
Next, a fourth embodiment of the present invention will be described. In the nanowire forming method according to the fourth embodiment, first, catalyst metal fine particles are arranged on a substrate in a first step (fine particle arranging step). For example, a plurality of fine particles of about 10 nm in diameter made of Au are arranged on an InP substrate whose main surface has a (111) B plane orientation. For example, a dispersion liquid (colloid solution) in which Au fine particles are dispersed may be applied, and then the dispersion medium may be removed.

  Next, in the second step, as described above, a raw material gas composed of an organic metal is supplied onto a substrate on which fine particles are arranged, and nanowire nanowires crystallized from the raw material gas using the fine particles as a catalyst are grown (nanowires). Growth process).

Here, in the fourth embodiment, in the step of growing the nanowire, first, the first impurity material that becomes the first conductivity type impurity is supplied together with the source gas, and the first conductivity type nanowire is grown using the fine particles as a catalyst ( First conductivity type nanowire growth step). For example, TMIn 1 × 10 ⁻⁶ mol / min and TBP 1.2 × 10 ⁻³ mol / min are supplied into the growth chamber of the MOCVD apparatus, and at the same time, TBCl 3 × 10 ⁻⁶ mol / min is supplied into the growth chamber. In addition, DTBS (ditertiary butyl sulfur) 5 × 10 ⁻⁸ mol / min is introduced as the first impurity material, and an n-InP nanowire made of n-type InP is grown for 15 minutes at a growth temperature condition of 370 ° C. In this case, the first conductivity type is n-type.

Next, the source gas is supplied, and the fine particles are used as a catalyst to grow i-type nanowires in which impurities are not continuously introduced into the first conductivity type nanowires (i-type nanowire growth step). For example, TMIn 1 × 10 ⁻⁶ mol / min and TBAs 5.0 × 10 ⁻⁵ mol / min are supplied into the growth chamber, and at the same time, TBCl 3 × 10 ⁻⁶ mol / min is supplied, and the growth temperature condition is 340 ° C. An i-InAs nanowire made of a type of InAs is grown for 10 seconds. In this step, impurities are not introduced.

Next, the second impurity raw material which becomes the second conductive type impurity is supplied together with the raw material gas, and the second conductive nanowire is grown continuously with the i-type nanowire using the fine particles as a catalyst (second conductive nanowire growth step) ). For example, TMIn 2 × 10 ⁻⁶ mol / min and TBP 1.2 × 10 ⁻³ mol / min are supplied into the growth chamber, and at the same time, TBCl 1 × 10 ⁻⁶ mol / min is supplied into the growth chamber. In addition, DEZn (diethyl zinc) 5 × 10 ⁻⁷ mol / min is introduced as the second impurity material, and p-InP nanowires made of p-type InP are grown for 15 minutes under a growth temperature condition of 370 ° C. In this case, the second conductivity type is p-type.

  Through the above steps, as shown in FIG. 5, n-InP nanowires 503, i-InAs nanowires 504, and p-InP nanowires 505 are grown and laminated on the InP substrate 501 using Au fine particles 502 as a catalyst. A pin-type nanowire 511 having a hetero-connected structure is obtained. Moreover, the obtained nanowire is more excellent in straightness in a state where the change in diameter is small. Further, there is no growth (deposition) of other compounds on the side of the nanowire.

Next, the pin-type nanowire 511 is separated from the InP substrate 501 and placed on the sapphire substrate 601 as shown in FIG. Then, to connect the AuZnN i or Ranaru p-type electrode 602 on the p-InP nanowires 505 is formed by connecting the n-type electrode 603 composed of AuGeNi in n-InP nanowire 503.

  For example, the position on the pin-type nanowire 511 is confirmed with a scanning electron microscope, and then electrode patterns are formed on each side by electron beam lithography. Next, the p-type electrode material and the n-type electrode material are each deposited by an electron beam deposition apparatus, the electrode pattern is lifted off, and the respective electrodes are formed. Moreover, after forming each electrode, it heat-processes to 350 degreeC and takes the ohmic contact of each electrode and nanowire.

  According to the light-emitting element manufactured as described above, the current supplied from the p-type electrode 602 and the n-type electrode 603 is efficiently injected into the i-InAs nanowire 504 serving as an active layer, and light emission is obtained. By changing the length of the i-InAs nanowire 504, 1.55 μm light emission in the communication wavelength band is possible.

As described above, according to the present invention, when a nanowire is grown from catalytic metal particles by metal organic vapor phase epitaxy, (CH ₃ ) ₃ CCl gas is also supplied in addition to the supply of the source gas. As a result, high quality nanowires can be formed more easily. According to the present invention, a nanowire growth technique based on the VLS method can grow high-quality nanowires with fewer stacking faults and less impurities at higher growth temperatures. Thereby, for example, a large-area optical device can be manufactured relatively easily with bottom-up and good controllability.

  The present invention is not limited to the embodiment described above, and many modifications and combinations can be implemented by those having ordinary knowledge in the art within the technical idea of the present invention. It is obvious. For example, in the fourth embodiment, the n-InP nanowire, the i-InAs nanowire, and the p-InP nanowire are grown in this order. However, the p-InP nanowire, the i-InAs nanowire, and the n-InP nanowire may be grown in this order.

  301 ... InP substrate, 302 ... Au fine particles, 303 ... InP nanowire, 304 ... InAs nanowire, 305 ... InP nanowire, 306 ... InP nanowire.

Claims (6)

A fine particle placement step of placing catalytic metal fine particles on the substrate;
A nanowire growth step of supplying a raw material gas composed of an organic metal on the substrate on which the fine particles are arranged, and growing nanowires crystallized from the raw material gas using the fine particles as a catalyst, and
In the nanowire growth step, a gas of (CH ₃ ) ₃ CCl is supplied in addition to the source gas. In the manufacturing method of the nanowire of Claim 1,
The nanowire growth process includes:
A first nanowire growth step of supplying a predetermined source gas and growing the first nanowire using the fine particles as a catalyst;
A nanowire comprising: a second nanowire growth step of supplying a source gas having a composition different from that of the growth of the first nanowire and growing the second nanowire continuously with the first nanowire using the fine particles as a catalyst. Manufacturing method. The method for producing a nanowire according to claim 2,
A method of manufacturing a nanowire, wherein (CH ₃ ) ₃ CCl gas is supplied in the first nanowire growth step and the second nanowire growth step. The method for producing a nanowire according to claim 2,
In the first nanowire growth process, (CH ₃ ) ₃ CCl gas is not supplied,
In the second nanowire growth step, a gas of (CH ₃ ) ₃ CCl is supplied. In the manufacturing method of the nanowire of Claim 1,
The nanowire growth process includes:
A first conductivity type nanowire growth step of growing a first conductivity type nanowire using the fine particles as a catalyst by supplying a first impurity source material that becomes a first conductivity type impurity together with the source gas;
An i-type nanowire growth step of supplying the source gas and growing an i-type nanowire in which impurities are not continuously introduced into the first conductive nanowire by using the fine particles as a catalyst;
A second conductivity type nanowire growth step of supplying a second impurity source material which becomes an impurity of the second conductivity type together with the source gas, and growing the second conductivity type nanowire continuously with the i type nanowire using the fine particles as a catalyst; A method for producing a nanowire, comprising: In the manufacturing method of the nanowire of any one of Claims 1-5,
The method for producing a nanowire, wherein the catalytic metal is Au.