JP2006253415A - METHOD FOR GROWING ZnO-BASED COMPOUND CRYSTAL - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a growing method of ZnO-based compound crystal for restraining an increase in costs, and decreasing the concentration of residual electrons by reducing the oxygen defect of the ZnO-based compound crystal. <P>SOLUTION: The method has a growth process for supplying first raw material gas containing a raw material containing a zinc atom and a transportation gas, and a second raw material gas containing an oxygen atom into a reactor 2 in which a substrate 3 is stored; and for performing epitaxial growth to the ZnO-based compound crystal on the substrate 3 by allowing the zinc atom to react with the oxygen one. In this case, the oxygen atom is supplied much more than the zinc atom, and the growth speed of the ZnO-based compound crystal is set to 3 [nm/hour] or higher and 300 [nm/hour] or lower. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for growing a ZnO-based compound crystal.

  For example, Patent Document 1 discloses a method of epitaxially growing a ZnO-based compound on a surface (for example, A surface) orthogonal to the C-plane of a sapphire substrate in order to form a ZnO-based compound semiconductor layer having excellent crystallinity. ing.

In the method disclosed in Patent Document 2, in order to obtain flatness, a buffer layer made of a ZnO-based oxide semiconductor is first formed on a substrate at a low temperature. And in order to raise crystallinity, the substrate temperature is raised and the ZnO type oxide semiconductor layer is grown sequentially. In the method disclosed in Non-Patent Document 1, DEZn is used as a zinc raw material and N ₂ O is used as an oxygen raw material. First, a buffer layer is grown at 500 ° C., and then a single crystal layer is formed thereon at 700 ° C. to It has been confirmed that the crystallinity of the single crystal layer is improved by growing at 800 ° C.

JP 2001-44500 A JP 2002-76025 A K.OGATA etal., “ZnO Growth Toward Optical Devices by MOVPE Using N2O”, Journalof ELECTRONIC MATERIALS, Vol.30, No.6, pp.659-661 (2001)

  When growing a ZnO-based compound crystal, if there are crystal defects such as oxygen defects, the residual electron concentration increases and it is difficult to obtain desired electrical characteristics. In the methods disclosed in the above-mentioned documents, the residual electron concentration due to oxygen defects is not taken into consideration at all, and there is a risk that the suppression of the residual electron concentration may be insufficient.

  Regarding this problem, a method of reducing the residual electron concentration by molecular beam epitaxy (MBE method) has been attempted at present, but in this method, it is necessary to perform film formation in an ultrahigh vacuum. The apparatus becomes large and expensive, and the mass productivity is poor, and it is difficult to suppress the manufacturing cost.

  The present invention has been made in view of the above problems, and provides a method for growing a ZnO-based compound crystal that can reduce the residual electron concentration by reducing oxygen defects in the ZnO-based compound crystal while suppressing an increase in cost. The purpose is to provide.

  In order to solve the above-described problems, a method for growing a ZnO-based compound crystal according to the present invention includes a first source gas including a zinc atom-containing source and a transport gas, and oxygen atoms in a reaction chamber in which a substrate is accommodated. A growth step of growing a ZnO-based compound crystal on a substrate by supplying a second source gas containing oxygen, supplying more oxygen atoms than zinc atoms during the growth step, and growing a ZnO-based compound crystal The speed is 3 [nm / hour] or more and 300 [nm / hour] or less.

  According to the above-described method for growing a ZnO-based compound crystal, by supplying more oxygen atoms than zinc atoms, oxygen atoms become excessive in the crystal growth process, and oxygen defects in the ZnO-based compound crystal can be reduced. The residual electron concentration of the compound crystal can be reduced. Also, according to this method, unlike the MBE method, a large apparatus is not required, so that oxygen defects can be reduced at a low cost. According to the study by the present inventors, the growth rate of the ZnO-based compound crystal is set to 3 [nm / hour] or more and 300 [nm / hour] or less, so that the ZnO-based compound crystal is crystallized in an excessive oxygen atom state. It has been found that the residual electron concentration can actually be reduced with good growth.

  The ZnO-based compound crystal growth method according to the present invention includes a first source gas containing a zinc atom-containing source and a transport gas and a second source gas containing an oxygen atom in a reaction chamber containing a substrate. And a growth step of growing a ZnO-based compound crystal on the substrate. During the growth step, the ZnO-based compound crystal is grown on the {1-102} plane of the substrate, and the second source gas The supply rate is 4 / n to 600 / n times the supply rate of the first source gas (n: the number of oxygen atoms contained in one molecule of the second source gas).

  According to the growth method of the above-described ZnO-based compound crystal, by supplying more second source gas containing oxygen atoms than first source gas containing zinc atoms, oxygen atoms become excessive in the crystal growth process, Since oxygen defects in the ZnO-based compound crystal can be reduced, the residual electron concentration of the ZnO-based compound crystal can be reduced. Also, according to this method, unlike the MBE method, a large apparatus is not required, so that oxygen defects can be reduced at a low cost. Further, by growing the ZnO-based compound crystal on the {1-102} plane of the substrate, it is possible to suppress the formation of columnar crystals perpendicular to the main surface of the substrate and to form a flat and dense crystal film. Further, the present inventors have found that the residual electron concentration can be effectively reduced by setting the supply rate of the second source gas to 4 / n times or more the supply rate of the first source gas. It was done. Further, by setting the supply rate of the second source gas to 600 / n times or less the supply rate of the first source gas, the deterioration of crystallinity caused by excessive supply of oxygen atoms is prevented, and the residual It has been found that the electron concentration can be kept low.

  The {1-102} plane here means that it includes the (1-102) plane and its equivalent plane. In the above-described method for growing a ZnO-based compound crystal, the substrate is preferably sapphire (including mainly sapphire).

In the method for growing a ZnO-based compound crystal, the transport gas is preferably nitrogen gas (N ₂ ). In the method for growing a ZnO-based compound crystal, the second source gas is preferably oxygen gas (O ₂ ).

  In the method for growing a ZnO-based compound crystal, the raw material containing zinc atoms is preferably a β-diketone compound. In this case, the β-diketone compound is more preferably acetylacetone zinc or a hydrate thereof. In addition, when acetylacetone zinc or a hydrate thereof is used as a raw material containing zinc atoms, the acetylacetone zinc or the hydrate can be supplied to the reaction chamber while being sublimated or vaporized by heating to 60 ° C or higher and 120 ° C or lower. preferable.

  According to the method for growing a ZnO-based compound crystal according to the present invention, it is possible to reduce the residual electron concentration by reducing oxygen defects in the ZnO-based compound crystal while suppressing an increase in cost.

  Hereinafter, embodiments of a method for growing a ZnO-based compound crystal according to the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.

(Embodiment)
First, before describing embodiments and examples of the ZnO-based compound crystal growth method according to the present invention, the configuration of a film forming apparatus suitably used in the present method will be described. FIG. 1 is a schematic view showing a configuration of a film forming apparatus 1 used in the present method. The film forming apparatus 1 is an apparatus for forming a crystal film by metal organic chemical vapor deposition (MOCVD). Referring to FIG. 1, a film forming apparatus 1 includes a reactor 2, a substrate holder 4, a substrate heater 5, gas supply pipes 6 to 9, valves 11 to 13, a material cylinder 14, a material boat 15, a material heater 16, and An exhaust port 17 is provided.

  The reactor 2 is a reaction chamber in the film forming apparatus 1. The reactor 2 includes a substrate holder 4 and a substrate heater 5. The substrate holder 4 and the substrate heater 5 are attached to the tip of a rotatable shaft 19. In this embodiment, the substrate 3 on which the ZnO-based compound crystal film is formed is mounted on the substrate holder 4. The substrate heater 5 heats the substrate 3 mounted on the substrate holder 4.

The gas supply pipes 6 to 9 are pipes for supplying the raw material gas to the reactor 2. Among these, the gas supply pipe 6 has a gas introduction port 6 a and a gas supply port 6 b connected to the inside of the reactor 2. A valve 13 is provided between the gas introduction port 6a and the gas supply port 6b. The gas supply pipe 6 can supply, for example, oxygen gas (O ₂ ), which is the second raw material gas in the present embodiment, into the reactor 2.

  One end of each of the gas supply pipes 7 and 8 is a gas inlet 7a and 8a. The other ends of the gas supply pipes 7 and 8 are both connected to one end of the gas supply pipe 9. The other end of the gas supply pipe 9 is a gas supply port 9 a connected to the inside of the reactor 2. The gas supply pipes 7 and 8 are provided with valves 11 and 12, respectively. For example, the gas supply pipe 7 can supply the same type of gas as the transport gas for transporting the zinc raw material to the reactor 2 via the gas supply pipe 9. The gas supply pipe 8 can supply a transport gas and a raw material containing zinc atoms (for example, zinc acetylacetonate) to the reactor 2 through the gas supply pipe 9.

  The gas supply pipe 8 is provided with a raw material cylinder 14 for sublimating or vaporizing the raw material, and a raw material boat 15 for containing the raw material is installed in the raw material cylinder 14. The material boat 15 can accommodate a material containing, for example, zinc atoms. A raw material heater 16 is provided around the raw material cylinder 14. The raw material heater 16 heats and sublimates or vaporizes the raw material stored in the raw material boat 15.

  The exhaust port 17 is provided for discharging the residual gas generated as a result of the reaction in the reactor 2. The discharge of the residual gas is controlled by a valve 18 provided at the exhaust port 17.

  Here, the growth process of the ZnO-based compound crystal using the film forming apparatus 1 will be described. First, a substrate made of a material constituting a hexagonal crystal such as sapphire or ZnO is prepared as the substrate 3. Then, the substrate 3 is mounted on the substrate holder 4.

Subsequently, the same kind of gas as the transport gas (for example, nitrogen gas (N ₂ )) is introduced into the gas supply pipe 7, and the valve 12 is opened to supply the gas into the reactor 2. The substrate 3 is heated to, for example, 500 ° C. to 600 ° C. by the substrate heater 5 and the pressure in the reactor is increased to, for example, 60 Torr (8000 Pa). In parallel with this, a raw material containing zinc is accommodated in the raw material boat 15 of the raw material cylinder 14, and the raw material is sublimated or vaporized by, for example, heating the raw material to 40 ° C. to 250 ° C. by the raw material heater 16. . If the temperature of the raw material is lower than 40 ° C., the sublimation (vaporization) of the raw material becomes insufficient, and if the temperature of the raw material is higher than 250 ° C., the raw material is dissolved and easily adheres to the inside of the apparatus.

或いは、亜鉛を含む原料として、酢酸亜鉛Ｚｎ（ＣＨ_３ＣＯＯ）_２またはその二水和物（亜鉛アセテートジハイドレート）を用いることもできる。なお、亜鉛を含む原料として亜鉛アセチルアセトナートまたはその水和物を用いる場合、原料用ヒータ１６によってこの原料を６０℃以上１２０℃以下に加熱することにより気化または昇華させつつ、該原料をリアクタ２内へ供給するとよい。これにより、該原料が好適に気化または昇華される。 As a raw material containing zinc, a material containing zinc atoms and oxygen atoms, for example, a β-diketone compound containing zinc may be used. Examples of such β diketone compounds include acetylacetone zinc (including zinc acetylacetonate and hydrates thereof) represented by the following chemical formula.

Alternatively, zinc acetate Zn (CH ₃ COO) ₂ or a dihydrate thereof (zinc acetate dihydrate) can also be used as a raw material containing zinc. When zinc acetylacetonate or a hydrate thereof is used as a raw material containing zinc, the raw material is vaporized or sublimated by heating the raw material to 60 ° C. or higher and 120 ° C. or lower by the raw material heater 16, while the raw material is removed from the reactor 2. It is good to supply inside. Thereby, the raw material is suitably vaporized or sublimated.

Subsequently, the valve 12 is closed and the valve 11 is opened, and a transport gas (for example, nitrogen gas (N ₂ )) is introduced into the gas supply pipe 8. Thereby, a raw material gas (first raw material gas) including the raw material vaporized in the raw material cylinder 14 and the transport gas is supplied into the reactor 2. Further, the valve 13 is opened and, for example, oxygen gas (O ₂ ) is introduced into the gas supply pipe 6 as a source gas containing oxygen atoms (second source gas). Oxygen gas is supplied into the reactor 2. On the main surface of the substrate 3, zinc atoms and oxygen atoms react at a high temperature of 500 ° C. to 600 ° C., and a ZnO-based compound crystal grows epitaxially, thereby forming a ZnO-based compound film. In addition to the nitrogen gas, for example, an inert gas such as hydrogen gas, argon gas, or helium gas can be used as the transport gas.

  Here, in this embodiment, in order to reduce oxygen defects in the ZnO-based compound crystal, the ZnO-based compound crystal is epitaxially grown by any of the following methods.

(First method)
When supplying the first and second source gases into the reactor 2, oxygen atoms contained in the second source gas are supplied more than zinc atoms contained in the first source gas. That is, with respect to the supply rate A _Zn [mol / hour] of zinc atoms in the first raw material gas, the supply rate A _O [mol / hour] of oxygen atoms in the second raw material gas is expressed as A _O > A _Zn . Thus, the supply speed (flow rate) of the first and second source gases is adjusted. Further, the reaction rate between the zinc atom and the oxygen atom is set to the supply rate of the first and second source gases so that the growth rate of the ZnO-based compound crystal is 3 [nm / hour] or more and 300 [nm / hour] or less. And adjust according to substrate temperature.

(Second method)
First, as the substrate 3, a substrate having an R surface ({1-102} surface) as a main surface (growth surface) is prepared. Then, the substrate 3 is mounted on the substrate holder 4 so that the ZnO-based compound crystal grows on the R plane. Further, when supplying the first and second source gases into the reactor 2, the supply rate (flow rate) of the second source gas is set to 4 / n times or more 600 / n times the supply rate of the first source gas. Less than or equal to twice (n: the number of oxygen atoms contained in one molecule of the second source gas). For example, since oxygen gas (O ₂ ) is supplied as the second source gas in the present embodiment, n = 2, and the oxygen gas supply rate is not less than 2 times and not more than 300 times the first source gas supply rate. To do.

  By the steps described above, a substrate product in which a ZnO-based compound crystal film is formed on the substrate 3 is completed. In the above step, impurities such as nitrogen (N) and phosphorus (P) may be doped when the ZnO-based compound crystal is grown or after the growth. Thereby, a semiconductor layer having desired conductivity such as p-type can be formed. Thereafter, a semiconductor element such as a light-emitting element or a light-receiving element can be manufactured by cutting the substrate product into a chip shape through processes such as electrode formation.

  According to the method for growing a ZnO-based compound crystal according to the present embodiment, the following effects can be obtained. That is, according to the first method described above, by supplying more oxygen atoms than zinc atoms, oxygen atoms become excessive in the crystal growth process, and oxygen defects in the ZnO-based compound semiconductor crystal can be reduced. The residual electron concentration of the compound crystal can be reduced. Also, according to this method, unlike the MBE method, a large apparatus is not required, so that oxygen defects can be reduced at a low cost.

表１及び図２に示すように、ＺｎＯ系化合物結晶の成長速度が過度に低い場合、或いは過度に高い場合には、ＺｎＯ系化合物結晶の残留電子濃度が増大してしまう。これに対し、ＺｎＯ系化合物結晶の成長速度を３［ｎｍ／時］以上３００［ｎｍ／時］以下とすることにより、残留電子濃度を顕著に低減し得ることがわかる。これは、ＺｎＯ系化合物結晶の成長速度を上記範囲とすることにより、酸素原子が過剰な状態においてＺｎＯ系化合物結晶を結晶性良く成長させることができるためと考えられる。 The inventors have also found that there is a correlation between the growth rate of the ZnO-based compound crystal and the residual electron concentration. Table 1 below shows changes in residual electron concentration when the growth rate of the ZnO-based compound crystal is changed. FIG. 2 is a graph showing the contents of Table 1.

As shown in Table 1 and FIG. 2, when the growth rate of the ZnO-based compound crystal is excessively low or excessively high, the residual electron concentration of the ZnO-based compound crystal increases. In contrast, it can be seen that the residual electron concentration can be significantly reduced by setting the growth rate of the ZnO-based compound crystal to 3 [nm / hour] or more and 300 [nm / hour] or less. This is presumably because by setting the growth rate of the ZnO-based compound crystal in the above range, the ZnO-based compound crystal can be grown with good crystallinity in a state where oxygen atoms are excessive.

  Further, according to the second method described above, by supplying a larger amount of the second source gas than the first source gas, oxygen atoms become excessive during the crystal growth process, and oxygen defects in the ZnO-based compound crystal are reduced. Therefore, the residual electron concentration of the ZnO-based compound crystal can be reduced. Also in this method, unlike the MBE method, a large apparatus is not required, so that oxygen defects can be reduced at a low cost. Then, by growing a ZnO-based compound crystal on the R plane ({1-102} plane) of the substrate, formation of columnar crystals perpendicular to the main surface of the substrate 3 is suppressed, and a flat and dense crystal film is formed. And stable electrical characteristics can be obtained. Further, as shown in the following examples, the residual electron concentration can be effectively reduced by setting the supply rate of the second source gas to 4 / n times or more the supply rate of the first source gas. Further, by setting the supply rate of the second source gas to 600 / n times or less the supply rate of the first source gas, the deterioration of crystallinity caused by excessive supply of oxygen atoms is prevented, and the residual The electron concentration can be kept low.

First, a sapphire substrate having an R surface as a main surface was prepared as the substrate 3, and this sapphire substrate was set in the substrate holder 4 in the reactor 2. Then, while supplying nitrogen gas (N ₂ ) into the reactor 2 through the gas supply pipe 7, the temperature of the sapphire substrate was raised to 600 ° C. by the substrate heater 5. At this time, the pressure in the reactor was 60 Torr (8000 Pa). Further, zinc acetylacetonate was accommodated in the raw material boat 15 in the raw material cylinder 14, and the raw material cylinder 14 was heated to 100 ° C. by the raw material heater 16.

Subsequently, after closing the valve 12 of the gas supply pipe 7, the valve 11 of the gas supply pipe 8 is opened, and while supplying nitrogen gas as a transport gas to the gas supply pipe 8 at a supply speed of 40 sccm, The acetylacetonate was sublimated and the supply into the reactor 2 was started. Subsequently, the valve 13 was opened and supply of oxygen gas was started. At this time, the supply rate of oxygen gas was set to 20 times the supply rate of nitrogen gas (that is, 800 sccm). Thus, a ZnO crystal was epitaxially grown on the sapphire substrate in the reactor 2. As a result, a ZnO crystal film having a thickness of 620 nm was obtained after 7 hours. When this ZnO crystal was grown, 0.0028 mol of zinc atoms was consumed, so the supply rate of zinc atoms was 4 × 10 ⁻⁴ [mol / hour].

  Further, the supply rate of nitrogen gas for transporting zinc acetylacetonate is set to 100 sccm, the supply rate of oxygen gas is set to four times the supply rate of nitrogen gas (that is, 400 sccm) (other conditions are the same), Grown on a sapphire substrate. Further, the supply rate of nitrogen gas for transporting zinc acetylacetonate is set to 200 sccm, the supply rate of oxygen gas is set to one time the supply rate of nitrogen gas (that is, 200 sccm) (other conditions are the same), and ZnO crystals are further separated. Grown on a sapphire substrate.

  FIG. 3 is a graph showing the correlation between the ratio of the supply rate of oxygen gas (second source gas) to the supply rate of nitrogen gas (first source gas) and the residual electron concentration of the ZnO crystal. Referring to FIG. 3, it can be seen that the residual electron concentration is the lowest when the oxygen gas supply rate is 20 times the nitrogen gas supply rate, and the residual electron concentration is highest when it is 1 time.

  In order to further clarify the correlation between the supply rate ratio and the residual electron concentration shown in Example 1, the following experiment was performed. First, as in Example 1, a sapphire substrate having an R plane as a main surface was prepared as the substrate 3, and this sapphire substrate was set in the substrate holder 4 in the reactor 2. While supplying nitrogen gas from the gas supply pipe 7 at a supply rate of 200 ccm, the temperature of the sapphire substrate was raised to 600 ° C., and the pressure in the reactor was set to 60 Torr (8000 Pa). Moreover, zinc acetylacetonate was accommodated in the raw material boat 15, and it heated until it became 100 degreeC.

Subsequently, the sublimated zinc acetylacetonate was transported into the reactor 2 by nitrogen gas, and oxygen gas was supplied into the reactor 2. At this time, the oxygen gas supply rate to the nitrogen gas supply rate for transporting zinc acetylacetonate was changed to the magnifications shown in Table 2 below, and ZnO crystals were epitaxially grown on the sapphire substrate at the respective magnifications. The supply rate of zinc atoms for growing the ZnO crystal was 4 × 10 ⁻⁴ [mol / hour].

表２及び図４を参照すると、酸素ガスの供給速度を窒素ガスの供給速度の２倍以上３００倍以下とした場合に残留電子濃度が顕著に低くなることがわかる。なお、本実施例では酸素原子を供給するための原料として酸素ガス（Ｏ_２）を用いているが、他の原料（例えばＮ_２Ｏ）を用いる場合などに一般化すれば、酸素原子を含む原料ガスの供給速度を、亜鉛原子を輸送する輸送ガスの供給速度の４／ｎ倍以上６００／ｎ倍以下（ｎ：酸素原子を含む原料ガス一分子中に含まれる酸素原子の数）とすることにより、残留電子濃度を好適に低減できる。 Table 2 is a table showing the correlation between the ratio of the supply rate of oxygen gas (second source gas) to the supply rate of nitrogen gas (first source gas) and the residual electron concentration of the ZnO crystal. FIG. 4 is a graph of Table 2.

Referring to Table 2 and FIG. 4, it can be seen that the residual electron concentration is remarkably lowered when the oxygen gas supply rate is set to be not less than twice and not more than 300 times the nitrogen gas supply rate. In this embodiment, oxygen gas (O ₂ ) is used as a raw material for supplying oxygen atoms. However, when generalized to other raw materials (for example, N ₂ O), oxygen atoms are included. The feed rate of the source gas is 4 / n to 600 / n times the feed rate of the transport gas for transporting zinc atoms (n: the number of oxygen atoms contained in one molecule of the source gas containing oxygen atoms). As a result, the residual electron concentration can be suitably reduced.

  In order to investigate the correlation between the supply rate of zinc atoms and the residual electron concentration, the following experiment was conducted. First, as in Example 1, a sapphire substrate having an R plane as a main surface was prepared as the substrate 3, and this sapphire substrate was set in the substrate holder 4 in the reactor 2. And while raising the temperature of this sapphire substrate to 550 degreeC, the pressure in a reactor was 60 Torr (8000 Pa). Moreover, zinc acetylacetonate is accommodated in the raw material boat 15, and the sublimation rate of zinc acetylacetonate (that is, the supply rate of zinc atoms to the reactor 2) is changed to the values shown in Table 3 below by changing the heating temperature. The oxygen gas supply rate was set to 10 times the transport gas (nitrogen gas) supply rate, and a ZnO crystal was epitaxially grown on another sapphire substrate for each supply rate.

表３及び図５を参照すると、亜鉛原子の供給速度を５×１０^−５［ｍｏｌ／時］以上２×１０^−２［ｍｏｌ／時］以下とした場合に残留電子濃度が顕著に低くなることがわかる。 Table 3 is a table showing the correlation between the supply rate of zinc atoms and the residual electron concentration of the ZnO crystal. FIG. 5 is a graph of Table 3.

Referring to Table 3 and FIG. 5, when the supply rate of zinc atoms is 5 × 10 ⁻⁵ [mol / hour] or more and 2 × 10 ⁻² [mol / hour] or less, the residual electron concentration is significantly reduced. I understand.

  The growth method of the ZnO-based compound crystal according to the present invention is not limited to the above-described embodiment and examples, and various other modifications are possible. For example, in the above embodiment, a ZnO crystal is exemplified as the ZnO-based compound crystal. However, the method according to the present invention can be applied to other cases such as CdZnO crystal and MgZnO crystal.

FIG. 1 is a schematic view showing a configuration of a film forming apparatus used in the present method. FIG. 2 is a graph showing changes in residual electron concentration when the growth rate of the ZnO-based compound crystal is changed. FIG. 3 is a graph showing the correlation between the ratio of the supply rate of oxygen gas (second source gas) to the supply rate of nitrogen gas (first source gas) and the residual electron concentration of the ZnO crystal. FIG. 4 is a graph showing the correlation between the ratio of the supply rate of oxygen gas (second source gas) to the supply rate of nitrogen gas (first source gas) and the residual electron concentration of the ZnO crystal. FIG. 5 is a graph showing the correlation between the supply rate of zinc atoms and the residual electron concentration of the ZnO crystal.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Film-forming apparatus, 2 ... Reactor, 3 ... Substrate, 4 ... Substrate holder, 5 ... Substrate heater, 6-9 ... Gas supply pipe, 11-13, 18 ... Valve, 14 ... Raw material cylinder, 15 ... Raw material boat 16 ... Raw material heater, 17 ... Exhaust port, 19 ... Shaft.

Claims (8)

A first source gas containing a source material containing zinc atoms and a transport gas and a second source gas containing oxygen atoms are supplied into a reaction chamber in which the substrate is accommodated, and a ZnO-based compound crystal is grown on the substrate. With a growth process
In the growth step, oxygen atoms are supplied more than the zinc atoms, and the growth rate of the ZnO-based compound crystal is set to 3 [nm / hour] or more and 300 [nm / hour] or less. A method for growing a ZnO-based compound crystal. A first source gas containing a source material containing zinc atoms and a transport gas and a second source gas containing oxygen atoms are supplied into a reaction chamber containing the substrate, and a ZnO-based compound crystal is grown on the substrate. With a growth process
In the growth step, the ZnO-based compound crystal is grown on the {1-102} plane of the substrate, and the supply rate of the second source gas is set to 4 that is the supply rate of the first source gas. / N times to 600 / n times (n: the number of oxygen atoms contained in one molecule of the second source gas). A method for growing a ZnO-based compound crystal,   The method for growing a ZnO-based compound crystal according to claim 2, wherein the substrate is sapphire. Characterized in that the transport gas is nitrogen gas (N _2), growth method for a ZnO-based compound crystal according to any one of claims 1 to 3. The method for growing a ZnO-based compound crystal according to any one of claims 1 to 4, wherein the second source gas is oxygen gas (O ₂ ).   The method for growing a ZnO-based compound crystal according to any one of claims 1 to 5, wherein the raw material containing zinc atoms is a β-diketone compound.   The method for growing a ZnO-based compound crystal according to claim 6, wherein the β-diketone compound is zinc acetylacetone or a hydrate thereof.   The acetylacetone zinc or a hydrate thereof is supplied to the reaction chamber while being sublimated or vaporized by heating to 60 ° C or higher and 120 ° C or lower during the growth step. A method for growing a ZnO-based compound crystal.

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