JP2019189486A - Method for manufacturing group iii nitride crystal - Google Patents

Abstract

To provide a method for manufacturing a group III nitride crystal, capable of obtaining a group III nitride single crystal formed by suppressing stress from a base substrate to the group III nitride single crystal without damaging a member in a furnace.SOLUTION: The method for manufacturing a group III nitride crystal comprises the steps of: (i) using sapphire as a base substrate to prepare a seed substrate having a group III nitride layer on the base substrate; (ii) growing a group III nitride crystal on the group III nitride layer provided on the seed substrate using a mixed melt of a group III element and alkali metal; and putting lithium oxide into the mixed melt before cooling to react the molten mixture with a base substrate.SELECTED DRAWING: Figure 1A

Description

  The present invention relates to a method for producing a group III nitride crystal.

  Group III nitride single crystal semiconductors such as gallium nitride are attracting attention as materials for heterojunction high-speed electronic devices such as power semiconductors and semiconductor elements that emit blue and ultraviolet light. Blue laser diodes (LD) are applied to high-density optical discs and displays, and blue light-emitting diodes (LEDs) are applied to displays and lighting. In addition, the ultraviolet LD is expected to be applied to biotechnology and the like, and the ultraviolet LED is expected as an ultraviolet light source for fluorescent lamps.

A substrate of a group III nitride single crystal semiconductor (for example, gallium nitride) is usually formed by vapor phase epitaxial growth. For example, a substrate obtained by heteroepitaxially growing a group III nitride crystal on a base substrate made of sapphire is used. However, the sapphire substrate and the gallium nitride single crystal have a difference of 13.8% in the lattice constant and a difference of 25.8% in the linear expansion coefficient. For this reason, the gallium nitride single crystal thin film obtained by vapor phase epitaxial growth has insufficient crystallinity. The dislocation density of the crystal obtained by this method is usually 1e + 8 cm ^{−2 to} 1e + 9 cm ⁻² , and the reduction of the dislocation density is an important issue. In order to solve this problem, efforts have been made to reduce the dislocation density, and for example, an ELOG (Epitaxial Lateral Overgrowth) method has been developed. According to this method, the dislocation density can be lowered to about 1e + 5 cm ⁻² to 1e + 6 cm ^−2, but the manufacturing process is complicated.

  On the other hand, a method of performing crystal growth in a liquid phase instead of vapor phase epitaxial growth has been studied. Conventionally, the equilibrium vapor pressure of nitrogen at the melting point of a group III nitride single crystal such as a gallium nitride single crystal or an aluminum nitride single crystal is 1000 MPa or more. Therefore, in order to grow gallium nitride in a liquid phase, 800 MPa at 1200 ° C. Conditions have been needed. On the other hand, it has been proposed to use a sodium flux method in which nitrogen is dissolved using a mixed melt with a sodium melt. It has been clarified that this sodium flux method can synthesize gallium nitride single crystals under relatively low temperature and low pressure conditions of 870 ° C. and 4 MPa.

  In addition, in a nitrogen gas atmosphere containing ammonium, a mixture of gallium and sodium is melted at 800 ° C. and 5 MPa, and a single crystal having a maximum crystal size of about 1.2 mm is grown using this melt for 96 hours. (For example, refer to Patent Document 1).

  In addition, after a gallium nitride single crystal layer is formed on a sapphire substrate by metal organic chemical vapor deposition (MOCVD), a single crystal is grown by liquid phase epitaxy (LPE). A method has also been reported.

  In these methods, there is a difference in thermal expansion coefficient between the base substrate made of sapphire and the group III nitride single crystal. For this reason, when a group III nitride single crystal is grown using a base substrate made of sapphire, the group III nitride single crystal may be distorted or warped in the cooling step after the growth. As a result, the obtained group III nitride single crystal substrate is easily damaged, and it is difficult to manufacture a device using the same. Also, the stress in this case increases as the substrate becomes larger in diameter. Therefore, a manufacturing method including a step of creating a gap between a base substrate made of sapphire and a group III nitride single crystal substrate has been reported. As a result, it is possible to manufacture a group III nitride single crystal substrate made of only a high-quality group III nitride single crystal and having a small warp.

  As another method for reducing the warpage, a method of dissolving a base substrate made of sapphire by a chemical reaction between a base substrate made of sapphire and metallic lithium before a stress due to a difference in thermal expansion coefficient occurs is also reported. (For example, refer nonpatent literature 1.). This reduces the stress acting between the grown group III nitride single crystal substrate and the base substrate made of sapphire. In this method, inside a crucible containing a mixed melt of a metal raw material placed in a temperature and pressure environment (870 ° C., 40 atm., Etc.) for crystal growth and in a place where the mixed melt of the raw material is not touched. Metal lithium is arranged. Thereafter, after the group III nitride crystal growth step, metallic lithium is charged into the raw material mixed melt containing the group III nitride crystal substrate grown on the sapphire base substrate before cooling. As a result, metallic lithium reacts with sapphire constituting the base substrate to separate the group III nitride crystal substrate from the base substrate.

FIG. 2 shows a configuration example of a conventional method for producing a group III nitride single crystal.
(A) In the conventional Group III nitride single crystal manufacturing method by the sodium flux method, a mixed melt 101 of a Group III element melt and a sodium melt is placed in the crucible container 100, and the mixed melt 101 A seed crystal substrate 104 is disposed therein. In the seed crystal substrate 104, a group III nitride single crystal layer 103 is provided on the base substrate 102.
(B) The crucible container 100, the mixed melt 101, and the seed crystal substrate 104 in the manufacturing apparatus having the above configuration are placed in an environment of 840 ° C. to 900 ° C. and nitrogen gas 40 atm. Thus, nitrogen dissolved in the mixed melt 101 reacts with gallium in the mixed melt 101 in the group III nitride single crystal layer 103 on the base substrate 102 to generate a gallium nitride single crystal (the following formula) (See (I).)
Ga + N → GaN (I)

(C) In order to reduce the stress on the grown group III nitride crystal substrate by dissolving sapphire constituting the base substrate 102 with lithium, during the crystal growth, the mixed melt 101 is formed inside the crucible container 100. The metal lithium 111 is held by a jig (jig, metal lithium holder) 110 without touching it.
(D) After the gallium nitride single crystal is formed on the base substrate 102 and before cooling, the inside of the crucible container 100 containing the group III nitride crystal substrate grown on the sapphire base substrate and the mixed melt 101 is contained. Is charged with metal lithium 111. Thereby, the metal lithium 111 is reacted with sapphire constituting the base substrate 102 to separate the group III nitride crystal substrate from the base substrate 102.

JP 2009-234800 A

Takumi Yamada et al, 2016, Appl. Phys. Express 9 071002

In the above-described conventional method for melting sapphire with metallic lithium, during the growth of the group III nitride single crystal, the standby lithium in the crucible containing the metal melt cannot exist stably in the growing environment, A part of lithium and the lithium compound is vaporized at the growth temperature. Further, there is a problem that vaporized lithium corrodes a member made of alumina (Al ₂ O ₃ ) or yttria (Y ₂ O ₃ ) present in the crucible. This is thought to be due to the high reactivity of metallic lithium.

  Therefore, the present invention provides a Group III nitride crystal manufacturing method for obtaining a Group III nitride single crystal in which stress from the base substrate to the Group III nitride single crystal is suppressed without damaging the in-furnace member. For the purpose.

In order to achieve the above object, a method for producing a group III nitride crystal according to the present invention includes (i) a step of preparing a seed substrate having sapphire as a base substrate and a group III nitride layer provided on the base substrate. When,
(Ii) growing a group III nitride crystal on the group III nitride layer provided on the seed substrate using a mixed melt of a group III element and an alkali metal;
(Iii) introducing lithium oxide into the mixed melt before cooling to react with the base substrate;
including.

  The method for producing a Group III nitride crystal according to the present invention reduces the warpage of the Group III nitride single crystal caused by the difference in thermal expansion coefficient between the base substrate composed of sapphire and the Group III nitride crystal. It is possible to grow a group III nitride single crystal.

FIG. 3 is a schematic diagram illustrating an example of a group III nitride crystal growth step in the method for producing a group III nitride crystal according to the first embodiment. In the manufacturing method of the group III nitride crystal which concerns on Embodiment 1, it is the schematic which shows an example of the process of throwing lithium oxide into a mixed melt and making it react with a base substrate. In the manufacturing method of the group III nitride crystal concerning Embodiment 1, it is the schematic which shows an example of the state which the base substrate peeled from the group III nitride crystal. 3 is a schematic diagram illustrating an example of a main part of an apparatus configuration of a method for producing a group III nitride crystal described in Non-Patent Document 1. It is the schematic which shows an example of the principal part of the apparatus structure of Experimental example 1. FIG. It is the schematic which shows an example of the principal part of the apparatus structure of Experimental example 2. FIG.

The method for producing a group III nitride crystal according to the first aspect includes:
(I) preparing a seed substrate having sapphire as a base substrate and having a group III nitride layer provided on the base substrate;
(Ii) growing a group III nitride crystal on the group III nitride layer provided on the seed substrate using a mixed melt of a group III element and an alkali metal;
(Iii) introducing lithium oxide into the mixed melt before cooling to react with the base substrate;
including.

For the order of the above steps, for example,
(1) A step of preparing a seed substrate in which sapphire is used as a base substrate and a group III nitride film is provided on the base substrate;
(2) a step of preparing the metal and additive constituting the raw material mixed melt in the crucible;
(3) a step of preparing lithium oxide in the upper part of the crucible;
(4) preparing a crucible in the apparatus;
(5) A step of bringing the inside of the apparatus into an environment of the temperature and pressure of the growth conditions,
(6) Crystal growth process,
(7) A step of introducing lithium oxide prepared in the upper part of the crucible into the raw material mixed melt,
(8) Reaction process of lithium oxide and sapphire,
(9) cooling process,
It is the order.

  In the method for producing a group III nitride crystal according to a second aspect, in the first aspect, in the step (ii), the group III element is gallium, and the alkali metal is sodium, lithium, or potassium. And the group III nitride crystal may be a GaN crystal.

  In the method for producing a group III nitride crystal according to a third aspect, in the first or second aspect, in the step (ii), the mixed melt may further contain an alkaline earth metal.

  According to the said structure, the effect which suppresses polycrystallization may be acquired by including an alkaline-earth metal.

  In the method for producing a group III nitride crystal according to a fourth aspect, in any one of the first to third aspects, in the step (iii), the amount of the lithium oxide is 7% by weight of the base substrate. It may be 80% by weight or more.

  The method for producing a group III nitride crystal according to a fifth aspect may further include the step of (iv) cooling the grown group III nitride crystal in any one of the first to fourth aspects. Good.

  Hereinafter, a method for producing a group III nitride crystal according to an embodiment will be described with reference to the accompanying drawings. In the drawings, substantially the same members are denoted by the same reference numerals. In all the drawings, the size, ratio, and the like of each component may be different from actual ones.

(Embodiment 1)
Hereinafter, the method for producing a group III nitride crystal according to the first embodiment will be described with reference to an example. 1A is a schematic diagram illustrating an example of a group III nitride crystal growth step in the method for producing a group III nitride crystal according to Embodiment 1. FIG. FIG. 1B is a schematic diagram showing an example of a step of adding lithium oxide 106 to mixed melt 101 and reacting with base substrate 102 in the method for producing a group III nitride crystal according to Embodiment 1. FIG. 1C is a schematic diagram illustrating an example of a state in which the base substrate 102 is separated from the group III nitride crystal 112 in the method for manufacturing the group III nitride crystal according to the first embodiment.

(A) In this method, first, a composition formula Al _u Ga _v In _{1 -uv} N (where 0 ≦ u ≦ 1, 0 ≦ v ≦ 1) is formed on a base substrate 102 made of sapphire. The first group III nitride single crystal layer 103 is formed. A seed substrate 104 is constituted by the base substrate 102 and the first group III nitride layer 103 provided thereon (FIG. 1A). The first group III nitride single crystal layer 103 can be formed by, for example, MOCVD (Metal Organic Chemical Deposition), MBE (Molecular Beam Epitaxy), or HVPE (Hydrogen Vapor Phase Epitaxy). The first group III nitride layer 103 is preferably a single crystal having a main surface (upper surface) of (0001) plane (+ c plane).

(B) Next, a group III nitride crystal is formed on the first group III nitride single crystal layer 103 using the mixed melt 101 in an atmosphere containing nitrogen (preferably a pressurized atmosphere of 100 atm or less). A growth step is performed (FIG. 1A). The mixed melt 101 contains at least one group III element selected from gallium, aluminum, and indium and an alkali metal. In this step, the growth surface side surface of the group III nitride single crystal layer 103 made of the nitride of the selected group III element is brought into contact with the mixed melt 101. As a result, at least one group III element in the mixed melt 101 is reacted with nitrogen dissolved under pressure to grow a group III nitride crystal on the group III nitride single crystal layer 103. As the atmosphere containing nitrogen, for example, a nitrogen gas atmosphere or a nitrogen gas atmosphere containing ammonium can be applied. As the alkali metal, at least one selected from sodium, lithium and potassium, that is, one of them or a mixture thereof is used, and these are usually used in a flux state. Nitrogen molecules in the nitrogen gas supplied by pressurization are separated into nitrogen atoms for the crystal growth reaction and dissolved in the mixed melt 101. Therefore, as an alkali metal constituting the mixed melt 101, for example, sodium May be used. In the first embodiment, it is desirable to grow a group III nitride crystal using a sodium flux method.

  The mixed melt 101 in FIG. 1A is prepared, for example, by putting a material into the crucible container 100 and heating it. In order to promote mixing, the crucible container 100 may perform a swinging motion, a rotational motion, or a combination of both. After producing the mixed melt 101, a group III nitride single crystal grows by bringing the mixed melt 101 into a supersaturated state. In order to promote the supply of nitrogen and improve the reaction rate, the atmosphere containing nitrogen is preferably a pressurized atmosphere. The melting and crystal growth of the material are performed, for example, in an environment where the temperature is about 700 ° C. to 1100 ° C. and the pressure is about 0.1 to 5 megapascals. The mixed melt 101 may further contain an alkaline earth metal. As the alkaline earth metal, for example, calcium, magnesium, strontium, barium, beryllium and the like can be used. Use of these alkaline earth metals has an effect of suppressing the formation of polycrystals.

In this way, the base substrate 102 in configured to formula _{Al s Ga t In 1-st} N ( provided that 0 ≦ s ≦ 1,0 ≦ t ≦ 1) III -nitride crystal 112 represented by sapphire Grow (FIG. 1B). In the group III nitride crystal 112 to be grown, the crystal orientation (0001) plane (+ c plane) is the growth plane (principal plane). The thermal expansion coefficient between the III-nitride crystal represented by sapphire and the composition formula of the base substrate _{102 Al s Ga t In 1-} st N ( provided that 0 ≦ s ≦ 1,0 ≦ t ≦ 1) There is a big difference. When the temperature is lowered to take out the substrate from this step, stress is applied to the group III nitride crystal from the base substrate made of sapphire due to the difference in thermal expansion coefficient. As a result, the group III nitride crystal is warped, and if the stress is large, it leads to cracks or cracks.

(C) Therefore, before cooling, lithium oxide is put into the mixed melt to react sapphire constituting the base substrate 102 with the lithium oxide 106 (FIG. 1B). For example, all or part of the base substrate 102 can be dissolved. Thus, the base substrate 102 can be peeled off from the group III nitride crystal, or the bond between the base substrate 102 and the group III nitride crystal 112 can be weakened (FIG. 1C).

At this time, it is desirable that the amount of lithium oxide to be input is 7 wt% or more and 80 wt% or less with respect to the weight of the base substrate 102 made of sapphire to be reacted. When the amount is less than 7% by weight, the reaction (dissolution) amount of sapphire is not sufficient, and the group III nitride crystal is not peeled from the base substrate 102 made of sapphire. For this reason, stress from the base substrate 102 made of sapphire is applied to the group III nitride crystal, causing the group III nitride crystal to warp. Further, when the amount is more than 80% by weight, the lithium oxide is left by dissolution of the base substrate 102 made of sapphire. In this case, the excessive lithium oxide accelerates the decomposition of the group III nitride crystal, and the growth thickness of the group III nitride crystal decreases, which is not desirable. This upper limit (80 wt%) is obtained by converting the amount of Li (12 wt%) required to completely dissolve sapphire into Li ₂ O (24 wt%), the weight of lithium and the empirical utilization efficiency of lithium oxide 30 % And calculated. In order to accelerate the sapphire dissolution reaction, it is possible to raise the environmental temperature above the growth temperature of the group III nitride crystal. In addition, the result that the influence by Li concentration was not seen was obtained in Li concentration with respect to mixed melt in the range of 5 mol% to 15 mol%. Therefore, it is speculated that the total amount of lithium oxide to be dissolved should be in the above range regardless of the Li concentration.

  In this construction method, in order to prevent in-furnace contamination due to evaporation of the mixed melt at the time of pressurization and temperature rise with nitrogen, the crucible container 100 containing the mixed melt for crystal growth is contained in the mixed melt 101. No gap is provided except for a vent hole having a diameter of about 1 millimeter (1 mm) for supplying nitrogen to the seed substrate 104. In order to put the lithium oxide 106 into the mixed melt 101, the lithium oxide 106 is disposed in the vicinity of the mixed melt 101 inside the crucible container 100 containing the mixed melt 101. After growing the group III nitride crystal, the lithium oxide 106 is put into the mixed melt 101. In the process of holding the lithium oxide 106 with the jig (lithium oxide holder) 107 on the upper part of the mixed melt 101 during the growth and melting the base substrate 102 made of sapphire, the jig 107 is tilted or submerged. Thus, the lithium oxide 106 can be introduced into the mixed melt 101. At this time, the jig 107 is preferably made of a material having low reactivity with the lithium oxide 106, and for example, tantalum may be used.

Here, the reason for using lithium oxide instead of metallic lithium in this production method will be described. Since the melting point of metallic lithium is 180 ° C., it is considered that if metallic lithium is placed on the jig 107, it will be liquefied at the growth temperature of the group III nitride crystal and partially evaporated to cause contamination in the furnace. On the other hand, the melting point of lithium oxide is 1570 ° C., and it exists as a solid even under the growth temperature of the group III nitride crystal. Moreover, metallic lithium reacts with nitrogen under the growth conditions (temperature, pressure) of the group III nitride crystal. On the other hand, lithium oxide does not react with nitrogen under these conditions. Therefore, in this method, by using lithium oxide instead of metallic lithium, the contamination in the furnace and the reaction with nitrogen are prevented, thereby preventing the group III nitride crystal growth from being affected. be able to.
At this time, as will be described later, the inventors of the present invention similarly used the lithium oxide 106 to form the base substrate 102 made of sapphire in any of a powder state, a pressed state, and a sintered state. It has been found to have the ability to dissolve.

According to this method, the composition formula _{Al s Ga t In 1-st} N ( However, 0 ≦ s ≦ 1,0 ≦ t ≦ 1) III Group represented by nitride crystals are obtained. For example, a gallium nitride crystal can be obtained by using only gallium as a group III element as a material. For example, by using gallium and aluminum as a group III element as a material, a crystal represented by a composition formula Al _s Ga _1-s N (where 0 ≦ s ≦ 1) is obtained.

(Experimental example 1)
The configuration of this experimental example 1 is shown in FIG. This Experimental Example 1 is an element verification experiment on the corrosion of a jig (jig) due to evaporation of lithium. Specifically, lithium oxide 106 is placed on the bottom of a crucible container 100 made of alumina having an inner diameter of 19 mm, a crucible lid 108 made of alumina is used, and 870 is the same as that when growing a group III nitride single crystal. The sample was kept for 48 hours in an environment of 40 ° C., and the discoloration of the crucible lid 108 member was evaluated.

(Comparative Example 1)
Lithium nitride was installed instead of lithium oxide, and the other conditions were the same as in Experimental Example 1.

(Comparative Example 2)
Metal lithium and gallium were installed instead of lithium oxide, and the other conditions were the same as in Experimental Example 1.

(Comparative Example 3)
Instead of lithium oxide, lithium and gallium were heated and alloyed at 400 ° C., and the rest was the same as in Experimental Example 1.

  Table 1 shows the results of evaluating the corrosion of the crucible lid 108 made of an alumina member with each lithium compound under the conditions of Experimental Example 1 and Comparative Examples 1 to 3.

  From the above experiment, it was confirmed that the corrosion of the constituent members of the crucible container can be prevented by using lithium oxide.

(Experimental example 2)
The configuration of this experimental example 2 is shown in FIG. In this Experimental Example 2, an element verification experiment was conducted on the ability of sapphire dissolution with lithium oxide. The experiment was performed according to the following procedure.
(A) A sapphire substrate with a thickness of 2 millimeters was prepared with a square having a side of 10 millimeters as the bottom.
(B) The sapphire substrate was placed on the bottom of a crucible container with an inner diameter of 19 mm containing a mixed melt composed of a Group III element melt and an alkali metal melt.
(C) Next, powdery lithium oxide having a weight of 10% of the sapphire substrate was put into the mixed melt, and pressurization and heating were performed. The constituent elements of the mixed melt 101 of the Group III element melt and the alkali metal melt were gallium as the Group III element and sodium as the alkali metal, and the liquid height was 20 millimeters. The crucible container having the above configuration was held at 870 ° C. and 40 atm for 48 hours, then cooled to 30 ° C., and the weight of the sapphire substrate after removal was evaluated.

(Experimental example 3)
The state of the lithium oxide to be added was set to a state in which the powder was pressed instead of the powder, and the other conditions were the same as in Experimental Example 2.

(Experimental example 4)
The state of the lithium oxide to be added was set to a state in which the powder was sintered and hardened instead of the powder, and the other conditions were the same as in Experimental Example 2.

(Experimental example 5)
The holding time at 870 ° C. and 40 atm was 240 hours, and the other conditions were the same as in Experimental Example 2.

(Experimental example 6)
The lithium oxide to be added was 100% by weight of the sapphire substrate, the holding time at 870 ° C. and 40 atm was 240 hours, and the other conditions were the same as in Experimental Example 2.

  Table 2 shows the results of evaluating the amount of sapphire dissolved under the conditions of Experimental Example 2 to Experimental Example 6.

  From Experimental Examples 2 to 6, it was confirmed that sapphire in the mixed melt under crystal growth conditions can be dissolved using lithium oxide. Moreover, it was confirmed that lithium oxide can dissolve sapphire in any of a powder state, a compacted state, and a sintered state. In addition, it was found that the amount of sapphire dissolved tends to be increased by increasing the dissolution time and the amount of lithium oxide to be charged within the range of this experiment.

(Example 1)
(A) In order to conduct an experiment of sapphire dissolution after group III nitride crystal growth, an experiment was conducted with the configuration of FIG. 1 using 7 weight percent lithium oxide based on the weight of sapphire. A base substrate composed of sapphire and a mixed melt of gallium and sodium are placed in a crucible container composed of alumina with an inner diameter of 19 mm, and a crucible with an inner diameter of 9 mm composed of tantalum on the mixed melt. And lithium oxide in it.
(B) With the above configuration, a group III nitride single crystal was grown for 24 hours in a growth environment of 870 ° C. and 40 atm.
(C) Thereafter, a tantalum crucible containing lithium oxide was put into the mixed melt and kept at 900 ° C. for 24 hours. Here, the setting of temperature and pressure conditions in the sapphire dissolution process will be described. It has been reported that the higher the temperature, the higher the dissolution rate of sapphire by lithium (Non-Patent Document 1), but based on the results of small pressure vessels currently used, the temperature is higher than 900 ° C. to 40 atm. It was considered difficult to pressurize from the viewpoint of safety, and the above temperature condition was adopted. Moreover, about the pressure conditions in a sapphire reaction (dissolution) process, evaporation of mixed melt was suppressed by setting it as the same pressure as the time of a growth.

(Example 2)
30 weight percent lithium oxide based on the sapphire weight was used, and the other conditions were the same as in Example 1.

(Comparative Example 4)
The amount of lithium oxide to be added was 1 weight percent of the sapphire substrate, and the other conditions were the same as in Example 1.

  Table 3 shows the results of evaluating whether or not the base substrate made of sapphire is peeled off from the group III nitride single crystal grown under the conditions of Example 1, Example 2, and Comparative Example 4.

  According to the results of Examples 1 and 2 and Comparative Example 4, the group III nitride single crystal substrate cooled without melting sapphire had a radius of curvature of 1 meter, but succeeded in peeling. The warpage of the group III nitride single crystal substrate was reduced to 20 meters in terms of the radius of curvature.

  It should be noted that the present disclosure includes appropriately combining any of the various embodiments and / or examples described above, and each of the embodiments and / or examples. The effect which an Example has can be show | played.

  As described above, when the group III nitride crystal manufacturing method according to the present invention is used, a group III nitride crystal applicable to a heterojunction high-speed electronic device such as a power semiconductor field or an optoelectronic device such as an LED or laser field is obtained. Obtainable.

100 crucible container 101 mixed melt 102 base substrate 103 group III nitride layer 104 seed substrate 105 mixed melt 106 containing lithium oxide 106 lithium oxide 107 jig (lithium oxide holder)
108 crucible lid 110 jig (metal lithium holder)
111 Lithium metal or lithium alloy 112 Group III nitride crystal

Claims (5)

(I) preparing a seed substrate having sapphire as a base substrate and having a group III nitride layer provided on the base substrate;
(Ii) growing a group III nitride crystal on the group III nitride layer provided on the seed substrate using a mixed melt of a group III element and an alkali metal;
(Iii) introducing lithium oxide into the mixed melt before cooling to react with the base substrate;
A method for producing a group III nitride crystal containing In the step (ii),
The group III nitride according to claim 1, wherein the group III element is gallium, the alkali metal is at least one selected from sodium, lithium and potassium, and the group III nitride crystal is a GaN crystal. Method for producing physical crystals. In the step (ii),
The method for producing a group III nitride crystal according to claim 1 or 2, wherein the mixed melt further contains an alkaline earth metal. In the step (iii),
4. The method for producing a group III nitride crystal according to claim 1, wherein an amount of the lithium oxide is not less than 7 wt% and not more than 80 wt% of the weight of the base substrate. 5. (Iv) The method for producing a group III nitride crystal according to any one of claims 1 to 4, further comprising a step of cooling the grown group III nitride crystal.

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