JP6390157B2 - Method for producing group 13 nitride crystal - Google Patents

Description

  The present invention relates to a method for producing a group 13 nitride crystal and a group 13 nitride crystal.

  As one of the techniques for manufacturing a GaN substrate using the liquid phase growth method, a flux method is disclosed in which nitrogen is dissolved in a mixed melt of metallic sodium and metallic Ga to grow GaN crystals. The flux method is capable of crystal growth at a relatively low temperature of 700 ° C. to 900 ° C., and the internal pressure of the vessel is relatively low at about 3 MPa to 8 MPa.

  A method of manufacturing a GaN substrate using this flux method is disclosed (for example, see Patent Documents 1 to 3). Patent Document 1 discloses a method of growing a crystal by changing the stirring condition of the melt when the crystal is grown on the substrate. Patent Document 2 discloses that a patterned mask film is formed on a semiconductor layer, and a group 13 nitride crystal is grown in layers using the semiconductor layer exposed from the mask film as a seed crystal. Patent Document 3 discloses a method in which a semiconductor crystal is grown in layers in the a-axis direction on the a-plane of a seed crystal.

  In addition, as a method for manufacturing a polar substrate or a nonpolar substrate using the flux method, a nitride crystal is grown on the c plane and is grown in the c-axis direction, so that it is used for a semipolar substrate or a nonpolar substrate. Manufacturing bulk crystals of group nitride crystals is disclosed.

  However, when the crystal is grown in the c-axis direction, melt components such as metal sodium, metal gallium, or a mixture of sodium and gallium are likely to enter the crystal as crystals during crystal growth. For this reason, conventionally, it was necessary to stir the mixed melt during crystal growth. For this reason, it has been difficult to produce a group 13 nitride crystal in which inclusion is suppressed using the flux method.

  In order to solve the above-described problems, the present invention dissolves nitrogen from a gas phase in a mixed melt containing at least an alkali metal and a group 13 metal held in a reaction vessel. In the method for producing a group 13 nitride crystal in which a group 13 nitride crystal is grown, the reaction vessel has a long groove portion in the first direction in a first region in contact with the mixed melt inside the reaction vessel. A strip-shaped first crystal whose main surface is the (0001) plane, which is a crystal plane in which a group 13 nitride crystal grows by c-axis orientation, and whose longitudinal direction is substantially parallel to the a axis of the group 13 nitride crystal that grows. A first step of preparing a seed crystal, a second step of disposing the first seed crystal in the groove so that the principal surface of the first seed crystal faces the opening side of the groove, and the mixing The first seed crystal disposed in the groove in the melt A third step of starting crystal growth of a group 13 nitride crystal from the main surface, and a {10-11} surface of the group 13 nitride crystal starting crystal growth from the main surface as a main growth surface {10-11 } The fourth step of continuing the crystal growth while expanding the area of the surface. A method for producing a group 13 nitride crystal.

  According to the present invention, a group 13 nitride crystal in which inclusion is suppressed can be produced using a flux method.

FIG. 1 is a diagram illustrating a base substrate on which grooves are formed according to the embodiment. FIG. 2 is an explanatory diagram of the first seed crystal according to the embodiment. FIG. 3 is an explanatory diagram of the manufacturing process of the group 13 nitride crystal of the embodiment. FIG. 4 is a schematic diagram of the group 13 nitride crystal of the embodiment. FIG. 5 is a schematic diagram of the group 13 nitride crystal of the embodiment. FIG. 6 is a schematic diagram of a manufacturing apparatus according to the embodiment. FIG. 7 is an explanatory diagram of the base substrate according to the embodiment. FIG. 8 is an explanatory diagram of the base substrate according to the embodiment. FIG. 9 is an explanatory diagram of the manufacturing process of the group 13 nitride crystal of the embodiment. FIG. 10 is a schematic diagram showing a group 13 nitride crystal of the embodiment. FIG. 11 is a schematic diagram showing a group 13 nitride crystal of the embodiment. FIG. 12 is an explanatory diagram of the base substrate according to the embodiment. FIG. 13 is an explanatory diagram of the base substrate according to the embodiment. FIG. 14 is an explanatory diagram of the manufacturing process of the group 13 nitride crystal of the embodiment. FIG. 15 is a schematic diagram of the group 13 nitride crystal of the embodiment. FIG. 16 is a schematic diagram of the group 13 nitride crystal of the embodiment. FIG. 17 is an explanatory diagram of the base substrate according to the embodiment. FIG. 18 is an explanatory diagram of the base substrate according to the embodiment. FIG. 19 is an explanatory diagram of the manufacturing process of the group 13 nitride crystal of the embodiment. FIG. 20 is a schematic diagram showing a group 13 nitride crystal of the embodiment. FIG. 21 is a schematic diagram showing a group 13 nitride crystal of the embodiment.

  Hereinafter, a method for producing a group 13 nitride crystal and a group 13 nitride crystal according to the present embodiment will be described with reference to the accompanying drawings. In the following description, the drawings schematically show the shape, size, and arrangement of the components to the extent that the invention can be understood. For this reason, the present invention is not particularly limited by the contents described in the drawings. Moreover, the same code | symbol may be attached | subjected to the same component shown by several figures, and the overlapping description may be abbreviate | omitted.

(Embodiment 1)
In the method for producing a group 13 nitride crystal according to the present embodiment, nitrogen is dissolved from a gas phase in a mixed melt containing at least an alkali metal and a group 13 metal held in a reaction vessel, This is a method for producing a group 13 nitride crystal in which a nitride crystal is grown. That is, the manufacturing method of the group 13 nitride crystal of the present embodiment is a manufacturing method using a flux method.

  The reaction vessel used in the method for producing a group 13 nitride crystal of the present embodiment has a groove that is long in the first direction in the first region in contact with the mixed melt inside the reaction vessel. The first direction may be any direction inside the reaction vessel, and is not limited to one direction.

  The method for producing a group 13 nitride crystal of the present embodiment includes at least a first step, a second step, a third step, and a fourth step in this order. The first step is a step of preparing the first seed crystal. The first seed crystal has a (0001) plane, which is a crystal plane in which a group 13 nitride crystal grows by c-axis orientation, and the longitudinal direction is substantially parallel to the a axis of the group 13 nitride crystal. This is a strip-shaped crystal.

  The second step is a step of disposing the first seed crystal in the groove so that the main surface of the first seed crystal faces the opening side of the groove. The third step is a step of starting crystal growth of the group 13 nitride crystal from the main surface of the first seed crystal disposed in the groove in the mixed melt. The fourth step is to grow the crystal while increasing the area of the {10-11} plane with the {10-11} plane of the group 13 nitride crystal starting from the main plane of the first seed crystal as the main growth plane. Is a process of continuing.

  In the method for producing a group 13 nitride crystal of the present embodiment, inclusion is suppressed by including the first step, the second step, the third step, and the fourth step in this order using the specific reaction vessel. It is considered that a group 13 nitride crystal used for manufacturing a semipolar substrate or a nonpolar substrate formed can be obtained.

  The reason for the above effect is not clear, but is presumed as follows. However, the present invention is not limited by the following estimation.

  In the present embodiment, the first seed crystal is arranged in the groove so that the main surface of the first seed crystal faces the opening side of the groove. For this reason, in the first seed crystal, the (000-1) plane, which is the opposing surface of the (0001) plane that is the main surface, is in a state of facing the bottom side (opposite opening side) of the groove. That is, the space in contact with the (0001) plane side of the first seed crystal is larger than the space in contact with the (000-1) plane side of the first crystal in the space where the mixed melt in the reaction vessel is held. Becomes larger.

  For this reason, in the present embodiment, the crystal growth of the first seed crystal in the [000-1] axis direction is limited as compared with the crystal growth in the [0001] axis direction.

  That is, in the present embodiment, the groove has a function of limiting the crystal growth of the first seed crystal in the [000-1] axis direction. The group 13 nitride crystal that has started crystal growth from the (0001) plane, which is the main surface of the first seed crystal, has the {10-11} plane as the main growth plane and the area of the {10-11} plane is expanded. Crystal growth is continued.

  The {10-11} plane tends to be a flat crystal plane. For this reason, it is thought that inclusion is taken in into a crystal | crystallization.

  In addition, the (000-1) plane, which is a nitrogen polar plane, is considered to be easily polycrystallized due to polarity reversal or adhesion of microcrystals. For this reason, if the crystal growth on the (000-1) plane side proceeds, it may cause the roughness of the {10-11} plane. That is, the space in contact with the (0001) plane side of the first seed crystal is larger than the space in contact with the (000-1) plane side of the first crystal in the space where the mixed melt in the reaction vessel is held. If it is narrow, it may cause roughness of the {10-11} plane of the grown group 13 nitride crystal.

  On the other hand, in the present embodiment, the (0001) plane of the first seed crystal is larger than the space in contact with the (000-1) plane side of the first seed crystal in the space where the mixed melt in the reaction vessel is held. The space that touches the side is larger. For this reason, in the present embodiment, the crystal growth of the first seed crystal in the [000-1] axis direction is limited as compared with the crystal growth in the [0001] axis direction. For this reason, crystal growth on the (000-1) plane side can be suppressed. In this embodiment, since the formation of the (000-1) plane itself can also be suppressed, polycrystallization due to polarity reversal or adhesion of microcrystals does not occur, and continuous {10-11} planes Roughness can be suppressed.

  For the reasons described above, in the method for producing a group 13 nitride crystal of the present embodiment, the melt by means such as stirring required in the conventional flux method liquid phase epitaxial growth in which crystal growth is performed with the c-plane as the main growth surface. It is considered that a group 13 nitride crystal with reduced inclusion can be produced without precise control of the above.

  Therefore, in this Embodiment, it is estimated that the group 13 nitride crystal | crystallization with which inclusion was suppressed can be manufactured using a flux method.

  In this embodiment, a long strip-shaped crystal is used as the first seed crystal. For this reason, the time required for crystal growth for obtaining a larger group 13 nitride crystal can be shortened.

  Further, in the present embodiment, unlike a crystal manufacturing method in which a plurality of crystal start regions are formed on a substrate and adjacent crystals grown therefrom are combined to increase the size, crystal growth is performed from one first seed crystal. By doing so, a group 13 nitride crystal is produced. Therefore, a high-quality group 13 nitride crystal can be produced with no distortion or defects.

  Also, the first seed crystal is placed in the groove, and crystal growth is started from the main surface which is the (0001) plane. For this reason, the crystal region (sector) grown in the [10-11] direction or the [-1101] direction can be made larger.

  In addition, the group 13 nitride crystal obtained by the manufacturing method of the present embodiment has a group 13 nitride formed by forming a plurality of crystal start regions on a substrate and combining adjacent crystals grown therefrom to increase the size. Unlike a crystal, it is a crystal obtained by crystal growth from one first-type crystal. For this reason, inclusion is suppressed, and a high-quality group 13 nitride single crystal is obtained without the occurrence of distortion or defects.

  In the present embodiment, the a-axis and c-axis indicating the crystal axis of the periodic table group 13 metal nitride crystal having a hexagonal crystal structure (wurtzite type crystal structure) are opposite to the positive direction of each crystal axis. Regarding the notation indicating the direction, the notation “−” is used. For example, the [000-1] axis in the c-axis indicates the reverse direction of the [0001] axis. As described above, in the present embodiment, when the reverse direction is indicated, “−1” is used in which a negative sign is added before a number (for example, “1”).

  Details will be described below.

  First, the reaction vessel will be described. In the present embodiment, the reaction vessel includes a groove portion that is long in the first direction in the first region in contact with the mixed melt inside the reaction vessel. The groove may be formed directly on the inner wall of the reaction vessel, or a base substrate having a groove formed on the inner wall of the reaction vessel. Moreover, you may comprise a groove part combining the jig | tool of arbitrary shapes.

  The groove part should just be a shape opened to the inner side of the reaction vessel and elongated in the first direction. However, at least one of the groove portion and the region continuing to the groove portion in the first region is a {10-11} plane of a group 13 nitride crystal grown from the main surface of the first seed crystal disposed in the groove portion. It is a shape that enables crystal growth while expanding the area. In other words, at least one of the groove portion and the region continuing to the groove portion in the first region has the group 13 nitride crystal that has started crystal growth from the main surface in the fourth step directed from the inside of the groove portion or from the inside of the groove portion to the outside of the groove portion. This is a shape that enables crystal growth while expanding the area of the {10-11} plane outside the groove where the crystal has grown.

  That is, the groove is adjusted to a shape in a range that satisfies this characteristic. That is, the shape of the groove portion is adjusted in advance so as to satisfy this characteristic (that is, the angle, depth, size, etc. of the surface constituting the groove portion). In addition, the region in the first region that is continuous with the groove is also adjusted in advance so as to satisfy the above characteristics. For example, the cross-sectional shape in the orthogonal direction orthogonal to the first direction may be any of an arc shape, a V shape, a rectangular shape, a shape combining an arc and a rectangle, or the like. Moreover, it is preferable that the area | region continuous to the groove part in a 1st area | region is adjusted beforehand so that it may become parallel to the (0001) plane of a group 13 nitride crystal, for example.

  In addition, a groove part is not limited to the form comprised by one member. The groove part may be formed of a plurality of members. For example, the groove portion is not limited to a form in which a bottom surface and two wall surfaces continuous to the bottom surface are continuously and integrally configured, and includes three members (a bottom surface and two wall surfaces continuous to the bottom surface). It may be in the form. In the present embodiment, as an example, a case will be described in which the groove portion is configured by one member.

  The position of the groove portion in the reaction vessel may be any first region as long as it is in contact with the held mixed melt. For example, the groove may be formed on the inner wall of the reaction vessel, may be formed on the bottom inside the reaction vessel, or may be formed on various support members installed in the reaction vessel. It may be formed in the form.

  In this embodiment, as an example, a case will be described in which a base substrate having a groove portion having a V-shaped cross-sectional shape orthogonal to the first direction is installed at the bottom inside the reaction vessel.

  FIG. 1 is an explanatory diagram showing an example of the base substrate 27 in which the groove 27A is formed. As shown in FIG. 1A, a groove 27A that is long in the first direction (the Y direction in FIG. 1A) is formed in the base substrate 27. The groove 27A is manufactured by forming two V-shaped surfaces (surface 27B and surface 27C) on the base substrate 27.

  As shown in FIGS. 1A and 1B, the first seed crystal 100 is arranged in the groove 27A so that the main surface 100A of the first seed crystal 100 faces the opening side of the groove 27A. (Details will be described later).

  The depth of the groove 27 </ b> A is preferably larger than the thickness of the first seed crystal 100. The depth of the groove portion 27A indicates the length from the position of the tangent to the opening of the groove portion 27A in a straight line passing through the tangent line between the surface 27B and the surface 27C in the groove portion 27A. The thickness of the first seed crystal 100 indicates the length between the main surface and the opposing surface of the first seed crystal 100. Details of the first seed crystal 100 will be described later.

  The length in the first direction Y of the groove portion 27A is preferably longer than the length in the longitudinal direction of the first seed crystal 100 arranged in the groove portion 27A.

  The angle (refer to θA in FIG. 1B) formed by the two surfaces (surface 27B, surface 27C) constituting the groove 27A is not limited, but if it is too small, it grows in contact with the mixed melt {10-11 } The surface area is reduced. The angle (refer to θA in FIG. 1B) formed by the two surfaces (surface 27B, surface 27C) constituting the groove portion 27A is the suppression of adhesion of microcrystals to the (000-1) plane of the growing crystal, In order to prevent the area of the {10-11} plane from becoming too small, it is preferably in the range of 56 ° to 164 °, more preferably in the range of 118 ° to 146 °.

  In the example shown in FIG. 1, as an example, the case where the angle (see θA in FIG. 1B) formed by the two surfaces (surface 27 </ b> B, surface 27 </ b> C) forming the groove 27 </ b> A is 120 °.

  The material of the base substrate 27 having the groove 27A may be any material as long as the group 13 nitride is less likely to nucleate. In the case where the groove 27A is directly provided on the inner wall of the reaction vessel, the inner wall of the reaction vessel may be made of the material. As the material of the base substrate 27 and the inner wall of the reaction vessel, for example, a BN sintered body, a nitride such as P-BN, an oxide such as alumina or YAG, a carbide such as SiC or TaC, or the like is used.

  One groove portion 27A or a plurality of groove portions 27A may be formed in the reaction vessel. When a plurality of groove portions 27A are formed, the groove portions 27A are preferably arranged in a direction intersecting the first direction that is the longitudinal direction of the groove portions 27A. In this case, the spacing in the arrangement direction of the grooves 27A is such that the group 13 nitride crystals grown from the first seed crystal 100 installed in the grooves 27A do not contact each other during the crystal growth. What is necessary is just to adjust according to the magnitude | size of the group 13 nitride crystal to crystal-grow.

  By adjusting the interval between the adjacent groove portions 27A so as to be spaced apart from each other, it is possible to suppress the occurrence of distortion and defects caused by the adjacent group 13 nitride crystal grown during crystal growth.

  Next, the first step will be described. In the first step, the first seed crystal 100 is prepared. The first seed crystal 100 has a (0001) plane, which is a crystal plane on which a group 13 nitride crystal grows by c-axis orientation, and is substantially parallel to the a axis of the group 13 nitride crystal in which the longitudinal direction grows. It is a strip-like crystal.

  FIG. 2 is an explanatory diagram of the first seed crystal 100. FIG. 2A is a schematic view of the first seed crystal 100 viewed from the main surface 100A side. FIG. 2B is a cross-sectional view taken along the line A-A ′ of FIG. The first seed crystal 100 has a main surface 100A as a crystal plane on which a nitride crystal grows by c-axis orientation.

  As shown in FIG. 2, the first seed crystal 100 has a strip shape that is long in the a-axis direction. That is, the longitudinal direction of the first seed crystal 100 is parallel to or substantially parallel to the a-axis of the group 13 nitride crystal grown from the main surface 100A of the first seed crystal 100. In other words, the orthogonal direction orthogonal to the longitudinal direction on the main surface 100A of the first seed crystal 100 is parallel to or substantially parallel to the m-axis. Note that “substantially parallel” means that a deviation of ± 2 ° is included.

  The length of the first seed crystal 100 in the longitudinal direction is not particularly limited as long as it can be installed in the groove 27A. As the length of the first seed crystal 100 in the longitudinal direction is longer, a larger group 13 nitride crystal can be produced in a shorter time. For this reason, what is necessary is just to adjust the length of the 1st seed crystal 100 in the longitudinal direction beforehand according to the target manufacturing time etc. by the length which can be installed in the groove part 27A.

  The length (hereinafter referred to as the width) in the orthogonal direction orthogonal to the longitudinal direction on the main surface 100A of the first seed crystal 100 may be a size that can be installed in the groove 27A, and may be adjusted as appropriate. . As the width of main surface 100A of first seed crystal 100 increases, the c-plane of group 13 nitride crystal is more likely to be formed. For this reason, since the raw material is used for the growth of the c-plane as the width of the first seed crystal 100 on the main surface 100A increases, the crystal growth rate becomes slower. Moreover, since unevenness | corrugation is easy to be formed in c surface, inclusion (metal gallium, metal sodium, those compounds, etc.) becomes easy to enter. For this reason, it is preferable that the width of the main surface 100A of the first seed crystal 100 is not made larger than necessary, and specifically, it is preferable to be in the following range.

  Specifically, the width of main surface 100A of first seed crystal 100 is preferably 5 mm or less, more preferably 2 mm or less, and particularly preferably 1 mm or less. The lower limit value of the width may be adjusted as appropriate according to the ease of handling the first seed crystal 100.

  The material of the first seed crystal 100 is not particularly limited as long as the main surface 100A is a crystal plane on which a nitride crystal grows by c-axis orientation. The main surface 100A in the first seed crystal 100 is the (0001) plane among the four long surfaces along the a-axis direction in the strip-shaped first seed crystal 100.

  The first seed crystal 100 only needs to satisfy the above conditions, and may be a single crystal of the same material as a whole, or may be a stacked body in which the main surface 100A is stacked so as to satisfy the above conditions. .

  The formation method of the 1st seed crystal 100 is not specifically limited, It can select suitably. For example, a template substrate is produced by epitaxially growing a group 13 nitride crystal on the main surface of a different substrate. And it is good also as the 1st seed crystal 100 by cutting out this template board | substrate in strip shape.

  FIG. 2B shows an example of the first seed crystal 100 configured as a stacked body. In the example shown in FIG. 2B, the first seed crystal 100 is a stacked body in which a group 13 nitride crystal 102 is stacked on a heterogeneous substrate 101.

The material of the different substrate 101 is not particularly limited. For the dissimilar substrate 101, for example, a material in which a group 13 nitride is difficult to nucleate is used. Specifically, a single crystal substrate such as sapphire, SiC, ZnO, or MgAl ₂ O ₄ is used for the different substrate 101.

  As the first seed crystal 100, it is preferable to cut a free-standing substrate of the group 13 nitride crystal 102 from which the heterogeneous substrate 101 is removed into a strip shape, and use the cut crystal. This is because the thermal expansion coefficient of the group 13 nitride crystal to be grown on the first seed crystal 100 and the first seed crystal 100 is taken into consideration in the third step and the fourth step described later.

  Further, a group 13 nitride crystal produced by LPE by the Na Flux method is cut into a strip shape on the template substrate or the group 13 nitride crystal 102 free-standing substrate, and the cut crystal is a first type crystal. It is preferable to use as 100.

  Further, a bulk crystal is produced by crystal growth under the same conditions as the crystal growth in the third step and the fourth step described later (for example, Na flux method using Na as an alkali metal), and the bulk crystal is formed into a strip shape. The first seed crystal 100 may be manufactured by processing. Since the first seed crystal 100 manufactured by this manufacturing method is the longest crystal without using a heterogeneous substrate, the residual stress and warpage are small. In addition, the first seed crystal 100 manufactured by this manufacturing method has a large radius of curvature, and the c-axis and a-axis are aligned. Moreover, the dislocation density of the c-plane which is the main surface is also small. For this reason, it is preferable to use the first seed crystal 100 manufactured by this manufacturing method from the viewpoint of crystal growth of a higher quality group 13 nitride crystal.

  Next, the second step will be described.

  Returning to FIG. 1, the second step is a step of disposing the first seed crystal 100 in the groove 27A so that the main surface 100A of the first seed crystal 100 faces the opening side of the groove 27A.

  At this time, it is preferable to place the first seed crystal 100 in the groove 27A so that the longitudinal direction (a-axis direction) of the first seed crystal 100 substantially coincides with the first direction Y of the groove 27A.

  The two directions substantially coincide with each other means that a deviation of ± 5 ° is included. In the present embodiment, the main surface 100A faces the opening side of the groove portion 27A, and the first seed crystal 100 is installed in the groove portion 27A, whereby the two surfaces (surface 27B, surface 27C) constituting the groove portion 27A. The case where the first seed crystal 100 is arranged so as to straddle the tangent line will be described. For this reason, the first seed crystal 100 is supported by the surfaces 27B and 27C via both end portions in the m-axis direction of the opposing surface 100B of the first seed crystal 100 (see FIG. 1).

  In the present embodiment, the longitudinal direction (a-axis direction) of the first seed crystal 100, the first direction Y of the groove portion 27A, and the tangent line 27D of the two surfaces (surface 27B, surface 27C) constituting the groove portion 27A , Will be described in the same direction.

  Next, the third step will be described.

  The third step starts crystal growth of a group 13 nitride crystal from the main surface 100A of the first seed crystal 100 arranged in the groove 27A in the mixed melt.

  FIG. 3 is an explanatory diagram of the manufacturing process of the group 13 nitride crystal of the present embodiment. In FIG. 3, as an example, the angle formed between the surface 27B and the surface 27C (see θA in FIG. 3) in the base substrate 27 is 120 °, and the angle formed between each of the surfaces 27B and 27C and the straight line Z. The case where 60 ° (see θB in FIG. 3) is shown.

  Through the second step, the first seed crystal 100 is disposed in the groove 27A so that the main surface 100A faces the opening side of the groove 27A (see FIG. 3A).

  As shown in FIG. 3B, in the third step, a mixed melt 24 is formed in a reaction vessel (not shown), and nitrogen is dissolved from the gas phase. Crystal growth of group 13 nitride crystal 103 is started from main surface 100A of seed crystal 100.

  The mixed melt 24 includes a flux and a raw material such as a group 13 metal.

  As the flux, sodium or a sodium compound (for example, sodium azide) is used. As another example, other alkali metals such as lithium and potassium, and compounds of the alkali metals may be used. Moreover, you may use alkaline earth metals, such as barium, strontium, and magnesium, and the compound of the said alkaline earth metal as a flux. Note that a plurality of types of alkali metals or alkaline earth metals may be mixed and used as the flux.

  As the Group 13 metal used as a raw material, gallium is preferably used, but as another example, other Group 13 metals such as boron, aluminum, and indium, or a mixture thereof may be used.

In the mixed melt 24, a dopant substance such as Ge, Mg, Fe, Mn, and O (a simple substance or a compound such as B ₂ O ₃ ), an alkaline earth metal serving as a flux such as Ca, Ba, and Sr, Carbon having an effect of reducing miscellaneous crystals may be mixed.

  Nitrogen gas is generally used as nitrogen in the gas phase, but ammonia or other gas containing nitrogen can be used. In addition to the gas containing nitrogen, an inert gas such as Ar or other gas can be mixed in the gas phase.

  In the third step, a flux and a Group 13 metal as a raw material are placed in a reaction vessel in which the first seed crystal 100 is installed, and the temperature is raised to the crystal growth temperature in the pressure vessel.

  In this temperature raising process, the reaction vessel may not be filled with the nitrogen source gas, but in order to prevent the dissolution of the first seed crystal 100 as much as possible, it is desirable to fill the nitrogen source gas and raise the temperature. In this temperature rising process, the flux (for example, alkali metal) and the group 13 metal are dissolved to form a mixed melt 24.

  Then, under a predetermined crystal growth temperature and a predetermined nitrogen raw material gas pressure, nitrogen dissolved in the mixed melt 24 from the gas phase reacts with the group 13 metal in the mixed melt 24 to form the first seed crystal. Crystal growth of a group 13 nitride crystal is started from 100 main surfaces 100A.

  This crystal growth is started by adjusting the nitrogen partial pressure, the temperature of the mixed melt, the molar ratio of the raw material to the flux, etc. to the conditions under which the group 13 nitride crystal starts to grow. Is done.

  Specifically, in the second step, the nitrogen partial pressure is preferably in the range of 1 MPa to 6 MPa. In the second step, the temperature of the mixed melt (crystal growth temperature) is preferably in the range of 800 ° C to 900 ° C.

  For example, the ratio of the number of moles of alkali metal to the total number of moles of gallium and alkali metal (for example, sodium) is in the range of 50% to 90%, and the crystal growth temperature of the mixed melt is in the range of 850 ° C. to 900 ° C. Preferably, the nitrogen partial pressure is in the range of 1.5 MPa to 6 MPa.

  In a more preferred embodiment, the ratio of the number of moles of alkali metal to the total number of moles of gallium and alkali metal (for example, sodium) is in the range of 60% to 75%, and the crystal growth temperature is 860 ° C. to 870 ° C. More preferably, the nitrogen partial pressure is in the range of 2 MPa to 3.5 MPa.

  The group 13 nitride crystal 103 grown from the main surface 100A of the first seed crystal 100 is a c-axis oriented single crystal.

  Next, the fourth step will be described.

  FIG. 3C to FIG. 3E are explanatory diagrams of the fourth step.

  In the fourth step, the {10-11} plane of the group 13 nitride crystal 103 that has started crystal growth from the main surface 100A of the first seed crystal 100 in the third step, with the {10-11} plane as the main growth plane. The crystal growth is continued while increasing the area.

  The {10-11} plane of the group 13 nitride crystal 103 that has started crystal growth from the main surface 100A of the first seed crystal 100 is in contact with the mixed melt 24 and grows. Then, the crystal grows while increasing the area of the {10-11} plane (see FIGS. 3C to 3E).

  Here, in the crystal grown from the first seed crystal 100, the surface facing the opposite side of the opening of the groove 27A is the (000-1) plane. The (000-1) plane is easily polycrystallized. For this reason, the growth on the (000-1) plane may adversely affect the growth of the {10-11} plane, for example, the {10-11} plane continuous to the (000-1) plane is roughened. That is, in order to grow a single crystal, it is desirable not to continue the growth on the (000-1) plane side.

  In the present embodiment, in the group 13 nitride crystal 103 that has started crystal growth from the main surface 100A of the first seed crystal 100, the cross-sectional shape in the orthogonal direction perpendicular to the first direction Y is the V-shaped groove portion 27A. Until reaching the two wall surfaces (in FIG. 3, surface 27C and surface 27B), a (000-1) surface is formed and grows. However, after reaching the wall surfaces (the surface 27C and the surface 27B in FIG. 3) of the groove 27A, crystal growth is limited by these wall surfaces. For this reason, in the group 13 nitride crystal 103, formation of the (000-1) plane is suppressed, and growth in the [000-1] axial direction is also restricted.

  Thus, in the present embodiment, crystal growth on the (000-1) plane in the group 13 nitride crystal 103 is suppressed, so that polycrystallization on the (000-1) plane is suppressed. As a result, the roughness of the {10-11} plane is suppressed, and the group 13 nitride crystal 103 having a flat {10-11} plane can be obtained. In the example shown in FIG. 3, the case where the crystal growth is continued while the {10-11} plane is the main growth plane and the c-plane is slightly formed is shown (FIGS. 3C to 3C). e)).

  4 and 5 are schematic views of the group 13 nitride crystal 103 on which the crystal has grown. FIG. 4 is a schematic diagram showing a perspective view of the group 13 nitride crystal 103 on which the crystal has grown. FIG. 5 (a) is a schematic view of the group 13 nitride crystal 103 grown from the c-plane side. FIG. 5B is a cross-sectional view taken along the line A-A ′ of FIG.

  The grown group 13 nitride crystal 103 has a (000-1) plane whose bottom is long in the a-axis direction, and two planes continuous with the bottom are {10-11} planes.

  In the example shown in FIGS. 4 and 5, six {10-11} planes are formed in the group 13 nitride crystal 103, parallel to the longitudinal direction of the first seed crystal 100 and continuous to the bottom surface. The case where the two surfaces to be processed are {10-11} surfaces which are flat and have a large area is shown.

  Further, of the surfaces constituting the group 13 nitride crystal 103, a surface that is non-parallel to the bottom surface in contact with the main surface 100A of the first seed crystal 100 and is not perpendicular to the bottom surface is flat {10 -11} plane. In other words, among the planes constituting the group 13 nitride crystal 103, the crystal plane with the largest area grown in the mixed melt 24 is the {10-11} plane.

  Further, the grown group 13 nitride crystal 103 has a trapezoidal shape in which the cross section of the group 13 nitride crystal 103 is perpendicular to the longitudinal direction of the first seed crystal 100 and the first seed crystal 100 side is the base. In some cases, the upper side surface is a c-plane.

  That is, the group 13 nitride crystal 103 manufactured by the method for manufacturing a group 13 nitride crystal of the present embodiment has a (000-1) plane whose bottom surface is long in the a-axis direction, and two planes continuous to the bottom surface are { 10-11} plane.

  The conditions for crystal growth in the fourth step are realized by adjusting the nitrogen partial pressure, the temperature of the mixed melt, the ratio of the number of moles of alkali metal to the total number of moles of gallium and alkali metal (for example, sodium), etc. it can.

  Specifically, in the fourth step, the nitrogen partial pressure is adjusted to a partial pressure at which nitrogen in the mixed melt 24 has a relatively low degree of supersaturation. Specifically, it is preferable to be within a range of 2 MPa to 3.5 MPa. Further, in the fourth step, the temperature of the mixed melt 24 (crystal growth temperature) becomes a problem when a reaction vessel made of a material such as YAG or alumina dissolves or reacts with the melt to grow crystals. Adjust to a safe temperature. Specifically, it is preferable to set it within the range of 860 ° C to 870 ° C. Furthermore, when using a reaction vessel made of a material that is stable even at high temperatures, the temperature can be raised.

  Further, the ratio of the number of moles of alkali metal to the total number of moles of gallium and alkali metal (for example, sodium) is such that the {10-11} plane is easily formed under the aforementioned conditions of nitrogen and temperature, 50% to 80%. It is preferable that the content be within the range of 60% to 75%.

  By setting the third step to the same crystal growth conditions (temperature, partial pressure, alkali metal molar ratio, etc.) as the fourth step, the third step and the fourth step are continued under the same conditions. Can be advanced.

  FIG. 6 is a schematic diagram of the manufacturing apparatus 1 for performing the third step and the fourth step in the present embodiment.

  As shown in FIG. 6, the manufacturing apparatus 1 includes a closed pressure vessel 11 made of stainless steel. The pressure vessel 11 can be removed from the manufacturing apparatus 1 at the valve 21 portion, and only the pressure vessel 11 portion can be put in the glove box and operated.

  A reaction vessel 12 is provided in the pressure vessel 11. The reaction vessel 12 holds the mixed melt 24. A base substrate 27 is installed at the bottom inside the reaction vessel 12. A groove 27A is formed in the base substrate 27, and the first seed crystal 100 is provided by the first step and the second step.

  The material of the reaction vessel 12 can be selected as appropriate. For example, a BN sintered body, a nitride such as P-BN, an oxide such as alumina or YAG, a carbide such as SiC, or the like can be used for the reaction vessel 12. The reaction vessel 12 can be removed from the pressure vessel 11.

The pressure vessel 11 is connected to a gas supply pipe 14 for supplying nitrogen (N ₂ ) gas, which is a raw material for the group 13 nitride crystal, and dilution gas for adjusting the total pressure. The gas supply pipe 14 is branched into a nitrogen supply pipe 17 and a gas supply pipe 20, and can be separated by valves 15 and 18, respectively.

  As the diluent gas, it is desirable to use an argon (Ar) gas that is an inert gas, but the present invention is not limited to this, and other inert gases such as helium (He) may be used as the diluent gas.

  Nitrogen gas is supplied from a nitrogen supply pipe 17 connected to a gas cylinder of nitrogen gas and the like, and after the pressure is adjusted by the pressure control device 16, the nitrogen gas is supplied to the gas supply pipe 14 through the valve 15. On the other hand, a dilution gas (for example, argon gas) is supplied from a gas supply pipe 20 connected to a gas cylinder of the dilution gas and the pressure is adjusted by a pressure control device 19, and then the gas supply pipe is connected via a valve 18. 14. The nitrogen gas and the dilution gas whose pressures are adjusted in this way are respectively supplied to the gas supply pipe 14 and mixed.

  Then, a mixed gas of nitrogen and dilution gas is supplied from the gas supply pipe 14 to the pressure vessel 11 through the valve 21.

  The gas supply pipe 14 is provided with a pressure gauge 22 so that the pressure in the pressure vessel 11 can be adjusted while the pressure gauge 22 monitors the total pressure in the pressure vessel 11.

  Nitrogen gas is a raw material of gallium nitride, and argon, which is an inert gas, is mixed with it to increase the total pressure and suppress the evaporation of sodium, while controlling the pressure of the nitrogen gas independently. It is. Thereby, crystal growth with high controllability becomes possible.

  In this embodiment, the nitrogen partial pressure can be adjusted by adjusting the pressures of the nitrogen gas and the dilution gas with the valves 15 and 18 and the pressure control devices 16 and 19 as described above. Further, since the total pressure in the pressure vessel 11 can be adjusted, the total pressure in the pressure vessel 11 can be increased to suppress evaporation of alkali metal (for example, sodium) in the reaction vessel 12. That is, it is possible to separately control the nitrogen partial pressure, which is a nitrogen material that affects the crystal growth conditions of gallium nitride, and the total pressure that affects the suppression of evaporation of sodium (flux).

  Further, a heater 13 is disposed outside the pressure vessel 11, and the temperature of the mixed melt 24 can be adjusted by heating the pressure vessel 11 and the reaction vessel 12.

  In carrying out the third step and the fourth step, first, a substance used as a flux and a raw material are charged into the reaction vessel 12. And after setting a raw material etc., it supplies with electricity to the heater 13, and the pressure vessel 11 and the reaction vessel 12 inside it are heated to crystal growth temperature. Then, a substance used as a flux in the reaction vessel 12 and raw materials are melted to form a mixed melt 24. Further, nitrogen as a raw material can be supplied into the mixed melt 24 by bringing the partial pressure of nitrogen into contact with the mixed melt 24 and dissolving it in the mixed melt 24.

  Then, under a predetermined crystal growth temperature and a predetermined nitrogen partial pressure, nitrogen dissolved in the mixed melt 24 from the gas phase reacts with the group 13 metal in the mixed melt 24 to cause a reaction in the mixed melt 24. The crystal growth of the group 13 nitride crystal is started from the main surface 100A of the first seed crystal 100 placed in (third step).

  Further, by maintaining the crystal growth conditions in the fourth step, the group 13 nitride crystal 103 that has started crystal growth continues crystal growth with the {10-11} plane as the main growth plane.

  Through the first to fourth steps, the group 13 nitride crystal 103 is manufactured.

  Then, the group 13 nitride crystal 103 grown in the fourth step is cooled to room temperature. Thereafter, the group 13 nitride crystal 103 is separated from the base substrate 27 or the reaction vessel 12.

  Through the above process, the group 13 nitride crystal 103 can be manufactured.

(Embodiment 2)
In the present embodiment, a configuration in which a groove portion having a shape different from that of the first embodiment is provided in place of the groove portion having a V-shaped cross section in the first region in contact with the mixed melt inside the reaction vessel will be described. .

  7 and 8 are explanatory diagrams illustrating an example of the base substrate 270 in which the groove portion 270A according to the present embodiment is formed. Specifically, FIG. 7 is a perspective view showing a state in which the first seed crystal 200 is disposed in the groove 270A of the base substrate 270. FIG. 8A is a top view showing a state where the first seed crystal 200 is disposed in the groove 270A of the base substrate 270. FIG. FIG. 8B is a cross-sectional view taken along the line A-A ′ of FIG.

  In this embodiment, a case where the first seed crystal 200 is used instead of the first seed crystal 100 described in the first embodiment will be described. The first seed crystal 200 is composed of a single group 13 nitride crystal having a main surface 200A as a crystal plane on which the nitride crystal grows by c-axis orientation. The first seed crystal 200 is the same as the first seed crystal 100 except that it is a single layer group 13 nitride crystal. Note that the first seed crystal 100 may be used as in the first embodiment.

  As shown in FIGS. 7 and 8, the groove 270 </ b> A is long in the first direction Y. The groove portion 270A has a bottom surface 270D, a wall surface 270B, and a wall surface 270C. Similar to the first embodiment, first seed crystal 200 is arranged in groove portion 270A so that main surface 200A of first seed crystal 200 faces the opening side of groove portion 270A.

  The bottom surface 270D of the groove portion 270A is a surface that is long in the first direction Y and faces the facing surface 200B of the main surface 200 in the first seed crystal 200 installed in the groove portion 270A. The wall surface 270B and the wall surface 270C of the groove portion 270A are each a wall surface connecting the bottom surface 270D and each of the two opening edges 270E along the first direction Y of the groove portion 270A.

  In the present embodiment, as an example, a case will be described in which both of the two wall surfaces (wall surface 270B and wall surface 270C) are inclined in a direction away from each other as the distance from the bottom surface 270D increases.

  Note that at least one of the two wall surfaces (the wall surface 270B and the wall surface 270C) may be disposed so as to be inclined in a direction away from the bottom surface 270D.

  The depth of the groove portion 270 </ b> A is preferably larger than the thickness of the first seed crystal 200. The depth of the groove portion 270A indicates the length from the position corresponding to the bottom surface 270D to the position corresponding to the opening edge 270E in the perpendicular Z of the bottom surface 270D of the groove portion 270A. The thickness of the first seed crystal 200 indicates the length between the main surface 200A of the first seed crystal 200 and the facing surface 200B.

  The length in the first direction Y of the groove part 270A is preferably longer than the length in the longitudinal direction of the first seed crystal 200 disposed in the groove part 270A.

  The inclinations of the wall surface 270B and the wall surface 270C with respect to the perpendicular Z of the bottom surface 270D (see θA and θB in FIG. 9) may be the same or different. In addition, the inclination of the wall surface 270B and the wall surface 270C with respect to the perpendicular Z of the bottom surface 270D (see θC and θD in FIG. 8) is larger than 0 ° (matches the perpendicular Z) and 180 ° (opposite of the first seed crystal 200). It is not particularly limited as long as it is in the range of less than the surface 200B. For example, the inclination of the wall surface 270B and the wall surface 270C with respect to the perpendicular Z of the bottom surface 270D (see θC and θD in FIG. 8) is the suppression of the adhesion of microcrystals to the (000-1) plane of the growing crystal, {10− In order to prevent the area of the 11} surface from becoming too small, it is preferably in the range of 28 ° to 82 °, more preferably in the range of 59 ° to 78 °.

  As an example, FIGS. 7 to 9 show a case where the inclination of the wall surface 270B and the wall surface 270C with respect to the perpendicular Z of the bottom surface 270D (see θC and θD in FIG. 8) is 60 °.

  The material of the base substrate 270 having the groove 270A is the same as that of the base substrate 27 of the first embodiment. Further, as in the first embodiment, the groove 270A may be provided directly on the inner wall of the reaction vessel. One groove portion 270A or a plurality of groove portions 270A may be formed in the reaction vessel. When a plurality of groove portions 270A are formed, the groove portions 270A are preferably arranged in a direction intersecting the first direction Y that is the longitudinal direction of the groove portions 270A. In this case, the spacing in the arrangement direction of the grooves 270A is such that the group 13 nitride crystals grown from the first seed crystal 200 installed in the grooves 270A do not contact each other during the crystal growth. What is necessary is just to adjust according to the magnitude | size of the group 13 nitride crystal to crystal-grow.

  Next, a method for manufacturing the group 13 nitride crystal of the present embodiment will be described.

  In the present embodiment, the first step, the second step, the third step, described in the first embodiment, except that the reaction vessel having the groove portion 270A is used instead of the groove portion 27A described in the first embodiment. And through a 4th process, a group 13 nitride crystal is manufactured.

  In the first step, in the present embodiment, a first seed crystal 200 is prepared instead of the first seed crystal 100.

  Next, the 2nd process-the 4th process are explained.

  FIG. 9 is an explanatory diagram of the manufacturing process of the group 13 nitride crystal of the present embodiment.

  The second step is a step of disposing the first seed crystal 200 in the groove portion 270A so that the main surface 200A of the first seed crystal 200 faces the opening side of the groove portion 270A (see FIG. 9A).

  At this time, it is preferable to install the first seed crystal 200 in the groove portion 270A so that the longitudinal direction (a-axis direction) of the first seed crystal 200 substantially coincides with the first direction Y of the groove portion 270A.

  Note that the width of the bottom surface 270D of the groove portion 270A in the direction orthogonal to the first direction Y is preferably larger than the width in the direction orthogonal to both the longitudinal direction of the first seed crystal 200 and the c-axis direction. When this condition is satisfied, the first seed crystal 200 can be disposed in the groove portion 270A so that the opposing surface 200B of the first seed crystal 200 is in contact with the bottom surface 270D.

  In this case, in the space where the mixed melt in the reaction vessel is held, the first seed crystal 200 has a (( The space in contact with the (0001) plane side can be effectively increased. For this reason, crystal growth on the (000-1) plane side can be further suppressed.

  In the present embodiment, as an example, the case where the longitudinal direction (a-axis direction) of the first seed crystal 200 and the first direction Y of the groove portion 270A are the same direction will be described.

  Next, the third step will be described.

  The third step starts crystal growth of the group 13 nitride crystal from the main surface 200A of the first seed crystal 200 disposed in the groove 270A in the mixed melt.

  As shown in FIG. 9B, in the third step, a mixed melt 24 is formed in a reaction vessel (not shown), and nitrogen is dissolved from the gas phase. Crystal growth of the group 13 nitride crystal 203 is started from the main surface 200A of the seed crystal 200. The group 13 nitride crystal 203 that grows from the main surface 200A of the first seed crystal 200 is a c-axis oriented single crystal.

  Since the mixed melt 24, the flux, and the group 13 metal have been described in the first embodiment, they are omitted. The crystal growth conditions such as the crystal growth temperature and nitrogen source gas pressure in the third step are the same as those in the first embodiment.

  Next, the fourth step will be described.

  FIG.9 (c)-FIG.9 (e) are explanatory drawings of a 4th process.

  In the fourth step, the {10-11} plane of the group 13 nitride crystal 203 that has started crystal growth from the main surface 200A of the first seed crystal 200 in the third step, with the {10-11} plane as the main growth plane. The crystal growth is continued while increasing the area.

  The {10-11} plane of the group 13 nitride crystal 203 that has started crystal growth from the main surface 200A of the first seed crystal 200 is in contact with the mixed melt 24 and grows. Then, the crystal grows while increasing the area of the {10-11} plane (see FIGS. 9C to 9E).

  Here, in the present embodiment, in group 13 nitride crystal 203 which has started crystal growth from main surface 200A of first seed crystal 200, two wall surfaces (wall surface 270B and wall surface 270C) that are continuous with bottom surface 270D in groove portion 270A. ), A (000-1) plane is formed and grows. However, after reaching the wall surface of the groove 270A (in FIG. 9, the wall surface 270C and the wall surface 270B), the crystal growth is limited by these wall surfaces. For this reason, in the group 13 nitride crystal 203, the formation of the (000-1) plane is suppressed, and the growth in the [000-1] axial direction is also restricted.

  Thus, in the present embodiment, crystal growth on the (000-1) plane in the group 13 nitride crystal 203 is suppressed, so that polycrystallization on the (000-1) plane is suppressed. As a result, roughness of the {10-11} plane is suppressed, and a group 13 nitride crystal 203 having a flat {10-11} plane can be obtained (see FIGS. 9C to 9E). ).

  10 and 11 are schematic views showing the group 13 nitride crystal 203 with crystal growth. FIG. 10 is a schematic view showing a perspective view of the group 13 nitride crystal 203 on which the crystal has grown. FIG. 11A is a schematic view of a group 13 nitride crystal 203 grown from the c-plane side. FIG.11 (b) is A-A 'sectional drawing of Fig.11 (a).

  The grown group 13 nitride crystal 203 has a (000-1) plane whose bottom is long in the a-axis direction, and two planes continuous with the bottom are {10-11} planes.

  In the example shown in FIGS. 10 and 11, the group 13 nitride crystal 203 has six {10-11} planes, which are parallel to the longitudinal direction of the first seed crystal 200 and continuous to the bottom surface. The two planes to be processed are {10-11} planes that are flat and have a large area.

  The conditions for crystal growth in the fourth step can be realized by adjusting the nitrogen partial pressure, the temperature of the mixed melt, the ratio of the number of moles of alkali metal to the total number of moles of gallium and alkali metal (for example, sodium), and the like. These conditions are the same as in the fourth step of the first embodiment.

  Moreover, the 3rd process and 4th process in this Embodiment can be performed by using the manufacturing apparatus 1 demonstrated in Embodiment 1. FIG.

  Through the above process, the group 13 nitride crystal 203 can be manufactured.

(Embodiment 3)
In the present embodiment, a description will be given of a configuration in which a groove portion having a shape different from that of the above embodiment is provided in the first region in contact with the mixed melt inside the reaction vessel.

  In the present embodiment, as in the second embodiment, the case where the first seed crystal 200 is used as the first seed crystal will be described. Note that the first seed crystal 100 may be used as in the first embodiment.

  12 and 13 are explanatory diagrams illustrating an example of the base substrate 272 in which the groove portion 272A of this embodiment is formed. Specifically, FIG. 12 is a perspective view showing a state in which the first seed crystal 200 is disposed in the groove portion 272A of the base substrate 272. FIG. 13A is a top view showing a state in which the first seed crystal 200 is arranged in the groove 272A of the base substrate 272. FIG. FIG. 13B is a cross-sectional view taken along the line A-A ′ of FIG.

  As shown in FIGS. 12 and 13, the groove 272 </ b> A is long in the first direction Y. The groove portion 272A has a bottom surface 272D and two wall surfaces 272B. Similar to Embodiment 1, first seed crystal 200 is arranged in groove portion 272A such that main surface 200A of first seed crystal 200 faces the opening side of groove portion 272A.

  The bottom surface 272D of the groove portion 272A is a surface that is long in the first direction Y and faces the facing surface 200B of the main surface 200A in the first seed crystal 200 installed in the groove portion 272A. The two wall surfaces 272B of the groove portion 272A are each a wall surface connecting the bottom surface 272D and each of the two opening edges 272E along the first direction Y of the groove portion 272A.

  In this embodiment, as an example, a case will be described in which both two wall surfaces (wall surface 272B) are arranged perpendicular to the bottom surface 272D. That is, in this embodiment, each of the opposing surfaces of the two wall surfaces (wall surface 272B) is arranged in a direction perpendicular to the bottom surface 272D (see the Z direction in FIG. 12).

  One of the two wall surfaces (wall surface 272B) may be arranged perpendicular to the bottom surface 272D.

  The depth of the groove 272A allows crystal growth while expanding the area of the {10-11} plane of the group 13 nitride crystal grown from the main surface of the first seed crystal 200 disposed in the groove 272A. Is the depth. For this reason, the maximum value of the depth of the groove portion 272A is adjusted to a value satisfying this characteristic. Note that the lower limit of the depth of the groove portion 272 </ b> A is preferably larger than the thickness of the first seed crystal 200.

  The depth of the groove portion 272A indicates a length from a position corresponding to the bottom surface 272D to a position corresponding to the opening edge 272E in the perpendicular Z of the bottom surface 272D of the groove portion 272A. The thickness of the first seed crystal 200 indicates the length between the main surface 200A of the first seed crystal 200 and the facing surface 200B.

  The length in the first direction Y of the groove portion 272A is preferably longer than the length in the longitudinal direction of the first seed crystal 200 disposed in the groove portion 272A.

  The width of the bottom surface 272D of the groove 272A in the direction orthogonal to the first direction Y is larger than the width in the direction orthogonal to both the longitudinal direction of the first seed crystal 200 and the c-axis direction. By satisfying this condition, the first seed crystal 200 can be arranged in the groove portion 272A so that the opposing surface 200B of the first seed crystal 200 is in contact with the bottom surface 272D.

  The width of the bottom surface 272D is not limited as long as it satisfies this condition, but compared to the space in contact with the (000-1) plane side of the first seed crystal 200 in the space where the mixed melt in the reaction vessel is held. Thus, adjustment may be made in advance so as to satisfy the condition that the space in contact with the (0001) plane side of the first seed crystal 200 is larger.

  Further, in the first region of the groove portion 272A that is in contact with the mixed melt 24 in the reaction vessel, the region continuing to the groove portion 272A (see the surface 272E of the base substrate 272 in FIG. 14) is the first portion disposed in the groove portion 272A. This is a shape that allows crystal growth while expanding the area of the {10-11} plane of the group 13 nitride crystal 302 grown from the main surface 200A of the single crystal 200. In the example shown in FIG. 14, the surface 272E has been adjusted in advance so as to have a planar shape parallel to the (0001) plane of the group 13 nitride crystal 303 that has grown. The shape of the surface 272E may be any shape that satisfies the above characteristics, and is not limited to a shape parallel to the (0001) plane.

  The material of the base substrate 272 having the groove 272A is the same as that of the base substrate 27 of the first embodiment. Further, as in the first embodiment, the groove 272A may be provided directly on the inner wall of the reaction vessel. Further, one groove portion 272A or a plurality of groove portions 272A may be formed in the reaction vessel. When a plurality of groove portions 272A are formed, the groove portions 272A are preferably arranged in a direction intersecting the first direction Y that is the longitudinal direction of the groove portions 272A. In this case, the intervals in the arrangement direction of the grooves 272A are set so that the group 13 nitride crystals grown from the first seed crystal 200 installed in the grooves 272A do not contact each other during the crystal growth. What is necessary is just to adjust according to the magnitude | size of the group 13 nitride crystal to crystal-grow.

  Next, a method for manufacturing the group 13 nitride crystal of the present embodiment will be described.

  In the present embodiment, the first step, the second step, the third step, described in the first embodiment, except that the reaction vessel having the groove portion 272A is used instead of the groove portion 27A described in the first embodiment. And through a 4th process, a group 13 nitride crystal is manufactured.

  In the first step, in the present embodiment, a first seed crystal 200 is prepared instead of the first seed crystal 100.

  Next, the 2nd process-the 4th process are explained.

  FIG. 14 is an explanatory diagram of the manufacturing process of the group 13 nitride crystal of the present embodiment.

  The second step is a step of arranging the first seed crystal 200 in the groove portion 272A so that the main surface 200A of the first seed crystal 200 faces the opening side of the groove portion 272A (see FIG. 14A).

  At this time, it is preferable to install the first seed crystal 200 in the groove portion 272A so that the longitudinal direction (a-axis direction) of the first seed crystal 200 substantially coincides with the first direction Y of the groove portion 272A (see FIG. 13). ).

  In the present embodiment, as an example, a case where the longitudinal direction (a-axis direction) of the first seed crystal 200 and the first direction Y of the groove portion 272A are the same direction will be described.

  Next, the third step will be described.

  The third step starts crystal growth of the group 13 nitride crystal from the main surface 200A of the first seed crystal 200 arranged in the groove 272A in the mixed melt.

  As shown in FIG. 14B, in the third step, a mixed melt 24 is formed in a reaction vessel (not shown), nitrogen is dissolved from the gas phase, Crystal growth of group 13 nitride crystal 303 is started from main surface 200A of seed crystal 200. The group 13 nitride crystal 303 that grows from the main surface 200A of the first seed crystal 200 is a c-axis oriented single crystal.

  Since the mixed melt 24, the flux, and the group 13 metal have been described in the first embodiment, they are omitted. The crystal growth conditions such as the crystal growth temperature and nitrogen source gas pressure in the third step are the same as those in the first embodiment.

  Next, the fourth step will be described.

  FIG.14 (c)-FIG.14 (e) are explanatory drawings of a 4th process.

  In the fourth step, the {10-11} plane of the group 13 nitride crystal 303, which has started crystal growth from the main surface 200A of the first seed crystal 200 in the third step, is the {10-11} plane as the main growth plane. The crystal growth is continued while increasing the area.

  The {10-11} plane of the group 13 nitride crystal 303 that has started crystal growth from the main surface 200A of the first seed crystal 200 is in contact with the mixed melt 24 and grows. Then, the crystal grows while increasing the area of the {10-11} plane (see FIGS. 14C to 14E).

  Here, in the present embodiment, group 13 nitride crystal 303 that has started crystal growth from main surface 200A of first seed crystal 200 reaches two wall surfaces (wall surface 272B) continuous with bottom surface 272D in groove portion 272A. Until then, the (000-1) plane is formed and grows. However, after reaching the wall surface 272B of the groove 272A, crystal growth is limited by these wall surfaces. For this reason, in the group 13 nitride crystal 303, formation of the (000-1) plane is suppressed, and growth in the [000-1] axial direction is also restricted.

  Also, as shown in FIGS. 12 to 14, it is preferable to adjust in advance the width of the first seed crystal 200 and the width of the groove portion 272A so that the first seed crystal 200 fits in the groove portion 272A without a gap. . By adjusting in advance the width of the first seed crystal 200 and the width of the groove 272A so as to satisfy this condition, growth in the [000-1] axial direction can be effectively suppressed.

  Moreover, as shown in FIGS. 12-14, it is preferable to adjust beforehand so that the thickness of the 1st seed crystal 200 and the depth of the groove part 272A may become substantially the same. When the thickness of the first seed crystal 200 and the depth of the groove portion 272A are substantially the same, the group 13 nitride crystal 303 that has started crystal growth from the main surface 200A side of the first seed crystal 200 has a groove portion 272A due to crystal growth. After coming out of the substrate, it grows along the surface 272E of the base substrate 272. Here, when the main surface 200A of the first seed crystal 200 and the surface 272E of the base substrate 272 are parallel, the (000-1) plane is formed. However, since there is no gap between the base substrate 272 and the grown group 13 nitride crystal 303, crystal growth in the [000-1] axis direction is limited.

  Thus, in the present embodiment, crystal growth on the (000-1) plane in the group 13 nitride crystal 203 is suppressed, so that polycrystallization on the (000-1) plane is suppressed. In addition, it is possible to suppress the occurrence of polarity reversal due to crystal growth on the (000-1) plane side and the occurrence of polycrystallization due to adhesion of microcrystals. As a result, the roughness of the {10-11} plane is suppressed, and the group 13 nitride crystal 203 having a flat {10-11} plane can be obtained (see FIGS. 14C to 14E). ).

  FIG. 15 and FIG. 16 are schematic views showing a group 13 nitride crystal 303 with crystal growth. FIG. 15 is a schematic diagram showing a perspective view of a group 13 nitride crystal 303 with crystal growth. FIG. 16A is a schematic view of a group 13 nitride crystal 303 with crystal growth as viewed from the c-plane side. FIG. 16B is a cross-sectional view taken along the line A-A ′ of FIG.

  The grown group 13 nitride crystal 303 has a (000-1) plane whose bottom is long in the a-axis direction, and two planes continuous with the bottom are {10-11} planes.

  In the example shown in FIGS. 15 and 16, six {10-11} planes are formed in the group 13 nitride crystal 303, which is parallel to the longitudinal direction of the first seed crystal 200 and continuous to the bottom surface. The two planes to be processed are {10-11} planes that are flat and have a large area.

  The conditions for crystal growth in the fourth step can be realized by adjusting the nitrogen partial pressure, the temperature of the mixed melt, the ratio of the number of moles of alkali metal to the total number of moles of gallium and alkali metal (for example, sodium), and the like. These conditions are the same as in the fourth step of the first embodiment.

  Moreover, the 3rd process and 4th process in this Embodiment can be performed by using the manufacturing apparatus 1 demonstrated in Embodiment 1. FIG.

  Through the above process, the group 13 nitride crystal 303 can be manufactured.

(Embodiment 4)
In the present embodiment, a description will be given of a configuration in which a groove portion having a shape different from that of the above embodiment is provided in the first region in contact with the mixed melt inside the reaction vessel.

  In the present embodiment, as in the second embodiment, the case where the first seed crystal 200 is used as the first seed crystal will be described. Note that the first seed crystal 100 may be used as in the first embodiment.

  17 and 18 are explanatory views showing an example of the base substrate 274 in which the groove 274A of the present embodiment is formed. Specifically, FIG. 17 is a perspective view showing a state in which the first seed crystal 200 is disposed in the groove portion 274A of the base substrate 274. FIG. 18A is a top view showing a state where the first seed crystal 200 is arranged in the groove 274A of the base substrate 274. FIG. FIG. 18B is a cross-sectional view taken along the line A-A ′ of FIG.

  As shown in FIGS. 17 and 18, the groove portion 274 </ b> A is long in the first direction Y. The groove portion 274A has a bottom surface 274D and two wall surfaces 274B and 274C that are continuous with the bottom surface 274. Similar to Embodiment 1, first seed crystal 200 is arranged in groove portion 274A so that main surface 200A of first seed crystal 200 faces the opening side of groove portion 274A.

  The bottom surface 274D of the groove portion 274A is a surface that is long in the first direction Y and faces the facing surface 200B of the main surface 200A in the first seed crystal 200 installed in the groove portion 274A. The two wall surfaces 274B and 274C of the groove portion 274A are wall surfaces that connect the bottom surface 274D and each of the two opening edges 274E along the first direction Y of the groove portion 274A. Further, in these two wall surfaces (wall surface 274B, wall surface 274C), at least part of the region in the depth direction of the groove portion 274A is inclined in a direction away from the bottom surface 274D.

  In the present embodiment, at least one of the wall surface 274B and the wall surface 274C of the groove portion 274A is divided into a plurality of regions in the depth direction of the groove portion 274A, and the region disposed at a position away from the bottom surface 274D is perpendicular to the bottom surface 274D ( The inclination with respect to the arrow Z direction in FIGS. 17 and 18 is large.

  In the present embodiment, as an example, a case will be described in which both wall surface 274B and wall surface 274C are divided into a plurality of regions in the depth direction of groove portion 274A. In the present embodiment, the wall surface 274B is divided into two regions, a region 274F and a region 274G, in this order from the bottom surface 274D side to the opening edge 274E side in the depth direction of the groove portion 274A. In the present embodiment, the wall surface 274C is divided into two regions, a region 274H and a region 274I, in this order from the bottom surface 274D side to the opening edge 274E side in the depth direction of the groove portion 274A.

  In this embodiment, a perpendicular (refer to the Z direction) of a region (region 274F and region 274H) that continues to the bottom surface 274D among the plurality of regions (region 274F, region 274G, region 274H, region 274I). The case where the inclination with respect to is 0 ° will be described. In the present embodiment, a perpendicular (refer to the arrow Z direction) of the region (region 274G and region 274I) on the opening edge 274E side among the plurality of regions (region 274F, region 274G, region 274H, region 274I). ) (See θG, θI in FIG. 18) is 87 °.

  As described above, at least one of the wall surface 274B and the wall surface 274C of the groove portion 274A is divided into a plurality of regions in the depth direction of the groove portion 274A, and the perpendicular line of the bottom surface 274D is arranged in a position away from the bottom surface 274D. It is only necessary to satisfy the above condition that the inclination with respect to (refer to the Z direction in FIGS. 17 and 18) is large. That is, the number of divisions of the wall surface 274B and the wall surface 274C is not limited to two. Further, the inclination of each region is not limited to the combination of 0 ° and 87 °.

  The depth of the groove 274A is preferably larger than the thickness of the first seed crystal 200. The depth of the groove portion 274A indicates the length from the position corresponding to the bottom surface 274D to the position corresponding to the opening edge 274E in the perpendicular Z of the bottom surface 274D of the groove portion 274A.

  Further, the height (length in the perpendicular Z direction) of the region continuing to the bottom surface 274D in each of the wall surface 274B and the wall surface 274C of the groove portion 274A is preferably equal to or greater than the thickness of the first seed crystal 200. More preferably, it is substantially the same as the thickness of the crystal 200.

  The length of the groove part 274A in the first direction Y is preferably longer than the length of the first seed crystal 200 disposed in the groove part 274A in the longitudinal direction.

  The width of the bottom surface 274D of the groove portion 274A in the direction orthogonal to the first direction Y is preferably larger than the width in the direction orthogonal to both the longitudinal direction of the first seed crystal 200 and the c-axis direction. By satisfying this condition, the first seed crystal 200 can be disposed in the groove portion 274A so that the opposing surface 200B of the first seed crystal 200 is in contact with the bottom surface 274D.

  The width of the bottom surface 274D is not limited as long as it satisfies this condition, but compared to the space in contact with the (000-1) plane side of the first seed crystal 200 in the space where the mixed melt in the reaction vessel is held. Thus, adjustment may be made in advance so as to satisfy the condition that the space in contact with the (0001) plane side of the first seed crystal 200 is larger.

  The material of the base substrate 274 having the groove 274A is the same as that of the base substrate 27 of the first embodiment. Further, as in the first embodiment, the groove 274A may be provided directly on the inner wall of the reaction vessel. Further, one or a plurality of groove portions 274A may be formed in the reaction vessel. When a plurality of groove portions 274A are formed, the groove portions 274A are preferably arranged in a direction intersecting the first direction Y that is the longitudinal direction of the groove portions 274A. In this case, the interval in the arrangement direction of the grooves 274A is such that the group 13 nitride crystals grown from the first seed crystal 200 installed in the grooves 274A do not contact each other during crystal growth. What is necessary is just to adjust according to the magnitude | size of the group 13 nitride crystal to crystal-grow.

  Next, a method for manufacturing the group 13 nitride crystal of the present embodiment will be described.

  In the present embodiment, the first step, the second step, the third step, described in the first embodiment, except that the reaction vessel having the groove portion 274A is used instead of the groove portion 27A described in the first embodiment. And through a 4th process, a group 13 nitride crystal is manufactured.

  In the first step, in the present embodiment, a first seed crystal 200 is prepared instead of the first seed crystal 100.

  Next, the second to fourth steps will be described.

  FIG. 19 is an explanatory diagram of the manufacturing process of the group 13 nitride crystal of the present embodiment.

  The second step is a step of disposing the first seed crystal 200 in the groove portion 274A so that the main surface 200A of the first seed crystal 200 faces the opening side of the groove portion 274A (see FIG. 19A).

  At this time, it is preferable to install the first seed crystal 200 in the groove portion 274A so that the longitudinal direction (a-axis direction) of the first seed crystal 200 substantially coincides with the first direction Y of the groove portion 274A (see FIG. 18). ).

  In the present embodiment, as an example, a case where the longitudinal direction (a-axis direction) of the first seed crystal 200 and the first direction Y of the groove 274A are the same direction will be described.

  Next, the third step will be described.

  The third step starts crystal growth of the group 13 nitride crystal from the main surface 200A of the first seed crystal 200 disposed in the groove 274A in the mixed melt.

  As shown in FIG. 19B, in the third step, a mixed melt 24 is formed in a reaction vessel (not shown), and nitrogen is dissolved from the gas phase. Crystal growth of the group 13 nitride crystal 403 is started from the main surface 200A of the seed crystal 200. The group 13 nitride crystal 403 that grows from the main surface 200A of the first seed crystal 200 is a c-axis oriented single crystal.

  Since the mixed melt 24, the flux, and the group 13 metal have been described in the first embodiment, they are omitted. The crystal growth conditions such as the crystal growth temperature and nitrogen source gas pressure in the third step are the same as those in the first embodiment.

  Next, the fourth step will be described.

  FIG.19 (c)-FIG.19 (e) are explanatory drawings of a 4th process.

  In the fourth step, the {10-11} plane of the group 13 nitride crystal 403 that has started crystal growth from the main surface 200A of the first seed crystal 200 in the third step, with the {10-11} plane as the main growth plane. The crystal growth is continued while increasing the area.

  The {10-11} plane of the group 13 nitride crystal 403 that has started crystal growth from the main surface 200A of the first seed crystal 200 is in contact with the mixed melt 24 and grows. Then, the crystal grows while increasing the area of the {10-11} plane (see FIGS. 19C to 19E).

  Here, in the present embodiment, in group 13 nitride crystal 403 that has started crystal growth from main surface 200A of first seed crystal 200, two wall surfaces (wall surface 274B, wall surface 274C) that are continuous with bottom surface 274D in groove portion 274A. ) Until a region (region 274F, region 274H) closest to the bottom surface 274D is reached, a (000-1) plane is formed and grows. However, after reaching the region (274F, region 274H) closest to the bottom surface 274D in the wall surface 272B) of the groove portion 272A, crystal growth is limited by these regions (region 274F, region 274H). Further, the crystal grows along the region (region 274G, region 274I) closer to the opening edge 274E.

  For this reason, in the group 13 nitride crystal 403, the formation of the (000-1) plane is suppressed, and the growth in the [000-1] axial direction is also restricted.

  Thus, in the present embodiment, since the crystal growth on the (000-1) plane in the group 13 nitride crystal 403 is suppressed, polycrystallization on the (000-1) plane is suppressed. In addition, it is possible to suppress the occurrence of polarity reversal due to crystal growth on the (000-1) plane side and the occurrence of polycrystallization due to adhesion of microcrystals. As a result, roughness of the {10-11} plane is suppressed, and a group 13 nitride crystal 403 having a flat {10-11} plane can be obtained (see FIG. 19E).

  20 and 21 are schematic views showing a group 13 nitride crystal 403 that has undergone crystal growth. FIG. 20 is a schematic diagram showing a perspective view of a group 13 nitride crystal 403 that has undergone crystal growth. FIG. 21A is a schematic view of a group 13 nitride crystal 403 grown from the c-plane side. FIG. 21B is a cross-sectional view taken along the line A-A ′ of FIG.

  The grown group 13 nitride crystal 403 has a (000-1) plane whose bottom is long in the a-axis direction, and two planes continuous with the bottom are {10-11} planes.

  20 and FIG. 21, six {10-11} planes are formed in the group 13 nitride crystal 403, which is parallel to the longitudinal direction of the first seed crystal 200 and continuous to the bottom surface. The two planes to be processed are {10-11} planes that are flat and have a large area.

  The conditions for crystal growth in the fourth step can be realized by adjusting the nitrogen partial pressure, the temperature of the mixed melt, the ratio of the number of moles of alkali metal to the total number of moles of gallium and alkali metal (for example, sodium), and the like. These conditions are the same as in the fourth step of the first embodiment.

  Moreover, the 3rd process and 4th process in this Embodiment can be performed by using the manufacturing apparatus 1 demonstrated in Embodiment 1. FIG.

  By the above process, the group 13 nitride crystal 403 can be manufactured.

(Embodiment 5)
In the present embodiment, a method for manufacturing a group 13 nitride crystal substrate from the group 13 nitride crystal manufactured in the above embodiment will be described.

  The manufacturing method of the present embodiment includes a processing step of processing the group 13 nitride crystal manufactured in the above embodiment so that the c-plane, nonpolar plane, or semipolar plane is the main plane.

  A nonpolar plane is a crystal plane of a group 13 nitride crystal having a hexagonal crystal structure in which the number of group 13 atoms and nitrogen atoms is the same in the crystal plane and the charge is not biased and has no polarity in the crystal axis direction. is there. Specifically, the nonpolar plane is an m plane or a plane of a hexagonal crystal.

  The semipolar plane is a crystal plane excluding the c plane and the nonpolar plane, which are polar planes composed of only group 13 atoms or nitrogen atoms. The semipolar plane is defined as semipolar because the number of group 13 atoms and nitrogen atoms are not equal and the charge balance is lost and the polarity is polar, but the degree is between the c-plane polar plane and the nonpolar plane. Has been. Specifically, there are {10-11} plane, {20-21} plane, {11-22} plane, {-1103} plane, etc. of hexagonal crystals (other than c plane and nonpolar plane) All crystal planes are semipolar planes).

  The processing method used in the processing step may be a known method and is not limited.

Since the mixed melt 24 in which the group 13 nitride crystal is grown contains alkali metal, the crystal of the group 13 nitride substrate of the present embodiment contains a small amount of alkali metal as an impurity. In a GaN crystal grown using sodium as an alkali metal, 10 ¹⁴ to 10 ¹⁵ cm ⁻³ sodium is detected by SIMS analysis. The group 13 nitride crystal substrate of the present embodiment is a substrate obtained by processing a group 13 nitride crystal whose main growth surface is a {10-11} plane. For this reason, in the group 13 nitride crystal substrate of the present embodiment, inclusion of metal sodium, metal gallium, and a mixture thereof as they are into the crystal is suppressed.

  Further, since the main surface of the group 13 nitride crystal substrate of the present embodiment is a c-plane, a nonpolar plane, or a semipolar plane, a light-emitting device having an InGaN active layer is manufactured using these substrates. Thus, it is possible to suppress a decrease in light emission efficiency and blue shift of the InGaN active layer having a high In composition. As a result, a semiconductor laser that oscillates in the green wavelength region and a high-power LED can be manufactured.

  In addition, in the group 13 nitride crystal substrate of the present embodiment, the (10-11) plane, the (−1011) plane, the (10-1-1) plane, or the (−101−) whose main surface is semipolar. The substrate which is 1) surface can suppress the light emission efficiency reduction and the blue shift of the InGaN active layer having a high In composition by manufacturing a light emitting device having an InGaN active layer using this substrate. As a result, a semiconductor laser that oscillates in the green wavelength region and a high-power LED can be manufactured.

  Examples are shown below to describe the present invention in more detail, but the present invention is not limited to these Examples. The reference numerals correspond to the respective configurations described above with reference to the drawings.

Example 1
In this example, the group 13 nitride crystal 103 was manufactured by performing crystal growth using the manufacturing apparatus 1 (see FIG. 6) along the steps shown in FIG. In this example, sodium was used as the alkali metal, gallium was used as the group 13 metal, and GaN (gallium nitride) was manufactured as the group 13 nitride crystal 103.

―First step―
First, the first seed crystal 100 was prepared. In this example, as the first seed crystal 100, GaN was grown 15 μm epitaxially by MOCVD as a group 13 nitride crystal 103 on a sapphire substrate as the heterogeneous substrate 101. Thus, a φ2 inch template substrate was produced and cut into a strip shape, thereby producing a first seed crystal 100.

  At the time of cutting, the first seed crystal 100 was cut so that the longitudinal direction thereof was substantially parallel to the a-axis of GaN that is the group 13 nitride crystal 103. Specifically, using a dicing apparatus, along the m-axis of the sapphire substrate as the heterogeneous substrate 101, a plurality of grooves are formed by cutting from the back surface side of the substrate to the middle of the substrate, and then applying pressure. It was divided over. In this way, a strip-shaped first seed crystal 100 was produced in which the longitudinal direction was along the m-axis of the sapphire substrate, that is, the longitudinal direction was substantially parallel to the a-axis of GaN as the group 13 nitride crystal 102. .

  The major surface 100A (GaN-side surface) of the produced first seed crystal 100 had a length in the longitudinal direction of 45 mm, and the width (the length in the short direction) of the major surface 100A was 1 mm. The thickness (the length of the main surface 100A and the opposing surface 100B) was about 350 μm.

  Next, the 2nd process-the 4th process were performed using manufacturing device 1 shown in FIG.

  First, a container made of YAG was prepared as the reaction container 12. And the base substrate 27 provided with the V-shaped groove part 27A was installed in the bottom part inside the reaction container 12. In the present embodiment, alumina having a purity of 99.99% was used as the material of the base substrate 27. An angle (see θA in FIG. 3) formed by two wall surfaces (see the surface 27B and the surface 27C in FIG. 3) in the groove portion 27A was 120 °. Further, the two surfaces (surface 27B and surface 27C) constituting the groove portion 27A were formed so as to be inclined by 60 ° in directions away from each other with respect to the perpendicular Z passing through the tangent line 27D of these two surfaces.

  The pressure vessel 11 having the reaction vessel 12 therein was separated from the production apparatus 1 at the valve 21 portion, and placed in a glove box having a high purity Ar atmosphere with oxygen of 1 ppm or less and dew point of -80 ° C. or less.

-Second step-
Next, the main surface 100A of the first seed crystal 100 is disposed in the groove portion 27A of the base substrate 27 installed at the bottom of the reaction vessel 12 made of YAG and having an inner diameter of 92 mm so as to face the opening side of the groove portion 27A. . The first seed crystal 100 was disposed in the groove portion 27A so that the longitudinal direction of the first seed crystal 100 and the first direction Y of the groove portion 27A coincided with each other.

  For this reason, the first seed crystal 100 is disposed so as to straddle the tangent line 27D of the two wall surfaces (see the surface 27B and the surface 27C in FIG. 3) constituting the groove 27A. Further, the first seed crystal 100 is supported by two wall surfaces (refer to the surface 27B and the surface 27C in FIG. 3) at both ends in the m-axis direction of the facing surface 100B of the first seed crystal 100 in the groove portion 27A. It became the state that was done. Further, the main surface 100A of the first seed crystal 100 is disposed so as to face the bottom side of the groove 27A.

  Thus, by disposing the first seed crystal 100 in the groove 27A, the rear surface side of the group 13 nitride crystal 103 grown from the main surface 100A of the first seed crystal 100, that is, (000-1). The nitrogen polar surface of the surface is in a state facing the bottom side of the groove 27A.

-Third step-
Next, 100 g of gallium (Ga) as a group 13 metal raw material and 77 g of sodium (Na) as a flux were charged into the reaction vessel 12. The molar ratio of gallium to sodium was 0.3: 0.7. Furthermore, 0.34 g of carbon was added into the reaction vessel 12. Sodium was dissolved and made into a liquid state, then placed in the reaction vessel 12 and solidified, and then gallium and carbon were added.

  Next, the reaction vessel 12 was covered with a lid 25 and then placed in the pressure vessel 11.

  Next, the pressure vessel 11 was sealed, the valve 21 was closed, and the inside of the reaction vessel 12 was shut off from the external atmosphere. The series of operations in the manufacturing apparatus 1 were performed in a glove box having a high-purity Ar gas atmosphere. For this reason, the pressure vessel 11 was filled with Ar gas.

  Next, the pressure vessel 11 was taken out of the glove box and incorporated in the manufacturing apparatus 1. Specifically, the pressure vessel 11 was installed at a predetermined position of the heater 13 and connected to a nitrogen and argon gas supply pipe 14 at the valve 21 portion. Next, the valve 21 and the valve 18 were opened, Ar gas was introduced from the gas supply pipe 20, and the internal space 23 of the pressure vessel 11 was filled with Ar gas. At this time, since gas enters from the gap between the reaction vessel 12 and the lid 25, the internal space 28 in the reaction vessel 12 was also filled with Ar gas. Next, the pressure was adjusted by the pressure control device 19 so that the total pressure in the pressure vessel 11 was 2.5 MPa, and the valve 18 was closed.

  Next, nitrogen gas was introduced from the nitrogen supply pipe 17, the pressure was adjusted by the pressure control device 16, the valve 15 was opened, and the total pressure in the pressure-resistant vessel 11 was set to 4 MPa. That is, the partial pressure of nitrogen in the internal space 23 of the pressure vessel 11 was 1.5 MPa. Thereafter, the valve 15 was closed and the pressure control device 16 was set to 8 MPa.

  Next, the heater 13 was energized to raise the temperature of the reaction vessel 12 to the crystal growth temperature. The crystal growth temperature was 870 ° C. At the crystal growth temperature, gallium and sodium in the reaction vessel 12 melted to form a mixed melt 24. Note that the temperature of the mixed melt 24 is the same as the temperature of the reaction vessel 12. Further, when the temperature was raised to this temperature, in the manufacturing apparatus 1 of the present example, the gas in the pressure resistant vessel 11 was heated and the total pressure was 8 MPa. That is, the nitrogen partial pressure was 3 MPa.

  Next, the valve 15 was opened and a nitrogen gas pressure was applied at 8 MPa. This is because the nitrogen partial pressure in the pressure resistant vessel 11 is maintained at 3 MPa even when nitrogen is consumed by crystal growth of gallium nitride.

  In this way, nitrogen was dissolved in the mixed melt 24, and crystal growth of GaN as the group 13 nitride crystal 103 was started from GaN on the main surface 100A of the first seed crystal 100 (FIG. 3B). )).

-Fourth step-
Next, the temperature in the reaction vessel 12 was maintained at 870 ° C. and the nitrogen gas partial pressure was maintained at 3 MPa, and crystal growth was continued for 300 hours. When the GaN single crystal which is the group 13 nitride crystal 103 starts crystal growth from the main surface 100A of the first seed crystal 100 and continues the crystal growth, the crystal region in contact with the mixed melt 24 is the first type. The crystal grew out of the main surface 100A of the crystal 100.

  In this example, the {10-11} plane is the main crystal growth plane, and it is observed that the crystal growth continues while the area of the {10-11} plane is enlarged and the c plane is slightly formed. (FIG. 3 (c) to FIG. 3 (e)).

  Specifically, until the group 13 nitride crystal 103 that has started crystal growth from the main surface 100A of the first seed crystal 100 reaches the two wall surfaces (the surface 27C and the surface 27B in FIG. 3) of the groove 27A, A (000-1) plane was formed and grew. Then, after reaching the wall surfaces (the surface 27C and the surface 27B in FIG. 3) of the groove portion 27A, the crystal growth was restricted by these wall surfaces. For this reason, it was confirmed that the formation of the (000-1) plane in the group 13 nitride crystal 103 was suppressed and the growth in the [000-1] axial direction was also restricted.

  Then, after continuing crystal growth for 300 hours, the heater 13 was turned off, and the temperature of the mixed melt 24 was lowered to room temperature.

  When the pressure vessel 11 was opened after the pressure of the gas in the pressure vessel 11 was lowered, the group 13 nitride crystal 103 was grown on the first seed crystal 100 in the reaction vessel 12 (FIG. 3 (e)). )reference).

―Evaluation of group 13 nitride crystals―
GaN as the group 13 nitride crystal 103 obtained by this crystal growth has the shape shown in FIGS. Specifically, the GaN single crystal as the group 13 nitride crystal 103 obtained by this crystal growth has a (000-1) plane whose bottom is long in the a-axis direction, and two planes continuous with the bottom are {10 -11} plane (see FIGS. 4 and 5).

  The obtained GaN single crystal as the group 13 nitride crystal 103 has six {10-11} planes, which are parallel to the longitudinal direction of the first seed crystal 100 and continuous to the bottom surface. The two surfaces to be processed were flat and large {10-11} surfaces (see FIGS. 4 and 5).

  In addition, a c-plane Ga polar face was formed on the upper surface of the obtained group 13 nitride crystal 103. In addition, a recess 105 was formed in the c-plane along the longitudinal direction of the first seed crystal 100 (see FIGS. 4 and 5).

  Further, the bottom of the obtained group 13 nitride crystal 103 had a shape along the shape of the groove 27A of the base substrate 27 (see FIGS. 3E and 5B).

  The first seed crystal 100 was located on the bottom surface of the GaN single crystal as the group 13 nitride crystal 103. Further, the different substrate 101 of the first seed crystal 100 was cracked.

  The size of the GaN single crystal as the group 13 nitride crystal 103 obtained by crystal growth is such that the length in the longitudinal direction of the bottom surface is about 59 mm, the maximum width of the bottom surface is 9 mm, and the length in the longitudinal direction of the upper portion is about 45 mm. The height (the shortest distance between the bottom surface and the top surface) was about 10 mm.

Further, as a result of SIMS (Secondary Ion Mass Spectrometry) analysis of the GaN single crystal as the group 13 nitride crystal 103, 10 ¹⁴ to 10 ¹⁵ cm ⁻³ of sodium was detected. In addition, although the GaN single crystal as the group 13 nitride crystal 103 contained sodium at the impurity level, metal gallium, metal sodium, or an alloy of gallium and sodium that causes generation of cracks and voids. There was no such inclusion.

(Example 2)
In this embodiment, a group 13 nitride crystal is manufactured using a single-layer first seed crystal 200 instead of the first seed crystal 100 used in the first embodiment. Further, in this example, instead of the base substrate 27 used in Example 1, a base substrate 270 (see FIG. 7) provided with a groove portion 270A was used (details will be described later).

―First step―
First, the first seed crystal 200 was prepared. In this example, a crystal cut into a strip shape from a φ2 inch GaN free-standing substrate (manufactured by HVPE) having a (0001) plane as a main surface was prepared as the first seed crystal 200.

  Specifically, the first seed crystal 200 was cut into a strip shape by winding the back surface of the GaN free-standing substrate (made of HVPE) several times along the a-axis (m-plane) of GaN (FIGS. 7 to 9). reference).

  The cut first seed crystal 200 corresponds to the first seed crystal 200 described above, and is a single crystal made of the same material as a whole. The first seed crystal 200 thus cut out was a strip shape whose longitudinal direction was substantially parallel to the a-axis of GaN (that is, the longitudinal direction substantially coincided with the a-axis).

  The length of the first seed crystal 200 in the longitudinal direction was 45 mm, the width was 0.8 mm, and the height (distance between the main surface 200A and the opposing surface 200B) was 0.4 mm.

  Next, the 2nd process-the 4th process were performed using manufacturing device 1 shown in FIG. FIG. 9 is an explanatory diagram of the second to fourth steps.

  In addition, the 2nd process-4th process in a present Example are substantially the same as Example 1. FIG. For this reason, different parts will be described in detail.

  First, an alumina container having an inner diameter of 92 mm and a purity of 99.99% was prepared as the reaction container 12. In addition, a base substrate 270 was installed at the bottom inside the reaction vessel 12. In this embodiment, alumina having a purity of 99.99% was used as a material for the base substrate 270.

  As shown in FIGS. 7 and 8, the base substrate 270 is provided with a groove 270A. The groove portion 270A includes a bottom surface 270D and two wall surfaces (a wall surface 270B and a wall surface 270C) continuous to the bottom surface 270D. These two wall surfaces (the wall surface 270B and the wall surface 270C) are inclined in a direction away from each other as the distance from the bottom surface 270D increases.

  Note that at least one of the two wall surfaces (the wall surface 270B and the wall surface 270C) may be disposed so as to be inclined in a direction away from the bottom surface 270D. In this example, the inclination of the wall surface 270B and the wall surface 270C with respect to the perpendicular Z of the bottom surface 270D (see θC and θD in FIG. 8) was 60 °.

  The pressure vessel 11 provided with the reaction vessel 12 inside was put in a glove box in the same manner as in Example 1.

-Second step-
Next, the main surface 200A of the first seed crystal 200 was placed in the groove 270A provided in the base substrate 270, which was installed at the bottom of the reaction vessel 12, so that the main surface 200A was directed to the opening side of the groove 270A. The first seed crystal 200 was arranged in the groove 270A so that the longitudinal direction of the first seed crystal 200 and the first direction Y of the groove 270A coincided.

  Therefore, the first seed crystal 200 has a groove portion such that the main surface 200A that is the (0001) plane is the opening side of the groove portion 270A, and the facing surface 200B that is the (000-1) surface is in contact with the bottom surface 270D of the groove portion 270A. 270A (see FIG. 8).

-Third step, fourth step-
In this example, the amount of raw material charged was 110 g of gallium (Ga), which is a Group 13 metal raw material, and 77 g of sodium (Na), which is a flux, in the reaction vessel 12. Note that the molar ratio of gallium to sodium was 0.32: 0.68. Further, 0.36 g of carbon was added into the reaction vessel 12.

  Crystal growth conditions such as the crystal growth temperature and nitrogen gas partial pressure were the same as those in Example 1. The crystal growth time was also the same as in Example 1.

  Thereby, crystal growth of the GaN single crystal as the group 13 nitride crystal 203 is started from the main surface 200A of the first seed crystal 200 (FIG. 9B), and the crystal growth is continued (FIG. 9C). ) To FIG. 9 (e)). Thereby, crystal growth is started from the main surface 200A of the first seed crystal 200 in the reaction vessel 12, and the crystal region in contact with the mixed melt 24 is changed to the main surface 200A of the first seed crystal 200 by continuing the crystal growth. The crystals grew out of the way.

  In this example, the {10-11} plane is the main crystal growth plane, and it is observed that the crystal growth continues while the area of the {10-11} plane is enlarged and the c plane is slightly formed. (FIG. 9C to FIG. 9E).

  Specifically, the group 13 nitride crystal 203 that has started crystal growth from the main surface 200A of the first seed crystal 200 reaches the two wall surfaces (surface 270C and surface 270B in FIG. 9) of the groove 270A. A (000-1) plane was formed and grew. Then, after reaching the wall surfaces (surface 270C and surface 270B in FIG. 9) of the groove portion 270A, crystal growth was restricted by these wall surfaces. For this reason, it was confirmed that the formation of the (000-1) plane in the group 13 nitride crystal 203 was suppressed, and the growth in the [000-1] axial direction was also restricted.

  Then, after continuing crystal growth for 300 hours, the heater 13 was turned off, and the temperature of the mixed melt 24 was lowered to room temperature.

  When the pressure vessel 11 was opened after the pressure of the gas in the pressure vessel 11 was lowered, a group 13 nitride crystal 203 was grown on the first seed crystal 200 in the reaction vessel 12 (FIG. 9 (e)). )reference).

―Evaluation of group 13 nitride crystals―
GaN as the group 13 nitride crystal 203 obtained by this crystal growth had the shape shown in FIGS. Specifically, the GaN single crystal as the group 13 nitride crystal 203 obtained by this crystal growth has a (000-1) plane whose bottom is long in the a-axis direction, and two planes continuous with the bottom are {10 -11} plane (see FIGS. 10 and 11).

  The obtained GaN single crystal as the group 13 nitride crystal 203 has six {10-11} planes, which are parallel to the longitudinal direction of the first seed crystal 200 and continuous to the bottom surface. The two surfaces to be processed were {10-11} surfaces that were flat and had a large area (see FIGS. 10 and 11).

  In addition, a c-plane Ga polar face was formed on the upper surface of the obtained group 13 nitride crystal 203. In addition, a depression 205 was formed along the longitudinal direction of the first seed crystal 200 on the c-plane (see FIGS. 10 and 11).

  Further, the bottom of the obtained group 13 nitride crystal 203 had a shape along the shape of the groove 270A of the base substrate 270 (see FIGS. 9E and 11B).

  Further, the first seed crystal 200 was located on the bottom surface of the GaN single crystal as the group 13 nitride crystal 203. No cracks or the like were found in the first seed crystal 200.

  The size of the GaN single crystal as the group 13 nitride crystal 203 obtained by crystal growth is such that the length of the bottom surface in the longitudinal direction is about 59 mm, the maximum width of the bottom surface is 9 mm, and the length of the upper portion in the longitudinal direction is about 45 mm. The height (the shortest distance between the bottom surface and the top surface) was about 11 mm.

As a result of SIMS analysis of the GaN single crystal as the group 13 nitride crystal 203, 10 ¹⁴ to 10 ¹⁵ cm ⁻³ of sodium was detected. Further, the GaN single crystal as the group 13 nitride crystal 203 contained sodium at the impurity level, but metal gallium, metal sodium, or an alloy of gallium and sodium that causes generation of cracks and voids. There was no such inclusion.

(Example 3)
In this embodiment, a group 13 nitride crystal is manufactured using a single-layer first seed crystal 200 instead of the first seed crystal 100 used in the first embodiment. Further, in this example, instead of the base substrate 27 used in Example 1, a base substrate 272 (see FIG. 12) provided with a groove 272A was used (details will be described later).

―First step―
First, the first seed crystal 200 was prepared. In this example, first, a φ2 inch GaN free-standing substrate (manufactured by HVPE) having a main surface of (0001) plane was prepared. Then, on this GaN free-standing substrate, a free-standing substrate was manufactured by LPE (liquid phase epitaxy) by the NaFlux method. Then, a strip-shaped first seed crystal 200 whose longitudinal direction is substantially parallel to the a-axis of GaN is cut out from this free-standing substrate (see FIG. 14A).

  The first seed crystal 200 cut out is a single crystal made of the same material as a whole. The first seed crystal 200 thus cut out was a strip shape whose longitudinal direction was substantially parallel to the a-axis of GaN (that is, the longitudinal direction substantially coincided with the a-axis).

  The length of the first seed crystal 200 in the longitudinal direction was 45 mm, the width was 0.8 mm, and the height (distance between the main surface 200A and the opposing surface 200B) was 0.4 mm.

  Next, the 2nd process-the 4th process were performed using manufacturing device 1 shown in FIG. FIG. 14 is an explanatory diagram of the second to fourth steps.

  In addition, the 2nd process-4th process in a present Example are substantially the same as Example 1. FIG. For this reason, different parts will be described in detail.

  First, an alumina container having an inner diameter of 92 mm and a purity of 99.99% was prepared as the reaction container 12. In addition, a base substrate 272 was installed at the bottom inside the reaction vessel 12. In this embodiment, alumina having a purity of 99.99% was used as the material for the base substrate 272.

  The base substrate 272 is provided with a groove 272A as shown in FIGS. The groove portion 272A includes a bottom surface 272D and two wall surfaces (wall surface 272B) continuous to the bottom surface 272D. Both of these two wall surfaces (wall surface 272B) are arranged perpendicular to the bottom surface 272D. That is, the base substrate 272 has a configuration in which a groove portion 272A is formed on a flat plate.

  The depth of the groove portion 272A was 0.4 mm, which is the same as the height of the first seed crystal 200.

  The pressure vessel 11 provided with the reaction vessel 12 inside was put in a glove box in the same manner as in Example 1.

-Second step-
Next, the main surface 200A of the first seed crystal 200 was disposed in the groove 272A provided on the base substrate 272, which was installed at the bottom of the reaction vessel 12, so that the main surface 200A was directed to the opening side of the groove 272A. The first seed crystal 200 was arranged in the groove portion 272A so that the longitudinal direction of the first seed crystal 200 and the first direction Y of the groove portion 272A coincided with each other.

  Therefore, the first seed crystal 200 has a groove portion so that the main surface 200A that is the (0001) plane is the opening side of the groove portion 272A, and the facing surface 200B that is the (000-1) surface is in contact with the bottom surface 272D of the groove portion 272A. 272A (see FIG. 12).

-Third step, fourth step-
In this example, the amount of raw material charged was 110 g of gallium (Ga), which is a Group 13 metal raw material, and 77 g of sodium (Na), which is a flux, in the reaction vessel 12. Note that the molar ratio of gallium to sodium was 0.32: 0.68. Further, 0.36 g of carbon was added into the reaction vessel 12.

  Crystal growth conditions such as the crystal growth temperature and nitrogen gas partial pressure were the same as those in Example 1. The crystal growth time was also the same as in Example 1.

  Thereby, the crystal growth of the GaN single crystal as the group 13 nitride crystal 303 is started from the main surface 200A of the first seed crystal 200 (FIG. 14B), and the crystal growth is continued (FIG. 14C ) To FIG. 14 (e)). Thereby, crystal growth is started from the main surface 200A of the first seed crystal 200 in the reaction vessel 12, and the crystal region in contact with the mixed melt 24 is changed to the main surface 200A of the first seed crystal 200 by continuing the crystal growth. The crystals grew out of the way.

  In this example, the {10-11} plane is the main crystal growth plane, and it is observed that the crystal growth continues while the area of the {10-11} plane is enlarged and the c plane is slightly formed. (FIG. 14C to FIG. 14E).

  Specifically, the group 13 nitride crystal 303 that has started crystal growth from the main surface 200A of the first seed crystal 200 reaches (000−) until it reaches the two wall surfaces (surface 272B in FIG. 14) of the groove 272A. 1) A surface was formed and grew. Then, after reaching the wall surface of the groove portion 272A (surface 272B in FIG. 14), crystal growth was restricted by these wall surfaces. As the crystal growth proceeds, the crystal grows out of the groove 272 and expands on the upper surface 272E in the horizontal direction. The bottom of the crystal grown out of the groove is the (000-1) plane, but this plane grows in close contact with the upper surface 272E of the base substrate, so that there is no polarity reversal or adhesion of microcrystals. The {10-11} surface was not roughened.

  Then, after continuing crystal growth for 300 hours, the heater 13 was turned off, and the temperature of the mixed melt 24 was lowered to room temperature.

  When the pressure vessel 11 was opened after the pressure of the gas in the pressure vessel 11 was lowered, the group 13 nitride crystal 303 was grown on the first seed crystal 200 in the reaction vessel 12 (FIG. 14 (e)). )reference).

―Evaluation of group 13 nitride crystals―
GaN as the group 13 nitride crystal 303 obtained by this crystal growth has the shape shown in FIGS. 15 and 16. Specifically, the GaN single crystal as the group 13 nitride crystal 303 obtained by this crystal growth has a (000-1) plane whose bottom is long in the a-axis direction, and two planes continuous with the bottom are {10 -11} plane (see FIGS. 15 and 16).

  The obtained GaN single crystal as the group 13 nitride crystal 303 has six {10-11} planes, which are parallel to the longitudinal direction of the first seed crystal 200 and continuous to the bottom surface. The two surfaces to be processed were flat and large {10-11} surfaces (see FIGS. 15 and 16).

  Moreover, the cross-sectional shape orthogonal to the a axis of GaN as the obtained group 13 nitride crystal 303 was substantially triangular. Further, the shape of the bottom surface of the group 13 nitride crystal 303 was a hexagonal shape that was long in the a-axis direction.

  In addition, a c-plane Ga polar face was formed on the upper surface of the obtained group 13 nitride crystal 303. In addition, a recess 305 was formed in the c-plane along the longitudinal direction of the first seed crystal 200 (see FIGS. 15 and 16).

  Further, the bottom surface of the GaN single crystal as the group 13 nitride crystal 303 was a c-plane nitrogen polar plane (000-1) plane. The (000-1) plane was flat because crystal growth was limited by the base substrate 270 (see FIGS. 15 and 16).

  In addition, the first seed crystal 200 was located on the bottom surface of the GaN single crystal as the group 13 nitride crystal 303. No cracks or the like were found in the first seed crystal 200.

  The size of the GaN single crystal as the group 13 nitride crystal 303 obtained by crystal growth is such that the length in the longitudinal direction of the bottom surface is about 59 mm, the maximum width of the bottom surface is 12 mm, and the length in the longitudinal direction of the upper portion is about 45 mm. The height (the shortest distance between the bottom surface and the top surface) was about 11 mm.

As a result of SIMS analysis of the GaN single crystal as the group 13 nitride crystal 203, 10 ¹⁴ to 10 ¹⁵ cm ⁻³ of sodium was detected. Further, the GaN single crystal as the group 13 nitride crystal 203 contained sodium at the impurity level, but metal gallium, metal sodium, or an alloy of gallium and sodium that causes generation of cracks and voids. There was no such inclusion.

(Example 4)
In this embodiment, a group 13 nitride crystal is manufactured using a single-layer first seed crystal 200 instead of the first seed crystal 100 used in the first embodiment. Further, in this example, instead of the base substrate 27 used in Example 1, a base substrate 274 (see FIG. 17) provided with a groove 274A was used (details will be described later).

―First step―
First, the first seed crystal 200 was prepared. In this example, first, a bulk GaN crystal manufactured by a flux method was processed to prepare a GaN substrate having a (0001) plane as the main surface. A crystal cut into a strip shape from this GaN substrate was used as the first seed crystal 200. The strip-shaped first seed crystal 200 was cut out with a diamond pen by winding the back surface of the GaN substrate several times along the a-axis (m-plane) of GaN.

  The GaN substrate used in this example is manufactured by processing a bulk crystal that has been enlarged by crystal growth using a GaN crystal spontaneously grown by the flux method as a seed crystal.

Unlike the HVPE GaN free-standing substrate, the GaN substrate manufactured in this manner is obtained by crystal growth without using a heterogeneous substrate. Therefore, residual stress and warpage are small, the radius of curvature is large, and the c-axis and a-axis are aligned. Also, the dislocation density of the c-plane is the main surface also, to HVPE-made self-supporting substrate in the range of about ¹⁰ 6 ^{cm -2,} less 10 2 ^{cm -2} or less and more than four digits.

  In this example, such a high quality GaN crystal is used as the first seed crystal 200.

  The cut first seed crystal 200 corresponds to the single-layer first seed crystal 200 described above, and is a single crystal of the same material as a whole. The first seed crystal 200 thus cut out was a strip shape whose longitudinal direction was substantially parallel to the a-axis of GaN (that is, the longitudinal direction substantially coincided with the a-axis).

  The length of the first seed crystal 200 in the longitudinal direction was 15 mm, the width was 0.8 mm, and the height (distance between the main surface 200A and the opposing surface 200B) was 0.4 mm.

  Next, the 2nd process-the 4th process were performed using manufacturing device 1 shown in FIG. FIG. 19 is an explanatory diagram of the second to fourth steps.

  In addition, the 2nd process-4th process in a present Example are substantially the same as Example 1. FIG. For this reason, different parts will be described in detail.

  First, an alumina container having an inner diameter of 92 mm and a purity of 99.99% was prepared as the reaction container 12. A base substrate 274 was installed at the bottom inside the reaction vessel 12. In this embodiment, alumina having a purity of 99.99% was used as the material for the base substrate 274.

  The base substrate 274 is provided with a groove 274A as shown in FIGS. The groove portion 274A includes a bottom surface 274D and two wall surfaces (wall surface 274B and wall surface 274C) continuous to the bottom surface 274D (see FIGS. 17 and 18). Further, in these two wall surfaces 274B and 274C), at least a part of the region in the depth direction of the groove portion 274A is inclined in a direction away from the bottom surface 274D.

  In the present embodiment, the wall surface 274B and the wall surface 274C of the groove portion 274A are divided into a plurality of regions in the depth direction of the groove portion 274A, and the vertical line of the bottom surface 274D (FIG. 17 and FIG. The inclination with respect to the Z direction) is large.

  Specifically, the wall surface 274B is divided into two regions, a region 274F and a region 274G, in order from the bottom surface 274D side to the opening edge 274E side in the depth direction of the groove portion 274A. The wall surface 274C is divided into two regions of a region 274H and a region 274I in order from the bottom surface 274D side to the opening edge 274E side in the depth direction of the groove portion 274A.

  Of these plural regions (region 274F, region 274G, region 274H, region 274I), the region (region 274F and region 274H) continuous to the bottom surface 274D has an inclination of 0 ° with respect to the perpendicular (see Z direction). there were. In the present embodiment, a perpendicular (refer to the arrow Z direction) of the region (region 274G and region 274I) on the opening edge 274E side among the plurality of regions (region 274F, region 274G, region 274H, region 274I). ) (See θG and θI in FIG. 18) was 87 °.

  In addition, the height of each of the region 274F and the region 274H, which are regions continuous with the bottom surface 274D, was 0.4 mm, which is the same as the thickness of the first seed crystal 200.

  The pressure vessel 11 provided with the reaction vessel 12 inside was put in a glove box in the same manner as in Example 1.

-Second step-
Next, the main surface 200A of the first seed crystal 200 was disposed in the groove portion 274A provided in the base substrate 274 provided at the bottom portion in the reaction vessel 12 so as to face the opening side of the groove portion 274A. The first seed crystal 200 was disposed in the groove portion 274A so that the longitudinal direction of the first seed crystal 200 and the first direction Y of the groove portion 274A coincided with each other.

  Therefore, the first seed crystal 200 has a groove portion so that the main surface 200A that is the (0001) plane is the opening side of the groove portion 274A, and the facing surface 200B that is the (000-1) surface is in contact with the bottom surface 274D of the groove portion 274A. 274A (see FIG. 18).

-Third step, fourth step-
In this example, the amount of raw material charged was 110 g of gallium (Ga), which is a Group 13 metal raw material, and 77 g of sodium (Na), which is a flux, in the reaction vessel 12. Note that the molar ratio of gallium to sodium was 0.32: 0.68. Further, 0.36 g of carbon was added into the reaction vessel 12.

  Crystal growth conditions such as the crystal growth temperature and nitrogen gas partial pressure were the same as those in Example 1. The crystal growth time was also the same as in Example 1.

  Thereby, the crystal growth of the GaN single crystal as the group 13 nitride crystal 403 is started from the main surface 200A of the first seed crystal 200 (FIG. 19B), and the crystal growth is continued (FIG. 19C). ) To FIG. 19 (e)). Thereby, crystal growth is started from the main surface 200A of the first seed crystal 200 in the reaction vessel 12, and the crystal region in contact with the mixed melt 24 is changed to the main surface 200A of the first seed crystal 200 by continuing the crystal growth. The crystals grew out of the way.

  In this example, the {10-11} plane is the main crystal growth plane, and it is observed that the crystal growth continues while the area of the {10-11} plane is enlarged and the c plane is slightly formed. (FIG. 19C to FIG. 19E).

  Specifically, in group 13 nitride crystal 403 that has started crystal growth from main surface 200A of first seed crystal 200, the bottom surface of two wall surfaces (wall surface 274B and wall surface 274C) that are continuous with bottom surface 274D in groove portion 274A. Until reaching the region close to 274D (region 274F, region 274H), the (000-1) plane was formed and grown. However, after reaching the region (region 274F, region 274H) closest to the bottom surface 274D in the wall surface 272B of the groove portion 272A), it can be confirmed that these regions (274F, region 274H) restrict the crystal growth. It was. Further, it was confirmed that crystals grew along the regions (region 274G, region 274I) closer to the opening edge 274E.

  For this reason, in the group 13 nitride crystal 403, it was confirmed that the formation of the (000-1) plane was suppressed and the growth in the [000-1] axial direction was also restricted.

  Then, after continuing crystal growth for 300 hours, the heater 13 was turned off, and the temperature of the mixed melt 24 was lowered to room temperature.

  When the pressure vessel 11 was opened after the pressure of the gas in the pressure vessel 11 was lowered, a group 13 nitride crystal 403 was grown on the first seed crystal 200 in the reaction vessel 12 (FIG. 19 (e) )reference).

―Evaluation of group 13 nitride crystals―
GaN as the group 13 nitride crystal 403 obtained by this crystal growth has the shape shown in FIGS. Specifically, the GaN single crystal as the group 13 nitride crystal 403 obtained by this crystal growth has a (000-1) plane whose bottom is long in the a-axis direction, and two planes continuous with the bottom are {10 -11} plane (see FIGS. 20 and 21).

  The obtained GaN single crystal as the group 13 nitride crystal 403 has six {10-11} planes, which are parallel to the longitudinal direction of the first seed crystal 200 and continuous to the bottom surface. The two surfaces to be processed were flat and large {10-11} surfaces (see FIGS. 20 and 21).

  In addition, a c-plane Ga polar face was formed on the upper surface of the obtained group 13 nitride crystal 403. In addition, a recess 405 was formed on the c-plane along the longitudinal direction of the first seed crystal 200 (see FIG. 21).

  Further, the bottom portion of the obtained group 13 nitride crystal 403 had a shape along the shape of the base substrate 274 (see FIGS. 19E and 21B).

  Further, the first seed crystal 200 was located on the bottom surface of the GaN single crystal as the group 13 nitride crystal 403. No cracks or the like were found in the first seed crystal 200.

  The size of the GaN single crystal as the group 13 nitride crystal 403 obtained by crystal growth is such that the length of the bottom surface in the longitudinal direction is about 29 mm, the maximum width of the bottom surface is 11 mm, and the length of the upper portion in the longitudinal direction is about 15 mm. The height (the shortest distance between the bottom surface and the top surface) was about 11 mm.

Further, SIMS analysis was performed on the GaN single crystal as the group 13 nitride crystal 403, and as a result, 10 ¹⁴ to 10 ¹⁵ cm ⁻³ of sodium was detected. In addition, the GaN single crystal as the group 13 nitride crystal 403 contained sodium at an impurity level, but metal gallium, metal sodium, or an alloy of gallium and sodium that causes generation of cracks and voids. There was no such inclusion.

100, 200 First seed crystal 103, 203, 303, 403 Group 13 nitride crystal

International Publication No. 10/092736 JP 2005-12171 A JP 2010-37153 A

Claims (10)

A group 13 nitride in which nitrogen is dissolved from a gas phase in a mixed melt containing at least an alkali metal and a group 13 metal held in a reaction vessel, and a group 13 nitride crystal is grown in the mixed melt. In the method for producing a crystal,
The reaction vessel has a groove that is long in the first direction in a first region in contact with the mixed melt inside the reaction vessel,
A first strip-shaped first crystal whose main surface is the (0001) plane, which is a crystal plane in which a group 13 nitride crystal grows by c-axis orientation, and whose longitudinal direction is substantially parallel to the a axis of the group 13 nitride crystal growing. A first step of preparing a seed crystal;
A second step of disposing the first seed crystal in the groove so that the main surface of the first seed crystal faces the opening side of the groove;
A third step of starting crystal growth of a group 13 nitride crystal from the main surface of the first seed crystal disposed in the groove in the mixed melt;
A fourth step of continuing crystal growth while enlarging the area of the {10-11} plane with the {10-11} plane of the group 13 nitride crystal starting crystal growth from the main plane as the main growth plane;
A method for producing a group 13 nitride crystal.   At least one of the groove part and the region continuing to the groove part in the first region is a group 10 nitride crystal grown from the main surface of the first seed crystal disposed in the groove part. 11. The method for producing a group 13 nitride crystal according to claim 1, wherein the crystal growth is possible while increasing the area of the 11} plane.   3. The method for producing a group 13 nitride crystal according to claim 1, wherein the groove is provided as a first region on a bottom portion inside the reaction vessel. 4.   4. The method for producing a group 13 nitride crystal according to claim 1, wherein the groove has a V-shaped cross-sectional shape orthogonal to the first direction. 5.   The groove portion includes a bottom surface that is long in the first direction facing the opposing surface of the main surface in the first seed crystal disposed in the groove portion, and two bottom surfaces along the first direction of the bottom surface and the groove portion. The method for producing a group 13 nitride crystal according to any one of claims 1 to 3, comprising two wall surfaces connecting each of the opening edges.   The method for producing a group 13 nitride crystal according to claim 5, wherein at least one of the two wall surfaces is disposed perpendicular to the bottom surface.   6. The method for producing a group 13 nitride crystal according to claim 5, wherein at least one of the two wall surfaces is inclined in a direction away from each other as the distance from the bottom surface increases.   The at least one of the two wall surfaces is divided into a plurality of regions in the depth direction of the groove part, and the inclination angle with respect to the perpendicular to the bottom surface is larger as the region is located away from the bottom surface. The manufacturing method of the group 13 nitride crystal of description.   The width in the direction orthogonal to the first direction on the bottom surface is greater than the width in the direction orthogonal to both the longitudinal direction and the c-axis direction in the first seed crystal. A method for producing a group 13 nitride crystal according to claim 1.   In the second step, the longitudinal direction of the first seed crystal substantially coincides with the first direction of the groove part, and the main surface of the first seed crystal faces the opening side of the groove part. The method for producing a group 13 nitride crystal according to any one of claims 1 to 9, wherein the first seed crystal is disposed in the groove.

Images