HK1097009B - Oxygen doping method for a gallium nitride single crystal and oxygen-doped n-type gallium nitride single crystal substrate - Google Patents

Description

Method for doping oxygen into gallium nitride crystal and oxygen-doped n-type gallium nitride single crystal substrate

This application is a divisional application of a patent application No. 02105907.1 entitled "method for doping oxygen into gallium nitride crystal and n-type gallium nitride single crystal substrate doped with oxygen", filed on 9.4.2002.

Technical Field

The present invention relates to a light emitting diode comprising a group 3 to 5 nitride compound semiconductor, a light emitting device such as a semiconductor laser, and a method for doping oxygen into a gallium nitride (GaN) single crystal substrate crystal used in an electronic device. On a substrate, impurities are doped into a GaN crystal body during epitaxial growth of a GaN thin film and growth of a GaN bulk crystal. The film laminated is not only a GaN film, but also a laminated film such as a ternary mixed film, a quaternary mixed film, or the like In which In, P, As., or the like is added, as is the case with the nitride-based compound semiconductor. The light emitting active layer is GaInN. And the host is GaN. Since other components are contained, they will be described accurately together with the nitride system. Therefore, in the following description, a GaN-based device or a GaInN-based device can be considered to represent the same device.

Prior Art

Light emitting devices using nitride semiconductors, especially blue LEDs, have been put to practical use. Conventionally, a light-emitting device of a nitride semiconductor has been used, in which sapphire is used as a substrate. A GaN layer, a GaInN layer, or the like is epitaxially grown on a single crystal sapphire substrate to form an outer wafer. For GaN, Si is used as the n-type dopant. On the outer wafer, a GaInN-LED device is fabricated by a wafer process. Sapphire is an extremely stable, strong substrate. A GaN layer can be well epitaxially grown on a sapphire substrate and a GaInN layer can be well grown thereon. Currently, GaN-based blue LEDs can be fabricated on sapphire substrates. Sapphire (alpha-Al)₂O₃) And the lattice constant of GaN (mismatch), however, GaN layers grow well on sapphire substrates. Further, the GaN layer is not deteriorated, though it has a large dislocation rearrangement, and is still strong.

Since sapphire is a trigonal single crystal, a GaN thin film is grown on the C-plane. Since sapphire and GaN have different crystal systems, GaN is epitaxially grown only on the C-plane having 3-dimensional symmetry. Therefore, the GaInN-LEDs that are actually used at present are each configured by collecting thin films grown in the C-axis direction on a C-plane sapphire substrate.

That is, the surface layers of GaN and GaInN thin films on the sapphire plane are all C-plane grown. C-plane growth is performed only on a substrate using sapphire. In other plane orientations, epitaxial growth is not possible. Therefore, all of the GaInN-LEDs and GaInN-LDs currently used are formed by collecting GaN and GaInN layers grown on the C-plane, and there is no thin film having other plane orientations. However, ELO (epitaxial lateral overgrowth) and pendeo-epi exhibit a surface other than the C-plane at the end in the middle of growth, but are not limited thereto.

Sapphire and GaN have a large lattice mismatch and many defects, however, GaN is strong near ceramics, defects cannot grow, and defects cannot be said to grow and become brittle. The high defect density enables the GaN-LED to have long service life, has obvious practical performance and obtains quite high evaluation.

However, sapphire substrates have several disadvantages. The sapphire substrate is extremely hard and cannot be separated from the surface. Therefore, with the wafer process, it is not possible to perform separation by cleaving when dicing the wafer after forming devices on the wafer. Other methods using mechanical cutting (dicing) are not feasible. Since a dicing process is required, the cost increases.

In the case of an LED, however, in the case of an LD (semiconductor laser), the reflecting mirror surfaces forming the resonator must be on both sides of the active layer. Since there is no dissociation plane, a mirror surface cannot be formed by natural dissociation. The end face is processed to be flat and smooth with good accuracy by gas phase etching such as RIE (reactive ion etching) to produce a mirror surface. This is not a simple task. And complicated operations are required for processing various substrates. The work for producing the resonator surface is a cause of the increase in the manufacturing cost of the GaInN-based LD.

Since sapphire is an insulator, an electrode cannot be formed on the bottom surface. A p-electrode, an n-electrode, etc. must be formed thereon. On a sapphire substrate, an n-type layer is laminated with several layers. Since a current flows laterally, a thick n-type conductive layer must be formed. On the laminated n-type layer, a p-type layer is stacked to form a pn junction. However, it is complicated to expose the n-type layer by removing the p-type layer in the outer peripheral portion a little and to resistively join the n-electrode in this portion. The number of processes and the time of the processes are increased, and the cost is increased. Since it is necessary to form electrodes at two locations on the same surface, the necessary wafer area is increased. This causes an increase in cost. GaN-based LEDs of sapphire substrates have been put to practical use, however, the above-mentioned disadvantages have not been overcome.

An ideal substrate that can solve these problems is a GaN single crystal substrate. Since surface layers of GaN, GaInN, etc. are deposited, the problem of mismatch of crystal lattices is completely eliminated in the case of a GaN substrate. If n-type GaN is thus produced, it is possible to produce an n-type electrode from the bottom surface of the wafer. If the p-electrode and the n-electrode are arranged on the upper and lower sides, the device can be manufactured more easily, and wire bonding can be performed easily when the device is actually mounted on a module. The necessary wafer area can be reduced.

Since GaN has dissociation properties, the substrate can be cut into wafers by natural dissociation. However, the cleavage plane is in the direction of the regular triangle side, and there is no rectangular cleavage plane. Therefore, the wafer is simply dissociated and cannot be cut into a rectangular wafer. From this point of view, unlike Si semiconductors and GaAs semiconductors, this is a disadvantage. However, by partial dissociation, the wafers may be separated. Therefore, with dicing, the cutting process can be reduced. In particular, in the case of a semiconductor Laser (LD), a necessary resonator mirror surface can be cut out by the dissociation. If a flat and smooth mirror surface can be obtained by dissociation, the GaInN-based blue LD can be produced more easily.

However, a high-quality large-area GaN single crystal cannot be grown for a long time. Since a GaN substrate cannot be obtained, it is impossible to produce a GaInN-based LED or LD on the GaN substrate. Therefore, practical LEDs and LDs on GaN substrates cannot be fabricated.

Since the nitrogen vapor pressure is high, it is not feasible to produce a GaN crystal by pulling the GaN crystal by a conventional pulling method by adding a seed crystal to a crucible containing a GaN melt. By applying an ultra-high pressure, a GaN single crystal can be synthesized, however, only a small single crystal is produced. Growth of a very practical large GaN crystal is not possible. Further, the boat method in which polycrystal was added to the boat in which the quartz tube was sealed and heated to melt, and solidified from the end portion, could not produce a GaN single crystal. Large GaN substrates cannot be fabricated using other crystal growth techniques.

However, various improvements have been proposed in recent years for growing GaN single crystals by vapor phase growth. Since a large GaN substrate is not used and a different material substrate is used. On the substrate, a GaN single crystal layer is accumulated by a vapor phase synthesis method similar to that for thin film growth. The vapor phase growth method is a method originally used for thin film growth, but a thick crystal layer can be obtained by continuing the growth with time. The substrate after the growth of the thick GaN crystal is removed by etching or polishing to obtain a GaN single substrate. It goes without saying that a high-quality GaN crystal cannot be easily obtained by a simple vapor phase synthesis method. There are various methods.

There are several different methods for gas phase synthesis. Any of these methods has been developed for growing a GaN thin layer on a sapphire substrate. The Metal Organic Chemical Vapor Deposition (MOCVD) method in which a metal organic (e.g., trimethylgallium, TMG) and ammonia are used as raw materials, the HVPE method (hydride vapor phase epitaxy method) in which a gallium monomer is put in a boat and oxidized with hydrogen chloride gas to produce GaCl, the MOC method (metal organic chloride vapor deposition) in which a metal organic is reacted with HCl to produce GaCl and then reacted with ammonia, and the sublimation method in which GaN polycrystal is heated to sublimate and accumulated on a substrate. Grown on a sapphire substrate, and can be used for manufacturing the GaInN-based LED. Which have various advantages and disadvantages, respectively.

(1) Metal organic vapor phase growth method (MOCVD method)

Among them, the MOCVD method is preferably used. In a cold wall reactor, a raw material gas obtained by diluting TMG and ammonia with hydrogen gas was injected onto a heated substrate, and the reaction was immediately carried out on the substrate to synthesize GaN. The large amount of gas thus injected is only partially used for forming a GaN thin film, and the rest is useless. The yield is low. The growth rate cannot be increased. Can be used for the formation of a thin GaN layer that forms part of an LED, however, the concentration of a thick GaN crystalline layer cannot be faced. This causes carbon contained in the organic metal to be mixed therein as an impurity, and may deteriorate the characteristics.

(2) Organo-metal chloride growth process (MOC process)

The MOC method is a method in which TMG and HCl are reacted in a hot-wall type reaction furnace to produce GaCl once, and then the GaCl is reacted with ammonia in the vicinity of a heated substrate to produce GaN. This method uses GaCl, and therefore, the incorporation of carbon is less than that of the MOCVD method, but such incorporation of carbon also causes a decrease in electron mobility.

(3) Hydride vapor phase growth method (HVPE method)

The HVPE process starts from Ga monomer. This is illustrated by fig. 1. Around the hot wall type reaction furnace 1, a heater 2 is provided. Gas introduction pipes 3 and 4 for introducing a raw material gas are provided at the upper top of the reaction furnace 1. A Ga boat 5 is provided in the upper space inside the reaction furnace 1. The Ga melt 6 was placed in a Ga boat 5 and heated by a heater 2. A gas inlet 3 above the reaction furnace 1 was opened to the Ga boat. Thereby introducing H₂+ HCl gas. The other gas inlet pipe 4 is opened from the lower side of the Ga boat 5. Thereby introducing H₂+NH₃。

A susceptor 7 which can be freely rotated and lifted is supported by a rotary shaft 8 below the inner space of the reaction furnace 1. A GaAs substrate is carried above the susceptor 7. Alternatively, if GaN is produced from a GaAs substrate, a GaN substrate may be placed on the susceptor 7. The susceptor 7 and the substrate 9 are heated by the heater 2. HCl (+ H) is supplied from the gas inlet pipe 3₂) Gas is injected into the Ga melt 6 to produce a GaCl gaseous intermediate product. It falls into the furnace and contacts the ammonia in the vicinity of the heated substrate. On the substrate 9, GaCl and NH₃Reacting to synthesize GaN. Since the raw material of this method contains no carbon, carbon is not mixed into the GaN thin film, and deterioration of electrical characteristics is not caused, which is an advantage.

(4) Sublimation process

GaN is neither subjected to high pressure nor is it a molten liquid. Heating at low pressure to sublimate. In this method, GaN polycrystal is heated to sublimate and transported to a space, and is collected on a substrate having a relatively low temperature.

In addition, an improved method of growing a GaN thin film on a sapphire substrate has been proposed. One of the effective improvements is described below.

[ transverse Process of accretion ]

Please note that "growth of thick film GaN crystal using hydride VPE", the treatise of electronic information and communications, Vol.1, J81-C-II, No.1, P58-64 (1 month in 1998). Here, the GaN growth by the lateral overgrowth method is explained in detail. GaN is grown on a sapphire substrate on a mask with striped (or rod-shaped) windows. Individual dies are grown from the window, through the window, and integrated on the mask outside the window. Therefore, the defect density is reduced. This is a method for reducing the defect density when a GaN film is attached to a sapphire substrate.

The present inventors have also improved a method for producing a GaN crystal substrate by HVPE in a vapor phase synthesis method. Since a GaN substrate is desired to be manufactured, if sapphire is used as a substrate, it is impossible to remove only sapphire. It is not possible to remove only sapphire by grinding or etching due to its chemical, physical properties being robust.

In contrast, there is a method of using GaAs as a substrate. GaN was grown on a GaAs substrate having three-dimensional symmetry using Ga metal, hydrogen-diluted HCl, and hydrogen-diluted NH3 as raw materials. Of course, the growth plane growing in the C-axis direction is a C-plane. The crystal is translocated and grown into a linear shape without any change. The dislocation did not disappear and a permanent elongation was reached.

The present inventors have proposed a method of growing GaN directly on a GaAs substrate, or growing a GaN layer to some extent on a GaAs substrate, placing the GaN layer on a mask having a plurality of regularly aligned holes, and continuing to grow GaN through the holes of the mask. This is not a sapphire substrate, but GaN is grown on a GaAs substrate by lateral epitaxy. E.g. by the applicant

② the explanation of original Heiping No. 10-183446. This is a method of vapor-phase growing a GaN film on a substrate coated with a mask having a striped window, using a dotted GaAs (111) surface as the substrate. Since the crystal nuclei are integrated from the mask in which the isolated windows are grown independently, the number of defects can be reduced. The dislocation extension is cut to grow a crystal with few defects.

By this method, a GaN layer is vapor-grown on a GaAs (111) plane having three-dimensional symmetry, and the GaAs substrate is removed by etching (aqua regia) and polishing, thereby producing an independent film made of only GaN. Therefore, the surface of such a GaN crystal is the C-plane (0001). Namely, (0001) plane GaN crystal.

Moreover, document 2 proposes a GaN freestanding single crystal substrate having a diameter of 20mm or more and a thickness of 0.07mm or more, which is produced by such a production method. This is also a GaN (0001) crystal having a C-plane. In addition, the invention of the present inventor also relates to

③ TEYUANPING No. 10-171276

This application proposes to manufacture GaN freestanding single crystal substrates using such a manufacturing method. This is also a (0001) plane GaN crystal. In these inventions, since GaN is grown in a thick vapor phase on a GaAs substrate, it is inevitable to reverse the growth, and what method is used to reduce the reverse? This is a problem. Further, when the growth surface (C surface) is constituted by a flat surface or a jagged rough surface in some cases, the conditions are found. Conductivity type is almost no problem.

Kensaku motokki, Takuji Okahisa, Naoki Matsumoto, MasatoMatsushima, Hiroya Kimura, hitoshi kasai, Kikurou Takemoto, Koji Uematsu, Tetsuya Hirano, Masahiro Nakayama, Seiji Nakahata, Masaki Ueno, daijiiro hara, Yoshinao kumagaii, akiori Koukitu, and Hisashi Seki, "independent large GaN substrates were epitaxially produced using GaAs as a starting substrate and using hydride vapor phase orientation", jpn.j.appl.phys.vol.40(2001) pp.l140 to 143. A GaN single crystal independent film is produced by lateral epitaxy using a GaAs (111) crystal as a substrate. This is also (0001) GaN crystal. Crystals having a thickness of 500 μm and a diameter of 2 inches. The n-type conductivity will be described. Index density of 2X 10⁵cm^-2Carrier concentration n is 5 × 10¹⁸cm^-3Mobility of 170cm²Vs, resistivity of 8.5X 10^-3Omega cm. No n-type dopant is described.

'Wutai original Ping' No. 11-144151

The present inventors have found for the first time that oxygen is effective as an n-type dopant. And an n-type GaN freestanding film having oxygen as an n-type dopant was proposed. In addition, it was found that the activity ratio of oxygen in GaN is high, and is close to 1. Since carbon (C) is also an n-type impurity in GaN, it is necessary to exclude it as much as possible. Therefore, the MOCVD method, which is currently the mainstream, is not preferable. The HVPE process is considered to be preferred.

Since GaN is a three-dimensionally symmetric hexagonal crystal, the method of expressing the crystal plane is different from that of a cubic crystal system such as GaAs (zinc blende). The crystal representation of the hexagonal system will be briefly described. There are 3-parameter representation methods, and there are also 4-parameter representation methods. Here a 4-parameter representation is used. First, 3 main axes are defined as an a axis, a b axis, and a d axis. The major axes are in a plane forming a central angle of 120 degrees. And a-b-d.

And any one of a, b, d is an axis that perpendicularly intersects. This is the c-axis. The c-axis is independent for the a-axis, b-axis, and d-axis. There are a plurality of parallel crystallographic planes. The 1 st crystal plane was sliced from the origin at a distance of a/h, b/k, d/m, c/n from the origin. The intersection points of the reverse extensions with-a, -b, -d are considered when not cutting the forward portions of these axes. h. k, m, n must be integers. The face index at this time is written as (hkmn) for constraint.

With indices relating to the 3 principal axes a, b, d, there is a geometrical constraint h + k + m equal to 0. The intersection index n with the c-axis is free. In expressing the face index, it is customary not to add commas, and therefore, 4 positive and negative integers are put in parentheses for expression. Negative numbers, underlined above the numbers, are mineralogically determined. Since this cannot be done, it is indicated here with a minus sign in the front.

Denoted by (hkmn) is a representation of the individual face. Denoted by hkmn is a representation of all the faces. By the symmetry operation of the crystal, the overall expression including all the plane orientations obtained by the transformation is obtained.

The plane orientation is an indication of the direction of the additional display line. The individual directions are denoted by [ hkmn ]. This means the direction in which the individual face orientations (hkmn) intersect perpendicularly. The overall direction is denoted as < hkmn >. These are the set of all individual directions reached from an individual orientation (hkmn) by a symmetry operation allowed by crystallization.

The C-plane is the most representative plane. Conventionally, GaN produced by crystal growth is considered to be grown on all C-planes. When a different single crystal substrate such as sapphire or GaAs is used, only a three-dimensional symmetry plane is used, and therefore the plane on which the growth occurs is limited to the C-plane. There are 2 important facets other than the C facet (0001).

One is the {1-100} plane. This is the release surface. The plane perpendicular to the C-plane is a set of 6 individual planes. All of (1-100), (10-10), (01-10), (-1100), (-1010), and (0-110) are referred to as M-plane. The planes of dissociation are at an angle of 60 degrees to each other and do not intersect perpendicularly.

Another important plane is the 11-20 plane. Commonly referred to as the a-plane. The a side is not a release side. The a-plane is also a collective name for the 6 individual planes. All of (11-20), (1-210), (-2110), (2-1-10), (-12-10), and (-1-120) are referred to as "A" plane.

The C plane is defined by 1, while the a and M planes have 3 different directions. A certain A-plane and a certain M-plane intersect perpendicularly. Thus, the a-plane, the M-plane, and the C-plane may constitute a group of planes that intersect perpendicularly. The inventors' method for making

Sixthly, Japanese patent application No. 10-147049 proposes a GaN device having a cleavage plane (M-plane) on its edge. This is also a GaN crystal having the C-plane as the surface. An invention having a problem in dissociation planes can be mentioned. Various methods have been proposed for reducing through-indexing. The inventors' method for making

Seventhly, No. 11-273882 suggests that the C-plane is not mirror-grown, but is grown in the C-axis direction of the facet other than the C-plane, and the index is lowered by sweeping the index on the facet. This is said to preserve the facets and grow evenly in the C-plane. Further, the inventors

The finding of the character of the through dislocation in GaN is that the through dislocation extends perpendicularly to the plane, examined by the experimental section of santoprene 2000-207783. The C-axis direction of C growth extends through the dislocation. The present invention proposes a so-called collective method in which GaN grown on the C-plane is cut out in the A-plane direction, on which GaN is grown on the A-plane or GaN is grown on the C-plane, and cut out in the M-plane direction, on which GaN is grown on the M-plane. Then, the crystal was cut out on the C-plane to obtain a GaN crystal with low dislocation.

Only this original technique (C) and (b) grow on the surface other than the surface C, which was proposed for the first time. It is different from the object of the present invention, which is described here since the invention is primarily directed to face orientation.

Problems to be solved by the invention

GaN vapor phase growth on a sapphire substrate grows without exception with the C-plane as the upper surface. On a sapphire substrate (alpha-Al)₂O₃) When GaN is grown on the three-dimensional symmetrical plane of (2), the C-plane constitutes a mirror surface having six-dimensional symmetry, which is most likely to grow. Therefore, a GaN layer and a GaInN layer are stacked on a C-plane GaN layer and a GaInN layer on a sapphire substrate, which are currently used for manufacturing.

When GaN is grown on the three-dimensional symmetric plane (111) of GaAs, the C-plane growth becomes the surface, as in the case of GaAs as the substrate.

The present inventors wanted oxygen (O) as the n-type dopant for GaN. Recently, the present inventors have found that when oxygen is used as a dopant, the oxygen is less likely to enter the growth plane (C-plane).

This is an unintelligible phenomenon. Therefore, who did not notice before. The present inventors analyzed the surface composition of a C-plane grown GaN sample by SIMS (secondary ion mass spectrometry). This method is a method of counting the number of secondary ions coming out from a sample of accelerated ions (primary ions) to determine the presence ratio of substances present on the surface of the sample. Since the ion peak is an ion peak having insufficient decomposition energy at the beginning and the range is quite wide, the secondary ion is emitted from the wide range. Here, it is found that the C-plane is also doped with oxygen because secondary ions of oxygen are also released from the sample plane.

However, it has been unexpectedly found that the SIMS decomposition energy can be increased by narrowing the peak. When the rough C-plane is viewed in a fine manner, many irregularities (facets) are formed in addition to the C-plane portion, and the C-plane grows while maintaining the inclined plane. The secondary ions may be emitted from the C-plane or from the concave-convex portion. When the oxygen secondary ions were measured by distinguishing the C-plane from the uneven portions (facets), it was found that almost no oxygen came out from the C-plane. After conversion, it was found that the oxygen concentration outside the C plane reached 5X 10¹⁸cm^-3In the case of the C face on the same crystal surface, the oxygen concentration is less than 1X 10¹⁷cm^-3. I.e. the capacity to take up oxygen differs by a factor of 50. The secondary oxygen ions are not actually emitted from the C-plane but are emitted from the facets.

Further, a C-plane sample of a full mirror surface was prepared by changing the growth conditions, and the oxygen concentration was thermally lowered to 1X 10 by SIMS analysis from the surface¹⁷cm^-3The following.

This indicates that the C-plane is hardly doped with oxygen. When the C surface grows, oxygen does not enter the C surface, and the oxygen enters the nature to form a small plane outside the C surface. This is known from the beginning.

Since a single crystal grows, the crystal orientation of which portion in the plane is the same. The facet portion also has a structure in which the upper side constitutes the c-axis. Therefore, the growth is in the c-axis direction. In short, the surface exposed to the outside is not the C-plane. Therefore, it can be said whether oxygen contained in the raw material gas does not enter the crystal, and is not due to the internal crystal structure of the site but due to the microstructure of the surface itself at the time of crystal growth. When a surface other than the C-plane having an inclined surface, for example, the M-plane and the a-plane are exposed, oxygen is taken in due to the independent oxygen adsorption capacity of the surfaces.

In GaN growth, the facet-forming portion often grows continuously along the average growth direction. The facets cannot be frequently annihilated and repeated. For example, when the crystal is grown in the c-axis direction, the facets are held, and GaN grows in the c-axis direction in the longitudinal direction. Therefore, the oxygen concentration was measured in the depth direction of the crystal and in the c-axis direction by combining SIMS and etching, and the oxygen concentration distribution was found to have substantially the same dispersion even at a certain depth. Therefore, even in the C-plane growth, oxygen doping is present on microscopic facets other than the C-plane.

The expert in the field is not aware of this. The reason why the oxygen-doped GaN forms an n-type is preliminarily understood by the present inventors through a research of (c). Oxygen replaces the nitrogen position and becomes an n-type impurity. However, the statement that oxygen is used as an n-type dopant in GaN has not been mainstream. The inventors agree only on this point. Silicon (Si) is the predominant n-type dopant in GaN. It is believed that Si replaces the gallium (Ga) site to become n-type. The assumption of oxygen as an n-type dopant has not been suggested by others other than the present inventors. In the case of oxygen doping, the case of having the plane orientation dependence is not known. Since GaN growth is grown from a three-dimensionally symmetric dissimilar material, it is not necessarily grown with the C-plane as the surface. However, it is found from the above experiment that oxygen hardly enters the C-plane. Therefore, if the C-mirror surface is grown, oxygen cannot be doped at a predetermined concentration. That is, it is impossible to fabricate an n-type GaN substrate having a desired resistivity. Based on such new findings, the present invention provides a GaN crystal growth method using oxygen as a dopant with good efficiency.

The invention comprises the following steps:

1. a method for doping oxygen into a gallium nitride crystal, characterized in that, on a gallium nitride substrate having a non-C-plane on the upper surface thereof, the following steps are performed: a gallium nitride crystal is vapor-grown by holding the surface other than the C-plane while a gallium source material containing no Si compound, a nitrogen source material and a source gas containing a small amount of water added quantitatively, and oxygen is doped into the crystal through the surface other than the C-plane.

2. The method of doping oxygen into a gallium nitride crystal according to item 1, wherein the gallium nitride crystal is grown while maintaining { kk-2kh } plane, and oxygen is doped into the crystal through the { kk-2kh } plane, wherein k and h are integers.

3. The method of doping oxygen into a gallium nitride crystal according to item 1, wherein the gallium nitride crystal is grown while maintaining the { k-k0h } plane, and oxygen is doped into the crystal through the { k-k0h } plane, wherein k and h are integers.

4. The method of doping oxygen into a gallium nitride crystal according to item 2, wherein the gallium nitride crystal is grown while maintaining the {11-20} plane, and oxygen is doped into the crystal through the {11-20} plane.

5. The method of doping oxygen into a gallium nitride crystal according to item 3, wherein the gallium nitride crystal is grown while maintaining the {1-100} plane, and oxygen is doped into the crystal through the {1-100} plane.

6. The method for doping oxygen into a gallium nitride crystal according to any one of items 1 to 5, wherein the growth method of the gallium nitride crystal is HVPE method, MOC method, MOCVD method, or sublimation method.

7. The method for doping oxygen into a gallium nitride crystal according to any one of items 1 to 5, wherein a trace amount of water quantitatively added to a raw material gas is used as an oxygen source for doping oxygen into a gallium nitride crystal.

8. An oxygen-doped n-type gallium nitride single crystal substrate, wherein on a substrate having a non-C-plane, there are provided: a gallium source material containing no Si compound, a nitrogen source material, and a source gas containing a small amount of water added in a fixed amount are grown in a non-C-axis direction by vapor phase growth of a gallium nitride crystal while maintaining a non-C-plane, oxygen is doped into the crystal through the non-C-plane, and oxygen obtained by removing the non-C-plane gallium nitride substrate is contained as an n-type impurity.

9. The oxygen-doped n-type gallium nitride single crystal substrate according to item 8, wherein the substrate having a { kk-2kh } plane is grown by growing a gallium nitride crystal while maintaining the { kk-2kh } plane, and the crystal is doped with oxygen through the { kk-2kh } plane to obtain an n-type gallium nitride substrate having a { kk-2kh } plane, wherein k and h are integers.

10. The oxygen-doped n-type gallium nitride single crystal substrate according to item 8, wherein a gallium nitride crystal is grown on a substrate having a { k-k0h } plane while keeping the { k-k0h } plane, and oxygen is doped into the crystal through the { k-k0h } plane to obtain an n-type gallium nitride substrate having a { k-k0h } plane, wherein k and h are integers.

11. The oxygen-doped n-type gallium nitride single crystal substrate according to item 8, wherein a gallium nitride crystal is grown on a substrate having {11-20} planes while keeping the {11-20} planes, and oxygen is doped into the crystal through the {11-20} planes to obtain an n-type gallium nitride substrate having { k-k0h } planes.

12. The oxygen-doped n-type gallium nitride single crystal substrate according to item 8, wherein a gallium nitride crystal is grown on a substrate having {1-100} planes while keeping the {1-100} planes, and oxygen is doped into the crystal through the {1-100} planes to obtain an n-type gallium nitride substrate having {1-100} planes.

13. A method for producing a gallium nitride single crystal substrate by growing a GaN crystal in the C-axis direction on a sapphire substrate, a GaAs substrate, a SiC substrate or a GaN substrate, characterized in that a raw material gas containing a small amount of water added in a fixed amount is supplied, and facets other than the C-plane and the C-plane are simultaneously formed and grown on the grown GaN crystal, whereby oxygen is contained in a region where the facets other than the C-plane are grown and simultaneously grown.

14. The method of producing a gallium nitride single crystal substrate according to item 13, wherein the growth method of the gallium nitride crystal is HVPE method, MOC method, MOCVD method, or sublimation method.

15. The method of producing a gallium nitride single crystal substrate according to item 14 or 15, wherein a trace amount of water in a raw material gas is quantitatively added as an oxygen source for doping oxygen into the gallium nitride crystal.

16. A gallium nitride single crystal substrate, which is a GaN crystal grown in the C-axis direction on a sapphire substrate, a GaAs substrate, a SiC substrate, or a GaN substrate using a raw material gas to which a trace amount of water is quantitatively added, characterized in that the substrate is grown simultaneously with a C-plane and a facet other than the C-plane, and that a region grown with the facet other than the C-plane contains more oxygen than a region grown with the C-plane.

Means for solving the problem

As a result of detailed studies on the growth of the crystal by changing the crystal to a long plane, the dependence of the amount of oxygen introduced on the orientation of the plane was found. It was found that the oxygen doping amount is dependent on the surface orientation as a result of the experiments conducted by the present inventors. From this, it is understood that oxygen which enters neither the C plane nor any plane orientation is absent. Outside the C-plane, there is a plane into which oxygen easily enters (is doped). The plane orientations susceptible to oxygen doping can be roughly classified into 2 types.

This is the following face orientation.

(1) { kk-2kh } (k, h are integers)

In particular, it is known that the {11-20} plane shows a significant effect. In the {11-22} plane, oxygen entry efficiency is high. With the formation of a high surface index, the oxygen incorporation efficiency tends to decrease.

(2) { k-k0h } (k, h are integers)

In particular, {1-100} planes show significant effects. The oxygen entry efficiency is high in the {1-101} plane. As the surface orientation becomes high, the oxygen incorporation efficiency tends to decrease.

I.e., intrinsic oxygen doping capability at the plane { hkmn }. It can be represented by the coefficient of OD { hkmn }.

The details of OD { hkmn } are not known, but the plane { hkmn } other than the C-plane may be said to be OD { hkmn } > OD {0001 }. That is, the C-plane can be said to be the most difficult plane to dope with oxygen.

For the A-plane {11-20}, OD {11-20} > 50OD {0001 }. It is considered that the a-plane is easier to dope with oxygen by more than 50 times than the C-plane.

For the M-plane {1-100}, OD {1-100} > 50OD {0001 }. The M-plane is easier to dope than the C-plane with oxygen by more than 50 times.

When oxygen doping is performed, the upper surface is made to have a surface other than the C-plane, and doping can be performed efficiently by crystal growth. When doping is performed by this method, oxygen is doped in the bulk crystal in a region other than the C-plane where crystal growth is delayed.

All the faces are not necessarily the crystal faces (except the C face). It is sufficient if the parts are present in the form of facets. Of course, when the C-plane growth part is present widely, the oxygen uptake and extraction efficiency of the part is lowered.

The phenomenon that the oxygen uptake is dependent on its plane orientation is only the discovery of the present inventors. The detailed mechanism is not clear. Since the bonding method of the specific element is different depending on the state of the atomic bond extending out of the crystal plane surface, it is considered that the method for collecting impurities is changed.

In particular, when the GaN (0001) Ga surface is used as an growth surface, it is presumed that a mechanism in which oxygen is incorporated into nitrogen as an n-type carrier is very difficult to be incorporated works at a site. Of course, this phenomenon is also common when a base substrate or seed crystal such as sapphire, SiC, GaN, or the like is used.

Embodiments of the invention

Oxygen doping is most effective when the raw material gas for crystal growth contains water. In the case of HVPE, in ammonia (NH)₃) The hydrogen chloride gas (HCl) may contain water. Conventionally, most of water contained in NH3 and HCl is impurities, and particularly, oxygen can be doped with water contained in the raw material gas even if water is not added to the raw material gas. However, for stable oxygen doping, a trace amount of water is required to be quantitatively added to the raw material gas.

According to the idea of the present invention, the method for effectively doping oxygen is largely divided into two methods. One is to grow in a direction other than the c-axis (non-c-axis growth), and the other is to grow facets in the c-axis direction. Namely, non-c-axis growth and facet c-axis growth.

The (A) non-C-axis growth is a method of producing a grown single crystal ingot in the plane orientation by using a seed crystal having a plane { hkmn } other than the C-plane on the surface (upper surface) and growing a crystal on the plane other than the C-plane.

A method in which oxygen doping is effectively performed over the entire surface when crystal growth is performed while maintaining the crystal plane { hkmn } of a seed crystal as it is.

For example, in the case of {1-100} plane (M-plane) or general { k-k0h } plane (k, h are integers), oxygen doping can be efficiently performed on the entire surface of the seed crystal.

The same applies to {11-20} (A-plane) or a general { kk-2kh } plane (k, h are integers). In this case, the doping efficiency of oxygen is simply the same as

OD＝OD{hkmn}

Symbolically represented. The principle of the method is simple, but the method has several problems in implementation. GaN single crystals with surfaces other than the C-plane are neither naturally occurring nor produced by vapor phase growth from different substrates. GaN and GaInN thin films grown on the three-dimensional symmetric plane of sapphire, which are currently used in LEDs and LDs, are C-plane crystals. As described above, when the GaN is grown on a sapphire substrate, a GaN crystal monomer cannot be obtained without removing sapphire.

When vapor phase growth is performed on a GaAs (111) plane, a GaN crystal having a C plane grows. After the GaAs substrate was removed by aqua regia, a GaN single crystal was obtained. However, the crystalline surface is also a C-plane. When a thick GaN crystal is produced, for example, a single crystal having an a-plane on the surface is produced by slicing the a-plane direction, it can be used as a seed crystal. Therefore, a pre-seeding step of preparing a seed crystal having a C-plane or outer surface is required.

The (B) facet C-axis growth is a method of growing a crystal having a C-plane as an upper surface and microscopically growing a facet having a plane other than the C-plane.

In the method B, the average crystal plane of the seed crystal surface is a C-plane, and when the growth of facets other than the C-plane is microscopically observed, the effect of oxygen doping can be obtained by the facets.

Specific examples of the facet include { k-k0h } planes such as {1-101} planes (k, h are integers). These are surfaces that incline the M-plane. The M-plane itself is perpendicular to the C-plane and therefore not a facet.

Alternatively, { kk-2kh } planes such as {11-22} planes may be used. These are surfaces that incline the a-plane. Since the a-plane itself is perpendicular to the C-plane, it is not a facet for C-plane growth. This is where a single facet is contained within the C-plane.

Although single, the GaN crystal has six-dimensional symmetry around the c-axis, so these planes are a collection of 6 individual planes. Although it is a single plane, a 6-angle spindle-shaped hole (pit) or a 6-angle spindle-shaped protrusion may be formed on the C-plane. All the surfaces may not be present, but 3-pyramid holes, 5-angle spindle shaped holes with irregular shapes of protrusions, and protrusions are formed.

This is the case with a single facet, however, by growing a C-plane containing a plurality of facets, oxygen doping can be efficiently performed. For example, when a crystal is grown to include a plurality of facets consisting of { kk-2kh } plane and { k-k0h } plane, oxygen may be doped. For example, 6 {11-21} planes and 6 {1-101} planes may form a regular 12 pyramid. Such a hole or protrusion can be formed by combining 2 surfaces. E.g., more than 3 facets, more complex shapes of pyramidal holes or protrusions can be made.

When the C-plane is grown while leaving the pit-like facets of inverse hexagonal pyramid (hexagonal pyramid) and inverse dodecapyramid (dodecapyramid) shapes composed of a set of { kk-2kh } planes and { k-k0h } planes (k, h is an integer), oxygen can be doped into the pit-like facets. The method is complex, and when the probability of the presence in the C-plane of the { hkmn } plane is expressed by ρ { hkmn },

OD＝∑ρ{hkmn}OD{hkmn}

the doping efficiency of oxygen can be symbolically expressed.

As a method for growing GaN on a sapphire substrate, any method such as an HVPE method, an MOC method, an MOCVD method, or a sublimation method can be effectively used.

Brief description of the drawings

FIG. 1 is a schematic cross-sectional view of a GaN crystal growth apparatus using HVPE.

FIG. 2 is a sectional view of a GaN crystal in the step of example 1 in which a GaN layer is grown by vapor phase growth on a GaN seed crystal having an M-plane (1-100). (a) Is a cross-sectional view of a GaN seed crystal having an M-plane (1-100); (b) is a sectional view of a GaN crystal in a state where a (1-100) crystal is grown on a GaN seed crystal; (c) removing the seed crystal to obtain a GaN crystal cross-sectional view of only the growth part; (d) is a cross-sectional view of the M-plane GaN crystal in a further polished state.

FIG. 3 is a sectional view of a GaN crystal in the step of comparative example 1 in which a GaN layer is grown by vapor phase growth on a GaN seed crystal having a C-plane (0001). (a) Is a cross-sectional view of a GaN seed crystal having a C-plane (0001); (b) a GaN crystal cross-sectional view of a (0001) crystal grown on a GaN seed crystal; (c) removing the seed crystal to obtain a GaN crystal cross-sectional view of the growth portion; (d) a cross-sectional view of the C-plane GaN crystal in a further polished state.

FIG. 4 is a sectional view of a GaN crystal obtained in the step of example 2 in which a GaN layer is grown by vapor phase growth while maintaining a facet on a GaN seed crystal having a C-plane (0001). (a) Is a cross-sectional view of a GaN seed crystal having a C-plane (0001); (b) a GaN crystal cross-sectional view in a state where a (0001) crystal having a plurality of facets is grown on a GaN seed crystal; (c) a cross-sectional view of the GaN crystal from which the seed crystal was removed and only the growing portion was formed; (d) is a cross-sectional view of a GaN crystal on the C-plane in a further polished state.

Examples

Example 1 (Crystal growth with M-plane (1-100) as the top; FIG. 2)

A GaN seed crystal having M-planes (1-100) was prepared from the surface sliced from the GaN single crystal ingot (FIG. 2 (a)). The GaN single crystal is grown on a GaAs substrate in the C-plane by the lateral overgrowth method, and the GaAs substrate is removed by dissolving with aqua regia. Therefore, the M-plane is cut on one plane parallel to the crystal growth direction.

The M-plane seed crystal was subjected to surface polishing to remove the surface-processed impurity layer and completely eliminate it.

On this seed crystal, a GaN crystal was grown by HVPE (fig. 2 (b)). The growth conditions were as follows. For NH as nitrogen feed gas₃Feed gas containing about 2ppm water was used. Water is contained as an oxygen source.

Growth temperature 1020 deg.C

·NH₃Partial pressure of 0.2 atmosphere (2X 10)⁴Pa)

HCl partial pressure 1X 10^-2Atmospheric pressure (10)³Pa)

Growth time 6 hours

The thickness of the grown film reaches about 500 μm. However, the seed portion of the substrate is polished away (fig. 2 (c)). The surface was further polished (fig. 2 (d)). The seed crystal was removed and only the grown portion of the crystal layer had a thickness of about 400 μm.

The electrical characteristics of the sample were measured by the Hall (Hall) method, and the average value of 4 points was substantially uniform in the crystal of the following values.

Carrier concentration 6 × 10¹⁸cm^-3

The carrier mobility is 160Vs/cm²

Also, SIMS (secondary ion mass spectrometry) analysis was performed near the surface of the same sample. The results of the measurement were as follows:

hydrogen (H) 2X 10¹⁷cm^-3

Carbon (C) 3X 10¹⁶cm^-3

Oxygen (O) 8X 10¹⁸cm^-3

Silicon (Si) 3X 10¹⁷cm^-3

Carrier concentration of 6X 10¹⁸cm^-3Oxygen concentration of 8X 10¹⁸cm^-3. In GaN, carbon (10) may exist as an n-type impurity¹⁶cm^-3Grade), silicon (10)¹⁷cm^-3Order), specific carrier concentration (10)¹⁸cm^-3Stage) is much lower. These carriers (electrons) are derived from oxygen. Oxygen functions as an n-type impurity, and its activity ratio is considerably high.

The resistivity was measured to be 7X 10^-3About Ω cm, and has a relatively high conductivity. Can be used as an n-type conductive GaN substrate. That is, on the upper surface of sapphire, it is not necessary to form an n-electrode, but it is also possible to form an n-electrode from the bottom surface of an n-type GaN substrate.

The sample produced in this example was a single 400 μm thick GaN substrate with a flat surface. On the GaN substrate, epitaxial growth is then performed to form a shape usable for device fabrication.

Comparative example 1 (Crystal growth with C plane (0001) as the upper surface; FIG. 3)

A GaN seed crystal having a surface constituted by a C-plane (0001) plane was prepared by slicing the GaN single crystal ingot (FIG. 3 (a)). The polarity of the surface is Ga-face. The C-plane seed crystal was subjected to surface polishing, and the surface was processed so that an impurity layer was not present at all.

GaN was grown on the seed crystal by HVPE. The growth conditions were as follows. As in example 1, the same procedure was repeated except that NH was added to the raw material gas containing nitrogen₃A feed gas having a water content of about 2ppm was used.

Growth temperature 1050 deg.C

·NH₃Partial pressure of 0.15 atmosphere (1.5X 10)⁴Pa)

HCl partial pressure5×10^-3Atmospheric pressure (5X 10)²Pa)

Growth time 10 hours

The growth film thickness reached about 500 μm (FIG. 3 (b)). The surface is a flat mirror surface state constituted by (0001) surfaces. It is known that the surface after growth also maintains the C-plane. Then, the seed crystal portion of the substrate is polished off (fig. 3 (c)). The surface was polished, and the seed crystal was removed, so that the thickness of the crystal layer was about 400 μm only in the grown portion (FIG. 3 (d)).

The electrical characteristics of this sample were determined by hall method, but could not be directly measured. This is because GaN crystals constitute a high resistance film, and the conductivity is extremely low, which cannot be measured by a conventional measuring instrument. Even at a certain point in the substrate plane, it cannot be measured. That is, free-moving electrons are deficient, the carrier concentration is too low, and sufficient current does not flow, and therefore, measurement cannot be performed.

In addition, SIMS (secondary ion mass spectrometry) analysis was performed near the sample surface. The measurement results are shown below.

Hydrogen (H) 1X 10¹⁸cm^-3

Carbon (C) 2X 10¹⁶cm^-3

Oxygen (O) 1X 10¹⁷cm^-3

Silicon (Si) 2X 10¹⁶cm^-3The following

This oxygen concentration is much lower than in example 1. Known to be about 1/100 lower. This is due to the difference in plane orientation (C-plane and M-plane) only. That is, this is because of the significant dependence of oxygen uptake on the face orientation. The reduction in Si was about 1/10, and the surface orientation dependence was also observed for Si. Carbon and hydrogen, rather, enter the crystal more during C-plane growth. But without dependency. Oxygen is shown to be the most significant in the dependence of the plane orientation.

In this comparative example, since the amount of oxygen taken up as an n-type impurity is small, n-type carriers (electrons) are not released and become insulators. Such a high-resistance substrate cannot emit electrons from the bottom surface, and therefore cannot be used as a conductive substrate of a GaN device.

Example 2 (Crystal growth with C-plane (0001) as the upper pit facet; FIG. 4)

A GaN seed crystal having a surface constituted by C-plane (0001) was prepared by slicing the GaN single crystal ingot (FIG. 4 (a)). The polarity of the surface is Ga-face. The C-plane seed crystal was subjected to surface polishing to remove the surface-affected layer and to make it completely absent.

On this seed crystal, GaN was grown by HVPE. The growth conditions were as follows. Ammonia NH as nitrogen component feed gas₃Feed gas having a water content of about 2ppm was used.

Growth temperature 1030 deg.C

·NH₃Partial pressure of 0.2 atmosphere (2X 10)⁴Pa)

HCl partial pressure 1X 10^-2Atmospheric pressure (10)³Pa)

Growth time 5 hours

The thickness of the grown film reached about 500 μm (4 (b)). The surface state was not a flat C-plane mirror surface as in comparative example 1. The grown crystal surface has a plurality of facets formed by facets other than the C-plane. The facets sparkle and the reflected light is visible. In particular, a pit-like shape is seen which is composed of facets in a reverse hexagonal pyramid shape or a reverse dodecagonal pyramid shape. I.e. a collection of pyramidal pits. These spindle faces are facets. In this sample, almost no C-plane was seen.

The various aspects of the face orientation blend together. Most of the planes are {1-101} planes, {11-22} planes, {1-102} planes, and {11-24} planes. They are collectively represented by { k-k0h } (k, h is an integer), { kk-2kh } planes (k, h is an integer).

Then, the seed crystal portion of the substrate is polished off (fig. 4 (c)). The seed crystals were removed and the thickness of the crystal layer was about 400 μm only in the growing portion. The substrate is a facet with an uneven surface. Both surfaces were polished to prepare a substrate having a thickness of 350 μm (FIG. 4 (d)).

The electrical characteristics of the sample were determined by Hall method, and the 4-point average was about

Carrier concentration 5 × 10¹⁸cm^-3

The carrier mobility is 170Vs/cm²

Is almost uniform in the crystal (2).

In addition, SIMS (secondary ion mass spectrometry) analysis was performed near the surface of the same sample. The measurement results are shown below.

Hydrogen (H) 2X 10¹⁷cm^-3

Carbon (C) 3X 10¹⁶cm^-3

Oxygen (O) 5X 10¹⁸cm^-3

Silicon (Si) 4X 10¹⁶cm^-3The following

Carrier concentration of 5X 10¹⁸cm^-3Oxygen concentration of 5X 10¹⁸cm^-3. In GaN, carbon (10) which may be an n-type impurity¹⁶cm^-3Grade), silicon (10)¹⁶cm^-3Order), specific carrier concentration (10)¹⁸cm^-3Stage) is much lower. These carriers (electrons) are derived from oxygen. When the oxygen concentration and the carrier concentration are about the same, it is said that oxygen acts as an n-type impurity and the activity ratio thereof is considerably high.

The resistivity was measured to be 6X 10^-3About Ω cm, and has a relatively high conductivity. Can be used as an n-type conductive GaN substrate. That is, it is not necessary to form an n-electrode on the upper surface of sapphire, and it is possible to form an n-electrode from the bottom surface of an n-type GaN substrate. This example enables growth of a facet other than the C-plane while maintaining the facet, even if the growth is performed in the C-axis direction, and allows oxygen to be extracted from the facet, meaning that low power can be producedAnd (3) crystallizing the n-type GaN.

The test piece in this example was an n-type GaN substrate having a flat surface and a thickness of 350 μm. Then, epitaxial growth is further performed on the surface of the GaN substrate, thereby forming possible properties of the manufacturing apparatus.

ADVANTAGEOUS EFFECTS OF INVENTION

Heretofore, oxygen doping was almost impossible in the C-mirror surface growth of GaN. In the present invention, since the plane other than the C-plane is grown as an upper surface or the C-plane is grown while maintaining the facet, GaN growth is performed while the plane other than the C-plane is exposed. According to the present invention, oxygen can be efficiently taken into the GaN crystal. By determining the plane orientation, the amount of oxygen doped can be accurately controlled. Oxygen can be effectively made to function as an n-type dopant, and this is an extremely effective oxygen doping method.

Claims (14)

1. A method for doping oxygen into a gallium nitride crystal, characterized in that, on a gallium nitride substrate having a non-C-plane on the upper surface thereof, the following steps are performed: a gallium nitride crystal is vapor-grown while maintaining the surface other than the C-plane, and a gallium source material, a nitrogen source material, and a source material gas containing water and no Si compound, and oxygen is doped into the crystal through the surface other than the C-plane.

2. The method of doping oxygen into a gallium nitride crystal according to claim 1, wherein the gallium nitride crystal is grown while maintaining { kk-2kh } plane, and oxygen is doped into the crystal through the { kk-2kh } plane, wherein k and h are integers.

3. The method of doping oxygen into a gallium nitride crystal according to claim 1, wherein the gallium nitride crystal is grown while maintaining the { k-k0h } plane, and oxygen is doped into the crystal through the { k-k0h } plane, wherein k and h are integers.

4. The method of doping oxygen into a gallium nitride crystal according to claim 2, wherein the gallium nitride crystal is grown while maintaining the {11-20} plane, and oxygen is doped into the crystal through the {11-20} plane.

5. The method of doping oxygen into a gallium nitride crystal according to claim 3, wherein the gallium nitride crystal is grown while maintaining the {1-100} plane, and oxygen is doped into the crystal through the {1-100} plane.

6. The method for doping oxygen into a gallium nitride crystal according to any one of claims 1 to 5, wherein the growth method of the gallium nitride crystal is HVPE method, MOC method, MOCVD method, or sublimation method.

7. An oxygen-doped n-type gallium nitride single crystal substrate, wherein on a substrate having a non-C-plane, there are provided: a gallium source material, a nitrogen source material and a source gas containing water and no Si compound, wherein the water is water originally contained in the source gas, a non-C-plane is maintained, a gallium nitride crystal is vapor-grown in a non-C-axis direction, oxygen is doped into the crystal through the non-C-plane, and oxygen obtained by removing the non-C-plane gallium nitride substrate is contained as an n-type impurity.

8. The oxygen-doped n-type gallium nitride single crystal substrate according to claim 7, wherein a gallium nitride crystal is grown on a substrate having a { kk-2kh } plane while keeping the { kk-2kh } plane, and an n-type gallium nitride substrate having a { kk-2kh } plane is obtained by doping the crystal with oxygen through the { kk-2kh } plane, wherein k and h are integers.

9. The oxygen-doped n-type gallium nitride single crystal substrate according to claim 7, wherein a gallium nitride crystal is grown on a substrate having a { k-k0h } plane while keeping the { k-k0h } plane, and an n-type gallium nitride substrate having a { k-k0h } plane is obtained by doping the crystal with oxygen through the { k-k0h } plane, wherein k and h are integers.

10. The oxygen-doped n-type gallium nitride single crystal substrate according to claim 8, wherein a gallium nitride crystal is grown on a substrate having {11-20} planes while keeping the {11-20} planes, and oxygen is doped into the crystal through the {11-20} planes to obtain an n-type gallium nitride substrate having { k-k0h } planes.

11. The oxygen-doped n-type gallium nitride single crystal substrate according to claim 9, wherein a gallium nitride crystal is grown on a substrate having {1-100} planes while keeping the {1-100} planes, and oxygen is doped into the crystal through the {1-100} planes to obtain an n-type gallium nitride substrate having {1-100} planes.

12. A method for producing a gallium nitride single crystal substrate by growing a GaN crystal in the C-axis direction on a sapphire substrate, a GaAs substrate, a SiC substrate or a GaN substrate, characterized in that a water-containing source gas is supplied, and facets other than the C-plane and the C-plane are simultaneously grown on the grown GaN crystal, whereby oxygen is contained in a region where the facets other than the C-plane are grown and the growth is simultaneously carried out, wherein the water is water originally contained in the source gas.

13. The method of producing a gallium nitride single crystal substrate according to claim 12, wherein the growth method of the gallium nitride crystal is HVPE method, MOC method, MOCVD method, or sublimation method.

14. A gallium nitride single crystal substrate, which is a GaN crystal grown in the C-axis direction on a sapphire substrate, a GaAs substrate, a SiC substrate, or a GaN substrate using a raw material gas containing water, characterized in that the substrate is grown simultaneously with a C-plane and a facet other than the C-plane, and that the region grown in the facet other than the C-plane contains more oxygen than the region grown in the C-plane, wherein the water is water originally contained in the raw material gas.