JP2005175275A - Semiconductor light emitting element employing group iii metal nitride crystal and process for producing group iii metal nitride crystal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a process capable of producing a nitride crystal of group III metal in a short time by increasing the growth rate thereof, and to provide a semiconductor light emitting element employing a nitride crystal of group III metal thus produced as a substrate. <P>SOLUTION: In the process for producing a nitride crystal of group III metal on the surface of a seed crystal by immersing the seed crystal into melt mixing at least one kind selected from group III metals and more than two kinds selected from alkaline metals or alkaline earth metals in a reaction vessel and then touching the melt to nitrogen, the process is carried out while increasing the concentration of N in the melt. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a semiconductor light emitting device using a nitride crystal of a group III metal and a manufacturing method for producing the nitride crystal of the group III metal, and more specifically, a cold color (ultraviolet to purple to blue to The present invention relates to a semiconductor light-emitting device used as a green light source and a method for producing a group III metal nitride crystal constituting the device.

  Semiconductor light-emitting elements using Group III metal nitride crystals are used as ultraviolet-violet-blue-green light sources. The basic structure is shown in FIG.

  FIG. 1 is a cross-sectional view for explaining the structure of a conventionally known semiconductor light emitting device. On a support substrate 101, an n layer 102 made of an n type semiconductor, a light emitting layer 103, and a p type semiconductor are formed. The p layer 104 is sequentially laminated. A p-type electrode 105 is provided on the p layer 104, while an exposed surface 107 on which the light emitting layer 103 and the p layer 104 are not provided is formed on a part of the n layer 102. An n-type electrode 106 is provided on the exposed surface 107. Then, by applying a forward bias between the p-type electrode 105 and the n-type electrode 106 (that is, applying a positive voltage to the p-type electrode), electrons and holes are combined in the light emitting layer 103. Emits light. At this time, by using a group III metal nitride crystal as a material for the n-layer 102, the light-emitting layer 103, and the p-layer 104, an ultraviolet-violet-blue-green light source is obtained.

By the way, as a material of the support substrate 101, sapphire, SiC, or the like has been conventionally used. However, to form the nitride crystal of the Group III metal on a sapphire or SiC, generation of dislocations due to lattice mismatch can not be avoided between the nitride crystal of the supporting substrate 101 and the group III metal (n layer), 10 ⁷ Crystal defects of ˜10 ⁸ cm ⁻¹ level are generated, and stress is generated at the interface. Moreover, since the difference in thermal expansion coefficient between sapphire or SiC and the group III metal nitride crystal is large, the quality of the semiconductor light emitting device is deteriorated. Furthermore, since sapphire is particularly hard, it has poor molding processability, and it has been difficult to form it into a desired shape.

  In order to solve these problems, semiconductor light emitting devices that do not use sapphire or SiC as a support substrate material are being developed, and the use of a group III metal nitride crystal itself as a support substrate material has been studied. ing. That is, if an n-layer, a light-emitting layer, a p-layer, etc. (sometimes referred to as a “group III metal nitride crystal layer”) are provided on a group III metal nitride crystal, the group III metal Since the group III metal nitride crystal is laminated on the nitride crystal, there is almost no difference in crystal defects and thermal expansion coefficient, and the group III metal nitride crystal is softer than sapphire and SiC, so it is easy to process. .

Therefore, as a method for growing a group III metal nitride crystal, for example, Patent Document 1 discloses that a seed crystal is formed from a region where a melt containing a group III metal, a flux (for example, a compound containing metal Na or Na) and a nitrogen source are in contact. A technique for growing a nitride crystal of a group III metal by using a metal has been proposed. However, with this technique, it was necessary to maintain the inside of the reaction vessel at a high temperature and high pressure of 750 ° C. and 100 kg / cm ² G in order to grow GaN crystals.
JP 2001-64098 A (see [Claims], [0026], [0058])

  Thus, various methods for producing a Group III metal nitride crystal at a lower pressure than the Na flux method proposed in Patent Document 1 have been studied. In addition to at least one metal selected from Group III metals, It has already been proposed that by using a melt obtained by mixing two or more metals selected from the group consisting of metals or alkaline earth metals, it is possible to produce group III metal nitride crystals even at low pressure [ Non-Patent Document 1 (Journal of the Japanese Society for Crystal Growth, Japanese Society for Crystal Growth, July 2003, Vol. 30, No. 2, p. 38-45)]. This technique makes it possible to produce Group III metal nitride crystals at a relatively low pressure. However, from the viewpoint of improving production efficiency, a method for increasing the growth rate of a group III metal nitride crystal and producing a group III metal nitride crystal in a short time has been desired.

  The present invention has been made in view of such a situation, and an object of the present invention is to increase the growth rate of a group III metal nitride crystal and to produce a group III metal nitride crystal in a short time. It is to provide a method. Another object of the present invention is to provide a semiconductor light emitting device using a group III metal nitride crystal obtained by such a manufacturing method as a base material.

  The method for producing a Group III metal nitride crystal according to the present invention that has solved the above-mentioned problems includes, in a reaction vessel, at least one selected from Group III metals and a group consisting of alkali metals or alkaline earth metals. A method for producing a group III metal nitride crystal on the surface of a seed crystal by immersing a seed crystal in a melt obtained by mixing two or more selected, and bringing the melt into contact with nitrogen. It has a gist in that the N concentration in the melt is increased, and by increasing the N concentration in the melt, the growth of a group III metal nitride crystal on the seed crystal surface can be promoted.

  A semiconductor light-emitting device having a group III metal nitride crystal obtained by the above-described manufacturing method is also included in the present invention.

  According to the present invention, since the growth rate of the group III metal nitride crystal can be increased, the group III metal nitride crystal can be produced in a short time, and the production efficiency can be increased.

  In addition, by using the group III metal nitride crystal obtained by the method of the present invention as a base material of a semiconductor light emitting device, generation of crystal defects in the group III metal nitride crystal layer formed on the base material is prevented. Since it can be suppressed, the non-luminescent center is reduced (ie, the change to heat is reduced), the semiconductor light emitting device has a high brightness and a long life, and the thermal expansion of the base material and the nitride crystal layer of the group III metal Since the difference in coefficients can also be reduced, a semiconductor light emitting device capable of emitting light with high brightness without generating cracks due to thermal stress.

  The inventors of the present invention have made extensive studies on a technique for increasing the growth rate of a group III metal nitride crystal with respect to the technique shown in Non-Patent Document 1. As a result, it has been found that such problems can be solved by increasing the N concentration in the melt when producing a group III metal nitride crystal, and the present invention has been completed. Hereinafter, the present invention will be described in detail.

  In the present invention, the method for producing a group III metal nitride crystal means that at least one metal selected from group III metals and two or more metals selected from the group consisting of alkali metals or alkaline earth metals in a reaction vessel. In the melt, a seed crystal is dipped, and a nitride crystal of a group III metal is grown on the surface of the seed crystal by bringing the melt into contact with nitrogen. It is important to increase the N concentration.

  The melt used in the production method of the present invention is a mixture of at least one metal selected from Group III metals and two or more metals selected from the group consisting of alkali metals or alkaline earth metals I. .

  Group III (Group 13) metals are Al, Ga and In, and in the present invention, a melt containing at least one metal selected from these groups is used. However, since the composition of the Group III metal nitride crystal layer formed on the substrate differs depending on the emission wavelength required for the semiconductor light emitting device, the generation of crystal defects in the Group III metal nitride crystal layer is suppressed. From the viewpoint of reducing the difference in thermal expansion coefficient between the base material and the group III metal nitride crystal layer, the composition of the base material (substrate) is preferably matched to the composition of the group III metal nitride crystal layer. . That is, in order to obtain a semiconductor light-emitting device that serves as a light source having a wavelength of about 250 to 500 nm, it is preferable to use a material containing Ga metal as a base material, and if necessary, an element such as Al or In is mixed. do it. In order to obtain such a substrate, a melt that essentially contains Ga metal may be used, and a melt in which an element such as Al or In is mixed may be used as necessary. The alkali metal is Li, Na, K, Rb, Cs, and Fr, and the alkaline earth metal is Ca, St, Ba, and Ra.

  In the present invention, a melt containing two or more metals selected from the group consisting of alkali metals or alkaline earth metals is used. This is because the use of two or more types increases the solubility of nitrogen in the melt and facilitates the formation of group III metal nitride crystals.

  Here, the melt containing two or more metals selected from the group consisting of alkali metals or alkaline earth metals is (a) a melt containing two or more metals selected from the group consisting of alkali metals. Or (b) a melt containing two or more metals selected from the group consisting of alkaline earth metals, or (c) at least one metal and alkaline earth selected from the group consisting of alkali metals. It may be a melt containing at least one metal from the group consisting of similar metals. Among these, it is particularly preferable to use the melt of the above (c). By using an alkali metal and an alkaline earth metal in combination, nitrogen is easily dissolved in the melt, and the growth of a nitride crystal of a group III metal is promoted. Can be promoted.

  As the alkali metal, Li, Na, or K is preferably used, and Na is particularly preferably used. Therefore, the melt is preferably selected from the group consisting of alkali metals or alkaline earth metals and containing two or more metals that essentially contain Li, Na, or K. More preferably, it is a melt containing two or more metals selected from the group consisting of alkali metals or alkaline earth metals and containing at least Na. On the other hand, it is preferable to use Ca as the alkaline earth metal. Therefore, the melt containing Na and Ca is most preferable.

  The proportion of metals selected from Group III metals in the melt is preferably at least 0.1 mol% in total, and the proportion of two or more metals selected from the group consisting of alkali metals or alkaline earth metals is: The total amount is preferably at least 0.1 mol%. For example, in the case of a melt obtained by selecting Ga from Group III metal and selecting and mixing Na and Ca from alkali metal or alkaline earth metal, Ga is 0.1 to 99.9 mol%, and Na and Ca are 0.1 to What is necessary is just to set it as 99.9 mol%. At this time, the ratio of Na and Ca is about 0.1: 99.9 to 99.9: 0.1 in terms of mol ratio.

The seed crystal immersed in the melt may be any crystal obtained by crystallizing a Group III metal nitride, and a Group III metal nitride crystal formed in advance may be used as a seed crystal. For example, a laminate in which a group III metal nitride crystal is previously formed on a base material such as sapphire, SiC, Si, ZrB ₂ , or AlN by a known method may be used as a seed crystal.

  In addition, when using the said laminated body as a seed crystal, what is necessary is just to provide the nitride crystal of the group III metal used as a seed | species (nucleus) on the said base material surface, The thickness is not specifically limited. Such a substrate can be peeled off and removed from the group III metal nitride crystal by using a laser or the like.

In order to easily peel and remove the seed crystal and the group III metal nitride crystal formed on the surface of the seed crystal, an SiN film or an SiO ₂ film is formed in advance on the surface of the seed crystal, and this film is formed. It is preferable to use a partially etched seed crystal and form a group III metal nitride crystal on the etched surface.

As described above, by forming a SiN film or SiO ₂ film between the seed crystal and the group III metal nitride crystal, the group III metal nitride crystal grows, This is because the nitride crystal of the group III metal can be easily recovered by dissolving the SiO ₂ film with phosphoric acid or the like.

As a method for forming a SiN film, a SiO ₂ film or the like on the surface of the seed crystal, for example, a method such as a CVD method can be employed.

  It is preferable that the group III metal nitride crystal used as the seed crystal is doped in advance with an impurity serving as a donor or an acceptor. That is, it is preferable that a group III metal nitride crystal used as a seed crystal is doped in advance with Si or Mg as an impurity to be n-type or p-type. When a group III metal nitride crystal doped with impurities is used as a seed crystal and a group III metal nitride crystal is grown by the method described later, the seed crystal is formed into a newly formed group III metal nitride crystal layer. This is because impurities such as Si and Mg diffuse therein, and n-type and p-type nitride crystals can be obtained. Group III metal nitride crystals that are not doped with impurities have high resistivity and cannot achieve high output of the semiconductor light emitting device.

  In order to dope a group III metal nitride crystal used as a seed crystal with impurities such as Si or Mg in advance, for example, when forming a group III metal nitride crystal as a seed crystal on a substrate surface such as sapphire A known doping method may be employed in a vapor deposition method [for example, a metal organic chemical vapor deposition method (MOCVD method) or the like].

  Note that the shape of the seed crystal is not particularly limited, and generally a plate-like shape may be used.

  In the production method of the present invention, a group III metal nitride crystal is formed on the surface of the seed crystal by bringing the melt into contact with nitrogen. That is, by bringing the melt in the reaction vessel into contact with nitrogen, nitrogen is dissolved into the melt, and this nitrogen combines with the group III metal in the melt to form a group III metal nitride crystal. A part of the generated nitride crystal floats in the melt, but since the group III metal nitride crystal is immersed in the melt as a seed crystal, most of the generated nitride crystal is a seed crystal. Grows sequentially from the surface.

  At this time, in the production method of the present invention, it is important to increase the N concentration in the melt. That is, the nitrogen dissolved in the melt is combined with a group III metal to form a nitride, and a part of the nitrogen also exists as a free N ion. Therefore, by increasing the N concentration in the melt as much as possible, the amount of N bonded to the Group III metal increases, nitrides are easily formed, and the generation rate of Group III metal nitride crystals increases accordingly.

  Here, the N concentration is a concentration when converted to N atoms, and is calculated by converting N constituting the nitride, free N ions, and the like into N atoms.

  The magnitude of the N concentration in the melt is evaluated using the degree of growth of the nitride crystal of the group III metal. That is, in the production method of the present invention, details will be described later, but as specific means for increasing the N concentration, nitrogen radicals are brought into contact with the melt, the melt near the seed crystal is heated, or nitrogen is melted. A method such as blowing into the liquid is adopted. At this time, if only the conditions such as presence / absence of nitrogen radicals, presence / absence of heating, presence / absence of blowing are changed and other conditions such as temperature, pressure and time are all made equal, nitriding of the group III metal formed on the surface of the seed crystal By measuring the thickness of the product crystal, it is possible to evaluate the influence of conditions such as presence / absence of nitrogen radicals, presence / absence of heating, presence / absence of blowing on crystal growth. That is, the thickness of the generated nitride crystal indicates that the group III metal and N ions existing in the melt are combined and crystallized, so that the thicker the thickness, the higher the N ion concentration in the melt. The present inventors think that this is shown.

  Next, specific modes for carrying out the production method of the present invention will be described in detail with reference to the drawings.

FIG. 2 is a schematic explanatory view of an apparatus used for producing a group III metal nitride crystal, and a means for irradiating a laser to N ₂ gas is provided in order to increase the N concentration in the melt. Yes. That is, the nitrogen cylinder 1 and the crucible 6 are connected by a pipe 2, and a chamber 4 is provided in the middle of the pipe 2. The chamber 4 is provided with a laser generator 3, and the nitrogen gas supplied from the nitrogen cylinder 1 to the chamber 4 through the pipe 2 is excited by the laser 3 a irradiated from the laser generator 3, and at least a part of the nitrogen gas is nitrogen. Nitrogen radicals (and nitrogen gas) generated as radicals are supplied into the crucible 6 through the pipe 2a. In the crucible 6 is stored a melt 8 in which at least one metal selected from Group III metals and two or more metals selected from the group consisting of alkali metals or alkaline earth metals are mixed. When the nitrogen radical (and nitrogen gas) comes into contact with the melt 8, it dissolves into the melt 8 and becomes a nitride of N ions or Group III metals. A seed crystal 7 is immersed in the melt 8, and a nitride crystal of a group III metal grows with the seed crystal 7 as a nucleus.

  As described above, the nitrogen concentration in the melt 8 can be increased by exciting the nitrogen gas with a laser to form nitrogen radicals and bringing the nitrogen radicals into contact with the melt 8. That is, nitrogen radicals are more reactive than nitrogen gas, and the solubility of nitrogen in the melt 8 is higher, so that contacting the nitrogen radicals with the melt 8 increases the N concentration in the melt 8. Can do.

  In this way, by increasing the N concentration in the melt 8, the crystal growth rate with the seed crystal 7 as a nucleus increases, and a group III metal nitride crystal can be produced in a shorter time.

  In addition, the crucible 6 is arrange | positioned in the muffle furnace 5, and the temperature in a furnace is heated by about 600-850 degreeC. The pressure in the crucible 6 is preferably about 0.1 to 15 MPa.

FIG. 3 is a schematic explanatory view for explaining another configuration example of the apparatus shown in FIG. 2, and means for applying a high-frequency electric field to N ₂ gas in order to increase the N concentration in the melt. Is provided. That is, it is the same as FIG. 1 except that the high frequency electric field generator 10 is provided instead of the laser generator 3 in the chamber 4.

  The nitrogen gas supplied from the nitrogen cylinder 1 to the chamber 4 through the pipe 2 is converted into a plasma state by the high-frequency electric field generator 10 in the chamber 4 so that at least a part thereof becomes nitrogen radicals, and the generated nitrogen radicals (and nitrogen gas) ) Is supplied into the crucible 6 through the pipe 2a.

  As described above, when a high-frequency electric field is applied to nitrogen gas to generate nitrogen radicals and the generated nitrogen radicals are brought into contact with the melt 8, the N concentration in the melt 8 can be further increased. .

  In this way, by increasing the N concentration in the melt 8, the crystal growth rate with the seed crystal 7 as a nucleus increases, and a group III metal nitride crystal can be produced in a short time.

  FIG. 4 is a schematic explanatory diagram of another apparatus used when manufacturing a group III metal nitride crystal, and the same parts as those in FIG.

  In the apparatus shown in FIG. 4, means for heating the melt near the seed crystal is provided in order to increase the N concentration in the melt. That is, the nitrogen cylinder 1 and the crucible 6 are connected by the pipe 2, and the nitrogen gas filled in the nitrogen cylinder 1 is supplied to the crucible 6 through the pipe 2. The crucible 6 is heated by the muffle furnace 5 as shown in FIG. 2. In the apparatus shown in FIG. 4, the seed crystal 7 is used to further heat the melt 8 in the vicinity of the seed crystal 7. A heater 11 is provided on the outer periphery of the crucible 6 so as to surround the vicinity where the is disposed. This heater 11 is connected to an AC power source 12 and efficiently heats the melt 8 in the vicinity of the seed crystal 7.

  As described above, by actively heating the melt 8 in the vicinity of the seed crystal 7, the solubility of nitrogen in the melt 8 can be increased, and the N concentration in the melt 8 can be increased. That is, the solubility of nitrogen in the melt 8 increases as the temperature increases.

  In this way, by increasing the N concentration in the melt 8, the crystal growth rate with the seed crystal 7 as a nucleus increases, and a group III metal nitride crystal can be produced on the surface of the seed crystal 7 in a short time. .

  FIG. 5 is a schematic explanatory diagram of another apparatus used when producing a nitride crystal of a group III metal, and nitrogen is blown into the melt in order to increase the N concentration in the melt. That is, the nitrogen cylinder 1 and the crucible 6 are connected by the pipe 2, and the nitrogen gas filled in the nitrogen cylinder 1 is supplied to the crucible 6 through the pipe 2. At this time, the tip 2 b of the pipe 2 is immersed in the melt 8, and nitrogen gas is blown into the melt 8 to cause bubbling.

  As described above, when nitrogen is blown into the melt 8, the contact area between the nitrogen gas bubbles 13 and the melt 8 is increased, and the amount of nitrogen dissolved in the melt 8 is increased. N concentration can be increased.

  In this way, by increasing the N concentration in the melt 8, the crystal growth rate with the seed crystal 7 as a nucleus increases, and a group III metal nitride crystal can be produced on the surface of the seed crystal 7 in a short time. .

  FIG. 5 shows a configuration in which nitrogen is blown into the melt 8 by immersing the tip 2b of the pipe 2 in the melt 8. At this time, the nitrogen blowing position (that is, the tip 2b of the pipe 2) is It is preferable to dispose the seed crystal 7 away. That is, when nitrogen is blown into the melt 8, the N concentration in the melt 8 increases and the growth rate of the group III metal nitride crystal increases, but by blowing nitrogen into the melt 8, the melt 8 This is because convection occurs therein, and the surface of the group III metal nitride crystal formed on the surface of the seed crystal 7 may become rough. When the surface of the nitride crystal of the group III metal becomes rough, it causes deterioration of characteristics when a semiconductor light emitting device is constructed. That is, as shown in FIG. 1, the semiconductor light emitting device has an n layer, a light emitting layer, and a p layer formed on the substrate surface, but the total thickness from the n layer to the p layer is about several μm (specifically 3 to 5 μm). Therefore, if irregularities occur on the surface of the group III metal nitride crystal, the characteristics of the device are greatly affected.

  Therefore, as shown in FIG. 6, it is preferable to dispose the nitrogen blowing position (that is, the tip 2 b of the pipe 2) away from the seed crystal 7.

  By separating the distance between the seed crystal 7 and the blowing position, when the group III metal nitride crystal grows, the surface is not uneven, and the surface property is kept good. Moreover, since nitrogen is blown into the melt 8, the N concentration in the melt 8 is increased, and the crystal growth rate is increased.

  The distance between the seed crystal 7 and the nitrogen blowing position is not particularly limited, and may vary depending on the flow rate when nitrogen is blown into the melt 8 and may be set as appropriate.

  FIG. 7 is a schematic explanatory diagram of another apparatus used when manufacturing a group III metal nitride crystal, and an electric field is applied to the melt near the seed crystal. That is, the seed crystal 7 is immersed in the melt 8 filled in the crucible 6 and is disposed below the crucible 6. A pair of electrodes 15 are provided outside the crucible 6 below the crucible 6 (that is, in the vicinity of the seed crystal), and the electrodes 15 are connected to a DC power source 16. A DC voltage is applied from the power supply 16.

As described above, by applying to the melt 8 in the vicinity of the seed crystal 7, nitrogen in the melt 8 can be forcibly moved from the negative electrode to the positive electrode, causing convection in the melt 8. Can be made. That is, since a part of nitrogen dissolved in the melt 8 exists as nitrogen ions (N ⁻ ), the flow of nitrogen ions can be controlled by applying it to the melt 8. Therefore, the nitride crystal growth rate of the group III metal can be increased.

  When an electric field is applied to the melt near the seed crystal, it is preferable to place the seed crystal 7 near the positive electrode as shown in FIG. This is because, by applying a DC voltage, nitrogen ions move to the positive electrode side and the nitrogen ion concentration increases in the vicinity of the positive electrode, so that the crystal growth rate increases.

  4 to 7 show a configuration in which the nitrogen gas filled in the nitrogen cylinder 1 is supplied to the crucible 6 through the pipe 2. As shown in FIGS. 2 and 3, the chamber 4 is disposed in the middle of the pipe 2. By providing the chamber 4 with the laser generator 3 and the high-frequency electric field generator 10, at least part of the nitrogen gas supplied from the nitrogen cylinder 1 to the chamber 4 through the pipe 2 is used as nitrogen radical, and the generated nitrogen radical (And nitrogen gas) may be supplied into the crucible 6 and brought into contact with the melt 8.

  2 to 4 and 7 show the configuration in which nitrogen and the melt 8 are brought into contact with each other by supplying nitrogen gas supplied from the nitrogen cylinder 1 through the pipe 2 to the crucible 6. As shown in FIG. 3, nitrogen gas may be blown into the melt 8 and bubbled by immersing the tip 2b of the pipe 2 in the melt 8.

  Next, a semiconductor light emitting device using a group III metal nitride crystal obtained by the above manufacturing method will be described with reference to FIG.

  The semiconductor light emitting device of the present invention uses a group III metal nitride crystal obtained by the above production method as a base material of the support substrate 101, and uses a group III metal nitride compound semiconductor as the n layer 102, the light emitting layer 103, and the p layer. Used as 104 material. That is, conventionally, sapphire, SiC, or the like is used as a material for the support substrate 101, and a group III metal nitride compound semiconductor is formed thereon. However, as described above, III is formed on sapphire, SiC, or the like. When a group III metal nitride compound semiconductor is formed, crystal defects may occur due to lattice mismatch between the support substrate and the group III metal nitride crystal.

  Therefore, in the semiconductor light emitting device of the present invention, the group III metal nitride crystal according to the present invention is used as the material of the support substrate 101, and the n layer 102 and the light emitting layer 103 made of a group III metal nitride compound semiconductor are formed thereon. If the p layer 104 is formed, the above problem is solved. In addition, the thickness of a support substrate is about 30-500 micrometers normally.

The n layer 102 is a layer made of an n-type group III metal nitride compound semiconductor, and preferably a layer made of an n-type GaN compound semiconductor. Specifically, it is composed of a compound represented by Al _a In _b Ga _1-ab N (0 ≦ a, 0 ≦ b, a + b ≦ 1). For example, Al _a Ga _1-a N where a is 0.5 or less and In _b Ga _1-b N where b is 0.5 or less are preferable.

Although FIG. 1 shows the case where a single layer is formed as the n layer 102, a stacked layer may be formed as the n layer. That is, a stacked structure in which an n-type contact layer and an n-type cladding layer are stacked in this order from the support substrate side may be employed. As the n-type contact layer, a layer made of GaN is common among the above-mentioned compounds constituting the n layer. As the n-type cladding layer, among the above-mentioned compounds constituting the n layer, a layer made of Al _0.3 Ga _0.7 N, a layer made of AlN, a layer made of GaN, etc. are common.

  If the n layer (including the n-type contact layer and the n-type cladding layer) is doped with an n-type impurity such as Si, the carrier concentration can be increased, which is desirable.

  When the n layer has a single layer structure, the thickness of the n layer is generally about 0.5 to 10 μm. On the other hand, when the n layer has a laminated structure of an n-type contact layer and an n-type cladding layer, the n-type contact layer is generally about 0.2 to 10 μm, and the n-type cladding layer is not particularly limited. It is about 0.01 to 3 μm.

The light emitting layer 103 is a layer made of a group III metal nitride compound semiconductor, and it is preferable to form a layer made of a GaN compound semiconductor. Specifically, composed of _{Al c In d Ga 1-cd} N (0 ≦ c, 0 ≦ d, c + d ≦ 1) represented by compounds. In this light emitting layer, for example, if the composition ratio of In and Al of the above compound is adjusted, or if the light emitting layer is doped with n-type impurities such as Si, Ge, and S and p-type impurities such as Mg and Zn The wavelength of the light to be adjusted can be adjusted in the range from blue to ultraviolet.

  Although FIG. 1 shows the case where a single layer is formed as the light emitting layer 103, for example, a so-called multiple quantum well structure in which the light emitting layer 103 has a laminated structure composed of a plurality of layers and the composition of the compounds constituting each layer is changed. It is also preferable that The total thickness of the light emitting layer is generally about 0.001 to 0.5 μm.

  The p layer 104 is a layer made of a group III metal nitride compound semiconductor, and preferably a layer made of a p-type GaN compound semiconductor. Although FIG. 1 shows a case where a single layer is formed as the p layer 104, it is general to have a laminated structure in which a p-type cladding layer and a p-type contact layer are laminated in this order from the light emitting layer side.

The p-type cladding layer is made of, for example, a compound represented by Al _e Ga _1-e N (0 <e ≦ 1), and is further doped with a p-type impurity. The value of e is preferably 0.05 or more. The p-type contact layer is made of, for example, p-type GaN doped with p-type impurities. Examples of the p-type impurity doped in the p-type cladding layer and the p-type contact layer include Mg and Zn. The thickness of the p-type cladding layer is generally about 0.001 to 1.5 μm, and the thickness of the p-type contact layer is generally about 0.01 to 2 μm.

  The material constituting the p-type electrode 105 is required to be in ohmic contact with the p-layer, and examples thereof include Ni, Rh, Pd, Pt, and alloys thereof. The thickness of the p-type electrode is usually about 0.05 to 5 μm.

  The material constituting the n-type electrode 106 is required to have an ohmic contact with the n layer, and examples thereof include Al, Ti, V, and alloys thereof. The thickness of the n-type electrode is usually about 0.05 to 5 μm.

  In forming the n layer 102, the light emitting layer 103, and the p layer 104, a known film forming method such as a known vapor phase growth method (MOCVD method) can be employed. The doping of the n-type impurity into the n layer and the doping of the p-type impurity into the p layer are performed simultaneously with the formation of these layers.

It is sectional drawing for demonstrating the structure of a semiconductor light-emitting device. It is a schematic explanatory drawing of the apparatus used when manufacturing a group III metal nitride crystal. It is a schematic explanatory drawing for demonstrating the other structural example of the apparatus shown in FIG. It is a schematic explanatory drawing of the other apparatus used when manufacturing a group III metal nitride crystal. It is a schematic explanatory drawing of the other apparatus used when manufacturing a group III metal nitride crystal. It is a schematic explanatory drawing for demonstrating the other structural example of the apparatus shown in FIG. It is a schematic explanatory drawing of the other apparatus used when manufacturing a group III metal nitride crystal.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Nitrogen cylinder 2 Piping 2a Piping 2b Piping tip 3 Laser generator 3a Laser 4 Chamber 5 Muffle furnace 6 Crucible 7 Seed crystal 8 Melt 10 High frequency electric field generator 11 Heater 12 AC power source 13 Bubble 15 Electrode 16 DC power source 101 Support substrate 102 n layer 103 light emitting layer 104 p layer 105 p type electrode 106 n type electrode 107 exposed surface

Claims (10)

In the reaction vessel,
At least one selected from Group III metals;
A seed crystal is immersed in a melt obtained by mixing two or more selected from the group consisting of alkali metals or alkaline earth metals, and the group III metal is nitrided on the seed crystal surface by contacting the melt with nitrogen. A method for producing a physical crystal comprising:
A method for producing a Group III metal nitride crystal, wherein the N concentration in the melt is increased. The process according to claim 1, wherein nitrogen radicals generated by irradiating a laser to N ₂ gas or applying a high frequency electric field are brought into contact with the melt in order to increase the N concentration in the melt.   The manufacturing method of Claim 1 or 2 which heats the melt near the said seed crystal in order to raise N density | concentration in the said melt.   The method according to any one of claims 1 to 3, wherein the nitrogen is blown into the melt in order to increase the N concentration in the melt.   The manufacturing method of Claim 4 which arrange | positions the said seed crystal away from the blowing position of the said nitrogen.   The manufacturing method according to claim 1, wherein an electric field is applied to the melt near the seed crystal.   The method according to claim 6, wherein the seed crystal is disposed near the positive electrode when an electric field is applied.   The method according to any one of claims 1 to 7, wherein the seed crystal is doped with an impurity that becomes a donor or an acceptor. As the seed crystal, method according to any one of claims 1 to 8 to use those provided with the SiN film or SiO ₂ film on a part of the surface. A group III metal nitride crystal obtained by the manufacturing method according to claim 1 is used as a base material of a semiconductor light emitting device.

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