JP4949181B2 - Substrate, method for growing gallium nitride compound semiconductor using the same, and gallium nitride compound semiconductor - Google Patents

Description

  The present invention relates to a substrate made of a gallium nitride compound semiconductor for growing, for example, a gallium nitride compound semiconductor, a method for growing a gallium nitride compound semiconductor using the substrate, and a gallium nitride compound semiconductor.

Gallium nitride (GaN), indium nitride (InN) as a gallium nitride-based compound semiconductor represented by the chemical formula Ga _1-xy In _y Al _x N (where 0 <x + y <1, x ≧ 0, y ≧ 0) ), Aluminum nitride (AlN), etc. are direct transition type compound semiconductors, and have a wide band gap (wide band gap), so light emission of blue light, blue violet light or violet light light emitting diode or laser diode, etc. It is used as a light-receiving element such as an element, a photodetector or a flame sensor.

  In addition, in electronic elements such as field effect transistors (FETs), MESFETs (Metal-Semiconductor FETs), MISFETs (Metal-Insulator-Semiconductor FETs), high electron mobility transistors (HEMTs), A material using a gallium nitride compound semiconductor has a carrier transport property close to that of GaAs, has a wide band gap, and has a high breakdown electric field. Therefore, it is considered promising as a material for a high-frequency and high-power transistor.

  In particular, in recent years, phosphors and phosphors that emit light from wavelength-converted light received from light-emitting elements made of gallium nitride-based compound semiconductors such as blue light-emitting elements, violet light-emitting elements, and ultraviolet light-emitting elements are provided. Development of lighting equipment products is progressing. In such an illumination device, it is important to improve the conversion efficiency of phosphors and phosphors and to improve the light emission efficiency of the light emitting element.

  In order to improve the light emission efficiency of the light emitting element, it is important to improve the internal quantum efficiency. For this purpose, it is necessary to grow a gallium nitride-based compound semiconductor in which crystal defects serving as non-radiative recombination centers are reduced.

For crystal growth of gallium nitride compound semiconductors, a high-quality substrate having high lattice matching with the gallium nitride compound semiconductor has not been realized. Therefore, dissimilar materials such as sapphire substrates and silicon nitride (6H-SiC) substrates (gallium nitride) A substrate made of a single crystal of a material having a low lattice matching with a system compound semiconductor is used. Incidentally, the lattice mismatch is 13.8% and the thermal expansion coefficient difference is 3.2 × 10 ⁻⁶ / K between the sapphire substrate and GaN, and the lattice mismatch is 3.4% between the 6H—SiC substrate and GaN. The expansion coefficient difference is 1.7 × 10 ⁻⁶ / K.

  In epitaxial growth of a gallium nitride compound semiconductor using a substrate having a large lattice mismatch with these gallium nitride compound semiconductors, a strain buffer layer (buffer layer) is inserted between the substrate and the gallium nitride compound semiconductor. Has been implemented. Specifically, when a gallium nitride compound semiconductor such as GaN is grown on a substrate made of sapphire, a gallium nitride compound semiconductor is grown after a buffer layer made of AlN or GaN is grown at a low temperature (400 to 800 ° C.). The method of growing is taken. In this case, the buffer layer made of AlN or GaN deposited on the substrate made of sapphire at a low temperature is almost deposited in an amorphous state.

  Thereafter, the buffer layer is crystallized in the temperature rising process to form a columnar structure. Next, on the buffer layer made of AlN or GaN with a columnar structure, the growth proceeds so that the gallium nitride compound semiconductor embeds the adjacent columnar structure, and a gallium nitride compound semiconductor layer having a flat surface grows. To do. Therefore, in the growth process of the gallium nitride compound semiconductor, the initial growth starts from three-dimensional island growth and finally becomes two-dimensional layer growth. Therefore, in contrast to the two-dimensional layer growth process of homoepitaxial growth in which a gallium arsenide compound semiconductor is grown on a gallium arsenide (GaAs) substrate, the dislocation region boundary in which the stacking order of Ga and N elements is reversed. (Inversion domain boundary), many defects that are considered to occur when microcrystals and microcrystals grow laterally and merge.

Therefore, when a gallium nitride compound semiconductor is grown on a substrate made of sapphire, dislocations having a density of 1 × 10 ⁸ to 1 × 10 ¹⁰ cm ⁻² are generated in the gallium nitride compound semiconductor.

In recent years, by combining hydride vapor phase epitaxy (HVPE) and epitaxial lateral growth (ELO), the threading dislocations inherited from the interface between the GaN and sapphire substrate are laterally curved, and several hundred μm A GaN layer grown to a thickness may be peeled off from a sapphire substrate and used as a bulk crystal substrate for gallium nitride compound semiconductor growth. The dislocation density of the substrate made of such a GaN bulk crystal is 1 × 10 ⁶ to 1 × 10 ⁷ cm ⁻² and is used for GaN homoepitaxy growth.
JP-A-2-229476

  In the conventional growth of gallium nitride compound semiconductors, a strain buffer layer (buffer layer) typified by a low-temperature deposition layer is used to alleviate lattice mismatch between the epitaxial growth layer of the gallium nitride compound semiconductor and the substrate. Is inserted between the substrate and the gallium nitride compound semiconductor. By inserting a strain buffer layer, a gallium nitride compound semiconductor layer applicable to devices such as light emitting elements and electronic devices can be grown on a substrate made of sapphire having a large lattice mismatch with the gallium nitride compound semiconductor. It became possible.

However, the crystal quality of the gallium nitride compound semiconductor layer formed on a substrate made of sapphire or the like is never sufficient when considering the realization of a light emitting element with high luminous efficiency for the purpose of application to a lighting device. I can not say. The improvement of the luminous efficiency of the device, the device reduces the defect density as the non-radiative recombination centers is required, the chemical formula _{Ga 1-x-y In y} Al x N ( However, in this regard, 0 <x + y <1 , X ≧ 0, y ≧ 0), it is homoepitaxial growth having the same thermal expansion coefficient and lattice constant as the gallium nitride compound semiconductor layer grown on the substrate. Therefore, realization of layer-by-layer mode is expected from the beginning of growth.

  In actual growth of a gallium nitride-based compound semiconductor, a substrate is placed on a susceptor made of graphite or the like to perform growth. The susceptor is heated by thermal contact with a resistance heater or eddy current generated in the susceptor by high frequency induction. From the heated susceptor to the substrate, heat is transferred to the substrate by thermal contact or radiation, and the substrate is heated to reach the desired growth temperature on the surface of the substrate.

However, since a substrate made of a gallium nitride compound semiconductor represented by Ga _1-xy In _y Al _x N (where 0 <x + y <1, x ≧ 0, y ≧ 0) is light transmissive, It cannot absorb the heat radiation from the susceptor and cannot be heated effectively. Therefore, since the substrate surface is mainly heated due to heat conduction from the susceptor, the substrate surface can only realize a growth temperature lower than the upper limit value of the control temperature of the film forming apparatus.

  Usually, the susceptor is counterbored to fix the substrate, but the counterbore and the edge of the substrate come into contact with each other, causing heat transfer due to thermal contact. The growth temperature of the gallium nitride compound semiconductor has a distribution. In particular, when the substrate does not receive heat due to heat radiation, a large distribution occurs in the growth temperature. Due to the large distribution of the growth temperature, the thickness distribution of the gallium nitride compound semiconductor layer, the distribution of the mixed crystal composition ratio, the distribution of the semiconductor impurity concentration, etc. occur in the plane of the growth surface of the substrate.

  Accordingly, the present invention has been completed in view of the above-described problems in the prior art, and an object of the present invention is to install a substrate made of a gallium nitride compound semiconductor on a susceptor in a film forming apparatus, and on the substrate. When the gallium nitride compound semiconductor layer is grown, the gallium nitride compound semiconductor layer can be grown at a desired growth temperature by effectively conducting the heat of the heated susceptor to the substrate. By providing a substrate capable of reducing the distribution of the thickness of the gallium nitride compound semiconductor layer, the distribution of the mixed crystal composition ratio, the distribution of the semiconductor impurity concentration, etc. by reducing the distribution of the growth temperature in the plane of the growth surface. is there. Another object of the present invention is to provide a method for growing a gallium nitride compound semiconductor using the substrate.

The substrate of the present invention is a substrate having a first main surface and a second main surface opposite to the first main surface, and a gallium nitride compound semiconductor layer is grown on the second main surface. , formula _{Ga 1-x-y in y} Al x N ( However, 0 <x + y <1 , x ≧ 0, y ≧ 0) consists gallium nitride compound semiconductor represented by a nitrogen-deficient to the first major surface It has the part.

  The substrate of the present invention is preferably characterized in that an uneven structure is formed on the first main surface.

The method for growing a gallium nitride-based compound semiconductor according to the present invention is represented by the chemical formula Ga _1-xy In _y Al _x N (where 0 <x + y <1, x ≧ 0, y ≧ 0) in the film forming apparatus. A substrate made of a gallium nitride compound semiconductor and having a nitrogen deficient portion on the first main surface is placed on the first main surface side on a susceptor made of graphite; By supplying the Group 3 element material and the Group 5 element material into the film forming apparatus, a chemical formula Ga _1-xy In _y Al _x N is formed on the second main surface of the substrate opposite to the first main surface. However, it is characterized by growing a gallium nitride-based compound semiconductor layer represented by (where 0 <x + y <1, x ≧ 0, y ≧ 0).

  In the method for growing a gallium nitride compound semiconductor according to the present invention, preferably, the substrate has a concavo-convex structure formed on the first main surface.

  The gallium nitride compound semiconductor growth method of the present invention is preferably characterized in that the susceptor has a main body made of graphite and a silicon carbide layer formed on the surface of the main body. is there.

The gallium nitride-based compound semiconductor of the present invention has the chemical formula Ga _1-xy In _y Al _x N (where 0 <x + y <1, x ≧ 0, y ≧ 0) on the second main surface of the substrate of the present invention. ) Is formed, and a gallium nitride compound semiconductor layer is formed.

The substrate of the present invention is made of a gallium nitride-based compound semiconductor represented by the chemical formula Ga _1-xy In _y Al _x N (where 0 <x + y <1, x ≧ 0, y ≧ 0). Since the main surface has a nitrogen deficient portion, electromagnetic waves generated by thermal radiation incident on the first main surface (surface opposite to the growth surface) of the substrate in the nitrogen deficient portion cause inelastic scattering of vacancies. In response to this inelastic scattering, the energy loss of photons becomes thermal energy, and the substrate is heated. Thereby, the temperature of the growth surface (second main surface) of the substrate can be easily set to a desired growth temperature, and the distribution of the growth temperature on the growth surface of the substrate can be made uniform.

  Moreover, since the uneven | corrugated structure is preferably formed in the 1st main surface, the board | substrate of this invention has the 1st main surface in which the uneven structure was formed, and the 2nd main surface in which the uneven structure was not formed. The effective refractive index difference at the interface with the outside differs from the surface. The first main surface on which the concavo-convex structure is formed has a small difference in effective refractive index at the interface with the outside (susceptor) due to the concavo-convex structure, so the first main surface (surface opposite to the growth surface). The electromagnetic waves generated by the heat radiation incident on are efficiently absorbed from the first main surface. On the other hand, the second main surface (growth surface) on which the concavo-convex structure is not formed has a large difference in the effective refractive index at the interface with the outside (air), and thus is caused by thermal radiation incident on the second main surface. Most of the electromagnetic waves are reflected by the second main surface into the substrate and partially absorbed by the substrate. As a result, the substrate can be heated effectively using thermal radiation, the substrate growth surface can be easily set to a desired growth temperature, and the growth temperature distribution on the substrate growth surface is more uniform. Can be.

The method for growing a gallium nitride-based compound semiconductor according to the present invention is represented by the chemical formula Ga _1-xy In _y Al _x N (where 0 <x + y <1, x ≧ 0, y ≧ 0) in the film forming apparatus. A substrate made of a gallium nitride compound semiconductor and having a nitrogen deficient portion on the first main surface is placed on the first main surface side on a susceptor made of graphite, and then the film is formed By supplying the Group 3 element material and the Group 5 element material into the apparatus, the chemical formula Ga _1-xy In _y Al _x N (however, 0% is applied to the second main surface opposite to the first main surface of the substrate). Since the gallium nitride compound semiconductor layer represented by <x + y <1, x ≧ 0, y ≧ 0) is grown, the electromagnetic waves caused by thermal radiation incident on the first main surface of the substrate in the nitrogen deficient portion are empty. The inelastic scattering of the fulcrum causes photon energy Ghee loss substrate becomes thermal energy is heated. Thereby, the temperature of the growth surface (second main surface) of the substrate can be easily set to a desired growth temperature, and the distribution of the growth temperature on the growth surface of the substrate can be made uniform. Therefore, by supplying the Group 3 element source and Group 5 element source to the growth surface of such a substrate, the gallium nitride compound semiconductor in which the thickness distribution, mixed crystal composition ratio distribution, semiconductor impurity concentration distribution, etc. are reduced Can grow.

  In the method for growing a gallium nitride-based compound semiconductor according to the present invention, preferably, since the substrate has a concavo-convex structure formed on the first main surface, the first main surface on which the concavo-convex structure is formed; The difference in effective refractive index at the interface with the outside is different from that of the second main surface where no structure is formed. The first main surface on which the concavo-convex structure is formed has a small difference in effective refractive index at the interface with the outside (susceptor) due to the concavo-convex structure, so the first main surface (surface opposite to the growth surface). The electromagnetic waves generated by the heat radiation incident on are efficiently absorbed from the first main surface. On the other hand, the second main surface (growth surface) on which the concavo-convex structure is not formed has a large difference in the effective refractive index at the interface with the outside (air), and thus is caused by thermal radiation incident on the second main surface. Most of the electromagnetic waves are reflected by the second main surface into the substrate and partially absorbed by the substrate. As a result, the substrate can be heated effectively using thermal radiation, the substrate growth surface can be easily set to a desired growth temperature, and the growth temperature distribution on the substrate growth surface is more uniform. Can be. Therefore, a gallium nitride compound in which the thickness distribution, the mixed crystal composition ratio distribution, the semiconductor impurity concentration distribution, and the like are further reduced by supplying the group 3 element material and the group 5 element material to the growth surface of such a substrate. A semiconductor layer can be grown.

  In the gallium nitride compound semiconductor growth method of the present invention, preferably, the susceptor has a main body made of graphite and a silicon carbide layer formed on the surface of the main body. The effective refractive index at the interface with the main body made of graphite can be reduced, and electromagnetic waves caused by thermal radiation incident on the first main surface (the surface opposite to the growth surface) are transmitted from the first main surface. It will be absorbed efficiently.

The gallium nitride-based compound semiconductor of the present invention has the chemical formula Ga _1-xy In _y Al _x N (where 0 <x + y <1, x ≧ 0, y ≧ 0) on the second main surface of the substrate of the present invention. Since the gallium nitride compound semiconductor layer is formed with a uniform growth temperature distribution on the growth surface of the substrate, nitriding with high crystal uniformity is formed. It becomes a gallium compound semiconductor.

  Hereinafter, the growth method of the substrate and the gallium nitride compound semiconductor of the present invention will be described in detail.

  FIG. 1 is a cross-sectional view showing an example of an embodiment of a method for growing a substrate and a gallium nitride compound semiconductor according to the present invention, and (a) to (c) are cross-sectional views for each step of the growth method. . In FIG. 1, 1 is a substrate, 1a is a nitrogen deficient portion, and 2 is a gallium nitride compound semiconductor.

  The gallium nitride compound semiconductor 2 is composed of at least one gallium nitride compound semiconductor layer.

Substrate 1 of the present invention has the formula _{Ga 1-x-y In y} Al x N ( However, 0 <x + y <1 , x ≧ 0, y ≧ 0) consists of a gallium nitride-based compound represented by the semiconductor, the first The main surface has a nitrogen deficient portion 1a. With this configuration, the electromagnetic wave due to thermal radiation incident on the first main surface (surface opposite to the growth surface) of the substrate 1 in the nitrogen deficient portion 1a is subjected to inelastic scattering of vacancies, and photons are generated by this inelastic scattering. The energy loss becomes thermal energy and the substrate 1 is heated. Thereby, the temperature of the growth surface (second main surface) of the substrate 1 can be easily set to a desired growth temperature, and the distribution of the growth temperature on the growth surface of the substrate 1 can be made uniform.

The nitrogen deficient portion 1a formed on the first main surface of the substrate 1 is represented by Ga _1-xy In _y Al _x N (where 0 <x + y <1, x ≧ 0, y ≧ 0). By subjecting the substrate 1 to a heat treatment (temperature of about 400 ° C. to 1200 ° C.) in a reducing atmosphere such as hydrogen gas or in a vacuum, heat detachment of nitrogen from the substrate 1 occurs, and nitrogen deficiency occurs. Can be formed. The pressure of the reducing atmosphere is 1013 hPa (hectopascal) or less. If it exceeds 1013 hPa, it becomes a pressure equal to or higher than the atmospheric pressure, and thus a special device that can withstand high pressure is required.

  Further, the nitrogen deficient portion 1a can be formed by ion collision by a dry etching method such as a reactive ion etching (RIE) method.

  The thickness of the nitrogen deficient portion 1a is preferably about 0.6 to 1 μm. The wavelength of the electromagnetic wave due to thermal radiation from the susceptor is 1.8 to 2.0 μm, and 0.6 to 1 μm in the gallium nitride compound semiconductor. Therefore, in order to absorb the electromagnetic wave caused by heat radiation with the nitrogen deficient portion 1a, a thickness of about the wavelength of the electromagnetic wave is suitable. If it is thicker than 1 μm, the crystallinity of the gallium nitride compound semiconductor tends to deteriorate.

  The thickness of the nitrogen deficient portion 1a can be controlled by adjusting the concentration of a reducing atmosphere gas such as hydrogen gas, the heating conditions for heat treatment in a vacuum, and the like. The thickness of the nitrogen deficient portion 1a can also be controlled by adjusting the number and collision energy of ions when forming the nitrogen deficient portion 1a by ion collision by a dry etching method such as a reactive ion etching method. it can.

  The presence of the nitrogen deficient portion 1a can be specified by the positron annihilation method. Specifically, this positron annihilation method is as follows. That is, when a positron is irradiated to a gallium nitride compound semiconductor, the positron annihilates with an electron in a vacancy defect in the gallium nitride semiconductor, and γ-rays generated by the annihilation are measured. Therefore, when γ-rays generated from the substrate 1 by positron irradiation are detected, it can be identified that the nitrogen deficient portion 1a is formed.

  Further, it can be confirmed visually that visible light is scattered in the vacant lattice portion and the substrate made of the gallium nitride compound semiconductor is light brown.

  Moreover, it is preferable that the uneven | corrugated structure is formed in the 1st main surface in the board | substrate 1 of this invention. In this case, the difference in effective refractive index at the interface with the outside (air) differs between the first main surface on which the concavo-convex structure is formed and the second main surface on which the concavo-convex structure is not formed. The first main surface on which the concavo-convex structure is formed has a small difference in effective refractive index at the interface with the outside (susceptor) due to the concavo-convex structure, so the first main surface (surface opposite to the growth surface). The electromagnetic waves generated by the heat radiation incident on are efficiently absorbed from the first main surface. On the other hand, the second main surface (growth surface) on which the concavo-convex structure is not formed has a large difference in the effective refractive index at the interface with the outside (air), and thus is caused by thermal radiation incident on the second main surface. The electromagnetic wave is mostly reflected by the second main surface into the substrate and partially absorbed by the substrate 1. As a result, the substrate 1 can be heated effectively using thermal radiation, the growth surface of the substrate 1 can be more easily set to a desired growth temperature, and the growth temperature distribution on the growth surface of the substrate 1 can be achieved. Can be made more uniform.

  In addition, since the difference in refractive index between the first main surface and the outside of the substrate 1 and the difference in refractive index between the second main surface and the outside are different, the refractive index is substantially different at one interface. Reflection occurs. As a result, multiple reflection occurs between the susceptor and the first main surface of the substrate 1. The amount of heat radiation absorbed by the substrate 1 increases due to multiple reflection. As a result, heat can be effectively transferred from the susceptor to the substrate 1.

  The concavo-convex structure formed on the first main surface of the substrate 1 can be formed by a dry etching method such as a reactive ion etching (RIE) method. The dry etching method has better processing accuracy for the shape and size of the unevenness than the wet etching method. Therefore, by designing the concavo-convex shape and size with precise control, the difference in effective refractive index from the outside (susceptor) on the first main surface can be adjusted with high precision, and thermal radiation can be adjusted. The amount of absorption can be adjusted with high accuracy.

  It is also possible to simultaneously form the nitrogen deficient portion 1a and the concavo-convex structure on the first main surface of the substrate 1 by ion collision by dry etching.

  Further, when the first main surface of the substrate 1 is a −c plane (N-polar plane) and the second main plane is a + c plane (Ga-polar plane), in order to form a concavo-convex structure, KOH (hydroxylation) Wet etching with an aqueous solution of potassium) is preferred. The -c surface, which is an N-polar surface, can be processed to be uneven with a KOH aqueous solution.

  The concavo-convex structure formed on the first main surface of the substrate 1 preferably has a periodic structure in which the concavo-convex period is 0.6 to 1 μm or less. In this case, the effective refractive index of the interface between the first main surface of the substrate 1 and the outside (susceptor) can be continuously changed, and the substrate 1 can effectively absorb electromagnetic waves caused by thermal radiation. it can.

The method for growing a gallium nitride-based compound semiconductor 2 of the present invention has a chemical formula Ga _1-xy In _y Al _x N (where 0 <x + y <1, x ≧ 0, y ≧ 0) in a film forming apparatus. A substrate 1 made of a gallium nitride-based compound semiconductor and having a nitrogen deficient portion 1a on the first main surface is placed on a susceptor made of graphite with the first main surface side placed thereon, By supplying the Group 3 element material and the Group 5 element material into the film forming apparatus, a chemical formula Ga _1-xy In _y Al _x N is formed on the second main surface opposite to the first main surface of the substrate 1. In this structure, a gallium nitride compound semiconductor layer represented by 0 <x + y <1, x ≧ 0, y ≧ 0 is grown.

  In addition, the substrate 1 preferably has a concavo-convex structure formed on the first main surface for the reason described above.

  The film forming apparatus for growing the gallium nitride-based compound semiconductor 2 in the present invention is capable of easily performing a heat treatment in a reducing atmosphere such as hydrogen gas, adjusting a partial pressure ratio of the gas, or in a vacuum. A MOVPE (Metal Organic Vapor Phase Epitaxy) apparatus is preferred.

The heating temperature of the substrate 1 when the gallium nitride compound semiconductor 2 is grown on the growth surface of the substrate 1 is preferably 600 ° C. or higher. By supplying a nitrogen source such as ammonia gas (NH ₃ ) to the growth surface of the substrate 1 in that temperature range, the adsorption and desorption of nitrogen on the growth surface of the substrate 1 is balanced, and the growth does not proceed any further. It becomes the self-stop state. However, since ammonia gas is not supplied to the first main surface of the substrate 1, the nitrogen deficient portion 1a is formed on the first main surface, and the gallium nitride compound semiconductor layer can be continuously grown as it is. .

  When the gallium nitride compound semiconductor 2 of the present invention constitutes a light emitting element, the layer configuration of the gallium nitride compound semiconductor 2 is as follows.

That is, for example, gallium nitride-based compound semiconductor 2 has the formula _{Ga 1-x1-y1 In y1} Al x1 N ( However, 0 <x1 + y1 <1 , x1> 0, y1 ≧ 0) of a gallium nitride-based compound represented by the semiconductor a first conductivity type gallium nitride compound semiconductor layer comprising the chemical formula _{Ga 1-x2-y2 in y2} Al x2 N ( However, 0 <x2 + y2 <1 , x2> 0, y2 ≧ 0) gallium nitride represented by between the compounds second conductivity type gallium nitride of semiconductor compound semiconductor layer, the chemical formula _{Ga 1-x3-y3 in y3} Al x3 N ( However, 0 <x3 + y3 <1 , x3> 0, y3 ≧ 0) A structure in which light-emitting layers made of gallium nitride-based compound semiconductors are sandwiched and bonded (where x1, x2> x3, y1, y2 ≦ y3).

  Further, for example, the first conductivity type and the second conductivity type are p-type and n-type, respectively. In order to make the gallium nitride compound semiconductor layer p-type, magnesium (Mg), which is an element of group 2 (II) in the periodic table, may be mixed into the gallium nitride compound semiconductor as a dopant. In order to make the gallium nitride compound semiconductor n-type, silicon (Si) or the like, which is an element of Group 4 (IV) in the periodic table, may be mixed into the gallium nitride compound semiconductor as a dopant.

  Both the first conductivity type and second conductivity type gallium nitride compound semiconductor layers are made of gallium nitride compound semiconductor containing aluminum (Al), both of which are contained more than aluminum contained in the light emitting layer. Increase the amount. In this case, the forbidden band widths of the first and second conductivity type gallium nitride compound semiconductor layers are both larger than the forbidden band width of the light emitting layer, so that electrons and holes are confined in the light emitting layer, These electrons and holes can be efficiently recombined to emit light with strong emission intensity.

  The first and second conductivity type gallium nitride compound semiconductor layers are made of a gallium nitride compound semiconductor containing aluminum, so that the forbidden band width in the first and second conductivity type gallium nitride compound semiconductor layers is increased. Becomes relatively large, and absorption of light on the short wavelength side such as ultraviolet light in the first and second conductivity type gallium nitride compound semiconductor layers can be reduced.

  The gallium nitride compound semiconductor layers of the first conductivity type and the second conductivity type may be n-type and p-type, respectively.

  In addition, a conductive layer (electrode) for injecting a current into the light emitting layer is formed in each of the first conductivity type and second conductivity type gallium nitride compound semiconductor layers. Thereby, a light emitting element such as a light emitting diode (LED) or a semiconductor laser (LD) is formed.

  Further, the composition of the gallium nitride-based compound semiconductor layer constituting the light emitting layer may be set to an appropriate one that can obtain a desired light emission wavelength. For example, if the light-emitting layer is made of GaN containing neither aluminum nor indium, the forbidden band width is about 3.4 electron volts (eV), and ultraviolet light having an emission wavelength of about 365 nanometers (nm) is obtained. The light emitting layer can emit light. When the emission wavelength is shorter than this, the emission layer is made of a gallium nitride compound semiconductor containing aluminum, which is an element for increasing the forbidden bandwidth, in an amount set according to the emission wavelength. And it is sufficient.

  In addition, the light emitting layer may contain indium (In), which is an element for reducing the forbidden band width, and a composition of aluminum, indium, and gallium by adding more aluminum so as to obtain a desired emission wavelength. The ratio may be set as appropriate. In addition, the light emitting layer is a multi-layer quantum well structure (MQW: Multiple Quantum) which is a superlattice in which a quantum well structure composed of a barrier layer with a wide forbidden band and a well layer with a narrow forbidden band is regularly stacked a plurality of times. Well).

  Such a light emitting device operates as follows. That is, a bias current is passed through a gallium nitride compound semiconductor including a light emitting layer to generate ultraviolet light to near ultraviolet light having a wavelength of about 350 to 400 nm in the light emitting layer, and the ultraviolet light to near ultraviolet light is emitted outside the light emitting element. Operates to take out.

  In addition, a lighting device can be manufactured using the gallium nitride compound semiconductor obtained by the method for growing a gallium nitride compound semiconductor of the present invention. This illuminating device includes the light-emitting element described above, and at least one of a phosphor and a phosphor that emit light upon receiving light emitted from the light-emitting element. With this configuration, a lighting device with high luminance and illuminance can be obtained. The lighting device may be configured so that the light emitting element is covered or encapsulated with a transparent resin or the like, and a phosphor or phosphor is mixed in the transparent resin or the like. ~ Near ultraviolet light can be converted into white light or the like. In addition, a light reflecting member such as a concave mirror can be provided in a transparent resin or the like in order to improve the light collecting property. Such an illuminating device consumes less power than a conventional fluorescent lamp or the like, and is small in size. Therefore, the illuminating device is effective as a small and high-luminance lighting device.

1 shows an example of an embodiment of a substrate and a method for growing a gallium nitride compound semiconductor according to the present invention, wherein (a) to (c) are cross-sectional views of the substrate in each step.

Explanation of symbols

1: Substrate 1a: Nitrogen deficient portion 2: Gallium nitride compound semiconductor

Claims (6)

A substrate having a first main surface and a second main surface opposite to the first main surface, on which a gallium nitride compound semiconductor layer is grown, wherein the chemical formula Ga _{1-x -y} in _y Al _x N (However, 0 <x + y <1 , x ≧ 0, y ≧ 0) consists gallium nitride compound semiconductor represented by, a nitrogen defect in the first main surface A substrate characterized by being.   2. The substrate according to claim 1, wherein an uneven structure is formed on the first main surface. In the film forming apparatus, the first film is made of a gallium nitride-based compound semiconductor represented by the chemical formula Ga _1-xy In _y Al _x N (where 0 <x + y <1, x ≧ 0, y ≧ 0). A substrate having a nitrogen deficient portion on the main surface is placed on the first main surface side on a susceptor made of graphite,
Next, by supplying a Group 3 element material and a Group 5 element material into the film forming apparatus, a chemical formula Ga _1-xy In is formed on a second main surface of the substrate opposite to the first main surface. A growth method of a gallium nitride compound semiconductor, characterized by growing a gallium nitride compound semiconductor layer represented by _y Al _x N (where 0 <x + y <1, x ≧ 0, y ≧ 0).   4. The method for growing a gallium nitride compound semiconductor according to claim 3, wherein the substrate has a concavo-convex structure formed on the first main surface.   5. The method for growing a gallium nitride-based compound semiconductor according to claim 3, wherein the susceptor includes a main body made of graphite and a silicon carbide layer formed on a surface of the main body. Claim 1 or the substrate 2, wherein the second major surface by the chemical formula _{Ga 1-x-y In y} Al x N ( However, 0 <x + y <1 , x ≧ 0, y ≧ 0) gallium nitride represented by A gallium nitride compound semiconductor, characterized in that a compound semiconductor layer is formed.

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