WO2022149183A1 - Procédé de production d'élément électroluminescent ultraviolet à semi-conducteur au nitrure, et élément électroluminescent ultraviolet à semi-conducteur au nitrure - Google Patents

Procédé de production d'élément électroluminescent ultraviolet à semi-conducteur au nitrure, et élément électroluminescent ultraviolet à semi-conducteur au nitrure Download PDF

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WO2022149183A1
WO2022149183A1 PCT/JP2021/000078 JP2021000078W WO2022149183A1 WO 2022149183 A1 WO2022149183 A1 WO 2022149183A1 JP 2021000078 W JP2021000078 W JP 2021000078W WO 2022149183 A1 WO2022149183 A1 WO 2022149183A1
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layer
region
well
algan
enriched
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PCT/JP2021/000078
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光 平野
陽祐 長澤
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創光科学株式会社
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Priority to PCT/JP2021/000078 priority patent/WO2022149183A1/fr
Priority to TW110140773A priority patent/TW202243282A/zh
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
    • H01L33/16—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a particular crystal structure or orientation, e.g. polycrystalline, amorphous or porous
    • H01L33/18—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a particular crystal structure or orientation, e.g. polycrystalline, amorphous or porous within the light emitting region
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
    • H01L33/26—Materials of the light emitting region
    • H01L33/30—Materials of the light emitting region containing only elements of Group III and Group V of the Periodic Table
    • H01L33/32—Materials of the light emitting region containing only elements of Group III and Group V of the Periodic Table containing nitrogen

Definitions

  • the present invention is a nitride semiconductor ultraviolet light emitting device provided with a light emitting device structure in which an n-type layer, an active layer, and a p-type layer made of an AlGaN-based semiconductor having a wurtzite structure are laminated in the vertical direction, and manufacturing thereof. Regarding the method.
  • nitride semiconductor light emitting devices in which a light emitting device structure composed of a plurality of nitride semiconductor layers is formed by epitaxial growth on a substrate such as sapphire.
  • the nitride semiconductor layer is represented by the general formula Al 1-x-y Ga x In y N (0 ⁇ x ⁇ 1,0 ⁇ y ⁇ 1,0 ⁇ x + y ⁇ 1).
  • the light emitting device structure of the light emitting diode has a double hetero structure in which an active layer made of a nitride semiconductor layer is sandwiched between two clad layers, an n-type nitride semiconductor layer and a p-type nitride semiconductor layer.
  • the active layer is an AlGaN-based semiconductor
  • the bandgap energy can be obtained by adjusting the AlN mole fraction (also referred to as Al composition ratio) to be the bandgap energy (about 3.4 eV and about 6.2 eV) that GaN and AlN can take.
  • an ultraviolet light emitting element having an emission wavelength of about 200 nm to about 365 nm can be obtained.
  • a forward current from the p-type nitride semiconductor layer toward the n-type nitride semiconductor layer the bandgap energy due to the recombination of carriers (electrons and holes) in the active layer was responded to. Light emission occurs.
  • a p electrode is provided on the p-type nitride semiconductor layer, and an n electrode is provided on the n-type nitride semiconductor layer.
  • the active layer is an AlGaN-based semiconductor
  • the n-type nitride semiconductor layer and the p-type nitride semiconductor layer sandwiching the active layer are composed of an AlGaN-based semiconductor having a higher AlN mole fraction than the active layer.
  • a p-type nitride semiconductor layer having a high AlN molar fraction to form good ohmic contact with a p-electrode
  • a p-type with a low AlN molar fraction is formed on the uppermost layer of the p-type nitride semiconductor layer.
  • a p-type contact layer capable of making good ohmic contact with a p-electrode made of an AlGaN-based semiconductor (specifically, p-GaN). Since this p-type contact layer has an AlN mole fraction smaller than that of the AlGaN-based semiconductor constituting the active layer, the ultraviolet rays emitted from the active layer toward the p-type nitride semiconductor layer side are absorbed by the p-type contact layer. , Cannot be effectively taken out of the element. Therefore, a general ultraviolet light emitting diode whose active layer is an AlGaN-based semiconductor adopts an element structure as schematically shown in FIG. 19, and ultraviolet rays emitted from the active layer toward the n-type nitride semiconductor layer side. Is effectively taken out to the outside of the device (see, for example, Patent Documents 1 and 2 below).
  • a general ultraviolet light emitting diode is an n-type AlGaN-based diode on a template 102 formed by depositing an AlGaN-based semiconductor layer 101 (for example, an AlN layer) on a substrate 100 such as a sapphire substrate.
  • the semiconductor layer 103, the active layer 104, the p-type AlGaN-based semiconductor layer 105, and the p-type contact layer 106 are sequentially deposited, and the active layer 104, the p-type AlGaN-based semiconductor layer 105, and a part of the p-type contact layer 106 are partially deposited.
  • the n-type AlGaN-based semiconductor layer 103 is removed by etching until it is exposed, and the n-electrode 107 is formed on the exposed surface of the n-type AlGaN-based semiconductor layer 103 and the p-electrode 108 is formed on the surface of the p-type contact layer 106.
  • the active layer has a multiple quantum well structure, an electron block layer is provided on the active layer, and the like. ..
  • composition modulation occurs due to segregation of Ga (segregation due to mass movement of Ga) in the clad layer composed of the n-type AlGaN-based semiconductor layer, and the AlN mole locally extends diagonally with respect to the surface of the clad layer. It has been reported that a layered region having a low fraction is formed (see, for example, Patent Document 3 and Non-Patent Documents 1 and 2 below). Since the bandgap energy of the AlGaN-based semiconductor layer having a locally low AlN mole fraction is also locally reduced, in Patent Document 3, the carriers in the clad layer are likely to be localized in the layered region, and the active layer is liable to be localized. It has been reported that a current path with low resistance can be provided and the luminous efficiency of the ultraviolet light emitting diode can be improved.
  • a multi-stage terrace parallel to the (0001) plane is exposed on the surface of each layer of the active layer having a multiple quantum well structure formed on the n-type clad layer, and each layer of the active layer is similar to the n-type clad layer.
  • Compositional modulation occurs due to segregation of Ga within, and a region with a relatively low AlN mole fraction is generated in the inclined region inclined with respect to the (0001) plane connecting the adjacent terraces, and is relative to the terrace region.
  • Non-Patent Document 1 A region with a high AlN mole fraction is generated, and as a result of synthesizing light emission from a gradient region having a different peak emission wavelength and light emission from a terrace region, a double peak is generated in the EL (electroluminescence) spectrum of the entire active layer. It is reported in Non-Patent Document 1 that the above can occur.
  • An ultraviolet light emitting device made of an AlGaN-based semiconductor is manufactured on a substrate such as a sapphire substrate by a well-known epitaxial growth method such as an organometallic compound vapor deposition (MOVPE) method.
  • MOVPE organometallic compound vapor deposition
  • the drift of the crystal growth device is caused by the change in the effective temperature of the crystal growth site due to the deposits such as the tray and the wall of the chamber. For this reason, in order to suppress drift, conventionally, the growth history is examined and an experienced person slightly changes the set temperature and the composition of the raw material gas, or the growth schedule for a certain period is fixed and cleaning etc. Although the maintenance of the above is carried out in the same way for a certain period of time, it is difficult to completely eliminate the drift.
  • the influence of the drift extends to the above-mentioned segregation of Ga, and due to the manufacturing variation of the AlN mole fraction difference between the inclined region and the terrace region in the well layer, remarkable peak separation with a large wavelength difference may occur in the EL spectrum.
  • the remarkable peak separation becomes a defective product that cannot be shipped as a product depending on the application, and causes a decrease in yield.
  • the present invention has been made in view of the above-mentioned problems, and an object thereof is to suppress remarkable peak separation having a large wavelength difference by suppressing characteristic fluctuations caused by drift of a crystal growth device or the like. It is an object of the present invention to stably provide a nitride semiconductor ultraviolet light emitting element.
  • the present invention is a nitride semiconductor including a light emitting device structure portion in which an n-type layer, an active layer, and a p-type layer made of an AlGaN-based semiconductor having a wurtzite structure are laminated in the vertical direction. It is a method of manufacturing an ultraviolet light emitting element.
  • the integer n is 3, 4, 5, or 6,
  • the target value Xwt of the AlN mole fraction at the time of epitaxial growth of the well layer is set. (N ⁇ 0.24) / 12 ⁇ Xwt ⁇ (n + 0.24) / 12 Set within the range that becomes In the well layer, a Ga-enriched well region having an AlN mole fraction lower than the average AlN mole fraction Xwa of the well layer and an Al rich having an AlN mole fraction higher than the average AlN mole fraction Xwa.
  • a semi-stable well region which is a semi-stable AlGaN having an AlGaN composition ratio of an integer ratio of Al n Ga 12-n N 12 , is to be grown.
  • a method for manufacturing a nitride semiconductor ultraviolet light emitting element which is the feature of 1.
  • the present invention is a slightly inclined substrate in which the sapphire substrate has a main surface inclined by a predetermined angle with respect to the (0001) plane, in addition to the first feature.
  • a multi-stage terrace parallel to the (0001) plane is exposed on each surface of the n-type layer and the active layer.
  • each semiconductor layer in the active layer has an inclined region inclined with respect to a (0001) plane connecting adjacent terraces of the multi-stage terrace, and a terrace region other than the inclined region.
  • the AlGaN-based semiconductor is represented by the general formula Al 1-x Ga x N (0 ⁇ x ⁇ 1), and the bandgap energy can be the lower limit and the upper limit of the bandgap energy that GaN and AlN can take, respectively. Within the range, impurities such as Group 3 elements such as B or In or Group 5 elements such as P may be contained in a trace amount. Further, the GaN-based semiconductor is a nitride semiconductor basically composed of Ga and N, but contains a small amount of impurities such as Group 3 elements such as Al, B or In or Group 5 elements such as P. You may.
  • the AlN-based semiconductor is a nitride semiconductor basically composed of Al and N, but contains a small amount of impurities such as Group 3 elements such as Ga, B or In, or Group 5 elements such as P. You may. Therefore, in the present application, the GaN-based semiconductor and the AlN-based semiconductor are each a part of the AlGaN-based semiconductor.
  • the n-type or p-type AlGaN-based semiconductor is an AlGaN-based semiconductor doped with Si, Mg, or the like as a donor or acceptor impurity.
  • AlGaN-based semiconductors not specified as p-type and n-type mean undoped AlGaN-based semiconductors, but even if they are undoped, they contain a small amount of donor or acceptor impurities that are inevitably mixed. obtain.
  • the first plane is not an exposed surface specifically formed in the manufacturing process of the n-type layer or a boundary surface with another semiconductor layer, but a virtual surface extending in the n-type layer in parallel in the vertical direction. It is a flat surface.
  • the AlGaN-based semiconductor layer, the GaN-based semiconductor layer, and the AlN-based semiconductor layer are semiconductor layers composed of an AlGaN-based semiconductor, a GaN-based semiconductor, and an AlN-based semiconductor, respectively.
  • a ternary mixed crystal such as AlGaN is a crystal state in which group 3 elements (Al and Ga) are randomly mixed, and is approximated by "random configuration". Is explained. However, since the covalent radius of Al and the covalent radius of Ga are different, the higher the symmetry of the atomic arrangement of Al and Ga in the crystal structure, the more stable the structure is.
  • An AlGaN-based semiconductor having a Wurtzite structure may have two types of arrays, a random array without symmetry and a stable symmetric array.
  • a state in which the symmetric array becomes dominant appears.
  • a symmetric array structure of Al and Ga is expressed.
  • the symmetrical arrangement structure even if the amount of Ga supplied to the crystal growth plane is slightly increased or decreased, the symmetry is high, so that the mixed crystal mole fraction is energetically stable, and the mass transfer of Ga is easy. It is possible to prevent the concentration from becoming uncontrollable.
  • each semiconductor layer is an epitaxial growth layer having a surface on which a multi-step terrace parallel to the (0001) plane is formed by step flow growth, Ga, which easily moves mass in the well layer, is adjacent to the well layer.
  • Ga which easily moves mass in the well layer
  • a Ga-enriched well region having an AlN molar fraction lower than the average AlN molar fraction in the well layer is formed. ..
  • the Al-enriched well region is formed by relatively increasing the density of Al in a part of the terrace region other than the inclined region due to the mass transfer of Ga at the time of forming the Ga-enriched well region. ..
  • a multi-stage terrace is formed in each semiconductor layer in the active layer by step flow growth, but the inclination angle of the sapphire substrate used is 0.
  • hexagonal columns or hexagonal pyramidal hillocks or pits can be formed on the flat crystal growth surface.
  • the crystal growth surface of the well layer is a flat surface, Ga, which tends to move mass, is concentrated around the hillock or the like, so that a Ga-enriched well region can be formed.
  • the density of Al is relative in a part of the terrace region other than the Ga-enriched well region due to the mass transfer of Ga at the time of formation of the Ga-enriched well region. Is increased and formed.
  • the fluctuation of the Ga supply amount into the Ga-enriched n-type region and the fluctuation of the average AlN mole fraction in the well layer are the relevant. Absorbed in the semi-stable well area. That is, in the Ga-enriched n-type region, when the Ga supply amount increases or the average AlN mole fraction decreases, the semi-stable well region increases and the Ga supply amount decreases, or the average AlN mole fraction decreases. As the fraction increases, the semi-stable well region decreases, and as a result, fluctuations in the AlN mole fraction within the Ga-enriched well region are suppressed. Similarly, when the semi-stable AlGaN is formed in the Al-enriched well region, the fluctuation of the AlN mole fraction in the Al-enriched well region is suppressed.
  • the target value Xwt of the AlN molar fraction is set to (n ⁇ 0.24) / 12 ⁇ Xwt.
  • the AlGaN composition ratio described later is quasi-equal to either the Ga-enriched well region or the Al-enriched well region formed in the well layer.
  • the average AlN mole fraction Xwa of the well layer is between each AlN mole fraction of the Ga-enriched well region and the Al-enriched well region, and the target value Xwt of the AlN mole fraction of the entire well layer or It becomes the vicinity value.
  • the target value Xwt of the AlN molar fraction is set within the range of ⁇ 2% of the AlN molar fraction (n / 12) of the semi-stable well region, but the target value Xwt is the AlN of the semi-stable well region.
  • the molar fraction is higher (n / 12 ⁇ Xwt)
  • the semi-stable well region is formed in the Ga-enriched well region
  • the target value Xwt is lower than the AlN molar fraction in the semi-stable well region (n / 12).
  • > Xwt the semi-stable well region is formed in the Al-enriched well region.
  • the average AlN mole fraction Xwa in the well layer is the target value Xwt or a value close thereto, but it may fluctuate in the wafer due to the influence of drift of the crystal growth apparatus and the like. Therefore, even if the target value Xwt is lower than the AlN mole fraction of the semi-stable well region, the semi-stable well region may be formed in the Ga-enriched well region, and the target value Xwt is the semi-stable well. The semi-stable well region may be formed within the Al-enriched well region even if it is higher than the AlN mole fraction of the region. Further, when the target value Xwt is a value near the AlN mole fraction of the metastable AlGaN, the above tendency becomes remarkable. However, regardless of whether the metastable well region is formed in the Ga-enriched well region or the Al-enriched well region, the occurrence of remarkable peak separation having a large wavelength difference in the EL spectrum is suppressed.
  • the nitride is formed by forming the semi-stable well region in the Ga-enriched well region or the Al-enriched well region.
  • the wavelength difference between the first and second smallest minimum extremum points of the second derivative of EL intensity expressed by a function whose wavelength is a variable is suppressed to 8 nm or less. It is preferable to be done.
  • the wavelengths of the peak and shoulder peak of the EL spectrum are specified by the wavelength of the extreme point of the minimum value, which is the first and second smallest derivative of the second derivative of EL intensity.
  • the shoulder peak is a single peak in which two emission peaks are not clearly separated in the EL spectrum, and the other peak is superimposed on the shoulder portion on the long wavelength side or the short wavelength side of one peak. It is a swelling of the luminescence intensity that develops. Therefore, the wavelength difference between the extreme points of the first and second smallest minimum values of the second derivative of EL intensity is 8 nm or less, which means that there is one peak between two peaks or one peak appearing in the EL spectrum.
  • the wavelength difference between the shoulder peaks is 8 nm or less, and the occurrence of remarkable peak separation with a large wavelength difference is suppressed in the EL spectrum.
  • the Ga-enriched well region or the Al-enriched well region in which the semi-stable well region is formed is formed. It is preferable to control the film thickness to be within the range of 4 to 12 monoatomic layers by an integral multiple of the monoatomic layer.
  • the peak or shoulder peak of the EL spectrum is the AlN mole fraction of the semi-stable AlGaN and the film thickness of the Ga-enriched well region or the Al-enriched well region in which the semi-stable well region is formed. It can be controlled within a predetermined wavelength range according to the above.
  • the AlGaN composition ratio is an integer ratio of Al n-1 Ga 13- .
  • the growth of the semi-stable well region, which is a semi-stable AlGaN having n N 12 is suppressed, and the AlGaN composition ratio in the Al-enriched well region becomes Al n + 1 Ga 11-n N 12 having an integer ratio. It is preferable that the growth of the semi-stable well region, which is the semi-stable AlGaN, is suppressed.
  • the AlN mole fraction is (n-1) / 12 and (n + 1) / 12.
  • the occurrence of peaks or shoulder peaks at the corresponding wavelengths is suppressed.
  • the emission intensity at the wavelength is extremely low.
  • the Ga enriched well region is described.
  • the first type chip in which the semi-stable well region grows and the second type chip in which the semi-stable well region grows are mixed in the Al-enriched well region.
  • the well layer made of an AlGaN-based semiconductor and the barrier layer made of an AlGaN-based semiconductor are alternately alternated. It is preferable to form the active layer having a multiple quantum well structure including two or more well layers by laminating them by epitaxial growth.
  • the active layer has a multiple quantum well structure, and improvement in luminous efficiency can be expected as compared with the case where the well layer is only one layer.
  • the present invention is a nitride semiconductor including a light emitting device structure portion in which an n-type layer, an active layer, and a p-type layer made of an AlGaN-based semiconductor having a wurtzite structure are laminated in the vertical direction. It is an ultraviolet light emitting element
  • the n-type layer is composed of an epitaxial growth layer of an n-type AlGaN-based semiconductor.
  • the active layer arranged between the n-type layer and the p-type layer has a quantum well structure including one or more well layers composed of an epitaxial growth layer of an AlGaN-based semiconductor.
  • the p-type layer is composed of an epitaxial growth layer of a p-type AlGaN-based semiconductor.
  • a Ga-enriched well region having an AlN mole fraction lower than the average AlN mole fraction Xwa of the well layer and an Al rich having an AlN mole fraction higher than the average AlN mole fraction Xwa.
  • the integer n is 3, 4, 5, or 6, and the AlGaN composition ratio is an integer ratio Al n Ga 12-n N 12 in the Ga-enriched well region or the Al-enriched well region.
  • the first feature of the EL spectrum is that the wavelength difference between the extreme points of the first and second smallest minimum values of the second derivative of the EL intensity represented by the function with the wavelength as a variable is 8 nm or less.
  • a nitride semiconductor ultraviolet light emitting element is provided.
  • a multi-stage terrace is formed in which the n-type layer, the active layer, and each semiconductor layer in the p-type layer are parallel to the (0001) plane. It is an epitaxial growth layer having a surface. Each semiconductor layer in the active layer has an inclined region inclined with respect to a (0001) plane connecting adjacent terraces of the multi-stage terrace, and a terrace region other than the inclined region.
  • the second feature is that the Ga-enriched well region exists in the inclined region of the well layer, and the Al-enriched well region exists in the terrace region of the well layer.
  • an ultraviolet light emitting element is provided.
  • the AlGaN composition ratio is quasi-equal to either the Ga-enriched well region or the Al-enriched well region formed in the well layer.
  • a semi-stable well region made of stable AlGaN By forming a semi-stable well region made of stable AlGaN, light emission from the Ga-enriched well region having different peak emission wavelengths and light emission from the Al-enriched well region and other regions in the well layer were combined.
  • the wavelength difference between two peaks or the wavelength difference between one peak and one shoulder peak is suppressed to 8 nm or less, and as a result, remarkable peak separation with a large wavelength difference is achieved. Occurrence is suppressed.
  • the film thickness of the Ga-enriched well region or the Al-enriched well region in which the semi-stable well region is formed is an integral multiple of the monoatomic layer. It is preferably in the range of 4 to 12 monoatomic layers.
  • the peak or shoulder peak of the EL spectrum is the AlN mole fraction of the semi-stable well region, and the film of the Ga-enriched well region or the Al-enriched well region where the semi-stable well region is formed. It is controlled within a predetermined wavelength range according to the thickness.
  • the nitride semiconductor ultraviolet light emitting device having the first or second feature has the average AlN mole fraction Xwa. (N-0.24) / 12 ⁇ Xwa ⁇ (n + 0.24) / 12 It is preferable that it is within the range of.
  • the wavelength difference is remarkable. The occurrence of peak separation is suppressed.
  • the active layer has a multiple quantum well structure including two or more well layers, and an AlGaN system is used between the two well layers. It is preferable that a barrier layer made of a semiconductor is present.
  • the active layer has a multiple quantum well structure, improvement in luminous efficiency can be expected as compared with the case where there is only one well layer.
  • the nitride semiconductor ultraviolet light emitting device of the first or second feature further includes a base portion including a sapphire substrate, and the sapphire substrate is a main surface inclined by a predetermined angle with respect to the (0001) plane.
  • the light emitting element structure is formed above the main surface. It is preferable that each semiconductor layer from the main surface to the p-type layer of the sapphire substrate is an epitaxial growth layer having a surface on which a multi-stage terrace parallel to the (0001) plane is formed.
  • epitaxial growth can be performed so that a multi-step terrace is exposed on the surface of each layer from the main surface of the sapphire substrate to the surface of the active layer. It is possible to realize a nitride semiconductor ultraviolet light emitting device having each feature.
  • a nitride semiconductor ultraviolet light emitting element having the above characteristics or the nitride semiconductor ultraviolet light emitting element According to the method for manufacturing a nitride semiconductor ultraviolet light emitting element having the above characteristics or the nitride semiconductor ultraviolet light emitting element, light emission from Ga-enriched well regions having different peak emission wavelengths, an Al-enriched well region, and other regions in the well layer.
  • the occurrence of remarkable peak separation having a large wavelength difference is suppressed.
  • FIG. 3 is a plan view showing the positional relationship between each site on the A plane and each site on the B plane when viewed from the c-axis direction of the wurtzite crystal structure shown in FIG. 1.
  • site planes (A3 plane, B3 plane) of Group 3 elements in each semi-stable AlGaN represented by Al 1 Ga 2 N 3 , Al 1 Ga 1 N 2 , and Al 2 Ga 1 N 3 whose AlGaN composition ratio is an integer ratio.
  • the figure which shows the symmetrical arrangement structure of Al and Ga schematically.
  • FIG. 3 is a cross-sectional view of a main part schematically showing an example of the structure of the nitride semiconductor ultraviolet light emitting device according to the first embodiment.
  • FIG. 4 is a cross-sectional view of a main part schematically showing an example of a laminated structure of an active layer of a nitride semiconductor ultraviolet light emitting device shown in FIG.
  • FIG. 5 is a diagram schematically showing a more detailed structure of the inclined region IA shown in FIG.
  • the AlN mole fraction of the Ga-enriched well region 220a is 50%, the emission wavelength of the quantum well structure composed of the AlGaN well layer and the AlGaN barrier layer, the film thickness of the well layer, and the AlN mole fraction of the barrier layer A graph showing the relationship.
  • the AlN mole fraction of the Ga-enriched well region 220a is 41.7%, the emission wavelength of the quantum well structure consisting of the AlGaN well layer and the AlGaN barrier layer, the thickness of the well layer and the AlN mole fraction of the barrier layer A graph showing the relationship with.
  • FIG. 5 is a plan view schematically showing an example of the structure when the nitride semiconductor ultraviolet light emitting device shown in FIG. 4 is viewed from the upper side of FIG. 4.
  • FIG. 5 is a cross-sectional view of a main part schematically showing an example of the structure of a nitride semiconductor ultraviolet light emitting device according to a second embodiment.
  • FIG. 17 is a cross-sectional view of the main part schematically showing an example of the laminated structure of the main part including the active layer of the nitride semiconductor ultraviolet light emitting device shown in FIG.
  • FIG. 6 is a cross-sectional view of a main part schematically showing an example of an element structure of a general ultraviolet light emitting diode.
  • the nitride semiconductor ultraviolet light emitting device (hereinafter, simply abbreviated as “light emitting device”) according to the embodiment of the present invention will be described with reference to the drawings.
  • the dimensional ratio of each part is not necessarily the same as that of the actual element because the main parts are emphasized and the contents of the invention are schematically shown for the sake of easy understanding of the explanation.
  • the dimensional ratios are not the same.
  • the light emitting element is a light emitting diode
  • FIG. 1 shows a schematic diagram of a 1-unit cell (2 monoatomic layers) in the c-axis direction of AlGaN.
  • white circles indicate sites where group 3 element atoms (Al, Ga) are located, and black circles indicate sites where group 5 element atoms (N) are located.
  • the monatomic layer is referred to as ML.
  • one unit cell is described as 2ML.
  • the site planes (A3 plane, B3 plane) of the Group 3 element and the site planes (A5 plane, B5 plane) of the Group 5 element shown by hexagons in FIG. 1 are both parallel to the (0001) plane.
  • Each site on the A3 surface and the A5 surface (collectively, the A surface) has six sites at each vertex of the hexagon and one site at the center of the hexagon.
  • Each site on the A plane overlaps in the c-axis direction
  • each site on the B plane overlaps in the c-axis direction.
  • the atom (N) at one site on the B5 plane is one of the atoms (Al, Ga) at the three sites on the A3 plane located above the B5 plane and one of the B3 planes located below the B5 plane.
  • a four-coordinate bond is formed with the site atom (Al, Ga), and the one site atom (Al, Ga) on the B3 plane is the one site atom (N) on the B5 plane located above the B3 plane.
  • each site of the A plane is the B plane. It does not overlap with each site in the c-axis direction.
  • FIG. 2 shows the positional relationship between each site on the A plane and each site on the B plane as a plan view of the A3 plane and the B3 plane as viewed from the c-axis direction.
  • the black circles and white circles in FIG. 2 distinguish whether the site surface is the A3 surface or the B3 surface.
  • each of the six vertices of the hexagon is shared by the other two adjacent hexagons, and the central site is not shared with the other hexagons, so within one hexagon, There are substantially 3 atomic sites. Therefore, there are 6 sites of group 3 element atoms (Al, Ga) and 6 sites of group 5 element atoms (N) per unit cell (2ML).
  • AlGaN composition ratio represented by the integer ratio excluding GaN and AlN.
  • Al 1 Ga 2 N 3 and Al 1 Ga 1 N 2 and Al 2 Ga 1 N 3 of the above 2) to 4) are the same Al and Ga on both the A3 surface and the B3 surface, as shown in FIG. Since a symmetric array structure can be obtained, the semi-stable AlGaN having an AlGaN composition ratio of 2) to 4) is formed in 1ML units in the c-axis direction.
  • FIG. 3 illustrates an arrangement structure of only one of the A3 plane and the B3 plane. In FIG. 3, Ga is indicated by a large black circle and Al is indicated by a small black circle.
  • one of the A3 surface and B3 surface is the sequence structure of Al 1 Ga 2 N 3 of 2) above, and the other is the array structure of GaN (sites of group 3 elements). It is possible to take a symmetrical array structure in units of 2ML, all of which are Ga). Further, in the Al 1 Ga 5 N 6 of the above 5), one of the A3 surface and the B3 surface is the arrangement structure of the Al 2 Ga 1 N 3 of the above 4), and the other is the arrangement structure of the AlN (the site of the group 3 element). It is possible to take a symmetrical array structure of 2ML units, all of which are Al).
  • one of the A3 plane and the B3 plane is the sequence structure of Al 1 Ga 1 N 2 of 3) above, and the other is the sequence structure of GaN (site of group 3 element).
  • Al 5 Ga 7 N 12 one of the A3 surface and the B3 surface has an arrangement structure of Al 1 Ga 2 N 3 of the above 2), and the other has an arrangement structure of Al 1 Ga 1 N 2 of the above 3). It is possible to take a symmetric array structure in units of 2ML.
  • Al 7 Ga 5 N 12 one of the A3 surface and the B3 surface is the arrangement structure of the Al 1 Ga 1 N 2 of the above 3), and the other is the arrangement structure of the Al 2 Ga 1 N 3 of the above 4). It is possible to take a symmetric array structure in units of 2ML.
  • Al 3 Ga 1 N 4 in 9) above has an array structure of Al 1 Ga 1 N 2 in 3) above, one of the A3 and B3 surfaces, and the other has an array structure of AlN (the sites of Group 3 elements are all Al).
  • the semi-stable AlGaN having an AlGaN composition ratio of 1), 5) to 9) above is formed in 2ML units in the c-axis direction.
  • each of the AlGaN composition ratios 1), 5) to 9) above for example, by synthesizing different symmetrical array structures on the A3 plane and the B3 plane described above in the same plane. , Al 1 Ga 2 N 3 and Al 1 Ga 1 N 2 and Al 2 Ga 1 N 3 in 2) to 4) above, each of the A3 and B3 planes has the same Al and Ga symmetrical array structure. It is thought to get. In that case, each metastable AlGaN having an AlGaN composition ratio of 1), 5) to 9) is formed in the c-axis direction in 1ML units, similarly to the metastable AlGaN having an AlGaN composition ratio of 2) to 4). Can be done.
  • the atomic arrangements of Al and Ga are symmetrical, and the AlGaN is energetically stable.
  • Ga is expected to move around at 1000 ° C. or higher even after the atom reaches the site on the crystal surface.
  • Al is easily adsorbed on the surface, and movement after entering the site is considered to move to some extent, but it is strongly restricted.
  • the light emitting device 1 of the first embodiment is a light emitting device including a base portion 10 including a sapphire substrate 11, a plurality of AlGaN-based semiconductor layers 21 to 24, a p electrode 26, and an n electrode 27.
  • the structure portion 20 is provided.
  • the light emitting element 1 is mounted (flip chip mounted) with the light emitting element structure portion 20 side (upper side in the drawing in FIG. 4) facing the mounting base (sub-mount or the like), and light is extracted.
  • the direction is the base portion 10 side (lower side in the figure in FIG. 4).
  • the direction perpendicular to the main surface 11a of the sapphire substrate 11 is defined as the “vertical direction” (or “vertical”).
  • the direction is referred to as “direction"), and the direction from the base portion 10 toward the light emitting element structure portion 20 is the upward direction, and the opposite is the downward direction.
  • a plane parallel to the vertical direction is referred to as a "first plane”.
  • a plane parallel to the main surface 11a of the sapphire substrate 11 (or the upper surface of the base portion 10 and each of the AlGaN-based semiconductor layers 21 to 24) is referred to as a "second plane", and a direction parallel to the second plane is referred to as “second plane”. It is called "horizontal direction”.
  • the base portion 10 includes a sapphire substrate 11 and an AlN layer 12 directly formed on the main surface 11a of the sapphire substrate 11.
  • the main surface 11a is inclined at an angle (off angle) within a certain range (for example, from 0.3 ° to about 6 °) with respect to the (0001) surface, and is multi-staged on the main surface 11a. It is a slightly inclined board that the terrace of is exposed.
  • the AlN layer 12 is composed of an AlN crystal epitaxially grown from the main surface of the sapphire substrate 11, and the AlN crystal has an epitaxial crystal orientation relationship with respect to the main surface 11a of the sapphire substrate 11. Specifically, for example, the AlN crystal grows so that the C-axis direction ( ⁇ 0001> direction) of the sapphire substrate 11 and the C-axis direction of the AlN crystal are aligned.
  • the AlN crystal constituting the AlN layer 12 may be an AlN-based semiconductor layer that may contain a trace amount of Ga or other impurities. In the present embodiment, the film thickness of the AlN layer 12 is assumed to be about 2 ⁇ m to 3 ⁇ m.
  • the structure of the base portion 10 and the substrate to be used are not limited to the above-mentioned configuration.
  • an AlGaN-based semiconductor layer having an AlN mole fraction equal to or higher than the AlN mole fraction of the AlGaN-based semiconductor layer 21 may be provided between the AlN layer 12 and the AlGaN-based semiconductor layer 21.
  • the AlGaN-based semiconductor layers 21 to 24 of the light emitting device structure portion 20 are, in order from the base portion 10 side, an n-type clad layer 21 (n-type layer), an active layer 22, an electron block layer 23 (p-type layer), and p. It has a structure in which type contact layers 24 (p-type layers) are sequentially epitaxially grown and laminated.
  • the AlN layer 12 of the base portion 10 epitaxially grown from the main surface 11a of the sapphire substrate 11, the n-type clad layer 21 of the light emitting device structure portion 20, each semiconductor layer in the active layer 22, and the electronic block.
  • the layer 23 has a surface on which a multi-stage terrace parallel to the (0001) plane derived from the main surface 11a of the sapphire substrate 11 is formed. Since the p-type contact layer 24 of the p-type layer is formed on the electron block layer 23 by epitaxial growth, a similar multi-stage terrace can be formed, but a similar multi-stage terrace is not necessarily formed. It does not have to have a surface.
  • the active layer 22, the electron block layer 23, and the p-type contact layer 24 in the light emitting element structure portion 20 are laminated on the second region R2 on the upper surface of the n-type clad layer 21.
  • the formed portion is removed by etching or the like, and is formed on the first region R1 on the upper surface of the n-type clad layer 21.
  • the upper surface of the n-type clad layer 21 is exposed in the second region R2 excluding the first region R1.
  • the height of the upper surface of the n-type clad layer 21 may differ between the first region R1 and the second region R2, in which case the n-type clad layer 21 may have a different height.
  • the upper surface is individually defined in the first region R1 and the second region R2.
  • the n-type clad layer 21 is composed of an n-type AlGaN-based semiconductor, and the layered region 21a having a low AlN mole fraction is locally dispersed in the n-type clad layer 21 in the n-type clad layer 21. exist.
  • the layered region 21a is elongated in an oblique direction with respect to the surface of the n-type clad layer 21, and the bandgap energy is locally reduced, so that carriers are easily localized. It functions as a low resistance current path.
  • the metastable n-type region is predominantly present.
  • the AlN mole fraction difference between the n-type main body region 21b other than the layered region 21a of the n-type clad layer 21 and the metastable n-type region in the layered region 21a is stably maintained at about 2% or more.
  • the effect of carrier localization can be obtained by the flow of electrons through the layered region 21a.
  • the film thickness of the n-type clad layer 21 is assumed to be about 1 ⁇ m to 2 ⁇ m, which is the same as the film thickness used in a general nitride semiconductor ultraviolet light emitting device. It may be about 2 ⁇ m to 4 ⁇ m.
  • the active layer 22 has two or more well layers 220 composed of AlGaN-based semiconductors (excluding AlN-based semiconductors and GaN-based semiconductors) and one or more barrier layers 221 composed of AlGaN-based semiconductors or AlN-based semiconductors. It is provided with a multiple quantum well structure in which the above are alternately stacked. It is not always necessary to provide the barrier layer 221 between the well layer 220 of the lowermost layer and the n-type clad layer 21. Further, in the present embodiment, the barrier layer 221 is not provided between the well layer 220 and the electron block layer 23 of the uppermost layer, but as a preferred embodiment, the barrier layer 221 is thinner and has a higher AlN mole fraction. An AlGaN layer or an AlN layer may be provided.
  • the electronic block layer 23 is composed of a p-type AlGaN-based semiconductor.
  • the p-type contact layer 24 is composed of a p-type AlGaN-based semiconductor or a p-type GaN-based semiconductor.
  • the p-type contact layer 24 is typically composed of p-GaN.
  • FIG. 5 schematically shows an example of a laminated structure (multiple quantum well structure) of the well layer 220 and the barrier layer 221 in the active layer 22.
  • FIG. 5 illustrates a case where the well layer 220 and the barrier layer 221 each have three layers. Three layers of the barrier layer 221 and the well layer 220 are laminated in this order on the n-type clad layer 21, and the electron block layer 23 is located on the uppermost well layer 220.
  • the structure in which the terrace T in the well layer 220, the barrier layer 221 and the electron block layer 23 shown in FIG. 5 grows in a multi-stage manner is a known structure as disclosed in Non-Patent Documents 1 and 2. be.
  • an inclined region IA inclined with respect to the (0001) plane is formed between the terraces T adjacent to each other in the lateral direction in each layer.
  • the area other than the inclined area IA whose upper and lower sides are sandwiched by the terrace T is referred to as a terrace area TA.
  • the depth of one terrace T (distance between adjacent inclined regions IA) is assumed to be several tens of nm to several hundreds of nm.
  • FIG. 6 schematically shows, for example, a stepped structure (macrostep structure) that appears on the surface of the inclined region IA of one well layer 220.
  • the AlN mole fraction is the average AlN mole fraction Xwa in the well layer 220 due to the mass transfer of Ga from the terrace region TA to the inclined region IA.
  • a lower Ga-enriched well region 220a is formed within the sloping region IA.
  • the density of Al is relative in a part of the terrace region TA.
  • a Ga-enriched barrier region 221a having an AlN mole fraction lower than the average AlN mole fraction Xba of the barrier layer 221 is formed in the inclined region IA.
  • an Al-enriched barrier region having an AlN mole fraction higher than the average AlN mole fraction Xba of the barrier layer 221 may be formed in a part of the terrace region TA.
  • a Ga-enriched EB region 23a having an AlN mole fraction lower than the average AlN mole fraction Xea of the electron block layer 23 is formed in the inclined region IA.
  • an Al-enriched EB region having an AlN mole fraction higher than the average AlN mole fraction Xea of the electron block layer 23 may be formed in a part of the terrace region TA. ..
  • carriers are likely to be localized in the layered region 21a having a locally low AlN mole fraction, and in the active layer 22, the local region existing in the inclined region IA of the well layer 220.
  • the Ga-enriched well region 220a having a low AlN mole fraction carriers are localized in the Ga-enriched barrier region 221a having a locally low AlN mole fraction existing in the inclined region IA of the barrier layer 221.
  • carriers are easily localized in the Ga-enriched EB region 23a having a locally low AlN mole fraction existing in the inclined region IA.
  • the element structure is such that carriers can be supplied to the well layer 220 and the light emission efficiency can be improved by recombination of carriers (electrons and holes) in the well layer 220.
  • the AlGaN composition ratio is a semi-stable AlGaN having an integer ratio of Al n Ga 12-n N 12 in the Ga-enriched well region 220a or the Al-enriched well region of the well layer 220.
  • a well area is formed.
  • the integer n is 3, 4, 5, or 6.
  • the target value Xwt of the AlN mole fraction at the time of epitaxial growth of the well layer 220 is set so as to satisfy the conditions shown by the following inequality. (N ⁇ 0.24) / 12 ⁇ Xwt ⁇ (n + 0.24) / 12
  • the average AlN mole fraction Xwa of the well layer 220 is the target value Xwt of the AlN mole fraction of the well layer 220 or a value close thereto, the quasi-aln formed in the well layer 220 is formed. It generally falls within the range of ⁇ 2% of the AlN mole fraction (n / 12) in the stable well region.
  • the terrace region TA to the inclined region IA. Due to the mass transfer of Ga to, the AlN mole fraction Xw0 of the Ga-enriched well region 220a in the inclined region IA decreases to the AlN mole fraction Xws of the semi-stable well region.
  • the AlN molar fraction of the AlGaN-based semiconductor constituting the well layer 220 is lower than that in the case of less than about 285 nm, so that it is relative.
  • the number of Al pores that become point defects is reduced, and the holes that reach the terrace region TA in the well layer 220 are luminescently recombined in the terrace region TA having a higher AlN molar fraction than the inclined region IA.
  • Light emission at a shorter wavelength than the tilted region IA occurs. In this case, double-peak emission may occur in which two emission peaks having different wavelengths appear separately without being combined into one peak in the EL spectrum.
  • the generation of Al vacancies in the well layer 220 can be suppressed by raising the growth temperature of each semiconductor layer of the active layer 22 to, for example, 1200 ° C. or higher, so that the peak emission wavelength is less than about 285 nm. Even so, the above-mentioned double peak emission can occur.
  • FIG. 8 shows a case where the EL spectrum has peaks P1 and P2 separated into two (case A) and a case where one peak P1 and a shoulder peak SP2 appearing on the shoulder portion on the long wavelength side thereof (case B). ), And three cases of having one peak P2 and a shoulder peak SP1 appearing on the shoulder portion on the short wavelength side thereof (case C) are schematically shown.
  • case A when the emission intensities of the two separated peaks P1 and P2 are almost the same (case A1), the emission intensity of the peak P1 on the short wavelength side is the peak P2 on the long wavelength side. It is subdivided into three cases: a case where it is larger (case A2) and a case where the emission intensity of the peak P2 on the long wavelength side is larger than the peak P1 on the short wavelength side (case A3).
  • cases B and C when the swelling of the emission intensity of the shoulder portions of the shoulder peaks SP1 and SP2 is not remarkable, it can be regarded as a pseudo single peak.
  • the peaks P1 and P2 and the shoulder peaks SP1 and SP2 shown in FIG. 8 are specified as extreme value points having a minimum value in the second derivative of the EL intensity represented by the function having the wavelength as a variable. ..
  • the peaks P1 and P2 are specified as the extremum points of the smallest minimum value
  • the shoulder peaks SP1 and SP2 are specified as the extremum points of the second smallest minimum value. Since the noise component at the time of measurement is superimposed on the EL spectrum, the quadratic derivative takes a minimum value with a small absolute value in addition to the minimum values corresponding to the peaks P1 and P2 and the shoulder peaks SP1 and SP2. There can be points.
  • the peaks P1 and P2 and the shoulder peaks SP1 and SP2 are specified by using the extreme points of the two minimum values, the first and the second smallest. It should be noted that the zero point of the first derivative of the EL intensity (the first derivative value of the EL intensity is 0) may be used to specify the peaks P1 and P2.
  • FIG. 9 as an example of the EL spectrum of Case B, the EL spectrum whose EL intensity is standardized at 1000000, the first derivative of the EL spectrum, and the second derivative of the EL spectrum are shown in the vertical wavelength direction.
  • the graphs aligned and aligned are shown respectively. From FIG. 9, it can be seen that the peak P1 and the shoulder peak SP2 are specified as the extreme points of the first and second smallest minimum values of the second derivative of the EL intensity. Further, it can be seen that the peak P1 is specified as the zero point of the first derivative of the EL intensity.
  • the wavelength difference between the peak P1 and the shoulder peak SP2 is as large as about 17 nm, the full width at half maximum is about 22 nm, and the peak P1.
  • the shoulder peak SP2 are clearly separated, and this is an example that cannot be regarded as a pseudo single peak.
  • the AlN mole fraction is the average AlN mole fraction of the well layer 220 in the terrace region TA. It is assumed that there is an intermediate region that is the same as or almost the same as the rate Xwa. Therefore, the EL spectrum of the light emitting element 1 is the EL spectrum from the Ga enriched well region 220a having an AlN mole fraction Xw0 and the Ga richness having an AlN mole fraction Xw0, regardless of the type of cases A to C.
  • the light emitting element structure portion 20 of the present embodiment efficiently covers the inclined region IA of the well layer 220 and its vicinity region via the layered region 21a from the n-type clad layer 21 side that functions as a low resistance current path. It is configured to supply carriers. Therefore, in the well layer 220, carriers are likely to be localized in the Ga-enriched well region 220a in the inclined region IA, and the EL spectrum from the Ga-enriched well region 220a is the main EL spectrum from the above three locations. It can be an EL spectrum.
  • the EL spectrum from the Al-enriched well region located near the inclined region IA is the above 3 It can be the main EL spectrum in the EL spectrum from the location.
  • the intermediate region in the terrace region TA which has a larger surface area than the inclined region IA, is considered to have insufficient carrier supply at a location separated from the inclined region IA, and therefore occupies the synthesized spectrum of the EL spectrum from the intermediate region.
  • the degree is considered to be limited.
  • the EL spectrum of the light emitting element 1 can be any type of the above cases A to C depending on the magnitude relationship of the EL spectra from the above three locations.
  • the wavelength difference of 5 nm corresponds to an AlN mole fraction difference of about 3% and a film thickness difference of about 1 ML.
  • the AlN mole fraction of 221a is 66.7% (2/3), 75% (3/4), and 83.3% (5/6), and the barrier is shown in FIG.
  • the AlN mole fraction of the Ga-enriched barrier region 221a of layer 221 was 66.7% (two-thirds).
  • the AlN mole fraction Xw0 of the Ga-enriched well region 220a is 41.7%
  • the emission wavelength is approximately 249 nm within the above range of the film thickness of the well layer 220 and the AlN mole fraction of the barrier layer 221.
  • the emission wavelength is approximately 261 nm within the above range of the film thickness of the well layer 220 and the AlN mole fraction of the barrier layer 221. It can be seen that the wavelength changes in the range of about 328 nm, and the emission wavelength changes in the range of approximately 261 nm to 315 nm when the thickness of the well layer 220 changes in the range of 4 ML to 12 ML. From FIG. 12, when the AlN mole fraction Xw0 of the Ga-enriched well region 220a is 33.3%, the emission wavelength is approximately 261 nm within the above range of the film thickness of the well layer 220 and the AlN mole fraction of the barrier layer 221. It can be seen that the wavelength changes in the range of about 328 nm, and the emission wavelength changes in the range of approximately 261 nm to 315 nm when the thickness of the well layer 220 changes in the range of 4 ML to 12 ML. From FIG.
  • the thickness of the well layer 220 is in the range of 4 ML to 12 ML, and the AlN mole fraction of the barrier layer 221 is 66.7%.
  • the emission wavelength varies in the range of approximately 275 nm to 320 nm.
  • the emission wavelength can be further expanded.
  • the AlN mole fraction of the enriched barrier region 221a within the range of 66.7% to 83.3%, the emission of the peak or shoulder peak corresponding to the AlN mole fraction Xws of the semi-stable well region is emitted.
  • the wavelength can be set in the range of approximately 252 nm to 310 nm.
  • the AlN mole fraction is AlN in addition to the lattice relaxation from the barrier layer and the semi-stable well region in the Ga-enriched well region 220a or the Al-enriched well region.
  • the emission wavelength of the peak or shoulder peak corresponding to the film thickness (4 ML to 10 ML) is expected to vary by about ⁇ 1.5 nm.
  • the AlN mole fraction Xws of the semi-stable well region, the AlN mole fraction of the barrier layer 221, and the emission wavelength range of the peak or shoulder peak determined according to the film thickness of the semi-stable well region are set.
  • it is referred to as "inherent wavelength range”.
  • the AlN mole fraction of the barrier layer 221 is the AlN mole fraction in the inclined region IA of the barrier layer 221 when the semi-stable well region is formed in the Ga-enriched well region 220a.
  • the AlN mole fraction in the terrace region TA of the barrier layer 221 is assumed. Therefore, for example, when the AlN mole fraction in the inclined region IA of the barrier layer 221 is 83.3% and the semi-stable well region is formed in the Al-enriched well region of the terrace region TA, the barrier is formed.
  • the AlN mole fraction in the terrace region TA of layer 221 is about several percent higher than 83.3%, the range of the above-mentioned variation of about ⁇ 1.5 nm in the natural wavelength range is the film thickness of the semi-stable well region. It can change slightly depending on the situation.
  • the AlN mole fraction of the terrace region TA of the barrier layer 221 is in the range of approximately 51% to 90%. Within, it is set to be 1% or more, preferably 2% or more, more preferably 4% or more, higher than the AlN mole fraction of the Ga-enriched barrier region 221a.
  • the AlN mole fraction difference between the Ga-enriched barrier region 221a in the barrier layer 221 and the terrace region TA should be 4 to 5% or more. However, even if it is about 1 to 2%, the effect of carrier localization can be expected.
  • a metastable barrier region predominates.
  • the AlN mole fraction difference between the Ga-enriched barrier region 221a and the terrace region TA of the barrier layer 221 is stably maintained at approximately 2% or more, and thus the carrier in the Ga-enriched barrier region 221a described above is maintained. The effect of localization of is stably exhibited.
  • the film thickness of the barrier layer 221 is set in the range of, for example, 6 nm to 8 nm including the terrace region TA and the inclined region IA.
  • the AlN mole fraction of the terrace region TA of the electron block layer 23 is approximately 69% to 90%, which is 20% or more, preferably 25% or more, more preferably 25% or more, more preferably than the AlN mole fraction of the terrace region of the well layer 220. Is set to be 30% or more higher. Further, the AlN mole fraction of the Ga-enriched EB region 23a of the electron block layer 23 is 20% or more, preferably 25% or more, more preferably 30 than the AlN mole fraction of the Ga-enriched well region 220a of the well layer 220. It is set to be higher than%.
  • a p-type metastable AlGaN having an AlGaN composition ratio of an integer ratio of Alm Ga 12-m N 12 (m 8, 9, or 10) in the Ga-enriched EB region 23a.
  • a metastable EB region predominates.
  • the AlN mole fraction difference between the Ga-enriched EB region 23a and the terrace region TA of the electron block layer 23 is stably maintained at about 2% or more, and therefore, in the above-mentioned Ga-enriched EB region 23a.
  • the effect of carrier localization is stably exerted.
  • the film thickness of the electronic block layer 23 is set in the range of, for example, 15 nm to 30 nm (optimum value is about 20 nm) including the terrace region TA and the inclined region IA.
  • the average AlN mole fractions Xna, Xba, and Xea of the n-type clad layer 21, the barrier layer 221 and the electron block layer 23 are the same as the average AlN mole fraction Xwa of the well layer 220. It is the target value of the AlN mole fraction at the time of film formation of the layer 21, the barrier layer 221 and the electron block layer 23, or a value close thereto.
  • the p electrode 26 is made of a multilayer metal film such as Ni / Au, and is formed on the upper surface of the p-type contact layer 24.
  • the n electrode 27 is made of a multilayer metal film such as Ti / Al / Ti / Au, and is formed in a part of the exposed surface in the second region R2 of the n-type clad layer 21.
  • the p-electrode 26 and the n-electrode 27 are not limited to the above-mentioned multilayer metal film, and the electrode structures such as the metal constituting each electrode, the number of layers, and the order of layers may be appropriately changed.
  • FIG. 14 shows an example of the shape of the p electrode 26 and the n electrode 27 as viewed from above of the light emitting element 1.
  • the line BL existing between the p electrode 26 and the n electrode 27 shows the boundary line between the first region R1 and the second region R2, and is the active layer 22, the electron block layer 23, and the p-type. It coincides with the outer peripheral side wall surface of the contact layer 24.
  • the plan view shape of the first region R1 and the p electrode 26 adopts a comb shape as an example, but the plane of the first region R1 and the p electrode 26.
  • the visual shape, arrangement, and the like are not limited to the examples shown in FIG.
  • the organometallic compound vapor phase growth (MOVPE) method the AlN layer 12 contained in the base portion 10 and the nitride semiconductor layers 21 to 24 contained in the light emitting device structure portion 20 are sequentially epitaxially grown on the sapphire substrate 11. And stack.
  • the n-type clad layer 21 is doped with, for example, Si as a donor impurity
  • the electron block layer 23 and the p-type contact layer 24 are doped with, for example, Mg as an acceptor impurity.
  • At least the AlN layer 12, the n-type clad layer 21, the active layer 22 (well layer 220, barrier layer 221), and the electron block layer 23 have a multi-stage terrace parallel to the (0001) plane on each surface.
  • the main surface 11a is tilted at an angle (off angle) within a certain range (for example, from 0.3 ° to 6 °) with respect to the (0001) surface.
  • a slightly inclined substrate having a multi-tiered terrace exposed on the main surface 11a is used.
  • the growth rate at which the multi-stage terrace is easily exposed (specifically, for example, the growth temperature, the raw material gas and the carrier).
  • the growth rate is achieved by appropriately setting various conditions such as the amount of gas supplied and the flow velocity). Since these conditions may differ depending on the type and structure of the film forming apparatus, it is sufficient to actually prepare some samples in the film forming apparatus and specify these conditions.
  • the growth start point of the layered region 21a is set in the stepped portion (inclined region) between the multi-stage terraces formed on the upper surface of the AlN layer 12 due to the mass transfer of Ga.
  • the growth temperature, growth pressure, and donor impurity concentration were increased so that the layered region 21a could grow diagonally upward due to segregation due to the mass transfer of Ga as the n-type clad layer 21 was subsequently formed and subsequently grew. Be selected.
  • the growth temperature is preferably 1050 ° C. or higher at which mass transfer of Ga is likely to occur, and 1150 ° C. or lower at which good n-type AlGaN can be prepared.
  • the mass transfer of Ga becomes excessive, and even in the case of semi-stable AlGaN, the AlN mole fraction tends to fluctuate randomly, so that the AlN mole fraction is 41.7% to 66.
  • the 0.7% semi-stable n-type region may be difficult to form stably.
  • As the growth pressure 75 Torr or less is preferable as a good growth condition of AlGaN, and 10 Torr or more is realistic and preferable as a control limit of the film forming apparatus.
  • the donor impurity concentration is preferably about 1 ⁇ 10 18 to 5 ⁇ 10 18 cm -3 .
  • the growth temperature, growth pressure, and the like are examples, and optimum conditions may be appropriately specified according to the film forming apparatus to be used.
  • the supply amount and flow velocity of the raw material gas (trimethylaluminum (TMA) gas, trimethylgallium (TMG) gas, ammonia gas) and carrier gas used in the organic metal compound vapor phase growth method are the average AlN of the n-type clad layer 21.
  • the molar fraction Xna is set as the target value.
  • the average AlN mole fraction Xna of the n-type clad layer 21 is as described above, and overlapping description will be omitted.
  • the donor impurity concentration does not necessarily have to be controlled uniformly in the vertical direction with respect to the film thickness of the n-type clad layer 21.
  • the impurity concentration of the predetermined thin film thickness portion in the n-type clad layer 21 is lower than the above set concentration, for example, less than 1 ⁇ 10 18 cm -3 , more preferably 1 ⁇ 10 17 cm -3 or less. It may be a controlled low impurity concentration layer.
  • the film thickness of the low impurity concentration layer is preferably larger than 0 nm and about 200 nm or less, more preferably about 10 nm or more and 100 nm or less, and further preferably about 20 nm or more and about 50 nm or less.
  • the donor impurity concentration of the low impurity concentration layer may be lower than the set concentration, and the undoped layer (0 cm -3 ) may be partially contained. Further, it is preferable that a part or all of the low impurity concentration layer is present in the upper layer region having a depth of 100 nm or less downward from the upper surface of the n-type clad layer 21.
  • the organic metal compound vapor phase growth (MOVPE) method or the like is continuously applied to the entire upper surface of the n-type clad layer 21.
  • the active layer 22 (well layer 220, barrier layer 221), the electron block layer 23, the p-type contact layer 24, and the like are formed by the well-known epitaxial growth method.
  • the acceptor impurity concentration of the electronic block layer 23 is preferably about 1.0 ⁇ 10 16 to 1.0 ⁇ 10 18 cm -3 as an example, and the acceptor impurity concentration of the p-type contact layer 24 is 1.0 as an example. It is preferably about ⁇ 10 18 to 1.0 ⁇ 10 20 cm -3 .
  • the acceptor impurity concentration does not necessarily have to be controlled uniformly in the vertical direction with respect to the film thicknesses of the electron block layer 23 and the p-type contact layer 24.
  • the well layer is formed in the same manner as the n-type clad layer 21, with the average AlN mole fraction Xwa of the well layer 220 as the target value under the growth conditions under which the above-mentioned multi-stage terrace is easily exposed. 220 is grown, and further, the barrier layer 221 is grown with the average AlN mole fraction Xba of the barrier layer 221 as a target value.
  • the average AlN mole fractions Xwa and Xba of the well layer 220 and the barrier layer 221 are as described above, and overlapping description is omitted.
  • the average AlN mole fraction Xea of the electronic block layer 23 is set as the target value under the growth conditions in which the above-mentioned multi-stage terrace is easily exposed in the same manner as in the n-type clad layer 21.
  • the electronic block layer 23 is grown.
  • the average AlN mole fraction Xea of the electron block layer 23 is as described above, and overlapping description will be omitted.
  • the growth temperature of the active layer 22 (well layer 220, barrier layer 221), the electron block layer 23, and the p-type contact layer is such that the growth temperature of the n-type clad layer 21 is T1 and the growth of the active layer 22.
  • the temperature is T2
  • the growth temperature of the electron block layer 23 is T3
  • the growth temperature of the p-type contact layer is T4, the following formulas (1) and (1) and (1) and ( It is preferable that the relationship shown in 2) is satisfied.
  • the growth temperature T3 of the electron block layer 23 is preferably 1150 ° C. or higher when the AlN mole fraction in the metastable EB region is 83.3%, and the AlN mole fraction in the metastable EB region is 75% or 66. In the case of 0.7%, 1100 ° C. or higher is preferable, and higher temperature than 1100 ° C. is more preferable. It should be noted that each of the above temperatures is an example, and for example, by increasing the flow rate of the nitrogen raw material gas and lowering the growth rate, the above 1150 ° C. and 1100 ° C. can be reduced to 1100 ° C. and 1050 ° C., respectively. It is possible.
  • GaN is decomposed in the well layer 220 located below the growth temperature in the transition process of the growth temperature, and the GaN is decomposed.
  • the characteristics of the light emitting element 1 may deteriorate due to the decomposition. Therefore, in order to suppress the decomposition of the GaN, between the well layer 220 of the uppermost layer and the electron block layer 23, in order to prevent the decomposition of the GaN, a thinner film than the barrier layer 221 (for example, 3 nm or less, preferably 3 nm or less) is preferable. , 2 nm or less), it is preferable to form an AlGaN layer or an AlN layer having a higher AlN mole fraction than the barrier layer 221 and the electron block layer 23.
  • the active layer 22 (well layer 220, barrier layer 221), the electron block layer 23, the p-type contact layer 24, etc. are formed on the entire upper surface of the n-type clad layer 21 in the above manner, then the p-type contact layer 24 and the like are formed.
  • the second region R2 of the nitride semiconductor layers 21 to 24 is selectively etched by a well-known etching method such as reactive ion etching until the upper surface of the n-type clad layer 21 is exposed, to obtain the n-type clad layer 21.
  • the second region R2 portion of the upper surface is exposed.
  • a p-electrode 26 is formed on the p-type contact layer 24 in the unetched first region R1 by a well-known film forming method such as an electron beam vapor deposition method, and n in the etched first region R2.
  • the n electrode 27 is formed on the mold clad layer 21.
  • heat treatment may be performed by a well-known heat treatment method such as RTA (instantaneous heat annealing).
  • the light emitting element 1 is flip-chip mounted on a base such as a submount and then sealed with a predetermined resin (for example, a lens-shaped resin) such as a silicone resin or an amorphous fluororesin. Can be used in state.
  • a predetermined resin for example, a lens-shaped resin
  • a silicone resin or an amorphous fluororesin such as silicone resin or an amorphous fluororesin.
  • a sample before etching of the p2nd region R2 and formation of the electrode 26 and the n electrode 27 is prepared, and a sample is prepared on the upper surface of the material.
  • a sample piece having a vertical (or substantially vertical) cross section can be processed with a focused ion beam (FIB) and observed by a HAADF-STEM image of the sample piece.
  • the HAADF-STEM image has a contrast proportional to the atomic weight, and heavy elements are displayed brightly. Therefore, the region having a low AlN mole fraction is displayed relatively brightly.
  • the HAADF-STEM image is more suitable for observing the difference in AlN mole fraction than a normal STEM image (bright field image).
  • FIG. 15 shows a cross section of a main part of a light emitting device 1 including an active layer 22 having a multi-quantum well structure in which the well layer 220 and the barrier layer 221 shown in FIG. 5 of the light emitting device 1 manufactured in the above manner are each three layers.
  • the HAADF-STEM image of the structure is shown.
  • TEM-EDX line analysis of energy dispersive X-ray spectroscopy
  • the probe (diameter: about 2 nm) was scanned to analyze the composition in the active layer 22, and the distribution of the obtained EDX counts of Ga in the scanning direction showed that the inclined region IA and the terrace region TA in the well layer 220 were obtained. Each film thickness can be measured.
  • composition analysis in the specific semiconductor layer in the AlGaN-based semiconductor layers 21 to 24 is performed by the energy dispersive X-ray spectroscopy (section TEM-EDX) or CL (cathodoluminescence) method using the above sample piece. Can be done with.
  • section TEM-EDX energy dispersive X-ray spectroscopy
  • CL cathodoluminescence
  • the target value of the film thickness of the well layer 220 is 8 ML to 9 ML, but there is a variation of about 1 ML between wafers and within the wafer, and the film thickness of the inclined region IA is about 1 ML larger than the film thickness of the terrace region TA. ..
  • the measurement results of the EL spectrum of a total of 12 chips of 5 types of wafers show that the emission wavelengths of the peak or shoulder peak of the EL spectrum are 286 nm to 289 nm (8 ML), 292 nm to 295 nm (9 ML), and 297 nm. It is classified into three types depending on which of the three natural wavelength ranges of ⁇ 300 nm (10 ML) exists.
  • the ML value in parentheses indicates the film thickness of the inclined region IA or the terrace region TA in which the metastable well region is formed.
  • the above three natural wavelength ranges are all in the wavelength region where double peak emission of 285 nm or more can occur, and therefore the well layer.
  • the average AlN molar fraction Xwa of 220 is ⁇ 2% of the AlN molar fraction (n / 12) of the semi-stable well region formed in either the Ga enriched well region 220a or the Al enriched well region. It is suitable for verifying whether or not the occurrence of remarkable peak separation having a large wavelength difference is suppressed in the light emitting element 1 manufactured so as to be within the range.
  • the measurement results of the EL spectrum are referred to as type A, type B, and type C in order from the short wavelength side of the above three natural wavelength ranges, and are divided into three graphs for each type and shown in FIG.
  • Wx-y a code
  • the horizontal axis is the wavelength and the vertical axis is the normalized EL intensity, and the origin of the EL intensity is shifted by 0.3 for each chip.
  • the emission wavelength of the long wavelength side peak or shoulder peak in the two peaks or one peak of the EL spectrum and one shoulder peak exists within any of the above-mentioned natural wavelength ranges of the first type.
  • the EL spectrum (corresponding to the state on the left side of FIG. 7) is shown by a solid line, and the emission wavelength of the peak on the short wavelength side or the shoulder peak is within any of the above-mentioned natural wavelength ranges of the second type EL spectrum (FIG. 7).
  • Corresponds to the state on the right side of is shown by a broken line.
  • the emission wavelengths of the peak and shoulder peaks of the EL spectrum are in the range of 280 nm to 310 nm in 12 chips of 5 types of wafers. Further, it can be confirmed that the emission wavelengths of the peak or shoulder peak of the EL spectrum exist within the corresponding natural wavelength range in the 12 chips of the five types of wafers, except for W2-2 and W3-1. Further, W2-2 and W3-1 are both EL spectra of the second type, but the peaks on the short wavelength side are close to each other with an error of 0.4 to 0.5 nm with respect to the corresponding natural wavelength range. It does not deviate significantly from the natural wavelength range. As a result, it can be confirmed that the metastable well region is formed in the Ga-enriched well region 220a or the Al-enriched well region in the well layer 220.
  • the film thickness of the inclined region IA or the terrace region TA in which the metastable well region of the above 12 chips is formed is 8. It can be seen that it is within the range of ⁇ 10 ML.
  • the target value Xwt of the AlN mole fraction at the time of epitaxial growth of the well layer 220 is the AlN mole fraction Xws (33.3%) in the semi-stable well region. Since it is set to be within the range of ⁇ 2%, the wavelength difference ⁇ between two peaks of the EL spectrum or the wavelength difference ⁇ between one peak and one shoulder peak in all of the above 12 chips. Is about 3.8 nm to about 7.6 nm, and it can be confirmed that it is suppressed to 8 nm or less, and the full width at half maximum (FWHM) of the EL spectrum is about 12.7 nm to about 15.6 nm.
  • FWHM full width at half maximum
  • the width is within the range of 12 nm to 20 nm, which is the target range of the full width at half maximum of the EL spectrum in the form.
  • the full width at half maximum of the EL spectrum is more preferably within the range of 12 nm to 16 nm, and the above 12 chips satisfy the more preferable conditions.
  • the target value Xwt of the AlN mole fraction at the time of epitaxial growth of the well layer 220 is set to be within ⁇ 2% of the AlN mole fraction Xws (33.3%) in the semi-stable well region. Therefore, in the wafers W1 to W3, the chip (first type EL spectrum) in which the semi-stable well region is formed in the Ga-enriched well region 220a and the semi-stable well region are Al-enriched wells in the same wafer. It can be confirmed that the chips (second type EL spectrum) formed in the region are mixed.
  • the wavelength difference ⁇ between two peaks or the wavelength difference ⁇ between one peak and one shoulder peak is suppressed to 8 nm or less, and the half-value full width of the EL spectrum falls within the range of 12 nm to 20 nm. Will be done.
  • the effect of suppressing double peak emission could be confirmed when the natural wavelength range of the peak or shoulder peak was 285 nm or more, but each semiconductor layer of the active layer 22 was confirmed.
  • the growth temperature of the above five types of wafers is set higher than the growth temperature of the above five types of wafers to suppress the generation of Al pores in the well layer 220, even when the natural wavelength range is less than 285 nm.
  • the effect of suppressing the double peak light emission of the light emitting element 1 can be confirmed.
  • the metastable well region is a Ga-enriched well in the same wafer. Chips formed in the region 220a and chips having a metastable well region formed in the Al-enriched well region may coexist.
  • the p-type layer constituting the light emitting element structure portion 20 was two layers of the electron block layer 23 and the p-type contact layer 24, but in the light emitting element 2 of the second embodiment.
  • the p-type layer has a p-type clad layer 25 composed of one or more p-type AlGaN-based semiconductors between the electron block layer 23 and the p-type contact layer 24.
  • the AlGaN-based semiconductor layers 21 to 25 of the light emitting device structure portion 20 are, in order from the base portion 10 side, the n-type clad layer 21 (n-type layer) and the active layer. 22, the electron block layer 23 (p-type layer), the p-type clad layer 25 (p-type layer), and the p-type contact layer 24 (p-type layer) are epitaxially grown and laminated in this order.
  • the base portion 10 of the light emitting device 2 of the second embodiment, the AlGaN-based semiconductor layers 21 to 24, the p electrode 26, and the n electrode 27 of the light emitting device structure portion 20 emit light from any of the first to third embodiments. Since it is the same as the AlGaN-based semiconductor layers 21 to 24, the p electrode 26, and the n electrode 27 of the base portion 10 of the element 1 and the light emitting element structure portion 20, overlapping description will be omitted.
  • the p-type clad layer 25 includes the AlN layer 12 of the base portion 10 epitaxially grown from the main surface 11a of the sapphire substrate 11, the n-type clad layer 21 of the light emitting element structure portion 20, and each semiconductor layer in the active layer 22. Similar to the electronic block layer 23, it has a surface on which a multi-stage terrace parallel to the (0001) plane derived from the main surface 11a of the sapphire substrate 11 is formed.
  • FIG. 18 schematically shows an example of a laminated structure (multiple quantum well structure) of the well layer 220 and the barrier layer 221 in the active layer 22.
  • the p-type clad layer 25 is formed on the electronic block layer 23 having the laminated structure described with reference to FIG. 5 in the first embodiment.
  • an inclined region IA inclined with respect to the (0001) plane is formed between the terraces T adjacent to each other in the lateral direction.
  • the area other than the inclined area IA whose upper and lower sides are sandwiched by the terrace T is referred to as a terrace area TA.
  • the film thickness of the p-type clad layer 25 is adjusted to, for example, in the range of 20 nm to 200 nm, including the terrace region TA and the inclined region IA.
  • the mass transfer of Ga from the terrace region TA to the inclined region IA causes Ga enrichment in the inclined region IA, which has a lower AlN mole fraction than the terrace region TA.
  • a p-type region 25a is formed.
  • the AlN mole fraction of the terrace region TA of the p-type clad layer 25 is set within the range of 51% or more and less than the AlN mole fraction of the terrace region TA of the electronic block layer 23. Further, the AlN mole fraction of the Ga-enriched p-type region 25a of the p-type clad layer 25 is set to be less than the AlN mole fraction of the Ga-enriched EB region 23a of the electron block layer 23.
  • the AlN mole fraction of the terrace region TA of the p-type clad layer 25 is 1% or more, preferably 2% or more, more preferably more than the AlN mole fraction of the Ga-enriched p-type region 25a within the above range. It is set to be 4% or more higher.
  • the AlN mole fraction difference between the Ga-enriched p-type region 25a of the p-type clad layer 25 and the terrace region TA is 4 to 5 It is preferably% or more, but even if it is about 1 to 2%, the effect of carrier localization can be expected.
  • the AlN molar ratio is 20% or more higher than the AlN molar ratio in the semi-stable well region, and the AlGaN composition ratio is an integer ratio Alm Ga.
  • the integer i is 6, 7, or 8, and satisfies i ⁇ m. Therefore, when the integer m is 8, the integer i is 6 or 7.
  • the AlN mole fraction difference between the Ga-enriched p-type region 25a and the terrace region TA of the p-type clad layer 25 is stably maintained at approximately 2% or more, and thus the above-mentioned Ga-enriched EB region is maintained.
  • the effect of carrier localization in 23a is stably exerted.
  • the growth method of the p-type clad layer 25 will be briefly described.
  • the p-type clad layer is formed in the same manner as the n-type clad layer 21 and the electronic block layer 23 described in the first embodiment under the growth conditions under which the above-mentioned multi-stage terrace is easily exposed.
  • the p-type clad layer 25 is grown with the average AlN mole fraction Xpa of 25 as the target value.
  • the well layer 220 and the barrier layer 221 in the active layer 22 are formed with a multi-stage terrace T by step flow growth, but the inclination angle of the sapphire substrate to be used is high.
  • the inclination angle of the sapphire substrate to be used is high.
  • hexagonal columns or hexagonal pyramidal hillocks or pits can be formed on the flat crystal growth surface.
  • the case where the Ga-enriched well region 220a is formed in the inclined region IA of the well layer 220 has been described, but another embodiment in which the crystal growth surface of the well layer 220 is a flat surface.
  • Ga which easily moves mass, is concentrated around the hillock or the like, so that a Ga-enriched well region 220a can be formed.
  • the density of Al is relative in a part of the terrace region TA other than the Ga-enriched well region 220a due to the mass transfer of Ga at the time of formation of the Ga-enriched well region 220a. Is increased and formed.
  • the Al GaN composition ratio is an integer ratio Al n Ga 12 in the Ga-enriched well region 220a or the Al-enriched well region of the well layer 220.
  • a semi-stable well region which is a semi-stable AlGaN having ⁇ n N 12 , is formed.
  • the integer n is 3, 4, 5, or 6.
  • the target value Xwt of the AlN mole fraction at the time of epitaxial growth of the well layer 220 is also set so as to satisfy the conditions shown by the following inequality, as in the first and second embodiments. (N ⁇ 0.24) / 12 ⁇ Xwt ⁇ (n + 0.24) / 12
  • each semiconductor layer other than the well layer 220 has a large crystal growth surface even if the crystal growth surface is a flat surface or a multi-stage terrace T is formed, but the other parts are large.
  • the AlN mole fraction, film thickness, etc. of the above are the same as those described in the first and second embodiments, and duplicated explanations are omitted.
  • the active layer 22 alternates between two or more well layers 220 made of AlGaN-based semiconductors and one or more barrier layers 221 made of AlGaN-based semiconductors or AlN-based semiconductors.
  • the active layer 22 is a single quantum well structure having only one well layer 220, and does not have a barrier layer 221 (quantum barrier layer). It may be configured. It is clear that the effect of the well layer 220 adopted in each of the above embodiments can be similarly exerted on such a single quantum well structure.
  • the supply amount and the flow velocity of the raw material gas and the carrier gas used in the organometallic compound vapor phase growth method constitute the n-type clad layer 21. It was explained that it is set according to the average AlN mole fraction of the entire n-type AlGaN layer. That is, when the average AlN mole fraction of the entire n-type clad layer 21 is set to a constant value in the vertical direction, it is assumed that the supply amount and the flow velocity of the raw material gas and the like are controlled to be constant. .. However, the supply amount and the flow velocity of the raw material gas and the like do not necessarily have to be controlled to be constant.
  • the plan view shape of the first region R1 and the p electrode 26 adopts a comb shape as an example, but the plan view shape is not limited to the comb shape. .. Further, a plurality of first regions R1 may exist, and each of them may have a plan view shape surrounded by one second region R2.
  • the size of the off-angle and the direction in which the off-angle is provided are the surfaces of the AlN layer 12. It may be arbitrarily determined as long as the multi-tiered terrace is exposed and the growth starting point of the layered region 21a is formed.
  • the light emitting element 1 including the base portion 10 including the sapphire substrate 11 is exemplified, but the sapphire substrate 11 (further, the base) is illustrated. Part or all of the layers contained in the portion 10) may be removed by lift-off or the like. Further, the substrate constituting the base portion 10 is not limited to the sapphire substrate.
  • the present invention can be used for a nitride semiconductor ultraviolet light emitting device including a light emitting device structure in which an n-type layer, an active layer, and a p-type layer made of an AlGaN-based semiconductor having a Wurtzite structure are laminated in the vertical direction. ..
  • Nitride semiconductor ultraviolet light emitting device 10 Base part 11: Sapphire substrate 11a: Main surface of sapphire substrate 12: AlN layer 20: Light emitting element structure part 21: n-type clad layer (n-type layer) 21a: Layered region (n-type layer) 21b: n-type body region (n-type layer) 22: Active layer 220: Well layer 220a: Ga-enriched well region 221: Barrier layer 221a: Ga-enriched barrier region 23: Electronic block layer (p-type layer) 23a: Ga-enriched EB region 24: p-type contact layer (p-type layer) 25: p-type clad layer (p-type layer) 25a: Ga-enriched p-type region 26: p-electrode 27: n-electrode 100: Substrate 101: AlGaN-based semiconductor layer 102: Template 103: n-type AlGaN-based semiconductor layer 104: Active layer 105: p-type AlGaN-based semiconductor layer 106:

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Abstract

L'invention concerne un procédé de production d'un élément électroluminescent ultraviolet à semi-conducteur au nitrure qui comporte une partie de structure d'élément électroluminescent qui est formée d'un semi-conducteur à base d'AlGaN ayant une structure wurtzite, où : une couche de type n d'un semi-conducteur à base d'AlGaN de type n est soumise à une croissance épitaxiale sur une partie de base qui comprend un substrat de saphir ; une couche active ayant une structure de puits quantique qui comprend une couche de puits qui est configurée à partir d'un semi-conducteur à base d'AlGaN est soumise à une croissance épitaxiale sur la couche de type n ; une couche de type p d'un semi-conducteur à base d'AlGaN de type p est soumise à une croissance épitaxiale sur la couche active ; la valeur cible Xwt de la fraction molaire d'AlN pendant la croissance épitaxiale de la couche de puits est définie dans la plage de (n – 0,24)/12 ≤ Xwt ≤ (n + 0,24)/12 (où n est égal à 3, 4, 5 ou 6) ; et tout en formant une région de puits enrichie en Ga, dans laquelle la fraction molaire d'AlN est inférieure à la fraction molaire moyenne d'AlN Xwa, et une région de puits enrichie en Al, dans laquelle la fraction molaire d'AlN est supérieure à la fraction molaire d'AlN moyenne Xwa, à l'intérieur de la couche de puits, une région d'AlGaN métastable qui est composée d'AlnGa12-nN12 ayant un rapport de composition d'AlGaN qui est exprimé par un rapport intégré est développée dans la région de puits enrichie en Ga ou dans la région de puits enrichie en Al.
PCT/JP2021/000078 2021-01-05 2021-01-05 Procédé de production d'élément électroluminescent ultraviolet à semi-conducteur au nitrure, et élément électroluminescent ultraviolet à semi-conducteur au nitrure WO2022149183A1 (fr)

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TW110140773A TW202243282A (zh) 2021-01-05 2021-11-02 氮化物半導體紫外線發光元件之製造方法及氮化物半導體紫外線發光元件

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Publication number Priority date Publication date Assignee Title
WO2016157518A1 (fr) * 2015-04-03 2016-10-06 創光科学株式会社 Dispositif émettant de la lumière ultraviolette à semi-conducteur au nitrure et appareil émettant de la lumière ultraviolette à semi-conducteur au nitrure
WO2019102557A1 (fr) * 2017-11-22 2019-05-31 創光科学株式会社 Élément électroluminescent semi-conducteur au nitrure

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Publication number Priority date Publication date Assignee Title
WO2016157518A1 (fr) * 2015-04-03 2016-10-06 創光科学株式会社 Dispositif émettant de la lumière ultraviolette à semi-conducteur au nitrure et appareil émettant de la lumière ultraviolette à semi-conducteur au nitrure
WO2019102557A1 (fr) * 2017-11-22 2019-05-31 創光科学株式会社 Élément électroluminescent semi-conducteur au nitrure

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KOJIMA K ET AL: "Carrier localization structure combined with current micropaths in AlGaN quantum wells grown on an AlN template with macrosteps", APPLIED PHYSICS LETTERS, AMERICAN INSTITUTE OF PHYSICS, 2 HUNTINGTON QUADRANGLE, MELVILLE, NY 11747, vol. 114, no. 1, 7 January 2019 (2019-01-07), 2 Huntington Quadrangle, Melville, NY 11747, XP012234428, ISSN: 0003-6951, DOI: 10.1063/1.5063735 *
NAGASAWA YOSUKE ET AL: "Comparison of Al x Ga 1− x N multiple quantum wells designed for 265 and 285 nm deep-ultraviolet LEDs grown on AlN templates having macrosteps", APPLIED PHYSICS EXPRESS, JAPAN SOCIETY OF APPLIED PHYSICS; JP, JP, vol. 12, no. 6, 1 June 2019 (2019-06-01), JP , pages 064009, XP055897835, ISSN: 1882-0778, DOI: 10.7567/1882-0786/ab21a9 *

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