WO2007055262A1 - Nitride semiconductor light-emitting diode device - Google Patents

Nitride semiconductor light-emitting diode device Download PDF

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Publication number
WO2007055262A1
WO2007055262A1 PCT/JP2006/322338 JP2006322338W WO2007055262A1 WO 2007055262 A1 WO2007055262 A1 WO 2007055262A1 JP 2006322338 W JP2006322338 W JP 2006322338W WO 2007055262 A1 WO2007055262 A1 WO 2007055262A1
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Prior art keywords
nitride semiconductor
semiconductor layer
emitting diode
light
semiconductor light
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PCT/JP2006/322338
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French (fr)
Japanese (ja)
Inventor
Hiroaki Okagawa
Tsuyoshi Takano
Shin Hiraoka
Hirokazu Taniguchi
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Mitsubishi Cable Industries, Ltd.
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Priority claimed from JP2005324873A external-priority patent/JP4074315B2/en
Priority claimed from JP2006302156A external-priority patent/JP2008047850A/en
Application filed by Mitsubishi Cable Industries, Ltd. filed Critical Mitsubishi Cable Industries, Ltd.
Publication of WO2007055262A1 publication Critical patent/WO2007055262A1/en

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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
    • 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
    • H01L33/005—Processes
    • H01L33/0062—Processes for devices with an active region comprising only III-V compounds
    • H01L33/0066—Processes for devices with an active region comprising only III-V compounds with a substrate not being a III-V compound
    • H01L33/007—Processes for devices with an active region comprising only III-V compounds with a substrate not being a III-V compound comprising nitride compounds
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104—Forming layers
    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
    • H01L21/02367—Substrates
    • H01L21/0237—Materials
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104—Forming layers
    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
    • H01L21/02367—Substrates
    • H01L21/0237—Materials
    • H01L21/024—Group 12/16 materials
    • H01L21/02403—Oxides
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104—Forming layers
    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
    • H01L21/02367—Substrates
    • H01L21/0237—Materials
    • H01L21/0242—Crystalline insulating materials
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104—Forming layers
    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
    • H01L21/02367—Substrates
    • H01L21/02428—Structure
    • H01L21/0243—Surface structure
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104—Forming layers
    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
    • H01L21/02436—Intermediate layers between substrates and deposited layers
    • H01L21/02439—Materials
    • H01L21/02455—Group 13/15 materials
    • H01L21/02458—Nitrides
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104—Forming layers
    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
    • H01L21/02518—Deposited layers
    • H01L21/02521—Materials
    • H01L21/02538—Group 13/15 materials
    • H01L21/0254—Nitrides
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104—Forming layers
    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
    • H01L21/02612—Formation types
    • H01L21/02617—Deposition types
    • H01L21/0262—Reduction or decomposition of gaseous compounds, e.g. CVD
    • 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
    • H01L33/20—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 shape, e.g. curved or truncated substrate

Definitions

  • the present invention relates to a nitride semiconductor light-emitting diode element (hereinafter also referred to as a nitride LED) in which a main part of a light-emitting element structure is composed of a nitride semiconductor, and in particular, a nitride LED including a striped uneven structure.
  • a nitride semiconductor light-emitting diode element hereinafter also referred to as a nitride LED
  • a main part of a light-emitting element structure is composed of a nitride semiconductor, and in particular, a nitride LED including a striped uneven structure.
  • a nitride LED nitride semiconductor light-emitting diode element
  • Nitride semiconductors have the chemical formula Al In Ga N (0 ⁇ a ⁇ 1, 0 ⁇ b ⁇ 1, 0 ⁇ a + b ⁇ 1) a b 1— a— b
  • nitride LEDs are widely used as light sources for display devices, but they are also expected to be used as light sources for lighting devices. Therefore, research and development aimed at further improving the luminous efficiency of nitride LEDs. Has been actively conducted.
  • FIG. 7 is a cross-sectional view showing a typical structure of a conventional nitride LED.
  • the nitride LED 100 shown in this figure is not shown on the sapphire substrate 101 using a vapor phase epitaxial growth method such as a metal organic compound vapor phase growth method (MOV PE method)!
  • MOV PE method metal organic compound vapor phase growth method
  • the n-type layer 102 and the p-type layer 103 made of a nitride semiconductor substrate are sequentially stacked, and the negative electrode 104 is formed on the exposed surface of the n-type layer 102 formed by dry etching.
  • a positive electrode 105 made of a light-transmitting metal thin film (film thickness: about lOnm) is formed.
  • a pn junction is formed at the boundary between the n-type layer 102 and the p-type layer 103, and the vicinity thereof is a light emitting portion.
  • Those having a double hetero structure with an active layer provided at the pn junction exhibit particularly high luminous efficiency.
  • the light generated in the light emitting portion is more likely to be confined in the nitride semiconductor layer N composed of the n-type layer 102 and the p-type layer 103. This is the luminous efficiency of the device. This is one of the factors that hinder the improvement. Such light confinement is relatively
  • the nitride semiconductor layer N is used as a core. This is caused by the construction of a plate-like waveguide structure.
  • the positive electrode having an opening When used, the positive electrode is In the case of a reflective electrode, it also occurs when the positive electrode is made of a transparent conductive oxide such as ITO (indium stannate), which generally has a lower refractive index than a nitride semiconductor. .
  • ITO indium stannate
  • Figure 8 illustrates the structure of a nitride LED with a striped uneven structure on the surface of a sapphire substrate, where Figure 8 (a) is a top view and Figure 8 (b) is the X in Figure 8 (a). — Cross section at the position of the Y line.
  • a plurality of stripe-shaped grooves T200 extending in a direction perpendicular to the XY line in FIG. 8 (a) are formed in parallel, and a buffer layer (not shown) is formed thereon.
  • a nitride semiconductor layer N composed of the n-type layer 202 and the p-type layer 203 is formed.
  • the trench T200 is filled with the n-type layer 202.
  • the striped concavo-convex structure is advantageous in that it is easy to fabricate and is relatively easy to fill with a nitride semiconductor layer.
  • Patent Document 1 Japanese Patent Laid-Open No. 2002-280611
  • Patent Document 2 1 ⁇ 2004,11316681
  • the stripe-shaped concavo-convex structure provided on the surface of the sapphire substrate 201 is parallel to the direction perpendicular to the longitudinal direction, that is, the XY line in FIG. 8 (a).
  • the thickness of the nitride semiconductor layer N varies along various directions. For this reason, the state in which light propagates in the direction parallel to the XY line in the waveguide structure with the nitride semiconductor layer N as the core is unstable. This is because the waveguide structure is in such a state that the force is also undulated along this direction (the effective refractive index is increased when traveling in this direction in the nitride semiconductor layer N).
  • the thickness of the nitride semiconductor layer N is constant in the longitudinal direction of the uneven structure, that is, in the longitudinal direction of the trench T200. For this reason, the state in which light propagates along this direction in the waveguide structure having the nitride semiconductor layer N as a core is not unstable, and thus light propagates along this direction. The component is strongly confined in the nitride semiconductor layer N.
  • the second reason is that the longitudinal direction of the concavo-convex structure is perpendicular to the two end faces of the nitride semiconductor layer N facing each other.
  • the light component propagating along the longitudinal direction of the concavo-convex structure is reflected at the end face of the nitride semiconductor layer N in the same direction as the original.
  • the propagation direction of this light component does not change before and after reflection, and continues to propagate in the direction along the longitudinal direction of the concavo-convex structure, so that the state force strongly confined in the nitride semiconductor layer N I can't take it off.
  • the present invention has been made in view of such circumstances, and its main purpose is to improve the light extraction efficiency in a nitride semiconductor light-emitting diode element including a stripe-shaped uneven structure, and thereby It is an object to provide a nitride semiconductor light-emitting diode element that is suitable for a light source for a lighting device and has high luminous efficiency.
  • a waveguide structure having a nitride semiconductor layer as a core in light generated in a light-emitting portion is changed so that the light component propagating in the longitudinal direction of the concavo-convex structure changes the propagation direction when reflected by the end face of the nitride semiconductor layer.
  • An angle formed by the direction and the end face of the nitride semiconductor layer is set.
  • the nitride semiconductor light-emitting diode device has the following features.
  • the nitride semiconductor layer has a square shape when the element is viewed from above, and a longitudinal force of the striped concavo-convex structure.
  • the square nitride A nitride semiconductor light-emitting diode element that is not parallel to any of the four sides of the semiconductor layer.
  • the shape of the nitride semiconductor layer is square, and the longitudinal direction of the striped uneven structure is any of the four sides of the square nitride semiconductor layer.
  • the nitride semiconductor light-emitting diode device according to (1) which is at an angle of about 45 degrees with respect to.
  • It has a waveguide structure having a nitride semiconductor layer including a light emitting portion as a core, and the nitride semiconductor layer has a structure in which thick portions and thin portions extending in one direction are alternately arranged.
  • the shape of the nitride semiconductor layer is square, and the extending direction of the thick part and the thin part is parallel to any of the four sides of the square nitride semiconductor layer. Not a nitride semiconductor light emitting diode device.
  • the first substance includes a transparent substrate, and the second substance includes at least one selected from an electrode made of a transparent conductive oxide, an insulating protective film, or a sealing material. 12) The nitride semiconductor light-emitting diode element as described.
  • the light-transmitting third material having the waveguide structure having a refractive index lower than that of the nitride semiconductor layer and the nitride semiconductor layer located on one main surface side of the nitride semiconductor layer
  • the nitride semiconductor light-emitting diode element according to (8) further comprising: a metal reflective film located on the other main surface side of the nitride semiconductor layer.
  • nitride semiconductor layer including a light emitting portion, wherein the nitride semiconductor layer is at least One main surface has a striped uneven structure, which destabilizes the state in which light propagates in the nitride semiconductor layer in a direction perpendicular to the longitudinal direction of the uneven structure.
  • the shape of the nitride semiconductor layer is square, and the longitudinal direction of the concavo-convex structure is not parallel to any of the four sides of the square nitride semiconductor layer.
  • Nitride semiconductor light emitting diode device Nitride semiconductor light emitting diode device.
  • the present invention it is possible to improve the light extraction efficiency in a nitride semiconductor light-emitting diode element including a striped uneven structure. Since the nitride semiconductor light-emitting diode device embodying the present invention has high luminous efficiency, it can be suitably used as a light source for a lighting device.
  • FIG. 1 is a diagram showing a structure of a nitride semiconductor light-emitting diode device according to an embodiment of the present invention.
  • FIG. 1 (a) is a top view
  • FIG. 1 (b) is FIG. It is a cross-sectional view at the position of PQ line in (a).
  • FIG. 2 is a top view illustrating only the nitride semiconductor layer included in the nitride semiconductor light-emitting diode element shown in FIG.
  • FIG. 2 (b) is a diagram for explaining the relationship between the light propagation direction in the nitride semiconductor layer shown in FIG. 2 (a) and the longitudinal direction of the stripe-shaped grooves.
  • FIG. 3 is a diagram illustrating the cross-sectional shape of grooves and ridges which are constituent elements of the concavo-convex structure. is there.
  • FIG. 4 shows the structure of a nitride semiconductor light emitting diode device according to an embodiment of the present invention.
  • FIG. 4 (a) is a top view
  • FIG. 4 (b) is a cross-sectional view at the position of the P—Q line in FIG. 4 (a).
  • FIG. 5 is a diagram showing a structure of a nitride semiconductor light-emitting diode device according to an embodiment of the present invention.
  • FIG. 5 (a) is a top view
  • FIG. 5 (b) is a diagram in FIG.
  • FIG. 6 is a cross-sectional view at the position of the PQ line.
  • FIG. 6 is a diagram showing the structure of a nitride semiconductor light-emitting diode device according to an embodiment of the present invention.
  • FIG. 6 (a) is a top view
  • FIG. 6 (b) is FIG. 6 (a).
  • FIG. 6 is a cross-sectional view at the position of the PQ line.
  • FIG. 7 is a cross-sectional view showing the structure of a conventional nitride semiconductor light-emitting diode element.
  • FIG. 8 is a diagram showing the structure of a conventional nitride semiconductor light-emitting diode device, where FIG. 8 (a) is a top view, and FIG. 8 (b) is an XY line in FIG. It is sectional drawing in a position.
  • FIG. 9 is a cross-sectional view showing the structure of a nitride semiconductor light-emitting diode device according to one embodiment of the present invention.
  • Fig. 1 is a diagram showing the structure of a nitride LED according to an embodiment of the present invention.
  • Fig. 1 (a) is a top view
  • Fig. 1 (b) is the position of the PQ line in Fig. 1 (a).
  • FIG. Shown in this figure In the nitride LED10, a plurality of stripe-shaped grooves T10 extending in the direction perpendicular to the P—Q line in FIG. 1 (a) are formed on the surface of the sapphire substrate 11 in parallel.
  • the nitride semiconductor layer N composed of the n-type layer 12 and the p-type layer 13 is formed via the buffer layer.
  • a part of the p-type layer 13 is removed by dry etching, whereby the negative electrode 14 is formed on the exposed surface of the n-type layer 12, and the positive electrode 15 is formed on almost the entire surface of the p-type layer 13.
  • the light emitting part of the LED 10 is near the boundary part (pn junction part) between the n-type layer 12 and the p-type layer 13.
  • FIG. 2 is a top view illustrating only the nitride semiconductor layer N included in the nitride LED 10 shown in FIG.
  • the outer shape of the nitride semiconductor layer N as viewed from above is a square.
  • the four corners are represented by symbols A, B, C, and D.
  • the direction of the P—Q line in Fig. 1 is the direction of the diagonal line BD.
  • the double arrows in FIGS. 2 (a) and 2 (b) indicate the longitudinal direction of the stripe-shaped groove T10 formed on the surface of the sapphire substrate 11.
  • the thickness of the nitride semiconductor layer N varies along the direction parallel to the P—Q line in FIG. Therefore, the state in which light propagates in the direction parallel to the PQ line in the waveguide structure with the nitride semiconductor layer N as the core is unstable. Therefore, the light component that propagates in the nitride semiconductor layer N in the direction parallel to the PQ line among the light generated in the light emitting part is likely to leak out of the waveguide structure. That is, the probability of being taken out of the element is high.
  • the light component propagating in the nitride semiconductor layer N along the direction perpendicular to the P-Q line, that is, along the longitudinal direction of the stripe-shaped groove T10 provided on the surface of the sapphire substrate 11, is nitride.
  • the waveguide structure having the semiconductor layer N as a core as shown in Fig. 2 (b)
  • P Change in the direction parallel to the Q line.
  • the angle formed by the longitudinal direction of the trench T10 and the four sides of the rectangular nitride semiconductor layer N when the element is viewed from above is Because it is 45 degrees.
  • the light whose propagation direction has been changed to the direction parallel to the P—Q line has a higher probability of being extracted outside the element as described above.
  • Power is higher than the conventional nitride LED200 shown in Figure 8.
  • the nitride LED shown in FIG. 1 can be manufactured as follows.
  • the sapphire substrate 11 having the stripe-shaped groove T10 is formed by forming an etching mask on the surface of a normal sapphire substrate, patterning the striped opening in the etching mask using photolithography technique, and then opening the opening. It can be formed by etching the exposed surface of the sapphire substrate. This etching is preferably performed using a dry etching method such as an ion beam etching method or a reactive ion etching method.
  • the width wl and the interval w2 of the groove T10 can be, for example, 0.5 m to 10 ⁇ m, and the depth d of the groove T10 can be, for example, 0.2 ⁇ m to 5 ⁇ m. it can.
  • a nitride semiconductor layer N is grown on the sapphire substrate 11 by filling the trench T10.
  • Preferred growth methods for nitride semiconductors include vapor phase epitaxy such as MOVPE, HVPE (noideride vapor phase growth), MBE (molecular beam epitaxy). It is preferable to interpose a nofer layer between the sapphire substrate 11 and the nitride semiconductor layer N.
  • the detailed configuration (layer structure, crystal composition, film thickness, etc.) of the n-type layer 12 and the p-type layer 13 constituting the nitride semiconductor layer N can be set with reference to known techniques. An annealing process and an electron beam irradiation process for activating the p-type impurity added to the p-type layer 13 can be appropriately performed.
  • the n-type layer 12 is partially exposed by a reactive ion etching method using chlorine gas, and the negative electrode 14 is provided on the surface thereof.
  • the negative electrode 14 can be formed of a simple substance such as A1, Ti, W, Ni, Cr, V, or an alloy thereof.
  • the positive electrode 15 is provided so as to cover substantially the entire surface on the p-type layer 13.
  • the positive electrode 15 can be formed of a simple substance such as a platinum group element (Rh, Pt, Pd, Ir, etc.), Au, Ni, Co, or an alloy thereof.
  • the positive electrode 15 can be a transparent electrode or a reflective electrode by adjusting the thickness of the metal film constituting the electrode.
  • the positive electrode 15 is made of ITO, indium oxide, tin oxide, ⁇ (indium zinc oxide), ⁇ (aluminum zinc oxide), zinc oxide and other transparent conductive oxides. It can also be formed. As shown in FIG. 1, the contact electrode (bonding pad) can be appropriately formed on the positive electrode 15. [0020] It is preferable to form an insulating protective film in a region where the surface of the nitride semiconductor layer is exposed without being covered with the electrode. In addition, it is desirable to cover the surface of the electrode with an insulating protective film except for a portion that needs to be exposed for bonding. Finally, a chip-shaped element is cut out from the Ueno using methods such as dicing and scribing that are usually used in this field.
  • nitride LED 10 shown in FIG. 1 a sapphire substrate is used as a transparent substrate! /, The above-mentioned effect can be obtained if the transparent substrate has a lower refractive index than the nitride semiconductor layer N.
  • Transparent substrates that can be used for the nitride LED of the present invention include sapphire, A1N, spinel, ZnO, NGO (NdGaO), LGO (LiGaO), LAO (LaAlO), etc.
  • a substrate single crystal substrate or template substrate having at least a single crystal layer of 3 2 3 as a surface layer.
  • a substrate can be used for the epitaxial growth of a nitride semiconductor layer after providing an uneven structure on the surface.
  • a transparent substrate refers to a substrate that transmits light emitted from a light-emitting element.
  • the transparent substrate can include a colored substrate, and can include a substrate that does not transmit light in the visible region when the emission wavelength of the light emitting element is outside the visible region.
  • the transparent substrate includes a cloudy but translucent substrate that is not limited to a transparent substrate.
  • the sapphire substrate 11 can be replaced with a glass substrate.
  • the glass substrate cannot be used for the epitaxial growth of the nitride semiconductor layer, but after forming the nitride semiconductor layer on the sapphire substrate, the sapphire substrate is dissolved and removed with phosphoric acid, and the remaining nitride is removed. It can be introduced into the element by thermocompression bonding to the semiconductor layer.
  • JP 2005-347700 A and JP 2006-41479 A can be referred to.
  • a nitride substrate is formed on a crystal substrate having stripe-like grooves.
  • the crystal substrate is selectively removed, and a glass substrate is formed on the surface of the uneven nitride semiconductor layer exposed thereby. Is thermocompression bonded.
  • the crystal substrate is selectively removed, thereby forming striped grooves on the surface of the flat nitride semiconductor layer exposed.
  • a glass substrate may be thermocompression bonded thereon.
  • a crystal substrate that can be easily etched or dissolved with respect to the nitride semiconductor layer, such as a Si substrate, a GaAs substrate, or a ZnO substrate, is formed. I prefer to use it.
  • a plurality of stripe-like grooves are formed in parallel on the surface of the sapphire substrate 11 to form a stripe-like concavo-convex structure.
  • a striped uneven structure is not limited to this.
  • a structure in which only one striped groove is covered on a flat surface, or a flat surface is used instead of a groove.
  • it may be a structure in which one or a plurality of striped ridges are formed.
  • the cross-sectional shapes of the grooves and ridges constituting the striped concavo-convex structure are the rectangular shape shown in Fig. 3 (a), the trapezoidal shape shown in Fig.
  • the width and cross-sectional shape of the groove or ridge, the depth of the groove, the height of the ridge, etc. may vary along the longitudinal direction.
  • the striped concavo-convex structure may be formed by combining grooves and ridges having different shapes and sizes.
  • the ridge may be formed of the same material as the crystal substrate, but it is not essential.
  • the ridge may be a mask used for selective lateral growth of nitride semiconductor crystals.
  • the striped uneven structure provided on the transparent substrate may be a periodic structure.
  • a structure having high periodicity for example, an uneven structure in which a plurality of grooves or ridges having a constant cross section in the longitudinal direction are arranged in parallel at equal intervals, has the advantage that it is easy to manufacture, and a nitride semiconductor There is an advantage that defects are hardly generated when the concavo-convex structure is filled by epitaxial growth.
  • the periodicity in the direction perpendicular to the longitudinal direction of the striped uneven structure is lowered, light propagates in the direction perpendicular to the longitudinal direction in the nitride semiconductor layer filling the uneven structure. Since this becomes more unstable, the light extraction efficiency of the element increases.
  • the size of the grooves and ridges constituting the striped concavo-convex structure is such that the concavo-convex structure is a nitride. It is necessary to set so as to affect the light propagation state in the semiconductor layer.
  • the depth of the groove or the height of the ridge is preferably 0.2 m or more, more preferably 0.5 m or more, particularly 1 ⁇ m or more. preferable.
  • the depth of the groove or the height of the ridge increases, the time and energy required to form the concavo-convex structure increase, and the manufacturing efficiency of the device decreases. Accordingly, the depth of the groove or the height of the ridge is preferably 5 m or less.
  • the width of the grooves or ridges, and the distance between adjacent grooves or grooves or the distance between ridges and ridges are difficult to manufacture if too small, and too large.
  • the effect of the uneven structure on the light propagation state in the nitride semiconductor layer is reduced. Accordingly, when an example of a concavo-convex structure in which a plurality of grooves or ridges having a constant cross section in the longitudinal direction are arranged in parallel at equal intervals, the width of the grooves or ridges is 0.5 ⁇ to: LO m It is preferable that the groove or ridge formation period in the width direction of the stripe is 1 m to 20 m.
  • FIG. 4 is a view showing an example of the structure of such a nitride LED
  • FIG. 4 (a) is a top view
  • FIG. 4 (b) is a cross-sectional view taken along the line P—Q in FIG. 4 (a).
  • the nitride LED 20 shown in this figure has a conductive transparent substrate 21 that is also strong, such as ZnO, and has a stripe-like shape that extends in a direction perpendicular to the P—Q line in FIG.
  • a plurality of grooves T20 are formed in parallel.
  • a nitride semiconductor layer N composed of an n-type layer 22 and a p-type layer 23 is formed on the transparent substrate 21 so as to fill the trench T20.
  • the negative electrode 24 and the p-type layer are formed on the back surface of the transparent substrate 21.
  • a positive electrode 25 is formed on the upper surface of 23.
  • the upper surface shape of the element is square, and the upper surface shape of the nitride semiconductor layer is the same.
  • the longitudinal direction of the trench T20 forms an angle of 45 degrees with any of the four sides of the square nitride semiconductor layer N.
  • the nitride semiconductor layer N itself is shown in Fig. 4 (a). Since light undulates along the direction of the P-Q line, light passes through the nitride semiconductor layer N through this P—
  • the state of propagation in the direction parallel to the Q line is unstable.
  • the shape of the nitride semiconductor layer N when the element is viewed from above is a square, but may be a rectangle. In order to prevent electric field concentration that causes electrostatic breakdown, or to prevent chipping when cutting a chip-like element from a wafer, the corners of the square may be rounded.
  • the angle formed by the longitudinal direction of the striped uneven structure provided on the transparent substrate and the four sides of the rectangular nitride semiconductor layer N is about 45 degrees (40 to 50 degrees). Is most preferred, but other angles are also possible. A preferred range is 30 to 60 degrees. If the angle formed by the direction of any one of the four sides of the nitride semiconductor layer N and the longitudinal direction of the striped uneven structure is less than 10 degrees, these directions are substantially parallel. The effect of improving the light extraction efficiency according to the present invention cannot be expected.
  • FIG. 5 is a diagram showing an example of the structure of such a nitride LED, FIG. 5 (a) is a top view, and FIG. 5 (b) is a cross-sectional view at the position of the P—Q line in FIG. 5 (a).
  • the mask M force that inhibits the crystal growth of the nitride semiconductor on the surface of the sapphire substrate 31 has a striped pattern extending in the direction perpendicular to the P—Q line in Fig. 1 (a). Formed.
  • This mask M is made of amorphous acid silicon, and has a film thickness t of 0.5 m and a width w3 of 3 m. The spacing w4 between adjacent masks M is also 3 ⁇ m.
  • the sapphire substrate 31 and the mask M form a stripe-shaped concavo-convex structure, and a nitride semiconductor layer N composed of an n-type layer 32 and a p-type layer 33 is formed thereon via a buffer layer (not shown). It is formed so as to fill the uneven structure.
  • the n-type layer 32 is grown from a region on the sapphire substrate 31 that is not covered by the mask M, and the portion covering the upper surface of the mask M is a low dislocation density region formed by lateral growth. Yes.
  • a partial force of the p-type layer 33 S is removed in a circular shape by dry etching, and the negative electrode with a circular upper surface shape is exposed on the exposed surface of the n- type layer 32 34 is formed. Almost all over p-type layer 33 is positive An electrode 35 is formed.
  • the outer peripheral region of the nitride semiconductor layer N is etched in a process different from the dry etching for forming the negative electrode 34, so that the upper surface of the sapphire substrate 31 is exposed at the outer peripheral portion of the element. ing. By this etching, the end surface of the nitride semiconductor layer N is made an inclined surface.
  • the end surface of the nitride semiconductor layer N Since the end surface of the nitride semiconductor layer N is inclined, the light propagating along the longitudinal direction of the stripe-shaped uneven structure in the nitride semiconductor N is reflected in the direction of propagation when reflected by this end surface. The probability of changing is even higher.
  • the angle formed by the exposed surface of the sapphire substrate 31 and the end face of the nitride semiconductor layer N is an obtuse angle ( ⁇ > 90 degrees), and thus the light reflected by this end face is not supported. Probability of proceeding toward the fire board 31 side increases. Therefore, the nitride LED 30 is suitable for use with a flip chip mounted. On the other hand, it is possible to incline this end face so that this angle becomes an acute angle ( ⁇ 90 degrees), and the nitride LED configured in this way uses the surface side of the positive electrode as the light extraction surface. It is preferable.
  • the nitride semiconductor layer formed on the substrate may have a striped uneven structure on the main surface opposite to the substrate side.
  • Figure 9 shows an example of such a nitride LED.
  • a nitride semiconductor layer composed of a p-type layer 53 and an n-type layer 52 on a ZnO substrate 51 having a flat surface.
  • a plurality of stripe-like grooves T50 extending in the direction intersecting with the paper surface are formed in parallel on the upper surface of the nitride semiconductor layer N (the surface on the n-type layer 52 side).
  • the top surface shape of the nitride semiconductor layer N is a square, and the longitudinal direction of the trench T50 forms an angle of about 45 degrees between the four sides of the square!
  • the negative electrode 54 is formed on the top surface of the nitride semiconductor layer N, and the positive electrode 55 is formed on the back surface of the ZnO substrate 51.
  • the negative electrode 54 is a transparent electrode made of ITO, and a bonding pad (not shown) is formed on a part of the surface thereof.
  • a bonding pad (not shown) is formed on a part of the surface thereof.
  • the material for the insulating protective film include silicon oxide, zirconium oxide, zirconium aluminum oxide, magnesium oxide, magnesium fluoride, nitride nitride, and nitride oxynitride.
  • nitride LED 50 To manufacture the nitride LED 50, first, an n-type layer 52 and a p-type layer 53 are sequentially grown on a sapphire substrate via a buffer layer by using the MOVPE method, and then a nitride semiconductor layer is formed. N is formed. Next, a ZnO substrate 51 is bonded to the upper surface of the p-type layer 53 by wafer bonding. For details on wafer bonding, see Japanese 'Journal' of 'Applied' Physitas, Vol. 45, No. 39, 2006, pages L1045 to L1047 (Japanese Journal of Applied Physics, Vol. 45, No. 39, 2006 , pp. L1045—L1047).
  • the sapphire substrate is removed by a method such as laser lift-off to expose the surface of the n-type layer 52, and a groove T50 is formed by etching on the exposed surface of the n-type layer 52.
  • the nitride semiconductor layer N has a thick portion (a portion having a relatively large thickness) extending in the longitudinal direction of the trench T50 and a portion having a relatively small thickness). It is formed.
  • the depth of the groove T50 (difference between the maximum thickness t51 of the thick portion and the minimum thickness t52 of the thin portion) is such that light propagates in the nitride semiconductor layer N in a direction perpendicular to the longitudinal direction of the trench T50.
  • the depth of the groove T50 is preferably 0.2 m or more, more preferably 0.5 m or more, and more preferably 1 m or more.
  • the depth of the groove T50 is preferably 20% or more of the maximum thickness t51 of the thick part [(t51 ⁇ t52) Zt51 ⁇ 0.2].
  • a waveguide structure is formed in which the nitride semiconductor layer N is a core, the ZnO substrate 51 is a cladding on one side, and the negative electrode 54 also having an ITO force is the cladding on the other side.
  • the insulating protective film can also contribute to the formation of the waveguide structure.
  • the LED 50 is covered with a translucent sealing material, and this sealing material can also contribute to the formation of the waveguide structure.
  • the sealing material is typically a resin material such as silicone resin or epoxy resin.
  • the nitride semiconductor layer N has a structure in which thick portions and thin portions extending in the longitudinal direction of the trench T50 are alternately arranged. That is, the film thickness varies along the direction orthogonal to the longitudinal direction of the groove T50. Therefore, the light component propagating in the nitride semiconductor layer N in the direction perpendicular to the longitudinal direction of the trench T50 is likely to leak out of the waveguide structure having the nitride semiconductor layer N as a core. That is, the probability of being taken out of the element is high.
  • the film thickness of the nitride semiconductor layer N is constant in the longitudinal direction of the trench T50.
  • the light component propagating in the nitride semiconductor layer N along this direction is the nitride semiconductor layer N. It is strongly confined in the waveguide structure with N as the core. However, since the angle between the longitudinal direction of the groove T50 and each of the four sides of the rectangular nitride semiconductor layer N is 45 degrees, the light component propagating in the longitudinal direction of the groove T50 is nitride. Due to reflection at the end face of the semiconductor layer N, the propagation direction is changed to a direction perpendicular to the longitudinal direction of the trench T50. Therefore, in the nitride LED 50, a state component that is strongly confined in the nitride semiconductor layer N is not generated, and thus there is a high probability that light generated in the light emitting portion is extracted outside the device. Become.
  • the stripe-shaped uneven structure formed on the upper surface of the nitride semiconductor layer has a structure in which light is perpendicular to the longitudinal direction of the uneven structure by forming the uneven structure. If the state propagating in the direction is unstable, Such a concavo-convex structure is not limited to a structure composed of a plurality of parallel striped groove caps, for example, a structure in which only one striped groove is processed on a flat surface, or Instead of the groove, a structure in which one or a plurality of striped ridges are formed on a flat surface may be used.
  • the cross-sectional shape of the grooves and ridges constituting the striped uneven structure can be various shapes in addition to the shape illustrated in FIG.
  • the width and cross-sectional shape of the groove or ridge, the depth of the groove, the height of the ridge, etc. may vary along the longitudinal direction.
  • the groove or ridge may have one or both ends that do not reach the end of the nitride semiconductor layer.
  • the angle between each of its four sides and the longitudinal direction of the striped relief structure should be approximately 45 degrees (40 degrees to 50 degrees). Is most preferred, but other angles may be used. A preferred range is 30 to 60 degrees. If the angle formed by any one of the four sides and the longitudinal direction of the striped uneven structure is less than 10 degrees, these directions are substantially parallel. The effect of improving the delivery efficiency cannot be expected.
  • a reflective electrode formed by laminating Ti (titanium) and A1 (aluminum) can be used instead of forming the negative electrode 54 of ITO in the nitride LED 50. wear.
  • a waveguide structure is formed in which the nitride semiconductor layer is the core, the ZnO substrate is one clad, and the reflective negative electrode is the other clad.
  • the positive electrode is partially formed on the back surface of the ZnO substrate so that light can be extracted from the ZnO substrate side force.
  • the ZnO substrate 51 can be bonded using solder instead of bonding by wafer bonding. At this time, preferably, a ZnO substrate is bonded after forming a metallic reflective film on the surface of the p-type layer.
  • a waveguide structure is formed in which a nitride semiconductor layer is a core, a negative electrode made of ITO is one clad, and a metal reflective film is the other clad.
  • FIG. 6 A fabrication example of the nitride LED shown in FIG. 6 is described below.
  • Fig. 6 shows the structure of a nitride LED according to an embodiment of the present invention.
  • Fig. 6 (a) is a top view
  • Fig. 6 (b) is the position of the PQ line in Fig. 6 (a).
  • reference numeral 41 denotes a sapphire substrate
  • a plurality of strip-like grooves T40 extending in a direction perpendicular to the PQ line are formed in parallel on the crystal growth surface.
  • the depth d of the groove T40 is 1 ⁇ m
  • the width w 1 is about 3 ⁇ m
  • the period p of the unevenness in the width direction of the groove is 6 ⁇ m.
  • 42 is an n-type layer
  • 42a is an n-type contact layer with a thickness of 3 m (thickness on the convex part of the substrate 41) that also has Si-doped GaN force
  • 42b is an undoped AlGaN layer thickness of lOOnm
  • 42c is an n-type cladding layer, which consists of an undoped InGaN (0 ⁇ x ⁇ 1) well layer with a thickness of 3 nm and a Si-doped InGa_N (0 ⁇ y ⁇ x) barrier layer with a thickness of 10 nm. It is an active layer with an MQW structure in which layers are stacked alternately.
  • the n-type contact layer 42a is formed so as to enter the trench T40 and to have a flat upper surface.
  • 43 is a p-type layer
  • 43a is a p-type cladding layer made of Mg-doped AlGaN with a thickness of 30 nm
  • 43b is a p-type contact layer made of Mg-doped GaN with a thickness of 150 nm.
  • 44 is a negative electrode for injecting current into the n-type layer 42
  • 45 is a positive electrode for injecting current into the p-type layer 43.
  • 46 is the bonding pad formed on the positive electrode 45 It is.
  • the shape of the chip when viewed from above is a square, and the shape of the nitride semiconductor layer N is the same.
  • a nitride LED shown in FIG. 6 was produced by the following procedure.
  • a stripe mask pattern made of photoresist was formed on one main surface of the C-plane sapphire substrate.
  • the stripe mask width is 3 ⁇ m
  • the period (mask width + substrate exposed part width) is 6 ⁇ m
  • the longitudinal direction of the stripe is the sapphire ⁇ 1 100> direction (a nitride semiconductor grown on the substrate) It is the ⁇ 11-20> direction of the crystal).
  • Reactive ion etching was performed on the mask to form a sapphire substrate 41 in which a groove 40 having a depth of 1 ⁇ m was formed in the exposed portion of the substrate and a stripe-shaped uneven pattern was formed on the crystal growth surface.
  • the sapphire substrate 41 was attached to a MOVPE apparatus, and the temperature was raised to 1100 ° C. in a hydrogen atmosphere to clean the surface.
  • TMG trimethylgallium
  • the temperature of the substrate is raised to 1000 ° C., TMG, silane, and ammonia are supplied, and the n-type contact layer 42a having a flat top surface is formed on the convex portion of the sapphire substrate 41 (groove T40 is formed. , Part) was grown to a thickness of 3 ⁇ m.
  • TMA trimethylaluminum
  • the substrate temperature is lowered to 750 ° C., and trimethylindium (TMI) is used as the indium raw material, so that well layers and barrier layers are grown alternately, and an MQW structure active layer 42c was formed.
  • TMI trimethylindium
  • TMA trimethylaluminum
  • TMG trimethylaluminum
  • ammonia trimethylaluminum
  • Cp Mg biscyclopentagel magnesium
  • a 2 0. 2 0. 8 type cladding layer 43a was grown by 30 nm.
  • the supply of TMA is stopped and the p-type contact layer 43b is grown to 150 nm.
  • the substrate temperature was lowered to room temperature in an atmosphere, and the wafer was removed from the MOVPE equipment.
  • the wafer obtained in the above process is annealed, exposed negative electrode formation surface by reactive ion etching, negative electrode 44 formation, positive electrode 45 formation, bonding 'pad 46 formation, electrode heat treatment Were performed sequentially.
  • the negative electrode 44, the positive electrode 45, and the bonding 'pad 46 shape' arrangement force with respect to the longitudinal direction of the stripe-shaped groove T40 on the crystal growth surface of the sapphire substrate 41 are as shown in FIG. I put a pattern.
  • the negative electrode 44 was formed by laminating Ti (titanium) with a film thickness of 30 nm and A1 (aluminum) with a film thickness of 300 nm in this order from the side in contact with the n-type contact layer 42a by vapor deposition.
  • the diameter of the negative electrode was 100 ⁇ m.
  • the positive electrode 45 was formed by sequentially depositing Ni (nickel) with a thickness of 20 nm and Au (gold) with a thickness of lOOnm in order of the side force in contact with the p-type contact layer 43b by vapor deposition. On the positive electrode 45, square windows (openings) of 8 m x 8 m are formed in a matrix, and the area of the window occupies the area of the positive electrode 45 spreading on the p-type contact layer 43b. A translucent electrode having a ratio of about 70% was obtained.
  • Bonding 'Pad 46 was formed by laminating Ti and Au, and its diameter was 100 m.
  • the lower surface of the sapphire substrate 41 is polished to a thickness of 100 m, and then a scribe line is written on the polished surface and braking is performed to form a 350 m square square shape. I got a chip.
  • the longitudinal direction of the stripe-shaped grooves formed on the crystal growth surface of the sapphire substrate is parallel to two of the four sides of the rectangular nitride semiconductor layer.
  • a nitride LED was fabricated in the same manner as in the example.
  • a nitride semiconductor light-emitting diode element having high light emission efficiency suitable for a light source for an illumination device is provided. be able to.

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Abstract

Disclosed is a nitride semiconductor light-emitting diode device (10) comprising a transparent substrate (11) having a striped uneven structure on the surface, and a nitride semiconductor layer (N) so formed as to fill the uneven structure. The nitride semiconductor layer (N) has a higher refractive index than the transparent substrate (11) and contains a light-emitting section. When the device is seen from overhead, the nitride semiconductor layer (N) has a rectangular shape, and the longitudinal direction of the striped uneven structure is not parallel to any of the four sides of the rectangular nitride semiconductor layer (N). Since the nitride semiconductor light-emitting diode device (10) has a high luminous efficiency, it can be suitably used as a light source for illuminating devices.

Description

明 細 書  Specification
窒化物半導体発光ダイオード素子  Nitride semiconductor light emitting diode device
技術分野  Technical field
[0001] 本発明は、発光素子構造の主要部を窒化物半導体で構成した窒化物半導体発光 ダイオード素子 (以下、窒化物 LEDともいう。 )に関し、特に、ストライプ状の凹凸構造 を含む窒化物 LEDに関する。  TECHNICAL FIELD [0001] The present invention relates to a nitride semiconductor light-emitting diode element (hereinafter also referred to as a nitride LED) in which a main part of a light-emitting element structure is composed of a nitride semiconductor, and in particular, a nitride LED including a striped uneven structure. About.
背景技術  Background art
[0002] 窒化物半導体は、化学式 Al In Ga N (0≤a≤ 1、 0≤b≤ 1、 0≤a+b≤ 1)で a b 1— a— b  [0002] Nitride semiconductors have the chemical formula Al In Ga N (0≤a≤ 1, 0≤b≤ 1, 0≤a + b≤ 1) a b 1— a— b
表される化合物半導体であり、 3族窒化物半導体、 GaN (窒化ガリウム)系半導体な どとも呼ばれる。上記化学式において、 3族元素の一部をホウ素（B)、タリウム (T1)な どで置換したもの、また、 N (窒素）の一部をリン (P)、ヒ素 (As)、アンチモン (Sb)、ビ スマス (Bi)などで置換したものも、窒化物半導体に含まれる。現在、窒化物 LEDは 表示装置用の光源として広く使用されているが、照明装置用の光源としても期待され ており、そのために、窒化物 LEDの発光効率の更なる改善を目的とした研究開発が 盛んに行われている。  It is a compound semiconductor that is also called a Group 3 nitride semiconductor or a GaN (gallium nitride) semiconductor. In the above chemical formula, a part of group 3 element is substituted with boron (B), thallium (T1), etc., and part of N (nitrogen) is phosphorus (P), arsenic (As), antimony (Sb ), Bismuth (Bi), etc. are also included in the nitride semiconductor. Currently, nitride LEDs are widely used as light sources for display devices, but they are also expected to be used as light sources for lighting devices. Therefore, research and development aimed at further improving the luminous efficiency of nitride LEDs. Has been actively conducted.
[0003] 図 7は従来の窒化物 LEDの典型的な構造を示す断面図である。この図に示す窒 化物 LED100は、サファイア基板 101の上に、有機金属化合物気相成長法 (MOV PE法)などの気相ェピタキシャル成長法を用いて、図示しな!、バッファ層を介して、 窒化物半導体カゝらなる n型層 102および p型層 103を順次積層し、ドライエッチング により形成した n型層 102の露出面に負電極 104を形成し、 p型層 103上のほぼ全面 に、透光性を有する金属薄膜 (膜厚約 lOnm)からなる正電極 105を形成すること〖こ より、構成されている。 n型層 102と p型層 103との境界部には pn接合が形成されて おり、その近傍が発光部となっている。 pn接合部に活性層を設けてダブルへテロ構 造を構成したものは、特に高い発光効率を示す。  FIG. 7 is a cross-sectional view showing a typical structure of a conventional nitride LED. The nitride LED 100 shown in this figure is not shown on the sapphire substrate 101 using a vapor phase epitaxial growth method such as a metal organic compound vapor phase growth method (MOV PE method)! The n-type layer 102 and the p-type layer 103 made of a nitride semiconductor substrate are sequentially stacked, and the negative electrode 104 is formed on the exposed surface of the n-type layer 102 formed by dry etching. In addition, a positive electrode 105 made of a light-transmitting metal thin film (film thickness: about lOnm) is formed. A pn junction is formed at the boundary between the n-type layer 102 and the p-type layer 103, and the vicinity thereof is a light emitting portion. Those having a double hetero structure with an active layer provided at the pn junction exhibit particularly high luminous efficiency.
[0004] 図 7に示す窒化物 LED100においては、発光部で生じる光が、 n型層 102および p 型層 103からなる窒化物半導体層 Nに閉じ込められる傾向が強ぐこのことが素子の 発光効率の向上を妨げる一因となっている。このような光の閉じ込めは、相対的に屈 折率が高い窒化物半導体層 Nを、相対的に屈折率が低いサファイア基板 101と (薄 V、正電極 105を介して)空気とが挟んで 、るために、窒化物半導体層 Nをコアとする 板状の導波路構造が構成されることによって生じる。このような導波路構造が形成さ れると、光が素子外部に出ないで、窒化物半導体層 N内を伝播する状態が安定ィ匕す るためである。この問題は、窒化物 LED100をエポキシなどの樹脂で封止しても、あ まり改善されない。榭脂材料の屈折率は空気よりは高いが、窒化物半導体の屈折率 と比べると、力なり低いためである。なお、このような導波路構造の形成による光の閉 じ込めは、金属薄膜からなる正電極 105を用いた場合に限って生じるものではなぐ 開口部を有する正電極を用いた場合、正電極を反射性の電極とした場合、正電極を ITO (インジウム錫酸ィ匕物)などの透明導電性酸化物 (一般に、窒化物半導体よりも 低 ヽ屈折率を有する)で形成した場合などにも生じる。 In the nitride LED 100 shown in FIG. 7, the light generated in the light emitting portion is more likely to be confined in the nitride semiconductor layer N composed of the n-type layer 102 and the p-type layer 103. This is the luminous efficiency of the device. This is one of the factors that hinder the improvement. Such light confinement is relatively In order to sandwich the nitride semiconductor layer N having a high refractive index between the sapphire substrate 101 having a relatively low refractive index and the air (through the thin V, positive electrode 105), the nitride semiconductor layer N is used as a core. This is caused by the construction of a plate-like waveguide structure. This is because when such a waveguide structure is formed, light does not go out of the device, and the state of propagating in the nitride semiconductor layer N is stabilized. This problem is not much improved even if the nitride LED 100 is sealed with a resin such as epoxy. This is because the refractive index of a resin material is higher than that of air, but is relatively low compared to the refractive index of a nitride semiconductor. Note that the confinement of light by the formation of such a waveguide structure does not occur only when the positive electrode 105 made of a metal thin film is used. When the positive electrode having an opening is used, the positive electrode is In the case of a reflective electrode, it also occurs when the positive electrode is made of a transparent conductive oxide such as ITO (indium stannate), which generally has a lower refractive index than a nitride semiconductor. .
[0005] 導波路構造の形成による窒化物半導体層への光閉じ込めを緩和するには、素子 の内部に凹凸構造を設けることによって、光が窒化物半導体層中を伝播する状態を 不安定ィ匕することが有効である (特許文献 1およびその対応米国特許出願公開公報 である特許文献 2)。図 8は、サファイア基板の表面にストライプ状の凹凸構造を設け た窒化物 LEDの構造を例示する図で、図 8 (a)は上面図、図 8 (b)は図 8 (a)の X— Y 線の位置における断面図である。サファイア基板 201の表面には、図 8 (a)の X— Y 線に直交する方向に伸びる、ストライプ状の溝 T200が複数、平行に形成されており 、その上に、図示しないバッファ層を介して、 n型層 202および p型層 203からなる窒 化物半導体層 Nが形成されている。溝 T200は n型層 202により埋められている。ここ で、ストライプ状の凹凸構造は、その作製が容易である他、窒化物半導体層により埋 めることが比較的容易であると 、う利点を有して 、る。  [0005] In order to alleviate light confinement in the nitride semiconductor layer due to the formation of the waveguide structure, an uneven structure is provided inside the device, so that the state in which light propagates in the nitride semiconductor layer is unstable. It is effective to do this (Patent Document 1 and its corresponding US Patent Application Publication 2). Figure 8 illustrates the structure of a nitride LED with a striped uneven structure on the surface of a sapphire substrate, where Figure 8 (a) is a top view and Figure 8 (b) is the X in Figure 8 (a). — Cross section at the position of the Y line. On the surface of the sapphire substrate 201, a plurality of stripe-shaped grooves T200 extending in a direction perpendicular to the XY line in FIG. 8 (a) are formed in parallel, and a buffer layer (not shown) is formed thereon. Thus, a nitride semiconductor layer N composed of the n-type layer 202 and the p-type layer 203 is formed. The trench T200 is filled with the n-type layer 202. Here, the striped concavo-convex structure is advantageous in that it is easy to fabricate and is relatively easy to fill with a nitride semiconductor layer.
特許文献 1：特開 2002 - 280611号公報  Patent Document 1: Japanese Patent Laid-Open No. 2002-280611
特許文献2 :1^2004,113166八1号公報  Patent Document 2: 1 ^ 2004,11316681
発明の開示  Disclosure of the invention
発明が解決しょうとする課題  Problems to be solved by the invention
[0006] 図 8に示す窒化物 LED200では、サファイア基板 201の表面に設けられたストライ プ状の凹凸構造の、長手方向に直交する方向、すなわち、図 8 (a)の X— Y線に平行 な方向に沿って、窒化物半導体層 Nの厚さが変動している。そのために、窒化物半 導体層 Nをコアとする導波路構造内を、光が X— Y線に平行な方向に伝播する状態 が不安定ィ匕されている。これは、この方向に沿って導波路構造があた力も波打ったか のような状態となっているからである（窒化物半導体層 N内をこの方向に沿って進む と、実効的な屈折率が最大となる位置が膜厚方向に振動して見える)。よって、窒化 物半導体層 N内を X— Y線に平行な方向に伝播する光成分は、導波路構造外に漏 れ出し易くなつている。いいかえると、素子外に取出される確率が高くなつている。 [0006] In the nitride LED 200 shown in FIG. 8, the stripe-shaped concavo-convex structure provided on the surface of the sapphire substrate 201 is parallel to the direction perpendicular to the longitudinal direction, that is, the XY line in FIG. 8 (a). The thickness of the nitride semiconductor layer N varies along various directions. For this reason, the state in which light propagates in the direction parallel to the XY line in the waveguide structure with the nitride semiconductor layer N as the core is unstable. This is because the waveguide structure is in such a state that the force is also undulated along this direction (the effective refractive index is increased when traveling in this direction in the nitride semiconductor layer N). The position where the maximum value appears to vibrate in the film thickness direction). Therefore, the light component propagating in the nitride semiconductor layer N in the direction parallel to the XY line is likely to leak out of the waveguide structure. In other words, the probability of being taken out of the element is increasing.
[0007] し力しながら、窒化物 LED200では、発光部で生じる光の、窒化物半導体層 N内 への閉じ込めが、十分に緩和されているとはいえない。その第一の理由は、凹凸構 造の長手方向、つまり、溝 T200の長手方向については、窒化物半導体層 Nの厚さ が一定となっているからである。このために、窒化物半導体層 Nをコアとする導波路 構造内を、光がこの方向に沿って伝播する状態は不安定ィ匕されておらず、よって、こ の方向に沿って伝播する光成分は、窒化物半導体層 N内に強く閉じ込められる。第 二の理由は、凹凸構造の長手方向が、窒化物半導体層 Nの向い合う 2つの端面に 対して垂直となっているからである。このために、凹凸構造の長手方向に沿って伝播 する光成分は、窒化物半導体層 Nの端面において、元と同じ方向に反射される。つ まり、この光成分は、反射前後で伝播方向が変わらず、凹凸構造の長手方向に沿つ た方向に伝播し続けることになるので、窒化物半導体層 N内に強く閉じ込められた状 態力 脱することができな 、。  However, in the nitride LED 200, it cannot be said that the confinement of the light generated in the light emitting portion in the nitride semiconductor layer N is sufficiently relaxed. The first reason is that the thickness of the nitride semiconductor layer N is constant in the longitudinal direction of the uneven structure, that is, in the longitudinal direction of the trench T200. For this reason, the state in which light propagates along this direction in the waveguide structure having the nitride semiconductor layer N as a core is not unstable, and thus light propagates along this direction. The component is strongly confined in the nitride semiconductor layer N. The second reason is that the longitudinal direction of the concavo-convex structure is perpendicular to the two end faces of the nitride semiconductor layer N facing each other. For this reason, the light component propagating along the longitudinal direction of the concavo-convex structure is reflected at the end face of the nitride semiconductor layer N in the same direction as the original. In other words, the propagation direction of this light component does not change before and after reflection, and continues to propagate in the direction along the longitudinal direction of the concavo-convex structure, so that the state force strongly confined in the nitride semiconductor layer N I can't take it off.
[0008] 本発明はこのような事情に鑑みなされたものであり、その主な目的は、ストライプ状 の凹凸構造を含む窒化物半導体発光ダイオード素子における光取出し効率の改善 を図り、それによつて、照明装置用の光源に適した、発光効率の高い窒化物半導体 発光ダイオード素子を提供することである。  [0008] The present invention has been made in view of such circumstances, and its main purpose is to improve the light extraction efficiency in a nitride semiconductor light-emitting diode element including a stripe-shaped uneven structure, and thereby It is an object to provide a nitride semiconductor light-emitting diode element that is suitable for a light source for a lighting device and has high luminous efficiency.
課題を解決するための手段  Means for solving the problem
[0009] 上記の目的を達成するために、本発明では、ストライプ状の凹凸構造を含む窒化 物半導体発光ダイオード素子において、発光部で生じる光のうち、窒化物半導体層 をコアとする導波路構造内をこの凹凸構造の長手方向に伝播する光成分が、窒化物 半導体層の端面で反射されるときに伝播方向を変えるように、この凹凸構造の長手 方向と窒化物半導体層の端面とがなす角度を設定する。 In order to achieve the above object, according to the present invention, in a nitride semiconductor light-emitting diode element including a striped uneven structure, a waveguide structure having a nitride semiconductor layer as a core in light generated in a light-emitting portion. The length of the concavo-convex structure is changed so that the light component propagating in the longitudinal direction of the concavo-convex structure changes the propagation direction when reflected by the end face of the nitride semiconductor layer. An angle formed by the direction and the end face of the nitride semiconductor layer is set.
すなわち、本発明の実施形態に係る窒化物半導体発光ダイオード素子は、次の特 徴を有する。  That is, the nitride semiconductor light-emitting diode device according to the embodiment of the present invention has the following features.
(1)表面にストライプ状の凹凸構造を有する透明基板と、該凹凸構造を埋めるように 形成された窒化物半導体層とを有し、前記窒化物半導体層は、前記透明基板よりも 高い屈折率を有し、かつ、発光部を含んでおり、当該素子を上面視したとき、前記窒 化物半導体層の形状が方形であり、かつ、前記ストライプ状の凹凸構造の長手方向 力 前記方形の窒化物半導体層の 4つの辺のいずれとも平行でない、窒化物半導体 発光ダイオード素子。  (1) It has a transparent substrate having a striped uneven structure on its surface and a nitride semiconductor layer formed so as to fill the uneven structure, and the nitride semiconductor layer has a higher refractive index than the transparent substrate. The nitride semiconductor layer has a square shape when the element is viewed from above, and a longitudinal force of the striped concavo-convex structure The square nitride A nitride semiconductor light-emitting diode element that is not parallel to any of the four sides of the semiconductor layer.
(2)当該素子を上面視したとき、前記窒化物半導体層の形状が方形であり、かつ、前 記ストライプ状の凹凸構造の長手方向が、前記方形の窒化物半導体層の 4つの辺の いずれに対しても約 45度の角度をなしている、前記（1)に記載の窒化物半導体発光 ダイオード素子。  (2) When the element is viewed from above, the shape of the nitride semiconductor layer is square, and the longitudinal direction of the striped uneven structure is any of the four sides of the square nitride semiconductor layer. The nitride semiconductor light-emitting diode device according to (1), which is at an angle of about 45 degrees with respect to.
(3)前記窒化物半導体層の端面が傾斜している、前記（1)または（2)に記載の窒化 物半導体発光ダイオード素子。  (3) The nitride semiconductor light-emitting diode element according to (1) or (2), wherein an end surface of the nitride semiconductor layer is inclined.
(4)前記透明基板が単結晶基板であり、その上に、前記窒化物半導体層がェピタキ シャル成長して 、る、前記（1)〜（3)の 、ずれかに記載の窒化物半導体発光ダイォ ード素子。  (4) The nitride semiconductor light-emitting device according to any one of (1) to (3), wherein the transparent substrate is a single crystal substrate, and the nitride semiconductor layer is epitaxially grown thereon. Diode element.
(5)前記透明基板がガラス基板である、前記（1)〜（3)の 、ずれかに記載の窒化物 半導体発光ダイオード素子。  (5) The nitride semiconductor light-emitting diode element according to any one of (1) to (3), wherein the transparent substrate is a glass substrate.
(6)前記凹凸構造が、前記透明基板の表面に形成された複数のストライプ状の溝か ら構成されて 、る、前記（1)〜（5)の 、ずれかに記載の窒化物半導体発光ダイォー ド素子。  (6) The nitride semiconductor light emitting device according to any one of (1) to (5), wherein the concavo-convex structure is composed of a plurality of stripe-shaped grooves formed on a surface of the transparent substrate. Diode element.
(7)前記凹凸構造が、前記透明基板と、その表面に形成された複数のストライプ状の マスクと、力も構成されている、前記（1)〜（3)のいずれかに記載の窒化物半導体発 光ダイオード素子。  (7) The nitride semiconductor according to any one of (1) to (3), wherein the concavo-convex structure includes the transparent substrate, a plurality of stripe-shaped masks formed on the surface, and force. Light emitting diode element.
(8)発光部を含む窒化物半導体層をコアとする導波路構造を有しており、前記窒化 物半導体層は、一方向に伸びる厚肉部および薄肉部が交互に並んだ構造を有して おり、当該素子を上面視したとき、前記窒化物半導体層の形状が方形であり、前記 厚肉部および薄肉部の伸長方向が前記方形の窒化物半導体層の 4つの辺のいず れとも平行でない、窒化物半導体発光ダイオード素子。 (8) It has a waveguide structure having a nitride semiconductor layer including a light emitting portion as a core, and the nitride semiconductor layer has a structure in which thick portions and thin portions extending in one direction are alternately arranged. The When the element is viewed from above, the shape of the nitride semiconductor layer is square, and the extending direction of the thick part and the thin part is parallel to any of the four sides of the square nitride semiconductor layer. Not a nitride semiconductor light emitting diode device.
(9)前記厚肉部および薄肉部の伸長方向力 前記方形の窒化物半導体層の 4つの 辺の 、ずれに対しても約 45度の角度をなして 、る、前記（8)記載の窒化物半導体発 光ダイオード素子。  (9) The elongation direction force of the thick part and the thin part The nitriding according to (8), wherein the four sides of the rectangular nitride semiconductor layer form an angle of about 45 degrees with respect to the deviation. Semiconductor light emitting diode element.
(10)前記厚肉部の最大膜厚と前記薄肉部の最小膜厚との差が 0. 2 m以上である 、前記 (8)記載の窒化物半導体発光ダイオード素子。  (10) The nitride semiconductor light-emitting diode element according to (8), wherein the difference between the maximum thickness of the thick portion and the minimum thickness of the thin portion is 0.2 m or more.
(11)前記厚肉部の最大膜厚と前記薄肉部の最小膜厚との差が、該厚肉部の最大 膜厚の 20%以上である、前記（10)記載の窒化物半導体発光ダイオード素子。 (11) The nitride semiconductor light-emitting diode according to (10), wherein the difference between the maximum thickness of the thick portion and the minimum thickness of the thin portion is 20% or more of the maximum thickness of the thick portion element.
(12)前記導波路構造が、前記窒化物半導体層と、該窒化物半導体層の一方の主 面側に位置する該窒化物半導体層よりも低い屈折率を有する透光性の第 1の物質と 、該窒化物半導体層の他方の主面側に位置する、該窒化物半導体層よりも低い屈 折率を有する透光性の第 2の物質とから構成されて 、る、前記 (8)記載の窒化物半 導体発光ダイオード素子。 (12) The light-transmitting first material having the waveguide structure having a refractive index lower than that of the nitride semiconductor layer and the nitride semiconductor layer located on one main surface side of the nitride semiconductor layer And the light-transmitting second substance having a lower refractive index than that of the nitride semiconductor layer and located on the other main surface side of the nitride semiconductor layer, (8) The nitride semiconductor light emitting diode element as described.
(13)前記第 1の物質が透明基板を含み、前記第 2の物質が、透明導電性酸化物か らなる電極、絶縁保護膜または封止材料カゝら選ばれるひとつ以上を含む、前記（12) 記載の窒化物半導体発光ダイオード素子。  (13) The first substance includes a transparent substrate, and the second substance includes at least one selected from an electrode made of a transparent conductive oxide, an insulating protective film, or a sealing material. 12) The nitride semiconductor light-emitting diode element as described.
(14)前記導波路構造が、前記窒化物半導体層と、該窒化物半導体層の一方の主 面側に位置する該窒化物半導体層よりも低い屈折率を有する透光性の第 3の物質と 、該窒化物半導体層の他方の主面側に位置する金属製の反射膜とから構成されて V、る、前記 (8)記載の窒化物半導体発光ダイオード素子。  (14) The light-transmitting third material having the waveguide structure having a refractive index lower than that of the nitride semiconductor layer and the nitride semiconductor layer located on one main surface side of the nitride semiconductor layer And the nitride semiconductor light-emitting diode element according to (8), further comprising: a metal reflective film located on the other main surface side of the nitride semiconductor layer.
(15)前記第 3の物質が透明基板を含む、前記（14)記載の窒化物半導体発光ダイ オード素子。  (15) The nitride semiconductor light-emitting diode device according to (14), wherein the third substance includes a transparent substrate.
(16)前記第 3の物質が、透明導電性酸化物からなる電極、絶縁保護膜または封止 材料カゝら選ばれるひとつ以上を含む、前記（14)記載の窒化物半導体発光ダイォー ド素子。  (16) The nitride semiconductor light-emitting diode device according to (14), wherein the third substance includes one or more selected from an electrode made of a transparent conductive oxide, an insulating protective film, or a sealing material.
(17)発光部を含む窒化物半導体層を有し、前記窒化物半導体層が、少なくともその 一方の主面に、ストライプ状の凹凸構造を有しており、そのために、光が該窒化物半 導体層内を該凹凸構造の長手方向に直交する方向に伝播する状態が不安定化さ れており、当該素子を上面視したとき、前記窒化物半導体層の形状が方形であり、前 記凹凸構造の長手方向が、前記方形の窒化物半導体層の 4つの辺のいずれとも平 行でない、窒化物半導体発光ダイオード素子。 (17) having a nitride semiconductor layer including a light emitting portion, wherein the nitride semiconductor layer is at least One main surface has a striped uneven structure, which destabilizes the state in which light propagates in the nitride semiconductor layer in a direction perpendicular to the longitudinal direction of the uneven structure. When the element is viewed from above, the shape of the nitride semiconductor layer is square, and the longitudinal direction of the concavo-convex structure is not parallel to any of the four sides of the square nitride semiconductor layer. Nitride semiconductor light emitting diode device.
(18)前記凹凸構造の長手方向が、前記方形の窒化物半導体層の 4つの辺のいず れに対しても約 45度の角度をなしている、前記（17)記載の窒化物半導体発光ダイ オード素子。  (18) The nitride semiconductor light emitting device according to (17), wherein a longitudinal direction of the concavo-convex structure forms an angle of about 45 degrees with respect to any of four sides of the rectangular nitride semiconductor layer. Diode element.
(19)前記凹凸構造が、前記窒化物半導体層の一方の主面に形成された、少なくと もひとつのストライプ状の溝を含んでいる、前記（17)記載の窒化物半導体発光ダイ オード素子。  (19) The nitride semiconductor light-emitting diode device according to (17), wherein the concavo-convex structure includes at least one stripe-shaped groove formed on one main surface of the nitride semiconductor layer. .
(20)前記凹凸構造が、前記窒化物半導体層の一方の主面に形成された、少なくと もひとつのストライプ状のリッジを含んでいる、前記（17)記載の窒化物半導体発光ダ ィオード素子。  (20) The nitride semiconductor light-emitting diode device according to (17), wherein the concavo-convex structure includes at least one stripe-shaped ridge formed on one main surface of the nitride semiconductor layer. .
発明の効果  The invention's effect
[0011] 本発明によれば、ストライプ状の凹凸構造を含む窒化物半導体発光ダイオード素 子における光取出し効率を改善することができる。本発明を実施した窒化物半導体 発光ダイオード素子は、発光効率の高いものとなるので、照明装置用の光源として好 適に用いることができる。  [0011] According to the present invention, it is possible to improve the light extraction efficiency in a nitride semiconductor light-emitting diode element including a striped uneven structure. Since the nitride semiconductor light-emitting diode device embodying the present invention has high luminous efficiency, it can be suitably used as a light source for a lighting device.
図面の簡単な説明  Brief Description of Drawings
[0012] [図 1]図 1は、本発明の一実施形態に係る窒化物半導体発光ダイオード素子の構造 を示す図であり、図 1 (a)は上面図、図 1 (b)は図 1 (a)の P— Q線の位置における断 面図である。  FIG. 1 is a diagram showing a structure of a nitride semiconductor light-emitting diode device according to an embodiment of the present invention. FIG. 1 (a) is a top view, and FIG. 1 (b) is FIG. It is a cross-sectional view at the position of PQ line in (a).
[図 2]図 2は、図 1に示す窒化物半導体発光ダイオード素子に含まれる窒化物半導体 層だけを抜き出して描いた上面図である。図 2 (b)は、図 2 (a)に示した窒化物半導体 層内における光の伝播方向と、ストライプ状の溝の長手方向との関係を説明する図 である。  FIG. 2 is a top view illustrating only the nitride semiconductor layer included in the nitride semiconductor light-emitting diode element shown in FIG. FIG. 2 (b) is a diagram for explaining the relationship between the light propagation direction in the nitride semiconductor layer shown in FIG. 2 (a) and the longitudinal direction of the stripe-shaped grooves.
[図 3]図 3は、凹凸構造の構成要素となる溝およびリッジの断面形状を例示する図で ある。 [FIG. 3] FIG. 3 is a diagram illustrating the cross-sectional shape of grooves and ridges which are constituent elements of the concavo-convex structure. is there.
[図 4]図 4は、本発明の一実施形態に係る窒化物半導体発光ダイオード素子の構造 FIG. 4 shows the structure of a nitride semiconductor light emitting diode device according to an embodiment of the present invention.
〇 Yes
を示す図であり、図 4 (a)は上面図、図 4 (b)は図 4 (a)の P— Q線の位置における断 面図である。 4 (a) is a top view, and FIG. 4 (b) is a cross-sectional view at the position of the P—Q line in FIG. 4 (a).
[図 5]図 5は、本発明の一実施形態に係る窒化物半導体発光ダイオード素子の構造 を示す図であり、図 5 (a)は上面図、図 5 (b)は図 5 (a)の P— Q線の位置における断 面図である。  FIG. 5 is a diagram showing a structure of a nitride semiconductor light-emitting diode device according to an embodiment of the present invention. FIG. 5 (a) is a top view, and FIG. 5 (b) is a diagram in FIG. FIG. 6 is a cross-sectional view at the position of the PQ line.
[図 6]図 6は、本発明の一実施形態に係る窒化物半導体発光ダイオード素子の構造 を示す図であり、図 6 (a)は上面図、図 6 (b)は図 6 (a)の P— Q線の位置における断 面図である。  FIG. 6 is a diagram showing the structure of a nitride semiconductor light-emitting diode device according to an embodiment of the present invention. FIG. 6 (a) is a top view, and FIG. 6 (b) is FIG. 6 (a). FIG. 6 is a cross-sectional view at the position of the PQ line.
[図 7]図 7は、従来の窒化物半導体発光ダイオード素子の構造を示す断面図である。  FIG. 7 is a cross-sectional view showing the structure of a conventional nitride semiconductor light-emitting diode element.
[図 8]図 8は、従来の窒化物半導体発光ダイオード素子の構造を示す図であり、図 8 ( a)は上面図、図 8 (b)は図 8 (a)の X—Y線の位置における断面図である。  [FIG. 8] FIG. 8 is a diagram showing the structure of a conventional nitride semiconductor light-emitting diode device, where FIG. 8 (a) is a top view, and FIG. 8 (b) is an XY line in FIG. It is sectional drawing in a position.
[図 9]図 9は、本発明の一実施形態に係る窒化物半導体発光ダイオード素子の構造 を示す断面図である。  FIG. 9 is a cross-sectional view showing the structure of a nitride semiconductor light-emitting diode device according to one embodiment of the present invention.
符号の説明 Explanation of symbols
20、 30、 40、 50 窒化物半導体発光ダイオード素子  20, 30, 40, 50 Nitride semiconductor light-emitting diode device
11、 21、 31、 41、 51 透明基板  11, 21, 31, 41, 51 Transparent substrate
12、 22、 32、 42、 52 n型層  12, 22, 32, 42, 52 n-type layer
13、 23、 33、 43、 53 P型層  13, 23, 33, 43, 53 P-type layer
14、 24、 34、 44、 54 負電極  14, 24, 34, 44, 54 Negative electrode
15、 25、 35、 45、 55 正電極  15, 25, 35, 45, 55 Positive electrode
N 窒化物半導体層  N Nitride semiconductor layer
T10、 T20、 T40、 T50 溝  T10, T20, T40, T50 groove
Μ マスク  Μ Mask
発明を実施するための最良の形態 BEST MODE FOR CARRYING OUT THE INVENTION
図 1は、本発明の一実施形態に係る窒化物 LEDの構造を示す図であり、図 1 (a)は 上面図、図 1 (b)は図 1 (a)の P— Q線の位置における断面図である。この図に示す 窒化物 LED10では、サファイア基板 11の表面に、図 1 (a)の P— Q線に直交する方 向に伸びる、ストライプ状の溝 T10が複数、平行に形成されており、その上に、図示 しな 、バッファ層を介して、 n型層 12および p型層 13からなる窒化物半導体層 Nが形 成されている。 p型層 13の一部がドライエッチングにより除去され、それによつて露出 した n型層 12の表面に負電極 14が形成され、また、 p型層 13上のほぼ全面に正電 極 15が形成されている。 LED10の発光部は n型層 12と p型層 13との境界部 (pn接 合部）近傍である。この部分に活性層を設けてダブルへテロ構造を構成すると、特に 高い発光効率が得られる。 Fig. 1 is a diagram showing the structure of a nitride LED according to an embodiment of the present invention. Fig. 1 (a) is a top view, and Fig. 1 (b) is the position of the PQ line in Fig. 1 (a). FIG. Shown in this figure In the nitride LED10, a plurality of stripe-shaped grooves T10 extending in the direction perpendicular to the P—Q line in FIG. 1 (a) are formed on the surface of the sapphire substrate 11 in parallel. However, the nitride semiconductor layer N composed of the n-type layer 12 and the p-type layer 13 is formed via the buffer layer. A part of the p-type layer 13 is removed by dry etching, whereby the negative electrode 14 is formed on the exposed surface of the n-type layer 12, and the positive electrode 15 is formed on almost the entire surface of the p-type layer 13. Has been. The light emitting part of the LED 10 is near the boundary part (pn junction part) between the n-type layer 12 and the p-type layer 13. When a double hetero structure is formed by providing an active layer in this portion, particularly high luminous efficiency can be obtained.
[0015] 図 2は、図 1に示す窒化物 LED10に含まれる窒化物半導体層 Nだけを抜き出して 描いた上面図である。上面視した窒化物半導体層 Nの外郭形状は正方形であり、図 2 (a)では、その 4つの角を記号 A、 B、 C、 Dで表している。図 1における P— Q線の方 向は、対角線 BDの方向である。図 2 (a)、 (b)中の両矢印は、サファイア基板 11の表 面に形成されたストライプ状の溝 T10の長手方向を示して 、る。  FIG. 2 is a top view illustrating only the nitride semiconductor layer N included in the nitride LED 10 shown in FIG. The outer shape of the nitride semiconductor layer N as viewed from above is a square. In FIG. 2 (a), the four corners are represented by symbols A, B, C, and D. The direction of the P—Q line in Fig. 1 is the direction of the diagonal line BD. The double arrows in FIGS. 2 (a) and 2 (b) indicate the longitudinal direction of the stripe-shaped groove T10 formed on the surface of the sapphire substrate 11.
[0016] 窒化物 LED10では、図 1における P— Q線に平行な方向に沿って、窒化物半導体 層 Nの厚さが変動している。そのために、窒化物半導体層 Nをコアとする導波路構造 内を、光が P— Q線に平行な方向に伝播する状態は不安定ィ匕されている。よって、発 光部で生じる光のうち、窒化物半導体層 N中を P— Q線に平行な方向に伝播する光 成分は、この導波路構造の外に漏れ出し易い。即ち、素子外に取出される確率が高 い。一方、窒化物半導体層 N中を P— Q線に直交する方向、すなわち、サファイア基 板 11の表面に設けられたストライプ状の溝 T10の長手方向に沿って伝播する光成 分は、窒化物半導体層 Nをコアとする導波路構造内に強く閉じ込められるが、図 2 (b )に示すように、窒化物半導体層の端面に達すると、該端面により反射を受けて、そ の伝播方向を P— Q線に平行な方向に変える。これは、図 2 (a)、（b)に示すように、 素子を上面視したときに、溝 T10の長手方向と、方形の窒化物半導体層 Nの 4つの 辺とがなす角度が、いずれも 45度であるからである。伝播方向を P— Q線に平行な方 向に変えられた光は、上記のように、素子外に取出される確率が高くなる。このように 、窒化物 LED10では、窒化物半導体層 Nに強く閉じ込められた状態力も脱すること ができない光成分が発生しないために、発光部で生じた光が素子外に取出される確 率力 図 8に示す従来の窒化物 LED200に比べて高くなる。 In the nitride LED 10, the thickness of the nitride semiconductor layer N varies along the direction parallel to the P—Q line in FIG. Therefore, the state in which light propagates in the direction parallel to the PQ line in the waveguide structure with the nitride semiconductor layer N as the core is unstable. Therefore, the light component that propagates in the nitride semiconductor layer N in the direction parallel to the PQ line among the light generated in the light emitting part is likely to leak out of the waveguide structure. That is, the probability of being taken out of the element is high. On the other hand, the light component propagating in the nitride semiconductor layer N along the direction perpendicular to the P-Q line, that is, along the longitudinal direction of the stripe-shaped groove T10 provided on the surface of the sapphire substrate 11, is nitride. Although it is strongly confined in the waveguide structure having the semiconductor layer N as a core, as shown in Fig. 2 (b), when it reaches the end face of the nitride semiconductor layer, it is reflected by the end face, and its propagation direction is changed. P— Change in the direction parallel to the Q line. As shown in FIGS. 2 (a) and 2 (b), the angle formed by the longitudinal direction of the trench T10 and the four sides of the rectangular nitride semiconductor layer N when the element is viewed from above is Because it is 45 degrees. The light whose propagation direction has been changed to the direction parallel to the P—Q line has a higher probability of being extracted outside the element as described above. In this manner, in the nitride LED 10, since the light component that cannot be released from the state force that is strongly confined in the nitride semiconductor layer N is not generated, it is likely that the light generated in the light emitting portion is extracted from the element. Power is higher than the conventional nitride LED200 shown in Figure 8.
[0017] 図 1に示す窒化物 LEDは、次のようにして製造することができる。 The nitride LED shown in FIG. 1 can be manufactured as follows.
ストライプ状の溝 T10を有するサファイア基板 11は、通常のサファイア基板の表面 にエッチングマスクを形成し、フォトリソグラフィ技法を用いてこのエッチングマスクにス トライプ状の開口部をパターユングした後、開口部に露出したサファイア基板の表面 をエッチングすることにより形成することができる。このエッチングは、イオンビームエツ チング法、反応性イオンエッチング法などのドライエッチング法を用いて行うことが好 ましい。溝 T10の幅 wlおよび間隔 w2は、例えば、 0. 5 m〜10 μ mとすることがで き、溝 T10の深さ dは、例えば、 0. 2 μ m〜5 μ mとすることができる。  The sapphire substrate 11 having the stripe-shaped groove T10 is formed by forming an etching mask on the surface of a normal sapphire substrate, patterning the striped opening in the etching mask using photolithography technique, and then opening the opening. It can be formed by etching the exposed surface of the sapphire substrate. This etching is preferably performed using a dry etching method such as an ion beam etching method or a reactive ion etching method. The width wl and the interval w2 of the groove T10 can be, for example, 0.5 m to 10 μm, and the depth d of the groove T10 can be, for example, 0.2 μm to 5 μm. it can.
[0018] 次に、サファイア基板 11上に、溝 T10を埋め込んで窒化物半導体層 Nを成長させ る。窒化物半導体の好ましい成長方法としては、 MOVPE法、 HVPE法 (ノヽイドライド 気相成長法）、 MBE法 (分子ビームエピタキシー法)などの気相ェピタキシャル成長 法が挙げられる。サファイア基板 11上と窒化物半導体層 Nとの間には、ノ ッファ層を 介在させることが好ま 、。窒化物半導体層 Nを構成する n型層 12と p型層 13の詳 細構成 (層構造、結晶組成、膜厚等）については、周知の技術を参照して設定するこ とができる。 p型層 13に添加した p型不純物を活性ィ匕させるためのアニーリング処理 や電子線照射処理は、適宜行うことができる。  Next, a nitride semiconductor layer N is grown on the sapphire substrate 11 by filling the trench T10. Preferred growth methods for nitride semiconductors include vapor phase epitaxy such as MOVPE, HVPE (noideride vapor phase growth), MBE (molecular beam epitaxy). It is preferable to interpose a nofer layer between the sapphire substrate 11 and the nitride semiconductor layer N. The detailed configuration (layer structure, crystal composition, film thickness, etc.) of the n-type layer 12 and the p-type layer 13 constituting the nitride semiconductor layer N can be set with reference to known techniques. An annealing process and an electron beam irradiation process for activating the p-type impurity added to the p-type layer 13 can be appropriately performed.
[0019] 窒化物半導体層 Nを形成した後、塩素ガスを用いた反応性イオンエッチング法によ つて n型層 12を部分的に露出させ、その表面に負電極 14を設ける。負電極 14は、 A 1、 Ti、 W、 Ni、 Cr、 V等の単体、または、その合金で形成することができる。一方、正 電極 15は、 p型層 13上の略全面を覆うように設ける。正電極 15は、白金族元素 (Rh 、 Pt、 Pd、 Irなど）、 Au、 Ni、 Co等の単体、または、その合金で形成することができる 。正電極 15は、電極を構成する金属膜の厚さを調節することによって、透明電極とし たり、反射性電極とすることができる。また、光が通過し得る窓部（開口部）を設けるこ とによって、透光性を付与することもできる。正電極 15は、 ITO、酸化インジウム、酸 化錫、 ΙΖΟ (インジウム亜鉛酸ィ匕物）、 ΑΖΟ (アルミニウム亜鉛酸ィ匕物）、酸化亜鉛そ の他の透明導電性酸ィ匕物を用いて形成することもできる。図 1には示して 、な 、が、 正電極 15上への接点用電極 (ボンディング 'パッド）の形成は、適宜行うことができる [0020] 窒化物半導体層の表面が電極に覆われずに露出した領域には、絶縁保護膜を形 成することが好ましい。また、電極の表面も、ボンディングのために露出させておく必 要のある部分を除いて、絶縁保護膜で被覆することが望ましい。最後に、この分野で 通常用いられている、ダイシング、スクライビング等の方法を用いて、ウエノ、からチッ プ状の素子を切り出す。 After forming the nitride semiconductor layer N, the n-type layer 12 is partially exposed by a reactive ion etching method using chlorine gas, and the negative electrode 14 is provided on the surface thereof. The negative electrode 14 can be formed of a simple substance such as A1, Ti, W, Ni, Cr, V, or an alloy thereof. On the other hand, the positive electrode 15 is provided so as to cover substantially the entire surface on the p-type layer 13. The positive electrode 15 can be formed of a simple substance such as a platinum group element (Rh, Pt, Pd, Ir, etc.), Au, Ni, Co, or an alloy thereof. The positive electrode 15 can be a transparent electrode or a reflective electrode by adjusting the thickness of the metal film constituting the electrode. Further, by providing a window portion (opening portion) through which light can pass, translucency can be imparted. The positive electrode 15 is made of ITO, indium oxide, tin oxide, ΙΖΟ (indium zinc oxide), ΑΖΟ (aluminum zinc oxide), zinc oxide and other transparent conductive oxides. It can also be formed. As shown in FIG. 1, the contact electrode (bonding pad) can be appropriately formed on the positive electrode 15. [0020] It is preferable to form an insulating protective film in a region where the surface of the nitride semiconductor layer is exposed without being covered with the electrode. In addition, it is desirable to cover the surface of the electrode with an insulating protective film except for a portion that needs to be exposed for bonding. Finally, a chip-shaped element is cut out from the Ueno using methods such as dicing and scribing that are usually used in this field.
[0021] 次に、本発明の好適な実施形態について説明する。  Next, a preferred embodiment of the present invention will be described.
図 1に示す窒化物 LED10では、透明基板としてサファイア基板が用いられて!/、る 力 透明基板が、窒化物半導体層 Nよりも低い屈折率を有するものであれば、前記 の効果が得られる。本発明の窒化物 LEDに使用できる透明基板として、サファイア、 A1N、スピネル、 ZnO、 NGO (NdGaO )、 LGO (LiGaO )、 LAO (LaAlO )などか  In the nitride LED 10 shown in FIG. 1, a sapphire substrate is used as a transparent substrate! /, The above-mentioned effect can be obtained if the transparent substrate has a lower refractive index than the nitride semiconductor layer N. . Transparent substrates that can be used for the nitride LED of the present invention include sapphire, A1N, spinel, ZnO, NGO (NdGaO), LGO (LiGaO), LAO (LaAlO), etc.
3 2 3 らなる単結晶層を少なくとも表層として有する基板 (単結晶基板またはテンプレート基 板)が挙げられる。このような基板は、表面に凹凸構造を設けたうえで、窒化物半導 体層のェピタキシャル成長に使用することができる。  And a substrate (single crystal substrate or template substrate) having at least a single crystal layer of 3 2 3 as a surface layer. Such a substrate can be used for the epitaxial growth of a nitride semiconductor layer after providing an uneven structure on the surface.
本明細書において、透明基板とは、発光素子の発光を透過する基板をいう。透明 基板は、着色した基板を含み得るし、発光素子の発光波長が可視域の外にある場合 には、可視域の光を透過しない基板を含み得る。透明基板は、曇りのない (transpare nt)基板に限定されるものではなぐ曇りはあるが光を通す (translucent)基板を含む。  In this specification, a transparent substrate refers to a substrate that transmits light emitted from a light-emitting element. The transparent substrate can include a colored substrate, and can include a substrate that does not transmit light in the visible region when the emission wavelength of the light emitting element is outside the visible region. The transparent substrate includes a cloudy but translucent substrate that is not limited to a transparent substrate.
[0022] 図 1に示す窒化物 LED10において、サファイア基板 11をガラス基板に置換するこ とも可能である。ガラス基板は、窒化物半導体層のェピタキシャル成長には使用でき ないが、サファイア基板上に窒化物半導体層を形成した後、このサファイア基板をリ ン酸により溶解して除去し、残った窒化物半導体層に対して熱圧着することにより、 素子中に導入することができる。ガラス基板の材料や熱圧着の方法については、特 開 2005— 347700号公報、特開 2006— 41479号公報などを参照することができる 。表面にストライプ状の凹凸構造を有するガラス基板の上に、該凹凸構造を埋めるよ うに窒化物半導体層が形成された構成を得るには、例えば、ストライプ状の溝を形成 した結晶基板上に窒化物半導体層をェピタキシャル成長させた後、結晶基板を選択 的に除去し、それによつて露出する凹凸状の窒化物半導体層の表面に、ガラス基板 を熱圧着する。他の方法として、平坦な結晶基板上に窒化物半導体層を成長させた 後、結晶基板を選択的に除去し、それによつて露出する平坦な窒化物半導体層の表 面にストライプ状の溝を加工し、その上にガラス基板を熱圧着してもよい。ェピタキシ ャル成長により結晶基板上に窒化物半導体層を形成する工程では、 Si基板、 GaAs 基板、 ZnO基板など、窒化物半導体層に対して選択的にエッチングまたは溶解する ことが容易な結晶基板を用いることが好ま 、。 In the nitride LED 10 shown in FIG. 1, the sapphire substrate 11 can be replaced with a glass substrate. The glass substrate cannot be used for the epitaxial growth of the nitride semiconductor layer, but after forming the nitride semiconductor layer on the sapphire substrate, the sapphire substrate is dissolved and removed with phosphoric acid, and the remaining nitride is removed. It can be introduced into the element by thermocompression bonding to the semiconductor layer. For the material of the glass substrate and the thermocompression bonding method, JP 2005-347700 A and JP 2006-41479 A can be referred to. In order to obtain a structure in which a nitride semiconductor layer is formed on a glass substrate having a stripe-like uneven structure on the surface so as to fill the uneven structure, for example, a nitride substrate is formed on a crystal substrate having stripe-like grooves. After epitaxial growth of the oxide semiconductor layer, the crystal substrate is selectively removed, and a glass substrate is formed on the surface of the uneven nitride semiconductor layer exposed thereby. Is thermocompression bonded. As another method, after a nitride semiconductor layer is grown on a flat crystal substrate, the crystal substrate is selectively removed, thereby forming striped grooves on the surface of the flat nitride semiconductor layer exposed. It may be processed and a glass substrate may be thermocompression bonded thereon. In the process of forming a nitride semiconductor layer on a crystal substrate by epitaxial growth, a crystal substrate that can be easily etched or dissolved with respect to the nitride semiconductor layer, such as a Si substrate, a GaAs substrate, or a ZnO substrate, is formed. I prefer to use it.
[0023] 図 1に示す窒化物 LED10では、サファイア基板 11の表面にストライプ状の溝を複 数、平行に形成することによって、ストライプ状の凹凸構造が構成されているが、本発 明の窒化物 LEDにおいて、ストライプ状の凹凸構造はこれに限定されるものではなく 、例えば、平坦面にストライプ状の溝が 1つだけカ卩ェされた構造や、あるいは、溝に 代えて、平坦面上にストライプ状のリッジ力 つまたは複数、形成された構造であって もよい。ストライプ状の凹凸構造を構成する溝やリッジの断面形状としては、図 3 (a)に 示す矩形状、図 3 (b)に示す台形状、図 3 (c)に示す V字状、図 3 (d)に示す半円状 など、種々の形状が例示される。溝やリッジの幅および断面形状、溝の深さ、リッジの 高さなどには、長手方向に沿って変動があってもよい。ストライプ状の凹凸構造は、 異なる形状 ·サイズを有する溝やリッジを複合して構成したものであってもよい。結晶 基板の表面にリッジを設ける場合、リッジを結晶基板と同じ材料で形成してもよいが、 必須ではない。例えば、リッジは、窒化物半導体結晶の選択横方向成長 (Epitaxial Lateral Overgrowth)に使用されるマスクであってもよい。  In the nitride LED 10 shown in FIG. 1, a plurality of stripe-like grooves are formed in parallel on the surface of the sapphire substrate 11 to form a stripe-like concavo-convex structure. In an LED, a striped uneven structure is not limited to this. For example, a structure in which only one striped groove is covered on a flat surface, or a flat surface is used instead of a groove. Alternatively, it may be a structure in which one or a plurality of striped ridges are formed. The cross-sectional shapes of the grooves and ridges constituting the striped concavo-convex structure are the rectangular shape shown in Fig. 3 (a), the trapezoidal shape shown in Fig. 3 (b), the V shape shown in Fig. 3 (c), and Fig. 3 Various shapes such as the semicircle shown in (d) are exemplified. The width and cross-sectional shape of the groove or ridge, the depth of the groove, the height of the ridge, etc. may vary along the longitudinal direction. The striped concavo-convex structure may be formed by combining grooves and ridges having different shapes and sizes. When a ridge is provided on the surface of the crystal substrate, the ridge may be formed of the same material as the crystal substrate, but it is not essential. For example, the ridge may be a mask used for selective lateral growth of nitride semiconductor crystals.
[0024] 透明基板に設けるストライプ状の凹凸構造は、周期構造であってもよい。周期性の 高い構造、例えば、長手方向に一定の断面を有する溝またはリッジを、複数、等間隔 で平行に配置してなる凹凸構造には、作製が容易であるといった利点、および、窒化 物半導体をェピタキシャル成長させて該凹凸構造を埋める際に、不良が発生し難い といった利点がある。一方、このストライプ状の凹凸構造の、長手方向に直交する方 向の周期性を低くすると、この凹凸構造を埋める窒化物半導体層内を、この長手方 向に直交する方向に光が伝播する状態がより不安定となるため、素子の光取出し効 率が高くなる。  [0024] The striped uneven structure provided on the transparent substrate may be a periodic structure. A structure having high periodicity, for example, an uneven structure in which a plurality of grooves or ridges having a constant cross section in the longitudinal direction are arranged in parallel at equal intervals, has the advantage that it is easy to manufacture, and a nitride semiconductor There is an advantage that defects are hardly generated when the concavo-convex structure is filled by epitaxial growth. On the other hand, if the periodicity in the direction perpendicular to the longitudinal direction of the striped uneven structure is lowered, light propagates in the direction perpendicular to the longitudinal direction in the nitride semiconductor layer filling the uneven structure. Since this becomes more unstable, the light extraction efficiency of the element increases.
[0025] ストライプ状の凹凸構造を構成する溝やリッジのサイズは、当該凹凸構造が窒化物 半導体層内における光の伝播状態に影響を与えるものとなるように設定する必要が ある。そのためには、溝の深さまたはリッジの高さは、 0. 2 m以上とすることが好まし く、 0. 5 m以上とすることがより好ましぐ 1 μ m以上とすることが特に好ましい。透明 基板と窒化物半導体層との屈折率差が小さい場合は、凹凸構造が窒化物半導体層 内における光の伝播状態に与える影響が小さくなるので、溝の深さまたはリッジの高 さを大きく設定することが望ましい。一方で、溝の深さまたはリッジの高さを大きくする 程、凹凸構造の形成に要する時間やエネルギーが大きくなり、素子の製造効率が低 下する。よって、溝の深さまたはリッジの高さは、 5 m以下とすることが好ましい。 [0025] The size of the grooves and ridges constituting the striped concavo-convex structure is such that the concavo-convex structure is a nitride. It is necessary to set so as to affect the light propagation state in the semiconductor layer. For that purpose, the depth of the groove or the height of the ridge is preferably 0.2 m or more, more preferably 0.5 m or more, particularly 1 μm or more. preferable. When the difference in refractive index between the transparent substrate and the nitride semiconductor layer is small, the effect of the concavo-convex structure on the light propagation state in the nitride semiconductor layer is reduced, so the groove depth or ridge height is set large. It is desirable to do. On the other hand, as the depth of the groove or the height of the ridge increases, the time and energy required to form the concavo-convex structure increase, and the manufacturing efficiency of the device decreases. Accordingly, the depth of the groove or the height of the ridge is preferably 5 m or less.
[0026] 透明基板に設けるストライプ状の凹凸構造における、溝またはリッジの幅、および、 隣あう溝と溝の間隔またはリッジとリッジの間隔は、小さくし過ぎると製造が難しくなり、 大きくし過ぎると、凹凸構造が窒化物半導体層内における光の伝播状態に与える影 響が小さくなる。従って、長手方向に一定の断面を有する溝またはリッジを、複数、等 間隔で平行に配置してなる凹凸構造を例にすると、溝またはリッジの幅は、 0. 5 μ ηι 〜： LO mとすることが好ましぐストライプの幅方向における溝またはリッジの形成周 期は、 1 m〜20 mとすること力 S好ましい。  [0026] In the striped uneven structure provided on the transparent substrate, the width of the grooves or ridges, and the distance between adjacent grooves or grooves or the distance between ridges and ridges are difficult to manufacture if too small, and too large. In addition, the effect of the uneven structure on the light propagation state in the nitride semiconductor layer is reduced. Accordingly, when an example of a concavo-convex structure in which a plurality of grooves or ridges having a constant cross section in the longitudinal direction are arranged in parallel at equal intervals, the width of the grooves or ridges is 0.5 μηι to: LO m It is preferable that the groove or ridge formation period in the width direction of the stripe is 1 m to 20 m.
[0027] 図 1に示す窒化物 LED10では、凹凸構造を有するサファイア基板 1 1上に形成さ れた窒化物半導体層 Nの上面が平坦となっている力 力かる構成は必須ではない。 本発明の窒化物 LEDは、透明基板の表面の凹凸構造を反映した、波打った形状の 窒化物半導体層を有するものであってもよ 、。図 4はそのような窒化物 LEDの構造 例を示す図で、図 4 (a)は上面図、図 4 (b)は図 4 (a)の P— Q線の位置における断面 図である。この図に示す窒化物 LED20は、 ZnOなど力もなる導電性の透明基板 21 を有しており、その表面には、図 4 (a)の P— Q線に直交する方向に伸びる、ストライプ 状の溝 T20が複数、平行に形成されている。透明基板 21上には、溝 T20を埋めるよ うに、 n型層 22および p型層 23からなる窒化物半導体層 Nが形成されており、透明基 板 21の裏面に負電極 24、 p型層 23の上面に正電極 25が形成されている。素子の上 面形状は正方形で、窒化物半導体層の上面形状も同じである。素子を上面視したと き、溝 T20の長手方向は、正方形状の窒化物半導体層 Nの 4辺のいずれとも、 45度 の角度をなしている。窒化物 LED20では、窒化物半導体層 Nそのものが、図 4 (a)の P - Q線の方向に沿って波打って 、るために、光が窒化物半導体層 N中をこの P—In the nitride LED 10 shown in FIG. 1, a forceful configuration in which the upper surface of the nitride semiconductor layer N formed on the sapphire substrate 11 having an uneven structure is flat is not essential. The nitride LED of the present invention may have a wavy nitride semiconductor layer reflecting the uneven structure on the surface of the transparent substrate. FIG. 4 is a view showing an example of the structure of such a nitride LED, FIG. 4 (a) is a top view, and FIG. 4 (b) is a cross-sectional view taken along the line P—Q in FIG. 4 (a). The nitride LED 20 shown in this figure has a conductive transparent substrate 21 that is also strong, such as ZnO, and has a stripe-like shape that extends in a direction perpendicular to the P—Q line in FIG. A plurality of grooves T20 are formed in parallel. A nitride semiconductor layer N composed of an n-type layer 22 and a p-type layer 23 is formed on the transparent substrate 21 so as to fill the trench T20. The negative electrode 24 and the p-type layer are formed on the back surface of the transparent substrate 21. A positive electrode 25 is formed on the upper surface of 23. The upper surface shape of the element is square, and the upper surface shape of the nitride semiconductor layer is the same. When the element is viewed from above, the longitudinal direction of the trench T20 forms an angle of 45 degrees with any of the four sides of the square nitride semiconductor layer N. In the nitride LED 20, the nitride semiconductor layer N itself is shown in Fig. 4 (a). Since light undulates along the direction of the P-Q line, light passes through the nitride semiconductor layer N through this P—
Q線に平行な方向に伝播する状態が不安定ィ匕されて 、る。 The state of propagation in the direction parallel to the Q line is unstable.
[0028] 図 1に示す窒化物 LED10では、素子を上面視したときの窒化物半導体層 Nの形 状を正方形としているが、長方形であってもよい。静電破壊の原因となる電界集中を 防止したり、ウエノ、からチップ状の素子を切り出す際に欠けが生じるのを防ぐために、 方形の角の部分には丸みを帯びさせてもよい。また、素子を上面視したときに、透明 基板に設けるストライプ状の凹凸構造の長手方向と、方形状の窒化物半導体層 Nの 4つの辺とがなす角は、約 45度 (40度〜 50度）とすることが最も好ましいが、他の角 度であってもよい。好ましい範囲は、 30度〜 60度である。窒化物半導体層 Nの 4辺 のうち、いずれかの辺の方向と、ストライプ状の凹凸構造の長手方向とがなす角が 10 度未満では、これらの方向が実質的に平行であるために、本発明による光取出し効 率の改善効果は望めなくなる。 In the nitride LED 10 shown in FIG. 1, the shape of the nitride semiconductor layer N when the element is viewed from above is a square, but may be a rectangle. In order to prevent electric field concentration that causes electrostatic breakdown, or to prevent chipping when cutting a chip-like element from a wafer, the corners of the square may be rounded. In addition, when the element is viewed from above, the angle formed by the longitudinal direction of the striped uneven structure provided on the transparent substrate and the four sides of the rectangular nitride semiconductor layer N is about 45 degrees (40 to 50 degrees). Is most preferred, but other angles are also possible. A preferred range is 30 to 60 degrees. If the angle formed by the direction of any one of the four sides of the nitride semiconductor layer N and the longitudinal direction of the striped uneven structure is less than 10 degrees, these directions are substantially parallel. The effect of improving the light extraction efficiency according to the present invention cannot be expected.
[0029] 図 1に示す窒化物 LED10においては、窒化物半導体層 Nの端面が、サファイア基 板 11の基板平面 (基板の厚さ方向と直交する平面）に対して垂直となっているが、か 力る構成は必須ではなぐ窒化物半導体層の端面は傾斜していてもよい。図 5はその ような窒化物 LEDの構造例を示す図で、図 5 (a)は上面図、図 5 (b)は図 5 (a)の P— Q線の位置における断面図である。この図に示す窒化物 LED30では、サファイア基 板 31の表面に、窒化物半導体の結晶成長を阻害するマスク M力 図 1 (a)の P— Q 線に直交する方向に伸びるストライプ状のパターンに形成されて 、る。このマスク M は非晶質の酸ィ匕ケィ素で形成されており、膜厚 tが 0. 5 m、幅 w3が 3 mである。 隣接するマスク M間の間隔 w4も 3 μ mである。サファイア基板 31とマスク Mとがストラ イブ状の凹凸構造を構成しており、その上に、図示しないバッファ層を介して、 n型層 32および p型層 33からなる窒化物半導体層 Nが、該凹凸構造を埋めるように形成さ れている。 n型層 32は、サファイア基板 31上の、マスク Mに覆われていない領域から 成長したものであり、マスク Mの上面を覆った部分は横方向成長によって形成された 低転位密度領域となっている。上面側から見た素子の中央部にて、 p型層 33の一部 力 Sドライエッチングにより円形状に除去され、それによつて露出した n型層 32の表面 に、上面形状が円形の負電極 34が形成されている。 p型層 33上のほぼ全面には正 電極 35が形成されている。負電極 34を形成するためのドライエッチングとは別のェ 程で、窒化物半導体層 Nの外周領域がエッチングされており、それによつて、素子の 外周部にはサファイア基板 31の上面が露出している。このエッチングによって、窒化 物半導体層 Nの端面が傾斜面とされて 、る。窒化物半導体層 Nの端面が傾斜して 、 るために、窒化物半導体 N内をストライプ状の凹凸構造の長手方向に沿って伝播す る光が、この端面で反射されたときにその伝播方向を変える確率が更に高くなる。な お、窒化物 LED30では、サファイア基板 31の露出した表面と窒化物半導体層 Nの 端面とがなす角が鈍角（ Θ > 90度）となっているので、この端面で反射された光はサ ファイア基板 31側に向力つて進む確率が高くなる。従って、窒化物 LED30はフリツ プチップ実装して使用するのに適している。一方、この角が鋭角（ Θく 90度）となるよ うに、この端面を傾斜させることも可能であり、そのように構成した窒化物 LEDは、正 電極の表面側を光取出し面として使用することが好ましい。 In the nitride LED 10 shown in FIG. 1, the end surface of the nitride semiconductor layer N is perpendicular to the substrate plane of the sapphire substrate 11 (a plane perpendicular to the thickness direction of the substrate). Such a structure is not essential, and the end face of the nitride semiconductor layer may be inclined. FIG. 5 is a diagram showing an example of the structure of such a nitride LED, FIG. 5 (a) is a top view, and FIG. 5 (b) is a cross-sectional view at the position of the P—Q line in FIG. 5 (a). In the nitride LED 30 shown in this figure, the mask M force that inhibits the crystal growth of the nitride semiconductor on the surface of the sapphire substrate 31 has a striped pattern extending in the direction perpendicular to the P—Q line in Fig. 1 (a). Formed. This mask M is made of amorphous acid silicon, and has a film thickness t of 0.5 m and a width w3 of 3 m. The spacing w4 between adjacent masks M is also 3 μm. The sapphire substrate 31 and the mask M form a stripe-shaped concavo-convex structure, and a nitride semiconductor layer N composed of an n-type layer 32 and a p-type layer 33 is formed thereon via a buffer layer (not shown). It is formed so as to fill the uneven structure. The n-type layer 32 is grown from a region on the sapphire substrate 31 that is not covered by the mask M, and the portion covering the upper surface of the mask M is a low dislocation density region formed by lateral growth. Yes. At the center of the device as seen from the upper surface side, a partial force of the p-type layer 33 S is removed in a circular shape by dry etching, and the negative electrode with a circular upper surface shape is exposed on the exposed surface of the n- type layer 32 34 is formed. Almost all over p-type layer 33 is positive An electrode 35 is formed. The outer peripheral region of the nitride semiconductor layer N is etched in a process different from the dry etching for forming the negative electrode 34, so that the upper surface of the sapphire substrate 31 is exposed at the outer peripheral portion of the element. ing. By this etching, the end surface of the nitride semiconductor layer N is made an inclined surface. Since the end surface of the nitride semiconductor layer N is inclined, the light propagating along the longitudinal direction of the stripe-shaped uneven structure in the nitride semiconductor N is reflected in the direction of propagation when reflected by this end surface. The probability of changing is even higher. In the nitride LED 30, the angle formed by the exposed surface of the sapphire substrate 31 and the end face of the nitride semiconductor layer N is an obtuse angle (Θ> 90 degrees), and thus the light reflected by this end face is not supported. Probability of proceeding toward the fire board 31 side increases. Therefore, the nitride LED 30 is suitable for use with a flip chip mounted. On the other hand, it is possible to incline this end face so that this angle becomes an acute angle (Θ 90 degrees), and the nitride LED configured in this way uses the surface side of the positive electrode as the light extraction surface. It is preferable.
(その他の実施形態） (Other embodiments)
本発明の窒化物 LEDは、基板上に形成された窒化物半導体層が、基板側とは反 対側の主面にストライプ状の凹凸構造を有するものであってもよい。そのように構成し た窒化物 LEDの一例を図 9に示す。図 9に断面図を示す窒化物 LED50では、平坦 な表面を有する ZnO基板 51の上に、 p型層 53と n型層 52とからなる窒化物半導体層 N力 p型層 53側を基板側に向けて形成されており、窒化物半導体層 Nの上面 (n型 層 52側の表面）に、紙面と交わる方向に伸びる複数のストライプ状の溝 T50が平行 に形成されている。窒化物半導体層 Nの上面形状は方形であり、溝 T50の長手方向 は、該方形の 4つの辺の 、ずれとも約 45度の角度をなして!/、る。  In the nitride LED of the present invention, the nitride semiconductor layer formed on the substrate may have a striped uneven structure on the main surface opposite to the substrate side. Figure 9 shows an example of such a nitride LED. In the nitride LED 50 whose cross-sectional view is shown in FIG. 9, a nitride semiconductor layer composed of a p-type layer 53 and an n-type layer 52 on a ZnO substrate 51 having a flat surface. A plurality of stripe-like grooves T50 extending in the direction intersecting with the paper surface are formed in parallel on the upper surface of the nitride semiconductor layer N (the surface on the n-type layer 52 side). The top surface shape of the nitride semiconductor layer N is a square, and the longitudinal direction of the trench T50 forms an angle of about 45 degrees between the four sides of the square!
負電極 54は窒化物半導体層 Nの上面に形成されており、正電極 55は ZnO基板 5 1の裏面に形成されている。負電極 54は ITOカゝらなる透明電極であり、その表面上 の一部にはボンディングパッド（図示せず）が形成されている。図示していないが、ボ ンデイングパッドの表面を除く素子の上側表面 (n型層 52の露出面、負電極 54の表 面など）には、絶縁保護膜を形成することが望ましい。絶縁保護膜の材料としては、 酸化ケィ素、酸ィ匕ジルコニウム、酸ィ匕アルミニウム、酸化マグネシウム、フッ化マグネ シゥム、窒化ケィ素、酸窒化ケィ素などが例示される。 [0031] 窒化物 LED50を製造するには、まず、 MOVPE法を用いてサファイア基板上にバ ッファ層を介して n型層 52と p型層 53を順次成長させて積層し、窒化物半導体層 Nを 形成する。次に、 p型層 53の上面にウェハボンディングにより ZnO基板 51を接合する 。ウェハボンディングの詳細については、ジャパニーズ 'ジャーナル'ォブ 'アプライド' フイジタス，第 45卷，第 39号， 2006年，第 L1045〜L1047頁 (Japanese Journal of Applied Physics, Vol. 45, No. 39, 2006, pp. L1045— L1047)などを 参照することができる。接合後、サファイア基板をレーザリフトオフなどの方法により除 去し、 n型層 52の表面を露出させ、露出した n型層 52の表面にエッチングにより溝 T 50を形成する。溝 T50の形成により、窒化物半導体層 Nに、溝 T50の長手方向に伸 びる厚肉部 (相対的に大きな膜厚を有する部分)および薄肉部湘対的に小さな膜 厚を有する部分)が形成される。溝 T50の深さ (厚肉部の最大膜厚 t51と薄肉部の最 小膜厚 t52との差）は、光が窒化物半導体層 N内を溝 T50の長手方向に直交する方 向に伝播する状態が不安定ィ匕されるように、定める。そのためには、溝 T50の深さは 、 0. 2 m以上とすること力 S好ましく、 0. 5 m以上とすること力 Sより好ましく、 1 m以 上とすることが更に好ましい。また、溝 T50の深さは、厚肉部の最大膜厚 t51の 20% 以上 [ (t51— t52) Zt51≥0. 2]とすることが好ましい。溝 T50の形成後、 n型層 52 上への負電極 54の形成と、負電極 54上へのボンディングパッドの形成を行う。更に 、 ZnO基板 51の裏面に正電極 55を形成する。最後に、ウェハをダイシングして切断 し、平面形状が方形の LEDチップを得る。このとき、 n型層 52の表面に形成した溝 T 50の長手方向と、方形を構成する 4つの辺とが 45度の角度をなすようにする。 The negative electrode 54 is formed on the top surface of the nitride semiconductor layer N, and the positive electrode 55 is formed on the back surface of the ZnO substrate 51. The negative electrode 54 is a transparent electrode made of ITO, and a bonding pad (not shown) is formed on a part of the surface thereof. Although not shown, it is desirable to form an insulating protective film on the upper surface of the element (exposed surface of the n-type layer 52, the surface of the negative electrode 54, etc.) excluding the surface of the bonding pad. Examples of the material for the insulating protective film include silicon oxide, zirconium oxide, zirconium aluminum oxide, magnesium oxide, magnesium fluoride, nitride nitride, and nitride oxynitride. [0031] To manufacture the nitride LED 50, first, an n-type layer 52 and a p-type layer 53 are sequentially grown on a sapphire substrate via a buffer layer by using the MOVPE method, and then a nitride semiconductor layer is formed. N is formed. Next, a ZnO substrate 51 is bonded to the upper surface of the p-type layer 53 by wafer bonding. For details on wafer bonding, see Japanese 'Journal' of 'Applied' Physitas, Vol. 45, No. 39, 2006, pages L1045 to L1047 (Japanese Journal of Applied Physics, Vol. 45, No. 39, 2006 , pp. L1045—L1047). After bonding, the sapphire substrate is removed by a method such as laser lift-off to expose the surface of the n-type layer 52, and a groove T50 is formed by etching on the exposed surface of the n-type layer 52. By forming the trench T50, the nitride semiconductor layer N has a thick portion (a portion having a relatively large thickness) extending in the longitudinal direction of the trench T50 and a portion having a relatively small thickness). It is formed. The depth of the groove T50 (difference between the maximum thickness t51 of the thick portion and the minimum thickness t52 of the thin portion) is such that light propagates in the nitride semiconductor layer N in a direction perpendicular to the longitudinal direction of the trench T50. Determine that the state to be performed is unstable. For this purpose, the depth of the groove T50 is preferably 0.2 m or more, more preferably 0.5 m or more, and more preferably 1 m or more. The depth of the groove T50 is preferably 20% or more of the maximum thickness t51 of the thick part [(t51−t52) Zt51≥0.2]. After the formation of the trench T50, the negative electrode 54 is formed on the n-type layer 52, and the bonding pad is formed on the negative electrode 54. Further, a positive electrode 55 is formed on the back surface of the ZnO substrate 51. Finally, the wafer is diced and cut to obtain a square LED chip. At this time, the longitudinal direction of the groove T 50 formed on the surface of the n-type layer 52 and the four sides constituting the square form an angle of 45 degrees.
[0032] 窒化物 LED50では、窒化物半導体層 Nをコアとし、 ZnO基板 51を一方側のクラッ ド、 ITO力もなる負電極 54を他方側のクラッドとする導波路構造が形成される。素子 の上側表面に窒化物半導体層 Nよりも低い屈折率を有する絶縁保護膜を形成した 場合には、該絶縁保護膜も上記導波路構造の形成に寄与し得る。また、この窒化物 LED50を実装する際には、透光性の封止材料で LED50を被覆するが、この封止 材料も上記導波路構造の形成に寄与し得る。封止材料は、典型的には、シリコーン 榭脂、エポキシ榭脂などの榭脂材料である。気密封止する場合には気体物質が封止 材料となる。 [0033] 窒化物半導体層 Nは、溝 T50の長手方向に伸びる厚肉部および薄肉部が、交互 に並んだ構造を有している。すなわち、その膜厚が、溝 T50の長手方向に直交する 方向に沿って変動している。そのために、窒化物半導体層 N内を溝 T50の長手方向 に直交する方向に伝播する光成分は、窒化物半導体層 Nをコアとする導波路構造の 外に漏れ出し易い。つまり、素子外に取り出される確率が高い。一方、窒化物半導体 層 Nの膜厚は、溝 T50の長手方向については一定であり、そのために、窒化物半導 体層 N内をこの方向に沿って伝播する光成分は、窒化物半導体層 Nをコアとする導 波路構造内に強く閉じ込められる。しかし、溝 T50の長手方向と方形の窒化物半導 体層 Nの 4つの辺のそれぞれとがなす角度が 45度となっているので、溝 T50の長手 方向に伝播する光成分は、窒化物半導体層 Nの端面での反射によって、その伝播 方向を溝 T50の長手方向に直交する方向に変える。従って、窒化物 LED50では、 窒化物半導体層 N内に強く閉じ込められた状態力 脱することができない光成分が 発生せず、そのために、発光部で生じた光が素子外に取り出される確率が高くなる。 In the nitride LED 50, a waveguide structure is formed in which the nitride semiconductor layer N is a core, the ZnO substrate 51 is a cladding on one side, and the negative electrode 54 also having an ITO force is the cladding on the other side. When an insulating protective film having a refractive index lower than that of the nitride semiconductor layer N is formed on the upper surface of the element, the insulating protective film can also contribute to the formation of the waveguide structure. Further, when the nitride LED 50 is mounted, the LED 50 is covered with a translucent sealing material, and this sealing material can also contribute to the formation of the waveguide structure. The sealing material is typically a resin material such as silicone resin or epoxy resin. In the case of hermetic sealing, a gaseous substance becomes the sealing material. [0033] The nitride semiconductor layer N has a structure in which thick portions and thin portions extending in the longitudinal direction of the trench T50 are alternately arranged. That is, the film thickness varies along the direction orthogonal to the longitudinal direction of the groove T50. Therefore, the light component propagating in the nitride semiconductor layer N in the direction perpendicular to the longitudinal direction of the trench T50 is likely to leak out of the waveguide structure having the nitride semiconductor layer N as a core. That is, the probability of being taken out of the element is high. On the other hand, the film thickness of the nitride semiconductor layer N is constant in the longitudinal direction of the trench T50. Therefore, the light component propagating in the nitride semiconductor layer N along this direction is the nitride semiconductor layer N. It is strongly confined in the waveguide structure with N as the core. However, since the angle between the longitudinal direction of the groove T50 and each of the four sides of the rectangular nitride semiconductor layer N is 45 degrees, the light component propagating in the longitudinal direction of the groove T50 is nitride. Due to reflection at the end face of the semiconductor layer N, the propagation direction is changed to a direction perpendicular to the longitudinal direction of the trench T50. Therefore, in the nitride LED 50, a state component that is strongly confined in the nitride semiconductor layer N is not generated, and thus there is a high probability that light generated in the light emitting portion is extracted outside the device. Become.
[0034] この実施形態において、窒化物半導体層の上面に形成するストライプ状の凹凸構 造は、当該凹凸構造の形成によって、光が窒化物半導体層内を当該凹凸構造の長 手方向に直交する方向に伝播する状態が不安定ィ匕されるものであればょ 、。そのよ うな凹凸構造は、複数の平行なストライプ状の溝カゝら構成されるものに限定されるも のではなぐ例えば、平坦面にストライプ状の溝がひとつだけ加工された構造や、ある いは、溝に代えて、平坦面上にストライプ状のリッジがひとつまたは複数、形成された 構造であってもよい。ストライプ状の凹凸構造を構成する溝やリッジの断面形状は、 図 3に例示した形状の他、種々の形状とすることができる。溝やリッジの幅および断面 形状、溝の深さ、リッジの高さなどには、長手方向に沿って変動があってもよい。溝や リッジは、その一端または両端が、窒化物半導体層の端部に達しないものであっても よい。窒化物半導体層 Nの上面形状を方形状とする場合、その 4つの辺のそれぞれ と、ストライプ状の凹凸構造の長手方向とがなす角は、約 45度 (40度〜 50度）とする ことが最も好ましいが、他の角度であってもよい。好ましい範囲は、 30度〜 60度であ る。 4辺のうち、いずれかの辺の方向と、ストライプ状の凹凸構造の長手方向とがなす 角が 10度未満では、これらの方向が実質的に平行であるために、本発明による光取 出し効率の改善効果は望めなくなる。 In this embodiment, the stripe-shaped uneven structure formed on the upper surface of the nitride semiconductor layer has a structure in which light is perpendicular to the longitudinal direction of the uneven structure by forming the uneven structure. If the state propagating in the direction is unstable, Such a concavo-convex structure is not limited to a structure composed of a plurality of parallel striped groove caps, for example, a structure in which only one striped groove is processed on a flat surface, or Instead of the groove, a structure in which one or a plurality of striped ridges are formed on a flat surface may be used. The cross-sectional shape of the grooves and ridges constituting the striped uneven structure can be various shapes in addition to the shape illustrated in FIG. The width and cross-sectional shape of the groove or ridge, the depth of the groove, the height of the ridge, etc. may vary along the longitudinal direction. The groove or ridge may have one or both ends that do not reach the end of the nitride semiconductor layer. When the top surface of nitride semiconductor layer N is rectangular, the angle between each of its four sides and the longitudinal direction of the striped relief structure should be approximately 45 degrees (40 degrees to 50 degrees). Is most preferred, but other angles may be used. A preferred range is 30 to 60 degrees. If the angle formed by any one of the four sides and the longitudinal direction of the striped uneven structure is less than 10 degrees, these directions are substantially parallel. The effect of improving the delivery efficiency cannot be expected.
[0035] 変形実施形態として、窒化物 LED50にお 、て、負電極 54を ITOで形成する代わり に、 Ti (チタン)および A1 (アルミニウム）を積層してなる反射性の電極とすることがで きる。このように構成した窒化物 LEDでは、窒化物半導体層をコアとし、 ZnO基板を 一方のクラッド、反射性の負電極を他方のクラッドとする導波路構造が形成される。こ の窒化物 LEDでは、負電極が反射膜として作用するので、 ZnO基板側力ゝら光を取り 出せるように、正電極を ZnO基板の裏面上に部分的に形成する。  As a modified embodiment, instead of forming the negative electrode 54 of ITO in the nitride LED 50, a reflective electrode formed by laminating Ti (titanium) and A1 (aluminum) can be used. wear. In the nitride LED configured as described above, a waveguide structure is formed in which the nitride semiconductor layer is the core, the ZnO substrate is one clad, and the reflective negative electrode is the other clad. In this nitride LED, since the negative electrode acts as a reflection film, the positive electrode is partially formed on the back surface of the ZnO substrate so that light can be extracted from the ZnO substrate side force.
[0036] 他の変形実施形態として、窒化物 LED50において、 ZnO基板 51をウェハボンディ ングにより接合する代わりに、ハンダを用いて接合することができる。このとき、好まし くは、 p型層の表面に金属製の反射膜を形成したうえで、 ZnO基板の接合を行う。こ のように構成した窒化物 LEDでは、窒化物半導体層をコアとし、 ITOカゝらなる負電極 を一方のクラッド、金属製の反射膜を他方のクラッドとする導波路構造が形成される。 実施例  As another modified embodiment, in the nitride LED 50, the ZnO substrate 51 can be bonded using solder instead of bonding by wafer bonding. At this time, preferably, a ZnO substrate is bonded after forming a metallic reflective film on the surface of the p-type layer. In the nitride LED configured as described above, a waveguide structure is formed in which a nitride semiconductor layer is a core, a negative electrode made of ITO is one clad, and a metal reflective film is the other clad. Example
[0037] 図 6に示す窒化物 LEDの作製例を以下に述べる。  A fabrication example of the nitride LED shown in FIG. 6 is described below.
図 6は、本発明の一実施形態に係る窒化物 LEDの構造を示す図で、図 6 (a)は上 面図、図 6 (b)は図 6 (a)の P— Q線の位置における断面図である。図 6において、 41 はサファイア基板であり、その結晶成長面には、 P— Q線に直交する方向に伸びるス トライプ状の溝 T40が、複数、平行に形成されている。溝 T40の深さ dは 1 μ m、幅 w 1は約 3 μ m、溝の幅方向の凹凸の周期 pは 6 μ mである。 42は n型層であって、 42a は Siドープ GaN力もなる層厚 3 m (基板 41の凸部上の厚さ）の n型コンタクト層であ り、 42bはアンドープ AlGaNからなる層厚 lOOnmの n型クラッド層であり、 42cは層厚 3nmのアンドープ In Ga N (0<x≤ 1)井戸層と層厚 10nmの Siドープ In Ga _ N (0≤y<x)障壁層とを各 6層交互に積層してなる MQW構造の活性層である。 n型コ ンタクト層 42aは、溝 T40に入り込むように、かつ、その上面が平坦面となるように、形 成されている。 43は p型層であって、 43aは層厚 30nmの Mgドープ AlGaNからなる p 型クラッド層であり、 43bは Mgドープ GaNからなる層厚 150nmの p型コンタクト層で ある。 44は n型層 42に電流を注入するための負電極であり、 45は p型層 43に電流を 注入するための正電極である。 46は正電極 45上に形成されたボンディング 'パッド である。図 6 (a)に示すように、上面視したときのチップの形状は正方形であり、窒化 物半導体層 Nの形状も同様である。 Fig. 6 shows the structure of a nitride LED according to an embodiment of the present invention. Fig. 6 (a) is a top view, and Fig. 6 (b) is the position of the PQ line in Fig. 6 (a). FIG. In FIG. 6, reference numeral 41 denotes a sapphire substrate, and a plurality of strip-like grooves T40 extending in a direction perpendicular to the PQ line are formed in parallel on the crystal growth surface. The depth d of the groove T40 is 1 μm, the width w 1 is about 3 μm, and the period p of the unevenness in the width direction of the groove is 6 μm. 42 is an n-type layer, 42a is an n-type contact layer with a thickness of 3 m (thickness on the convex part of the substrate 41) that also has Si-doped GaN force, and 42b is an undoped AlGaN layer thickness of lOOnm 42c is an n-type cladding layer, which consists of an undoped InGaN (0 <x≤1) well layer with a thickness of 3 nm and a Si-doped InGa_N (0≤y <x) barrier layer with a thickness of 10 nm. It is an active layer with an MQW structure in which layers are stacked alternately. The n-type contact layer 42a is formed so as to enter the trench T40 and to have a flat upper surface. 43 is a p-type layer, 43a is a p-type cladding layer made of Mg-doped AlGaN with a thickness of 30 nm, and 43b is a p-type contact layer made of Mg-doped GaN with a thickness of 150 nm. 44 is a negative electrode for injecting current into the n-type layer 42, and 45 is a positive electrode for injecting current into the p-type layer 43. 46 is the bonding pad formed on the positive electrode 45 It is. As shown in FIG. 6 (a), the shape of the chip when viewed from above is a square, and the shape of the nitride semiconductor layer N is the same.
[0038] 図 6に示す窒化物 LEDを、次の手順により作製した。 A nitride LED shown in FIG. 6 was produced by the following procedure.
〔サファイア基板の加工〕  [Sapphire substrate processing]
C面サファイア基板の一主面上に、フォトレジストによるストライプ状のマスクパター ンを形成した。ストライプ状のマスクの幅は 3 μ m、周期（マスクの幅 +基板露出部の 幅）は 6 μ m、ストライプの長手方向はサファイアの〈1 100〉方向（基板上に成長す る窒化物半導体結晶の〈11— 20〉方向となる）とした。該マスク上から反応性イオンェ ツチングを行うことにより、基板露出部に深さ 1 μ mの溝 Τ40を形成し、結晶成長面に ストライプ状の凹凸パターンが形成されたサファイア基板 41を得た。  A stripe mask pattern made of photoresist was formed on one main surface of the C-plane sapphire substrate. The stripe mask width is 3 μm, the period (mask width + substrate exposed part width) is 6 μm, and the longitudinal direction of the stripe is the sapphire <1 100> direction (a nitride semiconductor grown on the substrate) It is the <11-20> direction of the crystal). Reactive ion etching was performed on the mask to form a sapphire substrate 41 in which a groove 40 having a depth of 1 μm was formed in the exposed portion of the substrate and a stripe-shaped uneven pattern was formed on the crystal growth surface.
[0039] 〔積層体の形成〕 [Formation of laminate]
フォトレジストを除去後、 MOVPE装置に上記サファイア基板 41を装着し、水素雰 囲気下で 1100°Cまで昇温して、表面のクリーニングを行った。  After removing the photoresist, the sapphire substrate 41 was attached to a MOVPE apparatus, and the temperature was raised to 1100 ° C. in a hydrogen atmosphere to clean the surface.
次に、基板温度を 500°Cまで下げ、 3族原料としてトリメチルガリウム (TMG)、 5族 原料としてアンモニアを供給し、低温成長バッファ層を 30nm成長させた。  Next, the substrate temperature was lowered to 500 ° C., trimethylgallium (TMG) was supplied as a Group 3 source material, and ammonia was supplied as a Group 5 source material to grow a low temperature growth buffer layer by 30 nm.
次に、基板を 1000°Cに昇温し、 TMG、シラン、アンモニアを供給して、上面が平 坦な n型コンタクト層 42aを、サファイア基板 41の凸部 (溝 T40が形成されて 、な 、部 分）上の厚さが 3 μ mとなるように成長させた。  Next, the temperature of the substrate is raised to 1000 ° C., TMG, silane, and ammonia are supplied, and the n-type contact layer 42a having a flat top surface is formed on the convex portion of the sapphire substrate 41 (groove T40 is formed. , Part) was grown to a thickness of 3 μm.
その後、シランの供給を停止する一方、トリメチルアルミニウム (TMA)を供給し、 n 型クラッド層 42bを lOOnm成長させた。  Then, while the supply of silane was stopped, trimethylaluminum (TMA) was supplied, and the n-type cladding layer 42b was grown lOOnm.
n型クラッド層 42bの成長後、基板温度を 750°Cに下げ、インジウム原料にはトリメチ ルインジウム (TMI)を用いて、井戸層と障壁層とを交互に成長し、 MQW構造の活 性層 42cを形成した。井戸層の成長時は、発光波長が 405nmとなるように、 TMIの 供給量を調節した。  After the growth of the n-type cladding layer 42b, the substrate temperature is lowered to 750 ° C., and trimethylindium (TMI) is used as the indium raw material, so that well layers and barrier layers are grown alternately, and an MQW structure active layer 42c was formed. During the growth of the well layer, the TMI supply was adjusted so that the emission wavelength was 405 nm.
次に、基板を 1000°Cに昇温し、トリメチルアルミニウム（TMA)、 TMG、アンモニア 、ビスシクロペンタジェ-ルマグネシウム（Cp Mg)を供給し、 Al Ga Nからなる p  Next, the temperature of the substrate is raised to 1000 ° C., and trimethylaluminum (TMA), TMG, ammonia, and biscyclopentagel magnesium (Cp Mg) are supplied, and p of AlGaN is used.
2 0. 2 0. 8 型クラッド層 43aを 30nm成長させた。  A 2 0. 2 0. 8 type cladding layer 43a was grown by 30 nm.
続けて、 TMAの供給を停止して、 p型コンタクト層 43bを 150nm成長させた後、ァ ンモユア雰囲気中で基板温度を室温まで降下させ、ウェハを MOVPE装置力 取り 出した。 Subsequently, the supply of TMA is stopped and the p-type contact layer 43b is grown to 150 nm. The substrate temperature was lowered to room temperature in an atmosphere, and the wafer was removed from the MOVPE equipment.
[0040] 〔電極形成〕 [0040] [Electrode formation]
上記工程で得られたウェハに対して、アニーリング処理、反応性イオンエッチングに よる負電極形成面の露出、負電極 44の形成、正電極 45の形成、ボンディング 'パッ ド 46の形成、電極の熱処理を順次行った。  The wafer obtained in the above process is annealed, exposed negative electrode formation surface by reactive ion etching, negative electrode 44 formation, positive electrode 45 formation, bonding 'pad 46 formation, electrode heat treatment Were performed sequentially.
このとき、サファイア基板 41の結晶成長面のストライプ状溝 T40の長手方向に対し て、負電極 44、正電極 45、ボンディング 'パッド 46の形状'配置力 図 6に示す通りと なるように、これらをパターユングした。  At this time, the negative electrode 44, the positive electrode 45, and the bonding 'pad 46 shape' arrangement force with respect to the longitudinal direction of the stripe-shaped groove T40 on the crystal growth surface of the sapphire substrate 41 are as shown in FIG. I put a pattern.
負電極 44は、蒸着法を用いて、 n型コンタクト層 42aに接する側から順に、膜厚 30 nmの Ti (チタン）と、膜厚 300nmの A1 (アルミニウム）を積層することにより形成した。 負電極の直径は 100 μ mとした。  The negative electrode 44 was formed by laminating Ti (titanium) with a film thickness of 30 nm and A1 (aluminum) with a film thickness of 300 nm in this order from the side in contact with the n-type contact layer 42a by vapor deposition. The diameter of the negative electrode was 100 μm.
正電極 45は、蒸着法を用いて、 p型コンタクト層 43bに接する側力も順に、膜厚 20 nmの Ni (ニッケル）と、膜厚 lOOnmの Au (金）を積層することにより形成した。正電 極 45には、 8 mX 8 mの正方形の窓部（開口部）を行列状に形成し、 p型コンタク ト層 43b上に正電極 45が広がった領域の面積に占める窓部の面積比が約 70%の、 透光性電極とした。  The positive electrode 45 was formed by sequentially depositing Ni (nickel) with a thickness of 20 nm and Au (gold) with a thickness of lOOnm in order of the side force in contact with the p-type contact layer 43b by vapor deposition. On the positive electrode 45, square windows (openings) of 8 m x 8 m are formed in a matrix, and the area of the window occupies the area of the positive electrode 45 spreading on the p-type contact layer 43b. A translucent electrode having a ratio of about 70% was obtained.
ボンディング 'パッド 46は、 Tiと Auを積層することにより形成し、その直径は 100 mとした。  Bonding 'Pad 46 was formed by laminating Ti and Au, and its diameter was 100 m.
[0041] 〔チップへの分断〕 [0041] [Divide into chips]
電極形成の後、サファイア基板 41の下面を研磨して、その厚さを 100 mまで薄く した後、該研磨面にスクライブ線を鄞書き、ブレーキングを行って、 350 m角の正 方形状のチップを得た。  After electrode formation, the lower surface of the sapphire substrate 41 is polished to a thickness of 100 m, and then a scribe line is written on the polished surface and braking is performed to form a 350 m square square shape. I got a chip.
[0042] (比較例） [0042] (Comparative example)
素子を上面視したときに、サファイア基板の結晶成長面に形成されたストライプ状溝 の長手方向が、方形の窒化物半導体層の 4辺のうちの 2辺と平行となるようにしたこと を除き、実施例と同様にして、窒化物 LEDを作製した。  Except that when the device is viewed from above, the longitudinal direction of the stripe-shaped grooves formed on the crystal growth surface of the sapphire substrate is parallel to two of the four sides of the rectangular nitride semiconductor layer. A nitride LED was fabricated in the same manner as in the example.
[0043] (評価） 実施例および比較例で得た窒化物 LEDのチップ (ベアチップ)を、サファイア基板 側を下側にしてリードフレーム上に固定し、ワイヤボンディングを行った後、電流値 20 mAで通電を行い、そのときの出力を積分球を用いて測定したところ、実施例の窒ィ匕 物 LEDの出力は、比較例の窒化物 LEDの出力の約 1. 2倍であった。 [0043] (Evaluation) The nitride LED chips (bare chips) obtained in the examples and comparative examples were fixed on the lead frame with the sapphire substrate side down, and after wire bonding, current was applied at a current value of 20 mA. When the output was measured using an integrating sphere, the output of the nitride LED of the example was about 1.2 times the output of the nitride LED of the comparative example.
[0044] 本発明は上記に明示的に示した実施形態に限定されるものではなぐ発明の趣旨 を逸脱しな 、範囲で種々の変形が可能である。 The present invention is not limited to the embodiments explicitly described above, and various modifications can be made without departing from the spirit of the invention.
産業上の利用可能性  Industrial applicability
[0045] ストライプ状の凹凸構造を含む窒化物半導体発光ダイオード素子における光取出 し効率の改善を図ることによって、照明装置用の光源に適した、発光効率の高い窒 化物半導体発光ダイオード素子を提供することができる。 [0045] By improving the light extraction efficiency of a nitride semiconductor light-emitting diode element including a striped uneven structure, a nitride semiconductor light-emitting diode element having high light emission efficiency suitable for a light source for an illumination device is provided. be able to.
本出願は、日本で出願された特願 2005— 324873、特願 2006— 196469、特願 2006— 302156を基礎としており、それらの内容は本明細書に全て包含される。  This application is based on Japanese Patent Application Nos. 2005-324873, 2006-196469 and 2006-302156 filed in Japan, the contents of which are incorporated in full herein.

Claims

請求の範囲 The scope of the claims
[1] 表面にストライプ状の凹凸構造を有する透明基板と、該凹凸構造を埋めるように形 成された窒化物半導体層とを有し、  [1] A transparent substrate having a striped uneven structure on the surface, and a nitride semiconductor layer formed to fill the uneven structure,
前記窒化物半導体層は、前記透明基板よりも高い屈折率を有し、かつ、発光部を 含んでおり、  The nitride semiconductor layer has a refractive index higher than that of the transparent substrate, and includes a light emitting part,
当該素子を上面視したとき、前記窒化物半導体層の形状が方形であり、かつ、前 記ストライプ状の凹凸構造の長手方向が、前記方形の窒化物半導体層の 4つの辺の Vヽずれとも平行でな ヽ、窒化物半導体発光ダイオード素子。  When the element is viewed from the top, the shape of the nitride semiconductor layer is square, and the longitudinal direction of the striped uneven structure is a deviation of V between the four sides of the square nitride semiconductor layer. Nitride semiconductor light-emitting diode elements that are not parallel.
[2] 当該素子を上面視したとき、前記窒化物半導体層の形状が方形であり、かつ、前 記ストライプ状の凹凸構造の長手方向が、前記方形の窒化物半導体層の 4つの辺の V、ずれに対しても約 45度の角度をなして 、る、請求項 1に記載の窒化物半導体発光 ダイオード素子。 [2] When the element is viewed from above, the shape of the nitride semiconductor layer is square, and the longitudinal direction of the striped uneven structure is V on the four sides of the square nitride semiconductor layer. The nitride semiconductor light-emitting diode device according to claim 1, wherein the nitride semiconductor light-emitting diode device forms an angle of about 45 degrees with respect to the deviation.
[3] 前記窒化物半導体層の端面が傾斜している、請求項 1または 2に記載の窒化物半 導体発光ダイオード素子。  [3] The nitride semiconductor light-emitting diode element according to claim 1 or 2, wherein an end face of the nitride semiconductor layer is inclined.
[4] 前記透明基板が単結晶基板であり、その上に、前記窒化物半導体層がェピタキシ ャル成長している、請求項 1〜3のいずれかに記載の窒化物半導体発光ダイオード 素子。 4. The nitride semiconductor light-emitting diode device according to any one of claims 1 to 3, wherein the transparent substrate is a single crystal substrate, and the nitride semiconductor layer is epitaxially grown thereon.
[5] 前記透明基板がガラス基板である、請求項 1〜3のいずれかに記載の窒化物半導 体発光ダイオード素子。  5. The nitride semiconductor light-emitting diode element according to any one of claims 1 to 3, wherein the transparent substrate is a glass substrate.
[6] 前記凹凸構造が、前記透明基板の表面に形成された複数のストライプ状の溝から 構成されている、請求項 1〜5のいずれかに記載の窒化物半導体発光ダイオード素 子。 6. The nitride semiconductor light-emitting diode element according to any one of claims 1 to 5, wherein the concavo-convex structure is composed of a plurality of stripe-shaped grooves formed on the surface of the transparent substrate.
[7] 前記凹凸構造が、前記透明基板と、その表面に形成された複数のストライプ状のマ スクと、力 構成されている、請求項 1〜3のいずれかに記載の窒化物半導体発光ダ ィオード素子。  [7] The nitride semiconductor light emitting diode according to any one of [1] to [3], wherein the concavo-convex structure is composed of the transparent substrate, a plurality of stripe-shaped masks formed on the surface thereof, and a force. Diode element.
[8] 発光部を含む窒化物半導体層をコアとする導波路構造を有しており、  [8] It has a waveguide structure having a nitride semiconductor layer including a light emitting portion as a core,
前記窒化物半導体層は、一方向に伸びる厚肉部および薄肉部が交互に並んだ構造 を有しており、 当該素子を上面視したとき、前記窒化物半導体層の形状が方形であり、 The nitride semiconductor layer has a structure in which thick portions and thin portions extending in one direction are alternately arranged, When the element is viewed from above, the shape of the nitride semiconductor layer is square,
前記厚肉部および薄肉部の伸長方向が前記方形の窒化物半導体層の 4つの辺の Vヽずれとも平行でな ヽ、窒化物半導体発光ダイオード素子。  A nitride semiconductor light-emitting diode element, wherein the extending direction of the thick part and the thin part is not parallel to the V deviation of the four sides of the rectangular nitride semiconductor layer.
[9] 前記厚肉部および薄肉部の伸長方向が、前記方形の窒化物半導体層の 4つの辺 のいずれに対しても約 45度の角度をなしている、請求項 8記載の窒化物半導体発光 ダイオード素子。 9. The nitride semiconductor according to claim 8, wherein the extending direction of the thick part and the thin part forms an angle of about 45 degrees with respect to any of the four sides of the rectangular nitride semiconductor layer. Light emitting diode element.
[10] 前記厚肉部の最大膜厚と前記薄肉部の最小膜厚との差が 0. 2 m以上である、請 求項 8記載の窒化物半導体発光ダイオード素子。  [10] The nitride semiconductor light-emitting diode element according to claim 8, wherein the difference between the maximum thickness of the thick portion and the minimum thickness of the thin portion is 0.2 m or more.
[11] 前記厚肉部の最大膜厚と前記薄肉部の最小膜厚との差が、該厚肉部の最大膜厚 の 20%以上である、請求項 10記載の窒化物半導体発光ダイオード素子。  11. The nitride semiconductor light-emitting diode element according to claim 10, wherein a difference between the maximum thickness of the thick portion and the minimum thickness of the thin portion is 20% or more of the maximum thickness of the thick portion. .
[12] 前記導波路構造が、前記窒化物半導体層と、該窒化物半導体層の一方の主面側 に位置する該窒化物半導体層よりも低い屈折率を有する透光性の第 1の物質と、該 窒化物半導体層の他方の主面側に位置する、該窒化物半導体層よりも低い屈折率 を有する透光性の第 2の物質とから構成されている、請求項 8記載の窒化物半導体 発光ダイオード素子。  [12] The light-transmitting first substance, wherein the waveguide structure has a refractive index lower than that of the nitride semiconductor layer and the nitride semiconductor layer located on one main surface side of the nitride semiconductor layer And a light-transmitting second substance having a refractive index lower than that of the nitride semiconductor layer, which is located on the other main surface side of the nitride semiconductor layer. Semiconductor light-emitting diode element.
[13] 前記第 1の物質が透明基板を含み、前記第 2の物質が、透明導電性酸化物からな る電極、絶縁保護膜または封止材料カゝら選ばれるひとつ以上を含む、請求項 12記 載の窒化物半導体発光ダイオード素子。  [13] The first substance includes a transparent substrate, and the second substance includes one or more selected from an electrode, an insulating protective film, and a sealing material made of a transparent conductive oxide. 12. The nitride semiconductor light-emitting diode device according to 12.
[14] 前記導波路構造が、前記窒化物半導体層と、該窒化物半導体層の一方の主面側 に位置する該窒化物半導体層よりも低!、屈折率を有する透光性の第 3の物質と、該 窒化物半導体層の他方の主面側に位置する金属製の反射膜とから構成されている 、請求項 8記載の窒化物半導体発光ダイオード素子。  [14] The waveguide structure is lower than the nitride semiconductor layer and the nitride semiconductor layer located on one main surface side of the nitride semiconductor layer, and has a light-transmitting third property having a refractive index. 9. The nitride semiconductor light-emitting diode element according to claim 8, wherein the nitride semiconductor light-emitting diode element is composed of:
[15] 前記第 3の物質が透明基板を含む、請求項 14記載の窒化物半導体発光ダイォー ド素子。  15. The nitride semiconductor light emitting diode device according to claim 14, wherein the third substance includes a transparent substrate.
[16] 前記第 3の物質が、透明導電性酸化物からなる電極、絶縁保護膜または封止材料 力も選ばれるひとつ以上を含む、請求項 14記載の窒化物半導体発光ダイオード素 子。  16. The nitride semiconductor light-emitting diode device according to claim 14, wherein the third substance includes one or more of an electrode made of a transparent conductive oxide, an insulating protective film, or a sealing material force.
[17] 発光部を含む窒化物半導体層を有し、 前記窒化物半導体層が、少なくともその一方の主面に、ストライプ状の凹凸構造を 有しており、そのために、光が該窒化物半導体層内を該凹凸構造の長手方向に直 交する方向に伝播する状態が不安定化されており、 [17] having a nitride semiconductor layer including a light emitting portion, The nitride semiconductor layer has a striped concavo-convex structure on at least one main surface thereof. Therefore, light passes through the nitride semiconductor layer in a direction perpendicular to the longitudinal direction of the concavo-convex structure. The state of propagation is destabilized,
当該素子を上面視したとき、前記窒化物半導体層の形状が方形であり、 前記凹凸構造の長手方向が、前記方形の窒化物半導体層の 4つの辺のいずれと も平行でない、窒化物半導体発光ダイオード素子。  When the element is viewed from above, the shape of the nitride semiconductor layer is square, and the longitudinal direction of the concavo-convex structure is not parallel to any of the four sides of the square nitride semiconductor layer. Diode element.
[18] 前記凹凸構造の長手方向が、前記方形の窒化物半導体層の 4つの辺のいずれに 対しても約 45度の角度をなしている、請求項 17記載の窒化物半導体発光ダイォー ド素子。 18. The nitride semiconductor light-emitting diode device according to claim 17, wherein a longitudinal direction of the concavo-convex structure forms an angle of about 45 degrees with respect to any of the four sides of the rectangular nitride semiconductor layer. .
[19] 前記凹凸構造が、前記窒化物半導体層の一方の主面に形成された、少なくともひ とつのストライプ状の溝を含んで 、る、請求項 17記載の窒化物半導体発光ダイォー ド素子。  19. The nitride semiconductor light-emitting diode device according to claim 17, wherein the concavo-convex structure includes at least one stripe-shaped groove formed on one main surface of the nitride semiconductor layer.
[20] 前記凹凸構造が、前記窒化物半導体層の一方の主面に形成された、少なくともひ とつのストライプ状のリッジを含んで 、る、請求項 17記載の窒化物半導体発光ダイォ ード素子。  20. The nitride semiconductor light-emitting diode device according to claim 17, wherein the concavo-convex structure includes at least one stripe-shaped ridge formed on one main surface of the nitride semiconductor layer. .
PCT/JP2006/322338 2005-11-09 2006-11-09 Nitride semiconductor light-emitting diode device WO2007055262A1 (en)

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