WO2014192428A1 - Élément émetteur de lumière à semi-conducteurs au nitrure et procédé pour fabriquer ce dernier - Google Patents

Élément émetteur de lumière à semi-conducteurs au nitrure et procédé pour fabriquer ce dernier Download PDF

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WO2014192428A1
WO2014192428A1 PCT/JP2014/060240 JP2014060240W WO2014192428A1 WO 2014192428 A1 WO2014192428 A1 WO 2014192428A1 JP 2014060240 W JP2014060240 W JP 2014060240W WO 2014192428 A1 WO2014192428 A1 WO 2014192428A1
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layer
nitride semiconductor
contact
light emitting
contact layer
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PCT/JP2014/060240
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English (en)
Japanese (ja)
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晃平 三好
月原　政志
竹内　哲也
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ウシオ電機株式会社
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Priority claimed from JP2013115796A external-priority patent/JP5974980B2/ja
Priority claimed from JP2013157290A external-priority patent/JP6025058B2/ja
Priority claimed from JP2013163640A external-priority patent/JP2015032798A/ja
Application filed by ウシオ電機株式会社 filed Critical ウシオ電機株式会社
Priority to KR1020157034270A priority Critical patent/KR20160003845A/ko
Publication of WO2014192428A1 publication Critical patent/WO2014192428A1/fr

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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
    • H01L33/26—Materials of the light emitting region
    • H01L33/30—Materials of the light emitting region containing only elements of Group III and Group V of the Periodic Table
    • H01L33/32—Materials of the light emitting region containing only elements of Group III and Group V of the Periodic Table containing nitrogen
    • H01L33/325—Materials of the light emitting region containing only elements of Group III and Group V of the Periodic Table containing nitrogen characterised by the doping materials
    • 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
    • H01L33/36—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 electrodes
    • H01L33/40—Materials therefor

Definitions

  • the present invention relates to a nitride semiconductor light emitting device having a light emitting layer between an n-type nitride semiconductor layer and a p-type nitride semiconductor layer, and a method for manufacturing the same.
  • a conventional nitride semiconductor light emitting device has a structure in which a p-side contact layer overdoped with Mg, a p-type nitride semiconductor layer doped with Mg, a light emitting layer, and an n-type nitride semiconductor layer doped with Si are sequentially stacked. is doing.
  • the p-side contact layer is heavily doped in order to improve the contact property with the electrode formed on the p-side contact layer and realize ohmic connection. More specifically, a configuration is adopted in which ITO or Ni, which is a degenerate semiconductor, is provided as a contact electrode on the p-side contact layer, and a metal electrode (Ag, Al) is further provided on the contact electrode.
  • ITO or Ni which is a degenerate semiconductor
  • the contact electrode made of ITO or Ni used for making contact with the p-side contact layer doped with Mg at a high concentration absorbs light of a short wavelength. Therefore, there is a problem that the light emission intensity in the short wavelength region is lowered. For example, since ITO has an absorption edge near 365 nm and Ni has an absorption edge on the longer wavelength side than ITO, there is a strong concern that the emission intensity in the ultraviolet wavelength region is reduced.
  • the present invention realizes a nitride semiconductor light emitting device having contact characteristics equivalent to those of a conventional nitride semiconductor light emitting device without using a contact electrode formed of a material such as ITO or Ni, thereby transmitting in the ultraviolet wavelength region.
  • the object is to realize an element with a high rate.
  • a metal electrode can be formed directly on the p-type contact layer without providing a contact electrode made of ITO or Ni, the above problem of absorption of short wavelength light by the material forming the contact electrode is solved.
  • the present inventor has made an excellent study between a semiconductor layer and a metal electrode by providing a contact layer (semiconductor layer) by a method different from that of a conventional nitride semiconductor light-emitting device, without providing a contact electrode, through intensive research. Thus, a nitride semiconductor light emitting device exhibiting contact characteristics has been realized.
  • the second impurity material doped into the second contact layer (one or more of Zn, Cd, Be, Sr, Ca and C) is generally doped when forming the p-type nitride semiconductor layer.
  • a deeper impurity level is formed than the material (Mg). More specifically, the activation energy of the second impurity material doped to the second contact layer is higher than the activation energy of the first impurity material doped to the first contact layer.
  • the second impurity material may be selected. For example, when both the first contact layer and the second contact layer are made of GaN, the activation energy of Mg is 140 meV, whereas Zn is 350 meV.
  • the second contact layer since a deep level is formed by the second impurity material, it is not ionized even if an impurity is added to the semiconductor layer beyond the effective state density, and carriers are not in the valence band but between the sites formed by the impurity.
  • the hopping conduction When a voltage is applied between the elements, electrons that are trapped in a deep level and cannot move are thermally excited at a level capable of tunneling under the influence of an electric field, and then tunnel hopping. It is considered that the carrier can move with high efficiency.
  • Zn can be suitably used as the second impurity material.
  • better contact characteristics can be realized by setting the concentration of Zn to be doped to 1 ⁇ 10 19 / cm 3 to 5 ⁇ 10 21 / cm 3 .
  • the impurity concentration it is necessary to narrow the interval between the levels, so that it is preferable to set the impurity concentration to be equal to or higher than the effective state density.
  • Zn doped in the second contact layer forms a deeper impurity level than a generally doped material (Mg) when forming the p-type nitride semiconductor layer.
  • the Zn concentration of the second contact layer is higher than the Mg concentration of the first contact layer, the output of the light emitting element is reduced by continuous driving.
  • the Zn doped in the second contact layer is a material that is particularly easily diffused, so that this Zn passes through the first contact layer in the p-type nitride semiconductor layer, and further in the light emitting layer. This is presumably caused by solid phase diffusion until the pn junction is broken.
  • the concentration of Zn doped in the second contact layer is set lower than the concentration of Mg doped in the first contact layer.
  • the concentration of Zn doped in the second contact layer is set lower than the concentration of Mg doped in the first contact layer.
  • the nitride semiconductor light-emitting device of the present invention has a configuration in which a metal electrode containing one or more of Ag (including an Ag alloy), Al, or Rh is in contact with the second contact layer. It can be.
  • a metal electrode can be formed in direct contact with the second contact layer.
  • Ag including an Ag alloy
  • Rh having a high reflectivity as the metal electrode, light emitted from the light emitting layer to the p-type nitride semiconductor layer side in the light extraction direction. A function as a reflective electrode to be reflected can be realized.
  • the contact electrode there is no need to form the contact electrode with a material having an absorption edge longer than the emission wavelength, such as ITO or Ni, so that a light source element for deep ultraviolet light with high light extraction efficiency can be realized.
  • composition ratios of Al X Ga Y In Z N constituting the p-type nitride semiconductor layer, the first contact layer, and the second contact layer do not necessarily have to be all in common, and are different for each layer, for example. It does not matter as a ratio.
  • annealing is performed in an inert gas atmosphere after forming the second contact layer. It has been found that good ohmic characteristics can be realized between the metal electrode to be formed and the second contact layer and the first contact layer, that is, the semiconductor layer.
  • the method for manufacturing the nitride semiconductor light emitting device of the present invention includes: A step (a) of sequentially laminating an n-type nitride semiconductor layer, a light emitting layer, and a p-type nitride semiconductor layer on a substrate; Forming a first contact layer formed of a nitride semiconductor layer doped with a first impurity material at a higher concentration than the p-type nitride semiconductor layer on the p-type nitride semiconductor layer (b) When, Al X Ga Y In Z N (0 ⁇ X ⁇ 1, doped with one or more second impurity materials of any one of Zn, Cd, Be, Sr, Ca and C on the first contact layer.
  • step (d) of annealing in an inert gas atmosphere is provided after the step (c).
  • nitrogen is preferably used, but a gas such as argon, helium, or neon may be used.
  • step (c) when annealing is performed in an oxygen-containing atmosphere (for example, air), a good ohmic characteristic can be obtained by forming a metal electrode thereafter. It could not be realized, and it was found that Schottky characteristics were shown. On the other hand, a favorable ohmic characteristic is implement
  • an oxygen-containing atmosphere for example, air
  • this step (d) is preferably an annealing process by RTA (Rapid Thermal Anneal).
  • Processes (a) to (c) are generally realized by an MOCVD apparatus.
  • the MOCVD apparatus that is, the furnace is in a high temperature state. Therefore, it seems natural for the step (d) to perform annealing in the furnace by using the cooling period after the step (c) in an inert gas atmosphere in the furnace.
  • the method for manufacturing a nitride semiconductor light emitting device of the present invention includes: A step (e) of forming a metal electrode on the second contact layer after the step (d); Another feature is that after the step (e), there is a step (f) of annealing in an oxygen-containing atmosphere.
  • the contact property between the semiconductor layer and the metal electrode is improved by annealing in an oxygen-containing atmosphere instead of an inert gas atmosphere as in the above step (d). It has been found that the effect of further improvement can be obtained. This content will also be described later with reference to examples.
  • the oxygen-containing atmosphere used in the step (f) may be an atmosphere containing a certain amount of oxygen in addition to air.
  • the second contact layer has good ohmic characteristics, it is possible to form the second contact layer by directly contacting the metal electrode as in step (e) without using a separate contact electrode.
  • this metal electrode by using a highly reflective metal such as Ag or an Ag alloy, as a reflective electrode that reflects light emitted from the light emitting layer to the p-type nitride semiconductor layer side in the light extraction direction. This function can be realized.
  • an element having contact characteristics equivalent to those of a conventional nitride semiconductor light emitting element can be realized without using a contact electrode formed of a material such as ITO or Ni.
  • FIG. 1 is a schematic cross-sectional view showing a schematic configuration of a nitride semiconductor light emitting device according to a first embodiment of the present invention.
  • 6 is a schematic cross-sectional view showing a schematic configuration of a conventional example and a comparative example 1.
  • FIG. 6 is a graph showing current-voltage characteristics in each element of Example 1, a conventional example, and Comparative Example 1.
  • 6 is a table showing the results of verifying contact characteristics when the concentration of Zn doped in a second contact layer is changed in the element of Example 1. It is a part of process sectional drawing of the nitride semiconductor light-emitting device of 1st Embodiment.
  • nitride semiconductor light-emitting device of 2nd Embodiment is a table showing the results of verifying the degree of life deterioration when the concentration of Zn doped in the second contact layer is changed in the nitride semiconductor light emitting device of Example 2. It is a part of process sectional drawing of the nitride semiconductor light-emitting device of 4th Embodiment. It is a part of process sectional drawing of the nitride semiconductor light-emitting device of 4th Embodiment. It is a part of process sectional drawing of the nitride semiconductor light-emitting device of 4th Embodiment.
  • FIG. 6 is a graph showing current-voltage characteristics in each element of Example 3, a conventional example, and Comparative Example 1. It is typical sectional drawing which shows schematic structure of the element for evaluation. It is a typical top view which shows schematic structure of the element for evaluation. 10 is a graph showing current-voltage characteristics in the evaluation element of Example 4. 10 is a graph showing current-voltage characteristics in an evaluation element of Comparative Example 2. 10 is a graph showing current-voltage characteristics in an evaluation element of Example 5. 6 is a graph showing current-voltage characteristics in nitride semiconductor light emitting devices corresponding to Example 4 and Example 5. 7 is a graph showing current-voltage characteristics in nitride semiconductor light emitting devices corresponding to Example 3 and Example 6.
  • FIG. 1 is a schematic cross-sectional view of a nitride semiconductor light emitting device 1.
  • AlGaN AlGaN
  • FIG. 1 has shown the extraction direction of light.
  • the nitride semiconductor light emitting device 1 includes a support substrate 11, a conductive layer 20, an insulating layer 21, a semiconductor layer 30, an electrode 42, and a bonding electrode 43.
  • the semiconductor layer 30 includes a p-type nitride semiconductor layer 31, a first contact layer 32, a light emitting layer 33, a second contact layer 34, and an n-type nitride semiconductor layer 35.
  • the support substrate 11 is composed of a conductive substrate such as CuW, W, or Mo, or a semiconductor substrate such as Si.
  • a conductive layer 20 having a multilayer structure is formed on the upper layer of the substrate 11.
  • the conductive layer 20 includes a solder layer 13, a solder layer 15, a protective layer 17, and a metal electrode 19.
  • the solder layer 13 and the solder layer 15 are made of, for example, Au—Sn, Au—In, Au—Cu—Sn, Cu—Sn, Pd—Sn, Sn, or the like. As will be described later, the solder layer 13 and the solder layer 15 are bonded together after the solder layer 13 formed on the support substrate 11 and the solder layer 15 formed on another substrate are opposed to each other. It is formed by.
  • the protective layer 17 is made of, for example, Pt-based metal (an alloy of Ti and Pt), W, Mo, or the like. As will be described later, when bonding is performed via a solder layer, the material constituting the solder diffuses to the metal electrode 19 side described later, and functions to prevent a decrease in luminous efficiency due to a drop in reflectance.
  • the metal electrode 19 is made of, for example, Ag (including an Ag alloy), Al, Rh, or the like. It is assumed that the nitride semiconductor light emitting device 1 takes out the light emitted from the light emitting layer 33 of the semiconductor layer 30 in the upward direction on the paper surface of FIG. 1, and the metal electrode 19 faces down from the light emitting layer 33 (supported). It functions as a reflective electrode that reflects light emitted toward the substrate 11 side upward (on the n-type nitride semiconductor layer 35 side), and functions to increase luminous efficiency. In the nitride semiconductor light emitting device 1, a contact electrode such as ITO or Ni for improving the contact property is not formed on the metal electrode 19.
  • the conductive layer 20 is partially in contact with the semiconductor layer 30, and when a voltage is applied between the support substrate 11 and the bonding electrode 43, the support substrate 11, the conductive layer 20, the semiconductor layer 30, and the bonding electrode A current path that flows to the bonding wire 45 through 43 is formed.
  • Insulating layer 21 is composed for example SiO 2, SiN, Zr 2 O 3, AlN, etc. Al 2 O 3.
  • the insulating layer 21 has an upper surface in contact with the semiconductor layer 30, more specifically, a bottom surface of the second contact layer 34.
  • the insulating layer 21 has a function as an etching stopper layer at the time of element isolation (step S7), and also has a function of spreading current in a direction parallel to the substrate surface of the support substrate 11.
  • the semiconductor layer 30 includes the p-type nitride semiconductor layer 31, the first contact layer 32, the light emitting layer 33, the second contact layer 34, and the n-type nitride semiconductor layer 35.
  • the n-type nitride semiconductor layer 35 is composed of Al n Ga 1-n N (0 ⁇ n ⁇ 1). At least the n-type nitride semiconductor layer 35 is doped with n-type impurities such as Si, Ge, S, Se, Sn, and Te, and is preferably doped with Si.
  • the n-type nitride semiconductor layer 35 has irregularities formed on the upper surface. This is because the light emitted upward from the light emitting layer 33 (and the reflected light emitted upward from the metal electrode 19) is reduced in the amount of light reflected downward on the surface of the n-type nitride semiconductor layer 35, The purpose is to increase the amount of light extracted outside the element.
  • the n-type nitride semiconductor layer 35 has a thickness of about 0.5 ⁇ m to 1 ⁇ m. As described above, in the case where irregularities are formed on the upper surface of the n-type nitride semiconductor layer 35, the n-type nitride semiconductor layer 35 extends from the irregular recesses (valleys) to the interface with the light emitting layer 33. The thickness of the n-type nitride semiconductor layer 35 may be from the convex / concave portion (mountain portion) to the interface with the light emitting layer 33.
  • the light emitting layer 33 is formed of a semiconductor layer having a multiple quantum well structure in which, for example, a well layer made of InGaN and a barrier layer made of AlGaN are repeated. These layers may be undoped or p-type or n-type doped.
  • the p-type nitride semiconductor layer 31 and the first contact layer 32 are made of, for example, Al m Ga 1-m N (0 ⁇ m ⁇ 1).
  • the semiconductor materials constituting the p-type nitride semiconductor layer 31 and the first contact layer 32 may be different. That is, as an example, the p-type nitride semiconductor layer 31 may be made of AlGaN, and the first contact layer 32 may be made of GaN.
  • the first contact layer 32 is more highly doped with impurities than the p-type nitride semiconductor layer 31.
  • the impurity concentration of the p-type nitride semiconductor layer 31 is about 1 ⁇ 10 19 / cm 3 or more and 5 ⁇ 10 19 / cm 3 or less, and the first contact layer 32 is 5 ⁇ 10 19 / cm 3 or more, 5 ⁇ 10 20 / cm 3 or less Any of these layers may have Mg as a dopant.
  • the impurity concentration of the second contact layer 34 is about 1 ⁇ 10 19 / cm 3 or more and about 5 ⁇ 10 21 / cm 3 or less.
  • GaN doped with Zn can be used.
  • the impurity material doped into the second contact layer 34 (corresponding to “second impurity material”)
  • the impurity material doped into the first contact layer 32 (corresponding to “first impurity material”).
  • any material that forms an impurity level deeper than the impurity level formed in the first contact layer 32 may be used.
  • the impurity levels formed in the second contact layer 34 are the impurities formed in the first contact layer 32. The position is deeper than the level.
  • the nitride semiconductor light emitting device 1 uses the hopping conduction in the second contact layer 34 to achieve a good ohmic connection between the semiconductor layer 30 and the metal electrode 19 even without the contact electrode. It is a structure that is formed and can realize low-voltage driving.
  • the second impurity material doped in the second contact layer 34 a material that forms a deep level as described above is used.
  • the electrode 42 and the bonding electrode 43 are formed in the upper layer of the n-type nitride semiconductor layer 35 and are made of, for example, Cr—Au. More specifically, the electrode 42 and the bonding electrode 43 are positioned immediately above the region where the bottom surface (surface on the support substrate 11 side) of the semiconductor layer 30 and the top surface of the insulating layer 21 (surface on the semiconductor layer 30 side) are in contact. That is, it is formed in the upper layer of the n-type nitride semiconductor layer 35 at a position facing the direction orthogonal to the surface of the support substrate 11. As a result, a material with low conductivity is formed below the electrode, so that an effect of spreading the current in the light emitting layer 33 in the horizontal direction when a current is applied can be obtained.
  • a bonding wire 45 made of, for example, Au or Cu is connected to the bonding electrode 43, and the other end of the wire is connected to a power supply pattern (not shown) of the substrate on which the nitride semiconductor light emitting element 1 is disposed. Is done.
  • the semiconductor layer 30 includes an n-type nitride semiconductor layer 35 made of Al 0.06 Ga 0.94 N having a Si concentration of 3 ⁇ 10 19 / cm 3 , a well layer made of InGaN, and an n-type AlGaN.
  • FIG. 2A schematically shows a configuration of a conventional light emitting device 80.
  • the light emitting element 80 of this conventional example does not include the second contact layer 34 as compared with the embodiment, and the first contact layer 32 is in contact with the conductive layer 20a.
  • the conductive layer 20 a includes a contact electrode 83 made of Ni in addition to the metal electrode 19, and the contact electrode 83 is in contact with the first contact layer 32.
  • Other configurations are the same as those in the first embodiment.
  • FIG. 2B schematically shows the configuration of the light-emitting element 81 of Comparative Example 1.
  • the light emitting element 81 of the comparative example 1 is configured not to include the contact electrode 83 with respect to the light emitting element 80 of the conventional example. That is, the first contact layer 32 is in contact with the conductive layer 20, more specifically, the metal electrode 19.
  • FIG. 3 shows a case where a voltage V is applied between the bonding electrode 43 and the support substrate 11 for the light-emitting element 1 of Example 1, the light-emitting element 80 of the conventional example, and the light-emitting element 81 of Comparative Example 1, respectively.
  • the relationship between the current I and the voltage V is graphed.
  • the light emitting element 1 of Example 1 is not provided with the contact electrode 83 and the first contact layer 32 is in direct contact with the metal electrode 19, similarly to the light emitting element 80 of the conventional example provided with the contact electrode 83.
  • the voltage can be reduced as compared with the light emitting element 81 of the comparative example 1 having the above configuration. Therefore, according to the configuration of the present invention, it can be seen that good contact property equivalent to or higher than that of the conventional element 80 having the contact electrode 83 can be realized without forming the contact electrode 83. This is presumably due to the following reasons.
  • the first contact layer 32 is doped with Mg at a high concentration, shallow impurity levels are formed, and the acceptor is ionized at room temperature. Further, Ag formed as the metal electrode 19 has a small work function. For this reason, when Ag (metal electrode 19) is brought into direct contact with the first contact layer 32 as in Comparative Example 1, a large external voltage is required to cause a tunnel effect to flow current.
  • a contact electrode 83 formed of Ni or the like has been interposed (see FIG. 2A).
  • the contact electrode 83 is formed, NiO is formed by annealing in an oxygen atmosphere, and the work function difference from the first contact layer 32 is reduced.
  • the external voltage is lower than that of the element 81.
  • the light-emitting element 1 of Example 1 has the second contact layer 34 doped with Zn.
  • Zn unlike Mg, forms an impurity level at a deep level from the valence band in Al X Ga Y In ZN .
  • the acceptor is not ionized, and even if an impurity is added to the semiconductor layer above the effective state density, the energy level is localized, so that carriers are not in the valence band, but hopping conduction between the sites created by the impurity.
  • the operating voltage could be reduced as in the case of the light emitting element 80.
  • the energy level is localized even if it is doped at a high concentration, and hopping conduction can be realized.
  • a material that forms a deep level such as Zn
  • the width of the depletion layer can be narrowed by doping at a high concentration, an effect of facilitating movement of carriers to the metal electrode 19 side by tunneling can be obtained.
  • FIG. 4 is a result of verifying contact characteristics when the concentration of Zn doped in the second contact layer 34 is changed in the light-emitting element 1 of Example 1.
  • “ ⁇ ” indicates the best contact property
  • “ ⁇ ” indicates the next best contact property
  • “ ⁇ ” indicates that the contact property is poor compared to the former two. .
  • the contact characteristics are deteriorated.
  • the Zn concentration is set to 1 ⁇ 10 19 / cm 3 , the contact characteristics are improved as compared with the case of 8 ⁇ 10 18 / cm 3. It was.
  • the Zn concentration is 5 ⁇ 10 19 / cm 3 , 1 ⁇ 10 20 / cm 3 , 5 ⁇ 10 20 / cm 3 , 1 ⁇ 10 21 / cm 3 , extremely good contact characteristics can be obtained. It was.
  • the Zn concentration is 5 ⁇ 10 21 / cm 3
  • the contact characteristics are the same as the case of 1 ⁇ 10 19 / cm 3 , and when the concentration is higher (1 ⁇ 10 22 / cm 3 ), the contact characteristics are It got worse.
  • the Zn concentration is 8 ⁇ 10 18 / cm 3
  • the discrete level of localized impurity levels is high, and carrier hopping conduction is not efficiently performed. Is done.
  • the Zn concentration is 1 ⁇ 10 22 / cm 3
  • the resistance has increased due to the crystallinity of Al X Ga Y In ZN being deteriorated by doping at a very high concentration. It is guessed.
  • the Zn concentration doped into the second contact layer 34 is preferably 1 ⁇ 10 19 / cm 3 to 5 ⁇ 10 21 / cm 3 , and more preferably 5 ⁇ 10 9. It can be said that 19 / cm 3 to 1 ⁇ 10 21 / cm 3 is more preferable.
  • the contact electrode 83 As described above, according to the light-emitting element 1 of Example 1, it is preferable to use the contact electrode 83 using ITO having an absorption edge near 365 nm or Ni having an absorption edge longer than that. Since contact characteristics can be realized, the contact electrode 83 is not necessary. Thereby, absorption of ultraviolet light in the contact electrode 83 is suppressed, and an ultraviolet light emitting element with improved light extraction efficiency is realized.
  • Step S1 As shown in FIG. 5A, the epitaxial layer 40 is formed on the sapphire substrate 61. This step S1 is performed by the following procedure, for example.
  • ⁇ Preparation of sapphire substrate 61 First, the c-plane sapphire substrate 61 is cleaned. More specifically, for this cleaning, for example, a c-plane sapphire substrate 61 is placed in a processing furnace of a MOCVD (Metal Organic Chemical Vapor Deposition) apparatus, and hydrogen having a flow rate of 10 slm is placed in the processing furnace. While flowing the gas, the temperature in the furnace is raised to, for example, 1150 ° C.
  • MOCVD Metal Organic Chemical Vapor Deposition
  • a low-temperature buffer layer made of GaN is formed on the surface of the c-plane sapphire substrate 61, and a base layer made of GaN is further formed thereon. These low-temperature buffer layer and underlayer correspond to the undoped layer 36.
  • a more specific method for forming the undoped layer 36 is as follows. First, the furnace pressure of the ⁇ CVD apparatus is 100 kPa, and the furnace temperature is 480 ° C. Then, while flowing nitrogen gas and hydrogen gas with a flow rate of 5 slm respectively as carrier gas into the processing furnace, trimethylgallium (TMG) with a flow rate of 50 ⁇ mol / min and ammonia with a flow rate of 250,000 ⁇ mol / min are used as the raw material gas in the processing furnace. For 68 seconds. As a result, a low-temperature buffer layer made of GaN having a thickness of 20 nm is formed on the surface of the c-plane sapphire substrate 61.
  • TMG trimethylgallium
  • the furnace temperature of the MOCVD apparatus is raised to 1150 ° C. Then, while flowing nitrogen gas having a flow rate of 20 slm and hydrogen gas having a flow rate of 15 slm as a carrier gas in the processing furnace, TMG having a flow rate of 100 ⁇ mol / min and ammonia having a flow rate of 250,000 ⁇ mol / min are introduced into the processing furnace as source gases. Feed for 30 minutes. As a result, a base layer made of GaN having a thickness of 1.7 ⁇ m is formed on the surface of the first buffer layer.
  • n-type Nitride semiconductor layer 35 having a composition of Al n Ga 1-n N (0 ⁇ n ⁇ 1) is formed on the undoped layer 36.
  • a more specific method for forming the n-type nitride semiconductor layer 35 is, for example, as follows. First, with the furnace temperature kept at 1150 ° C., the furnace pressure of the MOCVD apparatus is set to 30 kPa. Then, while flowing nitrogen gas having a flow rate of 20 slm and hydrogen gas having a flow rate of 15 slm as a carrier gas into the processing furnace, TMG having a flow rate of 94 ⁇ mol / min, trimethylaluminum (TMA) having a flow rate of 6 ⁇ mol / min, Ammonia with a flow rate of 250,000 ⁇ mol / min and tetraethylsilane with a flow rate of 0.025 ⁇ mol / min are supplied into the treatment furnace for 60 minutes.
  • TMG trimethylaluminum
  • an n-type nitride semiconductor layer 35 having a composition of Al 0.06 Ga 0.94 N, a Si concentration of 3 ⁇ 10 19 / cm 3 and a thickness of 2 ⁇ m is formed in the upper layer of the undoped layer 36. Is done. Then, the n-AlGaN layer having a thickness of 2 ⁇ m is shaved with an ICP device so that the thickness becomes about 0.8 ⁇ m, and the thickness of the n-type nitride semiconductor layer 35 is adjusted.
  • silicon (Si), germanium (Ge), sulfur (S), selenium (Se), tin (Sn), tellurium (Te), or the like is used. be able to. Among these, silicon (Si) is particularly preferable.
  • a light emitting layer 33 having a multiple quantum well structure in which a well layer made of InGaN and a barrier layer made of n-type AlGaN are periodically repeated is formed on the n-type nitride semiconductor layer 35.
  • the furnace pressure of the MOCVD apparatus is set to 100 kPa, and the furnace temperature is set to 830 ° C. Then, while flowing nitrogen gas having a flow rate of 15 slm and hydrogen gas having a flow rate of 1 slm as a carrier gas in the processing furnace, TMG having a flow rate of 10 ⁇ mol / min, trimethylindium (TMI) having a flow rate of 12 ⁇ mol / min, and A step of supplying ammonia at a flow rate of 300,000 ⁇ mol / min into the processing furnace for 48 seconds is performed.
  • TMG having a flow rate of 10 ⁇ mol / min
  • TMA having a flow rate of 1.6 ⁇ mol / min
  • tetraethylsilane having a flow rate of 0.002 ⁇ mol / min
  • ammonia having a flow rate of 300,000 ⁇ mol / min
  • the light-emitting layer 33 having a multi-quantum well structure of 15 periods with a well layer made of InGaN having a thickness of 2 nm and a barrier layer made of n-type AlGaN having a thickness of 7 nm is formed into an n-type. It is formed on the surface of the nitride semiconductor layer 35.
  • a p-type nitride semiconductor layer 31 composed of Al m Ga 1-m N (0 ⁇ m ⁇ 1) is formed on the light emitting layer 33.
  • the furnace pressure of the MOCVD apparatus is maintained at 100 kPa, and the furnace temperature is raised to 1025 ° C. while nitrogen gas having a flow rate of 15 slm and hydrogen gas having a flow rate of 25 slm are supplied as carrier gases in the processing furnace.
  • nitrogen gas having a flow rate of 15 slm and hydrogen gas having a flow rate of 25 slm are supplied as carrier gases in the processing furnace.
  • TMG with a flow rate of 35 ⁇ mol / min
  • TMA with a flow rate of 20 ⁇ mol / min
  • ammonia with a flow rate of 250,000 ⁇ mol / min
  • biscyclopentadiene with a flow rate of 0.1 ⁇ mol / min for doping p-type impurities.
  • Enilmagnesium (CP 2 Mg) is fed into the processing furnace for 60 seconds.
  • a hole supply layer having a composition of Al 0.3 Ga 0.7 N having a thickness of 20 nm is formed on the surface of the light emitting layer 33.
  • a hole supply layer having a composition of Al 0.13 Ga 0.87 N having a thickness of 120 nm is formed on the surface of the light emitting layer 33.
  • a p-type nitride semiconductor layer 31 is formed by these hole supply layers.
  • the p-type impurity (Mg) concentration of the p-type nitride semiconductor layer 31 is about 3 ⁇ 10 19 / cm 3 .
  • the p-type impurity (Mg) concentration of the first contact layer 32 is about 1 ⁇ 10 20 / cm 3 .
  • Second Contact Layer 34 ⁇ Formation of Second Contact Layer 34> Next, the supply of CP 2 Mg is stopped, and in addition to the source gas, the second flow of diethyl zinc is supplied for 20 seconds in a state where the flow rate of diethyl zinc is 0.2 ⁇ mol / min. A contact layer 34 is formed. In addition to Zn, Cd, Be, Sr, Ca, C, etc. can be used as the dopant of the second contact layer 34. The impurity (Zn) concentration of the second contact layer 34 is about 1 ⁇ 10 20 / cm 3 .
  • an epitaxial layer comprising the undoped layer 36, the n-type nitride semiconductor layer 35, the light emitting layer 33, the p-type nitride semiconductor layer 31, the first contact layer 32, and the second contact layer 34. 40 is formed.
  • Step S2 an activation process is performed on the wafer obtained in step S1. More specifically, activation is performed at 650 ° C. for 15 minutes in a nitrogen atmosphere using an RTA (Rapid Thermal Anneal) device.
  • RTA Rapid Thermal Anneal
  • the insulating layer 21 is formed at a predetermined position on the p-type nitride semiconductor layer 31. More specifically, the insulating layer 21 is formed at a location (a location including a location facing the direction orthogonal to the substrate surface) located below a region where the electrode 42 and the bonding electrode 43 are formed in a later step. preferable.
  • the insulating layer 21 for example, SiO 2 is formed to a thickness of about 200 nm.
  • the material for forming the film may be an insulating material, such as SiN or Al 2 O 3 .
  • Step S4 As shown in FIG. 5C, the conductive layer 20 is formed so as to cover the upper surfaces of the p-type nitride semiconductor layer 31 and the insulating layer 21.
  • the conductive layer 20 having a multilayer structure including the metal electrode 19, the protective layer 17, and the solder layer 15 is formed.
  • a more specific method for forming the conductive layer 20 is as follows. First, Ag is formed on the entire surface so as to cover the upper surfaces of the second contact layer 34 and the insulating layer 21 by a sputtering apparatus, and the metal electrode 19 is formed. As described above, in the configuration of the present embodiment, since the deep impurity level is formed in the second contact layer 34 by Zn doping, the direct contact with the semiconductor layer without forming a contact electrode such as Ti or ITO. Good contact characteristics can be obtained by contacting Ag.
  • Ag is used as the metal electrode 19, but Al, Rh, or the like can be used in addition to Ag.
  • the protective layer 17 is formed by depositing 100 nm-thick Ti and 200 nm-thickness Pt on the upper surface (Ag surface) of the metal electrode 19 with an electron beam evaporation apparatus (EB apparatus) for three periods. . Further, after depositing Ti with a thickness of 10 nm on the upper surface (Pt surface) of the protective layer 17, Au—Sn solder composed of Au 80% Sn 20% is deposited with a thickness of 3 ⁇ m. Form.
  • the solder layer 13 may be formed on the upper surface of the support substrate 11 prepared separately from the sapphire substrate 61 (see FIG. 5D).
  • the solder layer 13 may be made of the same material as the solder layer 15, and is bonded to the solder layer 13 in the next step, whereby the sapphire substrate 61 and the support substrate 11 are bonded together.
  • CuW is used as the support substrate 11 as described in the section of the structure.
  • Step S5 Next, as shown in FIG. 5E, the sapphire substrate 61 and the support substrate 11 are bonded together. More specifically, the solder layer 15 and the solder layer 13 formed on the upper layer of the support substrate 11 are bonded together at a temperature of 280 ° C. and a pressure of 0.2 MPa.
  • the sapphire substrate 61 is peeled off. More specifically, the interface between the sapphire substrate 61 and the epitaxial layer 40 is decomposed by irradiating a KrF excimer laser from the sapphire substrate 61 side with the sapphire substrate 61 facing upward and the support substrate 11 facing downward. Then, the sapphire substrate 61 is peeled off. While the laser passes through the sapphire 61, the underlying GaN (undoped layer 36) absorbs the laser, so that this interface is heated to decompose GaN. As a result, the sapphire substrate 61 is peeled off.
  • GaN (undoped layer 36) remaining on the wafer is removed by wet etching using hydrochloric acid or the like, and dry etching using an ICP apparatus, and the n-type nitride semiconductor layer 35 is exposed.
  • the undoped layer 36 is removed, and the second contact layer 34, the first contact layer 32, the p-type nitride semiconductor layer 31, the light emitting layer 33, and the n-type nitride semiconductor layer 35 are stacked in this order.
  • the formed semiconductor layer 30 remains.
  • Step S7 Next, as shown in FIG. 5G, adjacent elements are separated. Specifically, the semiconductor layer 30 is etched using an ICP device until the upper surface of the insulating layer 21 is exposed in a boundary region with an adjacent element. As described above, the insulating layer 21 also functions as a stopper during etching.
  • Step S8 Next, as shown in FIG. 5H, irregularities are formed on the surface of the n-type nitride semiconductor layer 35. Specifically, the unevenness is formed by immersing an alkaline solution such as KOH. At this time, unevenness may not be formed in a portion where the electrode 42 and the bonding electrode 43 are formed later. By not forming irregularities at these locations, the surface of the n-type nitride semiconductor layer 35 where the electrodes are to be formed is maintained in a flat state.
  • an alkaline solution such as KOH
  • the bonding electrode 43 and the n-type nitride semiconductor layer 35 are formed particularly when wire bonding is performed after the bonding electrode 43 is formed.
  • the effect of preventing the generation of voids at the interface can be obtained.
  • Step S9 an electrode 42 and a bonding electrode 43 are formed on the upper surface of the n-type nitride semiconductor layer 35. More specifically, after forming an electrode made of Cr having a thickness of 100 nm and Au having a thickness of 3 ⁇ m, sintering is performed at 250 ° C. for 1 minute in a nitrogen atmosphere.
  • the exposed element side surface and the element upper surface other than the electrode 42 and the bonding electrode 43 are covered with an insulating layer 41 (see FIG. 1). More specifically, an SiO 2 film is formed by an EB apparatus. An SiN film may be formed. Then, the elements are separated from each other by, for example, a laser dicing apparatus, the back surface of the support substrate 11 is joined to the package by, for example, Ag paste, and wire bonding is performed on the bonding electrode 43. For example, wire bonding is performed by connecting a bonding wire 45 made of Au to a bonding region of ⁇ 100 ⁇ m with a load of 50 g. Thereby, the nitride semiconductor light emitting device 1 shown in FIG. 1 is formed.
  • Both the first contact layer 32 and the second contact layer 34 may be formed of AlGaN having a predetermined composition ratio, and the metal electrode 19 may be formed of Al.
  • Al X Ga Y In Z N by increasing the composition ratio of Al in, it is possible to shift the absorption edge on the shorter wavelength side, the nitride semiconductor light emitting element 1, forming a device that emits deep ultraviolet light Can do.
  • the contact electrode 83 formed of Ni, ITO or the like is not necessary, absorption of deep ultraviolet light in the contact electrode 83 is suppressed, and a deep ultraviolet light emitting element with improved light extraction efficiency is realized. .
  • step S1 When the first contact layer 32 and the second contact layer 34 are formed of AlGaN, the following method can be adopted in step S1. First, after the p-type nitride semiconductor layer 31 is formed, the flow rate of CP 2 Mg is changed to 0.2 ⁇ mol / min and a source gas is supplied for 20 seconds, whereby p + Al 0.13 Ga 0 having a thickness of 5 nm is supplied. A first contact layer 32 made of .87N is formed.
  • FIG. 6 is a schematic cross-sectional view of the nitride semiconductor light emitting device 1a of the second embodiment.
  • symbol is attached
  • the arrow in FIG. 6 has shown the extraction direction of light, and the light extraction direction is reverse with the nitride semiconductor light-emitting device 1a shown in FIG.
  • a sapphire substrate 61, a semiconductor layer 30a, metal electrodes 19, 19a, a power supply terminal 51, and a power supply terminal 52 are provided.
  • the semiconductor layer 30 a includes a p-type nitride semiconductor layer 31, a first contact layer 32, a light emitting layer 33, a second contact layer 34, an n-type nitride semiconductor layer 35, and an undoped layer 36.
  • the nitride semiconductor light emitting device 1a is assumed to extract light downward on the paper surface (sapphire substrate 61 side).
  • metal electrode 19 in order to distinguish from the metal electrode 19 formed on the upper surface of the p-side semiconductor layer 30a in the first embodiment, it is formed on the upper surface of the n-side semiconductor layer 30a (n-type nitride semiconductor layer 35).
  • the metal electrode to be used is referred to as “metal electrode 19a”, but both may be made of the same material.
  • the contact property is improved because the metal electrode 19 formed of Ag or the like is directly formed on the upper surface of the second contact layer 34, so that good contact characteristics can be obtained. Therefore, it is not necessary to form a contact electrode made of Ni or ITO. Thereby, even when the light from the light emitting layer 33 is emitted upward, the light that has reached the metal electrode 19 without being absorbed by the contact electrode can be reflected downward (in the extraction direction). Extraction efficiency is improved.
  • Step S1 and step S2 are executed as in the first embodiment.
  • Step S10 After step S2 (see FIG. 5A), as shown in FIG. 7A, the second contact layer 34, the first contact layer 32, and the p-type nitride semiconductor are used until a partial upper surface of the n-type nitride semiconductor layer 35 is exposed.
  • the layer 31 and the light emitting layer 33 are removed by dry etching using an ICP device.
  • the n-type nitride semiconductor layer 35 may be partially removed by etching.
  • the metal electrode 19 and the metal electrode 19a are formed by depositing Ag on the upper surface of the second contact layer 34 and the exposed upper surface of the n-type nitride semiconductor layer 35. Also in this embodiment, since a deep impurity level is formed in the second contact layer 34 by Zn doping, the metal made of the second contact layer 34 and Ag can be formed without forming a contact electrode such as Ni or ITO. Good contact characteristics can be obtained by bringing the electrodes (19, 19a) into contact. In the present embodiment, as the metal electrode (19, 19a), Al or Rh can be used in addition to Ag.
  • the n-type nitride semiconductor layer 35 is made of AlGaN having a high concentration of n-type impurity concentration higher than 1 ⁇ 10 19 / cm 3 .
  • a power supply terminal 51 is formed on the upper surface of the n-side metal electrode 19a, and a power supply terminal 52 is formed on the upper surface of the p-side metal electrode 19. More specifically, after forming a conductive material film (for example, a material film made of Cr with a thickness of 100 nm and Au with a thickness of 3 ⁇ m) to form the power supply terminals 51 and 52, the power supply terminals 51 and 52 are formed by lift-off. To do. Thereafter, sintering is performed at 250 ° C. for 1 minute in a nitrogen atmosphere.
  • a conductive material film for example, a material film made of Cr with a thickness of 100 nm and Au with a thickness of 3 ⁇ m
  • the nitride semiconductor light emitting element 1a shown in FIG. 2 is formed.
  • the schematic cross-sectional view of the nitride semiconductor light emitting device 1 of the third embodiment is the same as that shown in FIG. 1 described above in the first embodiment.
  • a description will be given centering on points different from the nitride semiconductor light emitting device 1 of the first embodiment.
  • the p-type nitride semiconductor layer 31 and the first contact layer 32 are made of, for example, Al m Ga 1-m N (0 ⁇ m ⁇ 1).
  • the first contact layer 32 is more highly doped with impurities than the p-type nitride semiconductor layer 31.
  • the impurity concentration of the p-type nitride semiconductor layer 31 is about 1 ⁇ 10 19 / cm 3 or more and about 5 ⁇ 10 19 / cm 3 or less, and the first contact layer 32 is 5 ⁇ 10 19 / cm 3 or more, 1 It is about ⁇ 10 21 / cm 3 or less. Any of these layers may have Mg as a dopant.
  • the first contact layer 32 is doped with Mg.
  • the second contact layer 34 is doped with impurities at a lower concentration than the first contact layer 32.
  • the impurity concentration of the second contact layer 34 is about 5 ⁇ 10 16 / cm 3 or more and about 1 ⁇ 10 21 / cm 3 or less.
  • GaN doped with Zn can be used.
  • Zn doped in the second contact layer 34 is a material that forms an impurity level deeper than the impurity level formed in the first contact layer 32 by Mg doped in the first contact layer 32. It is.
  • the nitride semiconductor light emitting device 1 of the present embodiment also uses the hopping conduction in the second contact layer 34 to provide a good ohmic connection between the semiconductor layer 30 and the metal electrode 19 even without a contact electrode.
  • low voltage driving is realized.
  • Zn doped in the second contact layer 34 forms a deep level in the second contact layer 34.
  • the Zn concentration doped in the second contact layer 34 is set to be lower than the Mg concentration doped in the first contact layer 32.
  • Zn is a dopant used to form a deep level in the second contact layer 34 in order to realize hopping conduction as described above, but has a property of high diffusion rate. Therefore, when the second contact layer 34 is doped with Zn at a high concentration, there is a possibility that the solid phase diffusion may occur to the p-type nitride semiconductor layer 31 and the light emitting layer 33 via the first contact layer 32. If such a situation occurs, it is considered that the pn junction is broken or the function of the light emitting layer is lowered, so that the output is lowered or the lifetime during continuous operation is lowered.
  • Mg having a lower diffusion rate than Zn has been diffused into the first contact layer 32 by doping the adjacent first contact layer 32 at a higher concentration than the Zn concentration with respect to the second contact layer 34.
  • Zn is allowed to remain in the layer, and further, solid phase diffusion to the p-type nitride semiconductor layer 31 side is suppressed. The verification of this effect will be described later with reference to an example.
  • the nitride semiconductor light emitting device 1 having the structure shown in FIG. 1 is used as an example (here, example 2).
  • the semiconductor layer 30 includes an n-type nitride semiconductor layer 35 made of Al 0.06 Ga 0.94 N having a Si concentration of 3 ⁇ 10 19 / cm 3 , a well layer made of InGaN, and an n-type AlGaN.
  • Example 2 compared with Example 1 in the first embodiment, the Mg concentration in the first contact layer 32 is higher than the Zn concentration in the second contact layer 34.
  • the conventional example and the comparative example 1 are the same as those in the first embodiment.
  • the energy level is localized even when doped at a high concentration, and hopping conduction can be realized.
  • the width of the depletion layer can be narrowed by doping at a high concentration, an effect of facilitating movement of carriers to the metal electrode 19 side by tunneling can be obtained.
  • FIG. 8 shows the results of verifying the degree of deterioration of the lifetime of the semiconductor light emitting device 1 of Example 2 when the concentration of Zn doped in the second contact layer 34 is changed.
  • the concentration of Mg doped in the first contact layer 32 is fixed at 1 ⁇ 10 20 / cm 3 .
  • FIG. 8 shows “ ⁇ ” for a little over and “x” for a little over 10%.
  • the concentration of Zn doped in the second contact layer 34 is set to a value of 1 ⁇ 10 20 / cm 3 , that is, lower than the concentration of Mg doped in the first contact layer 32 (1 ⁇ 10 18 / cm 3 , 1 ⁇ 10 19 / cm 3 , 5 ⁇ 10 19 / cm 3 ), the reduction in output was alleviated.
  • the concentration of Zn doped in the second contact layer 34 is reduced to be lower than the concentration of Mg doped in the first contact layer 32, so that the deterioration rate of the lifetime can be slowed down.
  • Mg having a lower diffusion rate than Zn is doped in the adjacent first contact layer 32 at a higher concentration than the Zn concentration with respect to the second contact layer 34, so that the first contact layer It is presumed that the effect of suppressing the diffusion of Zn diffused to 32 into the layer and further suppressing the solid-phase diffusion toward the p-type nitride semiconductor layer 31 side is enhanced.
  • the semiconductor light emitting device 1 according to the present embodiment is also good without using the contact electrode 83 using ITO having an absorption edge near 365 nm or Ni having an absorption edge longer than that. Since contact characteristics can be realized, the contact electrode 83 is not necessary. Thereby, absorption of ultraviolet light in the contact electrode 83 is suppressed, and an ultraviolet light emitting element with improved light extraction efficiency is realized.
  • the lifetime characteristics are obtained by making the concentration of Zn doped particularly in the second contact layer 34 lower than the concentration of Mg doped in the first contact layer 32.
  • an excellent element can be realized.
  • Step S1 After preparing the sapphire substrate 61 by the same method as in the first embodiment, the undoped layer 36, the n-type nitride semiconductor layer 35, and the light emitting layer 33 are sequentially formed.
  • a p-type nitride semiconductor layer 31 composed of Al m Ga 1-m N (0 ⁇ m ⁇ 1) is formed on the light emitting layer 33.
  • the furnace pressure of the MOCVD apparatus is maintained at 100 kPa, and the furnace temperature is raised to 1025 ° C. while nitrogen gas having a flow rate of 15 slm and hydrogen gas having a flow rate of 25 slm are supplied as carrier gases in the processing furnace.
  • nitrogen gas having a flow rate of 15 slm and hydrogen gas having a flow rate of 25 slm are supplied as carrier gases in the processing furnace.
  • TMG with a flow rate of 35 ⁇ mol / min
  • TMA with a flow rate of 20 ⁇ mol / min
  • ammonia with a flow rate of 250,000 ⁇ mol / min
  • biscyclopentadiene with a flow rate of 0.1 ⁇ mol / min for doping p-type impurities.
  • Enilmagnesium (CP 2 Mg) is fed into the processing furnace for 60 seconds.
  • a hole supply layer having a composition of Al 0.3 Ga 0.7 N having a thickness of 20 nm is formed on the surface of the light emitting layer 33. Thereafter, the flow rate is changed to TMG having a flow rate of 35 ⁇ mol / min and TMA having a flow rate of 4 ⁇ mol / min, and the source gas is supplied for 360 seconds, whereby holes having a composition of Al 0.1 Ga 0.9 N having a thickness of 120 nm are provided.
  • a supply layer is formed.
  • a p-type nitride semiconductor layer 31 is formed by these hole supply layers.
  • the p-type impurity (Mg) concentration of the p-type nitride semiconductor layer 31 is about 3 ⁇ 10 19 / cm 3 .
  • the p-type impurity (Mg) concentration of the first contact layer 32 is about 1 ⁇ 10 20 / cm 3 .
  • Second Contact Layer 34 ⁇ Formation of Second Contact Layer 34> Next, the supply of CP 2 Mg is stopped, and in addition to the raw material gas, the second flow rate of diethyl zinc is supplied for 20 seconds in a state where the flow rate of diethyl zinc is 0.1 ⁇ mol / min, whereby the second doped Zn-doped GaN having a thickness of 5 nm. A contact layer 34 is formed.
  • the impurity (Zn) concentration of the second contact layer 34 is about 5 ⁇ 10 19 / cm 3 .
  • an epitaxial layer comprising the undoped layer 36, the n-type nitride semiconductor layer 35, the light emitting layer 33, the p-type nitride semiconductor layer 31, the first contact layer 32, and the second contact layer 34. 40 is formed.
  • the impurity (Zn) concentration of the second contact layer 34 is lower than the p-type impurity (Mg) concentration of the first contact layer 32.
  • step S2 and subsequent steps are the same as those in the first embodiment, description thereof is omitted.
  • both the first contact layer 32 and the second contact layer 34 may be formed of AlGaN having a predetermined composition ratio, and the metal electrode 19 may be formed of Al.
  • the structure of the nitride semiconductor light emitting device 1a shown in FIG. 6 can be realized as in the second embodiment. That is, in the configuration of FIG. 6, the impurity (Zn) concentration of the second contact layer 34 is configured to be lower than the p-type impurity (Mg) concentration of the first contact layer 32. Thereby, since a deep impurity level is formed in the second contact layer 34 by Zn doping, the second contact layer 34 and the metal electrode 19 made of Ag and the silver electrode 19 can be formed without forming a contact electrode such as Ni or ITO. By contacting 19a, good contact characteristics can be obtained, and good life characteristics can be realized.
  • This embodiment has the same structure as the nitride semiconductor light emitting device of the first embodiment, and the manufacturing method is different. Hereinafter, the manufacturing method will be described. This manufacturing process is merely an example, and the gas flow rate, the furnace temperature, the furnace pressure, and the like may be appropriately adjusted.
  • Step S13 As shown in FIG. 9A, the epitaxial layer 40 is formed on the sapphire substrate 61. This step S13 is performed by the following procedure, for example.
  • ⁇ Preparation of sapphire substrate 61 First, the c-plane sapphire substrate 61 is cleaned. More specifically, for this cleaning, for example, a c-plane sapphire substrate 61 is placed in a processing furnace of a MOCVD (Metal Organic Chemical Vapor Deposition) apparatus, and hydrogen having a flow rate of 10 slm is placed in the processing furnace. While flowing the gas, the temperature in the furnace is raised to, for example, 1150 ° C.
  • MOCVD Metal Organic Chemical Vapor Deposition
  • a low-temperature buffer layer made of GaN is formed on the surface of the c-plane sapphire substrate 61, and a base layer made of GaN is further formed thereon. These low-temperature buffer layer and underlayer correspond to the undoped layer 36.
  • a more specific method for forming the undoped layer 36 is as follows. First, the furnace pressure of the ⁇ CVD apparatus is 100 kPa, and the furnace temperature is 480 ° C. Then, while flowing nitrogen gas and hydrogen gas with a flow rate of 5 slm respectively as carrier gas into the processing furnace, trimethylgallium (TMG) with a flow rate of 50 ⁇ mol / min and ammonia with a flow rate of 250,000 ⁇ mol / min are used as the raw material gas in the processing furnace. For 68 seconds. As a result, a low-temperature buffer layer made of GaN having a thickness of 20 nm is formed on the surface of the c-plane sapphire substrate 61.
  • TMG trimethylgallium
  • the furnace temperature of the MOCVD apparatus is raised to 1150 ° C. Then, while flowing nitrogen gas having a flow rate of 20 slm and hydrogen gas having a flow rate of 15 slm as a carrier gas in the processing furnace, TMG having a flow rate of 100 ⁇ mol / min and ammonia having a flow rate of 250,000 ⁇ mol / min are introduced into the processing furnace as source gases. Feed for 30 minutes. As a result, a base layer made of GaN having a thickness of 1.7 ⁇ m is formed on the surface of the first buffer layer.
  • n-type Nitride semiconductor layer 35 having a composition of Al n Ga 1-n N (0 ⁇ n ⁇ 1) is formed on the undoped layer 36.
  • a more specific method for forming the n-type nitride semiconductor layer 35 is, for example, as follows. First, with the furnace temperature kept at 1150 ° C., the furnace pressure of the MOCVD apparatus is set to 30 kPa. Then, while flowing nitrogen gas having a flow rate of 20 slm and hydrogen gas having a flow rate of 15 slm as a carrier gas into the processing furnace, TMG having a flow rate of 94 ⁇ mol / min, trimethylaluminum (TMA) having a flow rate of 6 ⁇ mol / min, Ammonia with a flow rate of 250,000 ⁇ mol / min and tetraethylsilane with a flow rate of 0.025 ⁇ mol / min are supplied into the treatment furnace for 60 minutes.
  • TMG trimethylaluminum
  • an n-type nitride semiconductor layer 35 having a composition of Al 0.06 Ga 0.94 N, a Si concentration of 3 ⁇ 10 19 / cm 3 and a thickness of 2 ⁇ m is formed in the upper layer of the undoped layer 36. Is done. Then, the n-AlGaN layer having a thickness of 2 ⁇ m is shaved with an ICP device so that the thickness becomes about 0.8 ⁇ m, and the thickness of the n-type nitride semiconductor layer 35 is adjusted.
  • n-type impurity contained in the n-type nitride semiconductor layer 35 has been described, but other n-type impurities include Ge, S, Se, Sn, Te, and the like. It can also be used.
  • a light emitting layer 33 having a multiple quantum well structure in which a well layer made of InGaN and a barrier layer made of n-type AlGaN are periodically repeated is formed on the n-type nitride semiconductor layer 35.
  • the furnace pressure of the MOCVD apparatus is set to 100 kPa, and the furnace temperature is set to 830 ° C. Then, while flowing nitrogen gas having a flow rate of 15 slm and hydrogen gas having a flow rate of 1 slm as a carrier gas in the processing furnace, TMG having a flow rate of 10 ⁇ mol / min, trimethylindium (TMI) having a flow rate of 12 ⁇ mol / min, and A step of supplying ammonia at a flow rate of 300,000 ⁇ mol / min into the processing furnace for 48 seconds is performed.
  • TMG having a flow rate of 10 ⁇ mol / min
  • TMA having a flow rate of 1.6 ⁇ mol / min
  • tetraethylsilane having a flow rate of 0.002 ⁇ mol / min
  • ammonia having a flow rate of 300,000 ⁇ mol / min
  • the light-emitting layer 33 having a multi-quantum well structure of 15 periods with a well layer made of InGaN having a thickness of 2 nm and a barrier layer made of n-type AlGaN having a thickness of 7 nm is formed into an n-type. It is formed on the surface of the nitride semiconductor layer 35.
  • a p-type nitride semiconductor layer 31 composed of Al m Ga 1-m N (0 ⁇ m ⁇ 1) is formed on the light emitting layer 33.
  • the furnace pressure of the MOCVD apparatus is maintained at 100 kPa, and the furnace temperature is raised to 1025 ° C. while nitrogen gas having a flow rate of 15 slm and hydrogen gas having a flow rate of 25 slm are supplied as carrier gases in the processing furnace.
  • nitrogen gas having a flow rate of 15 slm and hydrogen gas having a flow rate of 25 slm are supplied as carrier gases in the processing furnace.
  • TMG with a flow rate of 35 ⁇ mol / min
  • TMA with a flow rate of 20 ⁇ mol / min
  • ammonia with a flow rate of 250,000 ⁇ mol / min
  • biscyclopentadiene with a flow rate of 0.1 ⁇ mol / min for doping p-type impurities.
  • Enilmagnesium (CP 2 Mg) is fed into the processing furnace for 60 seconds.
  • a hole supply layer having a composition of Al 0.3 Ga 0.7 N having a thickness of 20 nm is formed on the surface of the light emitting layer 33. Thereafter, the flow rate is changed to TMG having a flow rate of 35 ⁇ mol / min and TMA having a flow rate of 4 ⁇ mol / min, and the source gas is supplied for 360 seconds, whereby holes having a composition of Al 0.1 Ga 0.9 N having a thickness of 120 nm are provided.
  • a supply layer is formed.
  • a p-type nitride semiconductor layer 31 is formed by these hole supply layers.
  • the p-type impurity (Mg) concentration of the p-type nitride semiconductor layer 31 is about 3 ⁇ 10 19 / cm 3 .
  • Mg is used as the p-type impurity contained in the p-type nitride semiconductor layer 31
  • Be, Zn, C, and the like can be used as other p-type impurities.
  • the p-type impurity (Mg) concentration of the first contact layer 32 is about 1 ⁇ 10 20 / cm 3 .
  • Second Contact Layer 34 ⁇ Formation of Second Contact Layer 34> Next, the supply of only CP 2 Mg, which was flowing when the first contact layer 32 was formed, was stopped, and after the growth of the first contact layer 32, the flow rate of diethylzinc was adjusted to 0.1 ⁇ mol / min without interrupting the growth.
  • the second contact layer 34 made of Zn-doped GaN having a thickness of 5 nm is formed.
  • the impurity (Zn) concentration of the second contact layer 34 is about 5 ⁇ 10 19 / cm 3 .
  • the first contact layer 32 and the second contact layer 34 are continuously formed without interruption.
  • the second contact layer 34 is not completely formed. It does not mean that deep impurity levels are not formed.
  • the present invention is not intended to exclude such a manufacturing method.
  • the impurity of the first contact layer 32 is Mg and the impurity of the second contact layer 34 is Zn is described.
  • the impurity material (the first contact layer 32) is formed so that the impurity level formed in the second contact layer 34 is deeper than the impurity level formed in the first contact layer 32.
  • the impurity material) and the impurity material (second impurity material) of the second contact layer 34 may be selected.
  • the first impurity material Be, Zn, C, etc. can be used in addition to Mg
  • the second impurity material Cd, Be, Sr, Ca, C, etc. can be used besides Zn.
  • an epitaxial layer comprising the undoped layer 36, the n-type nitride semiconductor layer 35, the light emitting layer 33, the p-type nitride semiconductor layer 31, the first contact layer 32, and the second contact layer 34. 40 is formed.
  • Step S14 an activation process is performed on the wafer obtained in step S13. More specifically, annealing is performed at about 700 ° C. for about 5 minutes in an inert gas atmosphere using an RTA (Rapid Thermal Anneal) apparatus. Nitrogen is preferably used as the inert gas, but a gas such as argon, helium, or neon may be used.
  • RTA Rapid Thermal Anneal
  • the insulating layer 21 is formed at a predetermined position on the p-type nitride semiconductor layer 31. More specifically, the insulating layer 21 is formed at a location (a location including a location facing the direction orthogonal to the substrate surface) located below a region where the electrode 42 and the bonding electrode 43 are formed in a later step. preferable.
  • the insulating layer 21 for example, SiO 2 is formed to a thickness of about 200 nm.
  • the material for forming the film may be an insulating material, such as SiN or Al 2 O 3 .
  • Step S16 As shown in FIG. 9C, the metal electrode 19 is formed so as to cover the upper surfaces of the second contact layer 34 and the insulating layer 21.
  • a metal electrode 19 is formed by depositing Ag on the entire surface so as to cover the upper surfaces of the second contact layer 34 and the insulating layer 21 with a sputtering apparatus.
  • the second contact layer 34 is doped with Zn as the second impurity material to form a deep impurity level, so that a contact electrode such as ITO or Ni is formed. Even if it is not formed, ohmic characteristics can be obtained by directly contacting the semiconductor layer with Ag.
  • Ag is used as the metal electrode 19, but Al, Rh, or the like may be used in addition to Ag.
  • the present inventor has conducted the research under an inert gas atmosphere such as nitrogen in step S14 that the ohmic characteristics can be realized even if the second contact layer 34 and the metal electrode 19 are brought into direct contact by earnest research. I found out that it was caused by being. This will be described later by comparing the current-voltage characteristics with a comparative example manufactured by annealing in an air atmosphere in step S14.
  • step S14 rather than annealing in the MOCVD apparatus in which the semiconductor layer 30 was formed in step S13, the wafer was once taken out from the MOCVD apparatus, placed in the RTA apparatus, and annealed in this RTA apparatus. It has been found that contactability is improved. This point will also be described later with reference to examples.
  • Step S17 After the metal electrode 19 is formed, an annealing process is performed in an atmosphere containing oxygen. More specifically, activation processing is performed at about 450 ° C. for about 1 minute in an RTA apparatus or MOCVD apparatus.
  • step S14 annealing was performed in an inert gas atmosphere before the formation of the metal electrode 19 in order to realize ohmic characteristics between the second contact layer 34 and the metal electrode 19.
  • step S16 the annealing process performed after the formation of the metal electrode 19 in an atmosphere containing oxygen instead of an inert gas. This point will also be described later with reference to examples.
  • Step S18 Next, as illustrated in FIG. 9D, the protective layer 17 and the solder layer 15 are sequentially formed on the metal electrode 19. Through steps S16 to S18, the conductive layer 20 having a multilayer structure is formed.
  • the protective layer 17 is formed by forming three cycles of 100 nm thick Ti and 200 nm thick Pt on the upper surface (Ag surface) of the metal electrode 19 with an electron beam evaporation apparatus (EB apparatus). Form. Further, after depositing Ti with a thickness of 10 nm on the upper surface (Pt surface) of the protective layer 17, Au—Sn solder composed of Au 80% Sn 20% is deposited with a thickness of 3 ⁇ m. Form.
  • the solder layer 13 may be formed on the upper surface of the support substrate 11 prepared separately from the sapphire substrate 61 (see FIG. 9E).
  • the solder layer 13 may be made of the same material as the solder layer 15, and is bonded to the solder layer 13 in the next step, whereby the sapphire substrate 61 and the support substrate 11 are bonded together.
  • CuW is used as the support substrate 11 as described in the section of the structure.
  • Step S19 Next, as shown in FIG. 9F, the sapphire substrate 61 and the support substrate 11 are bonded together. More specifically, the solder layer 15 and the solder layer 13 formed on the upper layer of the support substrate 11 are bonded together at a temperature of 280 ° C. and a pressure of 0.2 MPa.
  • the sapphire substrate 61 is peeled off. More specifically, the interface between the sapphire substrate 61 and the epitaxial layer 40 is decomposed by irradiating a KrF excimer laser from the sapphire substrate 61 side with the sapphire substrate 61 facing upward and the support substrate 11 facing downward. Then, the sapphire substrate 61 is peeled off. While the laser passes through the sapphire 61, the underlying GaN (undoped layer 36) absorbs the laser, so that this interface is heated to decompose GaN. As a result, the sapphire substrate 61 is peeled off.
  • GaN (undoped layer 36) remaining on the wafer is removed by wet etching using hydrochloric acid or the like, and dry etching using an ICP apparatus, and the n-type nitride semiconductor layer 35 is exposed.
  • the undoped layer 36 is removed, and the second contact layer 34, the first contact layer 32, the p-type nitride semiconductor layer 31, the light emitting layer 33, and the n-type nitride semiconductor layer 35 are viewed from below.
  • the semiconductor layer 30 that is sequentially stacked remains.
  • Step S21 Next, as shown in FIG. 9H, adjacent elements are separated. Specifically, the semiconductor layer 30 is etched using an ICP device until the upper surface of the insulating layer 21 is exposed in a boundary region with an adjacent element. As described above, the insulating layer 21 also functions as a stopper during etching.
  • Step S22 Next, as shown in FIG. 9I, irregularities are formed on the surface of the n-type nitride semiconductor layer 35. Specifically, the unevenness is formed by immersing an alkaline solution such as KOH. At this time, unevenness may not be formed in a portion where the electrode 42 and the bonding electrode 43 are formed later. By not forming irregularities at these locations, the surface of the n-type nitride semiconductor layer 35 where the electrodes are to be formed is maintained in a flat state.
  • an alkaline solution such as KOH
  • the bonding electrode 43 and the n-type nitride semiconductor layer 35 are formed particularly when wire bonding is performed after the bonding electrode 43 is formed.
  • the effect of preventing the generation of voids at the interface can be obtained.
  • Step S23 Next, as shown in FIG. 9J, an electrode 42 and a bonding electrode 43 are formed on the upper surface of the n-type nitride semiconductor layer 35. More specifically, after forming an electrode made of Cr having a thickness of 100 nm and Au having a thickness of 3 ⁇ m, sintering is performed at 250 ° C. for 1 minute in a nitrogen atmosphere.
  • the exposed element side surface and the element upper surface other than the electrode 42 and the bonding electrode 43 are covered with an insulating layer 41 (see FIG. 1). More specifically, an SiO 2 film is formed by an EB apparatus. An SiN film may be formed. Then, the elements are separated from each other by, for example, a laser dicing apparatus, the back surface of the support substrate 11 is joined to the package by, for example, Ag paste, and wire bonding is performed on the bonding electrode 43. For example, wire bonding is performed by connecting a bonding wire 45 made of Au to a bonding region of ⁇ 100 ⁇ m with a load of 50 g. Thereby, the nitride semiconductor light emitting device 1 shown in FIG. 1 is formed.
  • Example 3 The nitride semiconductor light emitting device 1 manufactured by the above method was taken as Example 3.
  • the semiconductor layer 30 includes an n-type nitride semiconductor layer 35 made of Al 0.06 Ga 0.94 N having a Si concentration of 3 ⁇ 10 19 / cm 3 , a well layer made of InGaN, and an n-type AlGaN.
  • FIG. 10 shows a case where a voltage V is applied between the bonding electrode 43 and the support substrate 11 for the light-emitting element 1 of Example 3, the light-emitting element 80 of the conventional example, and the light-emitting element 81 of Comparative Example 1, respectively.
  • the relationship between the current I and the voltage V is graphed.
  • FIG. 10 shows that the same result as in FIG. 3 is obtained. That is, the light-emitting element 1 of Example 3 has a configuration in which the first contact layer 32 is not in contact with the metal electrode 19 without including the contact electrode 83, similarly to the conventional light-emitting element 80 provided with the contact electrode 83.
  • the voltage can be lowered as compared with the light emitting element 81 of Comparative Example 1. Therefore, according to the configuration of the present invention, it can be seen that a good contact property equivalent to or higher than that of the conventional light emitting element 80 having the contact electrode 83 can be realized without forming the contact electrode 83.
  • the contact electrode 83 using ITO having an absorption edge near 365 nm or Ni having an absorption edge longer than that is good without using the contact electrode 83 Since contact characteristics can be realized, the contact electrode 83 is not necessary. Thereby, absorption of ultraviolet light in the contact electrode 83 is suppressed, and an ultraviolet light emitting element with improved light extraction efficiency is realized.
  • step S14 the fact that the ohmic characteristics of the second contact layer 34 and the metal electrode 19 can be realized by annealing in an inert gas (in this case, nitrogen) atmosphere in step S14 will be described with reference to an example.
  • an inert gas in this case, nitrogen
  • Example 4 After Step S13, annealing was performed at 700 ° C. for 5 minutes in a nitrogen atmosphere using the RTA apparatus in the same manner as Step S14. Thereafter, metal electrodes 18 a and 18 b made of Ag were formed on the second contact layer 34 with a gap 73.
  • FIG. 11A and FIG. 11B are schematic diagrams of an element formed in this process (hereinafter referred to as “evaluation element 70”). As the evaluation element 70 corresponding to Example 4, a plurality of elements were formed in which the distance of the gap 73 sandwiched between the metal electrodes 18a and 18b was increased by 5 ⁇ m from 5 ⁇ m to 30 ⁇ m.
  • Comparative Example 2 After step S13, annealing was performed at 700 ° C. for 5 minutes in an air atmosphere using an RTA apparatus. Thereafter, in the same manner as in Example 4, the metal electrodes 18a and 18b made of Ag were formed in the upper layer of the second contact layer 34 with the gap 73, thereby producing an evaluation element. .
  • the evaluation element 71 corresponding to Comparative Example 2 is the same as the evaluation element 70 of Example 4 except that the annealing method is different. That is, the structure is the same as FIG. 11A and FIG. 11B, and, similarly to the fourth embodiment, a plurality of distances of the gap 73 sandwiched between the metal electrodes 18a and 18b are increased by 5 ⁇ m from 5 ⁇ m to 30 ⁇ m. An element was formed.
  • the IV characteristic shows nonlinearity, and the second contact layer 34 and the metal electrodes 18a and 18b are in Schottky contact. Is suggested.
  • the IV characteristic shows linearity, and it can be seen that ohmic contact can be realized.
  • annealing is performed in an inert gas atmosphere, so that the ohmic contact between the metal electrode 19 (metal electrodes 18a and 18b) and the second contact layer 34 formed thereafter is performed. It can be seen that contact can be realized.
  • Example 5 Except that the epitaxial layer 40 is formed in the MOCVD apparatus through the step S13 and then annealed at 700 ° C. for 5 minutes in a nitrogen atmosphere in the furnace of the MOCVD apparatus as it is, the same as in Example 4. An evaluation element was produced by the method (evaluation element 72).
  • FIG. 12C shows the result of measuring IV characteristics of the evaluation element 72 of Example 5 by the same method as in Example 4 and Comparative Example 2. Similar to the evaluation element 70 of Example 4 shown in FIG. 12A, it shows a linear IV characteristic, and it can be seen that an ohmic contact can be realized. However, the voltage value necessary for flowing the same current is larger than that in the fourth embodiment. For example, in the evaluation element in which the distance of the gap 73 is 5 ⁇ m, the voltage required to pass 1.0 mA in Example 4 is about 0.25 V, whereas in Example 5, it is about 2.5 V. .
  • the nitride semiconductor light emitting device 1 corresponding to Example 4 and Example 5 was manufactured, and the IV characteristics when a voltage was applied between the electrode (electrode 42, bonding electrode 43) and the support substrate 11 were obtained.
  • the measurement results are shown in FIG.
  • the nitride semiconductor light emitting device 1 corresponding to Example 4 is the same as the nitride semiconductor light emitting device 1 according to the fourth embodiment.
  • step S14 after performing step S13 in which epitaxial growth is performed in the furnace of the MOCVD apparatus, in step S14, annealing in a nitrogen atmosphere is subsequently performed in the furnace, and thereafter The device manufactured through steps S15 to S16 and steps S18 to S23.
  • FIG. 13 shows that the voltage required for supplying the same current to the nitride semiconductor light emitting device 1 is lower in Example 4 than in Example 5. This is consistent with the results of FIG. 12C. That is, when Example 4 and Example 5 are compared, the annealing process (step S14) after forming the second contact layer 34 is performed in the RTA apparatus rather than in the MOCVD apparatus. It can be seen that the semiconductor layer 31 is activated and the effect of improving the specific resistance and the contact property is obtained.
  • step S14 an ohmic contact between the second contact layer 34 and the metal electrode 19 is realized by performing an annealing process in an inert gas atmosphere. Further, it can be seen that the effect of improving the specific resistance and the contact property can be obtained by performing the annealing in the inert gas atmosphere not in the furnace of the MOCVD apparatus but in the RTA apparatus.
  • step S17 an annealing process is performed in an oxygen-containing atmosphere, thereby further improving the contact property between the second contact layer 34 and the metal electrode 19. This will be described with reference to an embodiment.
  • the element 1 of Example 3 described above with reference to FIG. 10 is manufactured through steps S13 to S23. More specifically, in step S14 immediately before the formation of the metal electrode 19, annealing is performed in a nitrogen-containing atmosphere in the RTA apparatus. Further, in step S17 immediately after the formation of the metal electrode 19, in an air atmosphere. Annealing treatment is performed.
  • Element 1 of Example 4 is an element manufactured without performing Step S17. That is, in step S14 immediately before forming the metal electrode 19, annealing is performed in a nitrogen-containing atmosphere in the RTA apparatus as in the third embodiment, but after the metal electrode 19 is formed in step S16. Is manufactured by sequentially performing step S18 and subsequent steps without performing the annealing process according to step S17.
  • Example 6 Further, for verification, the light emitting device 1 manufactured in the same manner as in Example 3 except that annealing was performed in a nitrogen-containing atmosphere in Step S ⁇ b> 17 immediately after forming the metal electrode 19 was obtained as Example 6. did.
  • FIG. 14 shows a case in which the nitride semiconductor light emitting device 1 corresponding to Example 3 and Example 6 was manufactured, and IV was applied when a voltage was applied between the electrodes (electrode 42, bonding electrode 43) and the support substrate 11. It is a graph which shows a result when a characteristic is measured.
  • Example 4 Comparing Example 4 shown in FIG. 13, Example 3 and Example 6 shown in FIG. 14, for example, the voltage value necessary to supply 1 A is about 5.0 V in Example 4, whereas In Example 3, it is about 3.8V, and in Example 6, it is about 5.1V.
  • the voltage value necessary for supplying the same current in the third embodiment is further reduced. That is, after forming the metal electrode 19, annealing is performed in an atmosphere containing oxygen such as air (step S 17), whereby Ag diffuses into the second contact layer 34 using oxygen as a driving force, thereby further improving contact properties. It turns out that the effect to improve is acquired.
  • Example 4 and Example 6 when Example 4 and Example 6 are compared, it is suggested that the voltage value required in order to supply the same electric current has hardly changed.
  • the annealing process (step S17) after the formation of the metal electrode 19 is performed in an oxygen-containing atmosphere, unlike step S14, and an effect of further improving the contact property can be obtained.
  • step S17 the annealing process after the formation of the metal electrode 19 is performed in an oxygen-containing atmosphere, unlike step S14, and an effect of further improving the contact property can be obtained.
  • step S17 after the formation of the metal electrode 19 is performed in an oxygen-containing atmosphere, unlike step S14, and an effect of further improving the contact property can be obtained.
  • the effect of further improving the contact property is hardly obtained.
  • both the first contact layer 32 and the second contact layer 34 may be formed of AlGaN having a predetermined composition ratio, and the metal electrode 19 may be formed of Al.
  • the following method can be employed in step S13.
  • the thickness of 5 nm is obtained by changing the flow rate of CP 2 Mg to 0.2 ⁇ mol / min and supplying the source gas for 20 seconds without stopping the supply of TMA.
  • a first contact layer 32 made of p + Al 0.13 Ga 0.87 N is formed.
  • the p-type impurity (Mg) concentration of the first contact layer 32 is, for example, about 1 ⁇ 10 20 / cm 3 .
  • the second contact layer 34 is formed continuously without interruption of growth.
  • the supply of CP 2 Mg is stopped, diethylzinc is adjusted to 0.1 ⁇ mol / min, and the source gas is supplied for 20 seconds, whereby the Zn-doped Al 0.13 Ga having a thickness of 5 nm is formed.
  • a second contact layer 34 made of 0.87 N is formed.
  • the impurity (Zn) concentration of the second contact layer 34 is, for example, about 5 ⁇ 10 19 / cm 3 .
  • the nitride semiconductor light emitting device and the method for manufacturing the same according to the fifth embodiment of the present invention will be described below.
  • the nitride semiconductor light emitting device of the fifth embodiment is common to the structure of the nitride semiconductor light emitting device 1a of the second embodiment shown in FIG.
  • Step S13 and step S14 are executed as in the fourth embodiment.
  • Step S24 After step S14 (see FIG. 9A), as shown in FIG. 7A, the second contact layer 34, the first contact layer 32, and the p-type nitride semiconductor are used until a partial upper surface of the n-type nitride semiconductor layer 35 is exposed.
  • the layer 31 and the light emitting layer 33 are removed by dry etching using an ICP device.
  • the n-type nitride semiconductor layer 35 may also be partially removed by etching.
  • a metal electrode (19, 19a) is formed by depositing Ag on the upper surface of the second contact layer 34 and the exposed upper surface of the n-type nitride semiconductor layer 35. Also in this embodiment, since a deep impurity level is formed in the second contact layer 34 by Zn doping, the metal made of the second contact layer 34 and Ag can be formed without forming a contact electrode such as Ni or ITO. Good contact characteristics can be obtained by bringing the electrode 19 into contact. In the present embodiment, as the metal electrode (19, 19a), Al or Rh can be used in addition to Ag.
  • the n-type nitride semiconductor layer 35 is made of AlGaN having a high concentration of n-type impurity concentration higher than 1 ⁇ 10 19 / cm 3 .
  • Step S26 Similar to step S17 of the fourth embodiment, annealing is performed in an atmosphere containing oxygen. More specifically, activation processing is performed in an RTA apparatus or MOCVD apparatus at about 450 ° C. for about 1 minute in an air atmosphere. Thereby, the effect of further improving the contact characteristics between the metal electrode 19 and the second contact layer 34 can be obtained.
  • a power supply terminal 51 is formed on the upper surface of the n-side metal electrode 19a, and a power supply terminal 52 is formed on the upper surface of the p-side metal electrode 19. More specifically, after forming a conductive material film (for example, a material film made of Cr with a thickness of 100 nm and Au with a thickness of 3 ⁇ m) to form the power supply terminals 51 and 52, the power supply terminals 51 and 52 are formed by lift-off. To do. Thereafter, sintering is performed at 250 ° C. for 1 minute in a nitrogen atmosphere.
  • a conductive material film for example, a material film made of Cr with a thickness of 100 nm and Au with a thickness of 3 ⁇ m
  • the substrate 55 and the power supply terminal 51 are connected via the bonding electrode 53, and the substrate 55 and the power supply terminal 52 are connected via the bonding electrode 54, thereby forming the nitride semiconductor light emitting element 1a shown in FIG.
  • the second contact layer 34 is GaN or AlGaN doped with Zn.
  • the second contact layer 34 is formed of Al X Ga Y In Z N (0 ⁇ ⁇ ) doped with at least one second impurity material of Zn, Cd, Be, Sr, Ca, and C.
  • the contact property with the metal electrode 19 can be improved.
  • the second contact layer 34 is made of Al X Ga Y In Z N containing a trace amount of another substance (such as Sb), the same effect is exhibited. It is not intended to exclude an element in which the second contact layer 34 is formed of such a material from the scope of rights.
  • a conductive oxide film layer may be formed instead of the insulating layer 21.
  • the conductivity is higher than that of the insulating layer 21, so that current easily flows in the semiconductor layer 30 in the vertical direction.
  • the conductive layer is more conductive than a normal conductive material (metal or the like). Since the rate is significantly low, the effect of spreading the current in the horizontal direction is realized.
  • the conductive oxide film layer for example, ITO, IZO, In 2 O 3 , SnO 2 , IGZO (InGaZnOx), or the like can be used.
  • the insulating layer 21 and the conductive oxide film layer are orthogonal to the substrate surface with respect to the position immediately below the electrodes (42, 43), that is, the electrodes (42, 43), in the sense of spreading the current in the horizontal direction.
  • the present invention is not intended to exclude an element having no insulating layer 21 or conductive oxide film layer from the scope of the right.
  • FIGS. 1 and 6 The structure shown in FIGS. 1 and 6 and the manufacturing method described above with reference to FIGS. 5A to 5I, FIGS. 7A to 7B, and FIGS. 9A to 9J are examples of preferred embodiments. Not all of these configurations and processes must be provided.
  • the solder layer 13 and the solder layer 15 are formed so as to efficiently bond two substrates, and if the bonding of two substrates can be realized, the nitride semiconductor It is not always necessary to realize the function of the light emitting element.
  • the protective layer 17 is preferably provided from the viewpoint of preventing the diffusion of the solder material and the unevenness of the surface of the n-type nitride semiconductor layer 35 from the viewpoint of improving the light extraction efficiency. It is not intended to exclude an element having a configuration not provided from the scope of rights. The same applies to other embodiments.
  • the solder layer is formed on both the sapphire substrate 61 and the support substrate 11 (solder layers 13 and 15). I do not care.
  • the protective layer 17 is formed on the sapphire substrate 61 side, it may be formed on the support substrate 11 side. That is, instead of the configuration shown in FIG. 5D, the protective layer 17 formed on the support substrate 11 and the solder layer 13 formed thereon may be bonded to the sapphire substrate 61 in step S5. The same applies to other embodiments.

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Abstract

　L'invention porte sur un élément émetteur de lumière à semi-conducteurs au nitrure ayant des caractéristiques de contact comparables à celles d'éléments émetteurs de lumière à semi-conducteurs au nitrure conventionnels, sans utiliser des électrodes de contact formées à partir des matériaux ITO ou Ni. Cet élément émetteur de lumière à semi-conducteurs au nitrure possède une couche émettrice de lumière entre une couche de semi-conducteur au nitrure de type n et une couche de semi-conducteur au nitrure de type p, et possède une première couche de contact en contact avec la couche de semi-conducteur au nitrure de type p, et constituée par une couche de semi-conducteur au nitrure dopée avec un premier matériau à impuretés à une concentration supérieure à celle de la couche de semi-conducteur au nitrure de type p, et une seconde couche de contact en contact avec la première couche de contact, et composée de AlXGaYInXN (0 ≤ X ≤ 1, 0 ≤ Y ≤ 1, 0 ≤ Z ≤ 1, X + Y + Z = 1) dopé avec un ou plusieurs seconds matériaux à impuretés quelconques sélectionnés parmi Zn, Cd, Be, Sr, Ca et C.
PCT/JP2014/060240 2013-05-31 2014-04-09 Élément émetteur de lumière à semi-conducteurs au nitrure et procédé pour fabriquer ce dernier WO2014192428A1 (fr)

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JPH10335757A (ja) * 1997-01-09 1998-12-18 Nichia Chem Ind Ltd 窒化物半導体素子
JP2001203385A (ja) * 2000-01-17 2001-07-27 Nichia Chem Ind Ltd 窒化物半導体発光ダイオード
WO2005122290A1 (fr) * 2004-06-14 2005-12-22 Mitsubishi Cable Industries, Ltd. Dispositif luminescent semi-conducteur à nitrure
WO2007052628A1 (fr) * 2005-10-31 2007-05-10 Nichia Corporation Élément semi-conducteur au nitrure

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JP2007059830A (ja) 2005-08-26 2007-03-08 Visual Photonics Epitaxy Co Ltd 反射層を具えた高輝度発光ダイオード

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JPH10335757A (ja) * 1997-01-09 1998-12-18 Nichia Chem Ind Ltd 窒化物半導体素子
JP2001203385A (ja) * 2000-01-17 2001-07-27 Nichia Chem Ind Ltd 窒化物半導体発光ダイオード
WO2005122290A1 (fr) * 2004-06-14 2005-12-22 Mitsubishi Cable Industries, Ltd. Dispositif luminescent semi-conducteur à nitrure
WO2007052628A1 (fr) * 2005-10-31 2007-05-10 Nichia Corporation Élément semi-conducteur au nitrure

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