JP2004282106A - Semiconductor light emitting device and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light emitting device which can easily be worked and has an excellent function in luminescence. <P>SOLUTION: A conductive substrate 8 is made of iron-nickel alloy, and a conductive adhesive is made of Au-Sn solder 7. The manufacturing method of a semiconductor light emitting device comprises the steps of, laminating GaN based semiconductor layers including light emitting layer on a GaAs (111) A substrate 1, fixing an electrode surface provided on the above-mentioned lamination surface and the conductive substrate with a conductive adhesive, and removing the GaAs (111) A substrate 1. The GaAs (111) A substrate 1 is removed by wet etching by ammonia based etchant. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to mainly blue and green light emitting devices using a gallium nitride (GaN) semiconductor and a method for manufacturing the same.

  FIG. 6 is, for example, the Nikkei Science October issue (1994), p. FIG. 44 is a cross-sectional view showing a structure of a GaN-based blue and green light-emitting device using a currently commercially available sapphire substrate described in No. 44.

  The blue and green light emitting elements are formed on an epitaxial wafer composed of a sapphire substrate 11, a GaN buffer layer 12 formed on the substrate 11, and a hexagonal GaN epitaxial layer 13 formed on the GaN buffer layer 12. Then, a clad layer 14, a light emitting layer 15, a clad layer 16, and a GaN epitaxial layer 17 are sequentially formed to form a structure in which nitride-based semiconductor layers are stacked. Electrodes 18 and 19 are formed on the GaN epitaxial layers 13 and 17, respectively. In the blue and green light-emitting elements, the GaN buffer layer 12 is provided to reduce distortion due to a difference in lattice constant between the sapphire substrate 11 and the GaN epitaxial layer 13.

  Since the above blue and green light emitting elements use insulating sapphire as the substrate 11, it is necessary to form two kinds of electrodes on the same surface side when forming an element by forming electrodes. Therefore, patterning by photolithography is required twice or more, and it is also necessary to perform nitride etching by reactive ion etching, which requires a complicated process.

  In addition, sapphire has a high hardness, and thus has a problem in that it is difficult to cut the element during element isolation. Therefore, an attempt has been made to use conductive GaAs as a substrate instead of sapphire having such a defect.

  For example, in Journal of Crystal Growth 164 (1996), p149, growth of cubic GaN on a GaAs (100) plane is described in Journal of Electronic Materials vol. 24 No. 4 (1995), p213, reports the growth of GaN on GaAs (111) A and GaAs (111) B surfaces by MOVPE (metal organic vapor phase epitaxy).

Further, Japanese Patent Application Laid-Open No. 8-181070 discloses an organometallic chloride vapor phase epitaxial method capable of growing a GaN epitaxial layer having good characteristics in a temperature range of 700 ° C. (700 ° C.) or higher. In this method, a group III organic metal, which is a raw material of a III compound semiconductor, is introduced into a reaction tube at the same time as hydrogen chloride, whereby a group III element is supplied as chloride on a substrate.
JP-A-8-181070 Nikkei Science October issue (1994), p. 44 Journal of Crystal Growth 164 (1996), p149 Journal of Electronic Materials vol. 24 No. 4 (1995), p. 213

  Conventional GaN-based semiconductor light-emitting elements use insulating and hard sapphire for the substrate, which requires a complicated process for electrode fabrication and difficulties such as cutting during element isolation are also difficult. It is as follows. Thus, such a problem can be solved by using a substrate such as conductive GaAs.

  However, when a GaAs substrate is used, for example, light emitted from the light emitting layer of the GaN-based semiconductor layer is absorbed by the GaAs substrate, and the intensity of light reflected from the substrate decreases. Therefore, when a GaAs substrate is used, a sufficient emission intensity cannot be obtained. It is considered that the band gap (difference in quantum state energy of electrons in the crystal) of the GaAs substrate is smaller than that of the GaN-based semiconductor layer.

  An object of the present invention is to provide a semiconductor light emitting device which can easily be manufactured and solves the above-mentioned problems and emits good light.

  The semiconductor light emitting device according to the present invention includes a p-type GaN layer provided with a p-type electrode, a conductive substrate bonded to the p-type electrode with a conductive adhesive, and a GaN layer formed on the p-type GaN layer. A stacked structure of a base semiconductor layer, or an n-type GaN layer provided with an n-type electrode, a conductive substrate bonded to the n-type electrode with a conductive adhesive, and formed on the n-type GaN layer. It has a laminated structure of GaN-based semiconductor layers.

  In the semiconductor light emitting device of the present invention, the conductive substrate is an Fe-Ni alloy or a Cu-W alloy, and the conductive adhesive is Au-Sn solder or Pb-Sn solder.

  The method for manufacturing a semiconductor light emitting device according to the present invention includes growing a GaN-based semiconductor layer stack on a growth substrate of GaAs, InP, InAs or GaP, and then forming an electrode surface provided on the surface of the stack with a conductive adhesive. It adhered to the conductive substrate. Then, the growth substrate made of GaAs, InP, InAs or GaP is removed.

  Further, the growth substrate is a cubic (111) substrate, and the GaN-based semiconductor layer is hexagonal. In particular, the growth substrate is GaAs (111) A, and the GaN-based semiconductor layer is hexagonal. The growth substrate is removed by wet etching with an ammonia-based etchant.

  The semiconductor light emitting device according to the present invention is a p-type gallium nitride layer provided with a p-type electrode or an n-type gallium nitride layer provided with an n-type electrode, and is bonded to the p-type or n-type electrode with a conductive adhesive. A conductive substrate, and a gallium nitride-based semiconductor layer including a light-emitting layer grown on the p-type or n-type gallium nitride layer and on the surface opposite to the surface on which the p-type or n-type electrode is provided. And a laminate.

  In the semiconductor light emitting device of the present invention, the conductive substrate is preferably an iron-nickel (Fe-Ni) alloy or a copper-tungsten (Cu-W) alloy.

  In the semiconductor light emitting device of the present invention, the conductive adhesive may be gold-tin solder or lead-tin solder.

  The method for manufacturing a semiconductor light emitting device of the present invention includes the steps of: forming a conductive adhesive on an electrode surface provided on the surface of a stack of gallium nitride-based semiconductor layers including a light emitting layer grown on a growth substrate; After that, the substrate for growth is removed to manufacture.

  In the manufacturing method of the present invention, the growth substrate is preferably gallium arsenide (GaAs), indium phosphide (InP), indium arsenide (InAs), or gallium phosphide (GaP).

  In the manufacturing method of the present invention, the growth substrate is a cubic (111) substrate made of gallium arsenide (GaAs), indium phosphide (InP), indium arsenide (InAs) or gallium phosphide (GaP), and the gallium nitride-based semiconductor Preferably, the layer is hexagonal.

  In the manufacturing method of the present invention, the growth substrate is preferably a cubic (111) A substrate made of gallium arsenide (GaAs).

  In the manufacturing method of the present invention, the growth substrate may be removed by wet etching using an ammonia-based etchant.

  A semiconductor light-emitting device according to the present invention includes a stack including a gallium nitride-based semiconductor layer including a light-emitting layer, an electrode provided on a surface of the stack, and a conductive substrate bonded to the electrode with a conductive adhesive. .

  In the semiconductor light emitting device of the present invention, the conductive substrate is preferably made of an iron-nickel (Fe-Ni) alloy or a copper-tungsten (Cu-W) alloy.

  In the semiconductor light emitting device of the present invention, the conductive adhesive may be gold-tin (Au-Sn) solder or lead-tin (Pb-Sn) solder.

  As described above, according to the present invention, it is possible to provide a semiconductor light-emitting element that emits light with low absorption of light on a substrate and can easily manufacture the semiconductor light-emitting element.

  The description of the embodiments of the present invention mainly relates to a blue and green light emitting device using a gallium nitride (GaN) based semiconductor and a method of manufacturing the same. The semiconductor light emitting device according to the embodiment of the present invention does not include an insulating layer in the structure of the light emitting device. Therefore, a complicated process is not required for forming an electrode unlike the case where sapphire, which is an insulating layer, is used for a substrate. When a growth substrate is made of GaAs having a band gap smaller than that of the GaN-based semiconductor light-emitting layer, the GaN-based semiconductor layer including the light-emitting layer is stacked on the conductive substrate using a conductive adhesive. Then, if the growth substrate on which the stack is grown is removed, light is no longer absorbed by the growth substrate, resulting in good light emission.

  When an Fe—Ni alloy or a Cu—W alloy having excellent conductivity and thermal conductivity is used as the conductive substrate, light emission with low power consumption is possible and heat is released well.

  Au-Sn solder having a melting point of 250 ° C. (250 ° C.) or more (for example, a commercial product having a melting point of 280 ° C. (280 ° C.)) or Pb-Sn solder (eg, a melting point of 280 ° C. (280 ° C.)) is used for the conductive adhesive. The use of a commercial product of (degree)) can raise the temperature to about 200 ° C. (200 degrees Celsius) for electrode formation, and a good electrode can be easily formed.

  When GaAs, InP, InAs or GaP is used as a growth substrate on which a stack of GaN-based semiconductor layers is formed, the growth substrate can be easily removed by etching. When a cubic (111) substrate is used, hexagonal GaN can be epitaxially grown.

  Furthermore, when a GaAs (111) A substrate (a GaAs substrate in which the (111) plane is entirely Ga) is used, a good stack of GaN-based semiconductor layers can be manufactured.

  When wet etching is performed using an ammonia-based etchant for etching the GaAs substrate, the GaAs substrate can be easily removed by etching, and the GaN-based semiconductor layer and its lamination are not damaged. Is preferred.

  Next, an embodiment that specifically shows how to implement the present invention will be described.

(Example) Organometal chloride vapor phase epitaxial method (The outline of the apparatus is shown in FIG. 4, but a GaAs (111) A substrate 1 is placed in a reaction chamber 54 made of quartz. 52, an exhaust port 53, and a resistance heater 55. This apparatus is the same as the apparatus disclosed in Japanese Patent Application Laid-Open No. 8-181070 disclosed by the present inventors. A GaN buffer layer 2 having a thickness of 100 nm and a n-type GaN layer having a carrier concentration of 1 × 10 ¹⁹ (cm ⁻³ ) having a thickness of 2 μm on a GaAs (111) A substrate 1 having a micrometer (μm). 3. From the InGaN light emitting layer 4 having a thickness of 0.1 μm (μm), from the p-type GaN layer 5 having a thickness of 0.5 μm (μm) and a carrier concentration of 1 × 10 ¹⁸ (cm ⁻³ ) 0.5 μm (μm) GaN-based semiconductor layers were grown in this order.

  An electrode 6 is formed by evaporating Ni and Au in this order on the p-type GaN layer 5 which is the outermost surface of the GaN-based semiconductor layer stack, and alloyed at 400 ° C. (400 degrees Celsius) for 5 minutes. gave. FIG. 2 shows a cross section of an epitaxial wafer composed of a GaAs (111) A substrate 1, a lamination composed of a GaN-based semiconductor layer, and an electrode 6.

Thereafter, using a commercially available Au-Sn solder 7 having a melting point of 280 ° C. (280 degrees Celsius), the electrode 6 on the p-type GaN layer 5 on the outermost surface is made of an Fe—Ni alloy (46% by weight of Ni). The remaining portion is made of Fe and unavoidable impurities.). (FIG. 3)
The epitaxial wafer shown in FIG. 3 was immersed (wet-etched) for 90 minutes in a solution of ammonia water and hydrogen peroxide mixed at a ratio of 1: 2 and maintained at 25 ° C. (25 degrees Celsius). Only the substrate 1 was removed to obtain the structure shown in FIG.

  An indium (In) electrode is formed at 200 ° C. (200 degrees Celsius) on the GaN buffer layer 2 on the outermost surface of the structure in FIG. 1, and a current is applied between the electrode 6 and Ni and Au deposited in this order. And emitted blue light. In addition, instead of using an Fe-Ni alloy consisting of 46% by weight of Ni and the balance being Fe and unavoidable impurities, a good blue color can be obtained by using a sintered alloy of 80% by weight and 20% of Cu. Emitted.

  (Comparative Example) In order to observe the difference in light emission intensity due to light absorption of the two different substrates of the Fe-Ni alloy substrate and the GaAs substrate, the cross-section of the epitaxial wafer shown in FIG. 5 was compared. Example.

  That is, an electrode 9 having a laminated structure including an AuGeNi alloy layer, a Ni layer, and an Au layer is formed on the GaAs (111) A substrate 1 side in the structure of FIG. 2, and the electrode 9, Ni, and Au are deposited in this order. When a current was applied between the electrodes 6 and 6, the device emitted blue light. However, the light emission intensity of the comparative example was about 70% weaker than the light emission intensity of the above example.

FIG. 4 is a cross-sectional view showing the structure of the epitaxial wafer up to when the GaAs substrate is removed by etching in the example. It is sectional drawing which shows the structure of an epitaxial wafer until a p-type electrode is produced in an Example. FIG. 3 is a cross-sectional view showing the structure of the epitaxial wafer up to when the p-type GaN layer side is bonded to an iron-nickel alloy in the example. FIG. 1 is a diagram showing an outline of an apparatus of an organic metal chloride vapor phase epitaxial method. FIG. 4 is a cross-sectional view showing a structure of an epitaxial wafer up to when an electrode is formed on a GaAs substrate side in a comparative example. It is sectional drawing which shows the structure of an example of the blue semiconductor light emitting element using a sapphire substrate.

Explanation of reference numerals

1: GaAs (111) A substrate 2: GaN buffer layer 3: n-type GaN layer 4: InGaN light-emitting layer 5: p-type GaN layer 6: electrode 7 deposited in the order of Ni and Au 7: Au-Sn solder 8: Fe-Ni alloy conductive substrate 9: Electrode having a laminated structure composed of AuGeNi alloy layer, Ni layer and Au layer

Claims (3)

  a p-type gallium nitride layer provided with a p-type electrode or an n-type gallium nitride layer provided with an n-type electrode; a conductive substrate bonded to the p-type or n-type electrode with a conductive adhesive; Or, a stacked structure of a gallium nitride-based semiconductor layer including a light-emitting layer grown on a surface opposite to the surface on which the p-type or n-type electrode is provided on the n-type gallium nitride layer A semiconductor light emitting device characterized by the above-mentioned.   After bonding an electrode surface provided on the surface of a stack of gallium nitride-based semiconductor layers including a light emitting layer grown on a growth substrate and a conductive substrate using a conductive adhesive, the growth substrate The method for manufacturing a semiconductor light emitting device according to claim 1, wherein the semiconductor light emitting device is manufactured by removing. A stack of gallium nitride based semiconductor layers including a light emitting layer,
An electrode provided on the surface of the laminate;
And a conductive substrate bonded to the electrode with a conductive adhesive.

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