JP5097460B2 - COMPOUND SEMICONDUCTOR ELEMENT, LIGHTING DEVICE USING SAME, AND METHOD FOR PRODUCING COMPOUND SEMICONDUCTOR ELEMENT - Google Patents

Description

  The present invention relates to a compound semiconductor element such as a III-V compound semiconductor, a lighting device using the compound semiconductor element, and a method for manufacturing the compound semiconductor element. In particular, the semiconductor element includes a nanoscale nanocrystal or nanorod on a substrate. The present invention relates to a structure in which a columnar crystal structure is formed.

In recent years, compound semiconductor light emitting devices having a light emitting layer composed of a nitride semiconductor or an oxide semiconductor have attracted attention. The structure of this light-emitting element is mainly composed of an n-cladding layer and contact layer made of an n ⁺ -GaN layer doped with silicon (Si) at the lower part of the light-emitting layer, and magnesium (Mg) at the upper part of the light-emitting layer. ) Doped p-Al _x Ga _1-x N, and a p-GaN contact layer is formed on the electron block layer. These planar light emitting devices (LEDs) have a large difference in lattice constant between the sapphire of the substrate and the nitride or oxide semiconductor layer and are formed as a thin film on the substrate. Therefore, it is difficult to increase the efficiency of the light-emitting element.

  Therefore, Patent Document 1 is known as a conventional example of a technique for solving such a problem. In this conventional example, after forming an n-type GaN buffer layer on a sapphire substrate, a large number of the columnar crystal structures (nanocolumns) arranged in an array are formed, and columnar crystals are formed between the GaN nanocolumns. A transparent electrode and an electrode pad are formed after embedding a transparent insulating layer for structural protection or the like. In particular, the blue GaN nanocolumn is composed of an n-type GaN nanocolumn, an InGaN quantum well, and a p-type GaN nanocolumn.

In this GaN nanocolumn LED, unlike the planar LED, the growth nuclei scattered during the growth of the GaN epilayer are bonded in the lateral (plane) direction and then grown in the vertical direction on the plane. Is grown in the vertical direction before bonding in the lateral (plane) direction, so threading dislocations do not exist in principle, and point defects generated around threading dislocations are overwhelmingly less than in the planar type. I can expect. For this reason, it is expected that a GaN single crystal having an extremely good crystal quality as compared with the planar type LED can be obtained, and the internal quantum efficiency can be drastically improved.
JP 2005-228936 A

  Although the problem of threading dislocation has been solved in the nanocolumn LED configured as described above, the amorphous n-type GaN buffer layer formed at a low temperature on the lower electrode on the sapphire substrate is a problem with the planar LED. Therefore, there is a problem that the series resistance of the lower electrode is higher than that of a planar LED using a single crystal n-type GaN layer formed thick at a high temperature.

  On the other hand, it is possible to lower the series resistance using a conductive substrate, but the conductive substrate is generally not transparent to the light emission of the LED, especially the blue light emitted from the InGaN / GaN light emitting layer, and the growth of the nanocolumns. However, in a conductive substrate such as Si, Ge, or GaAs, it is difficult to control the crystal axis and polarity as compared to an insulating substrate. For example, it is easy for sapphire to reduce the loss by reducing the on voltage and to grow a nitrogen polar nanocolumn effective for Mg doping control. In addition, the Si substrate can only be grown with Ga polarity.

  An object of the present invention is to realize a low-cost process suitable for mass production while using a metal layer with high conductivity as a lower electrode in forming a nanoscale columnar crystal structure on a high-resistance substrate. It is providing the compound semiconductor element which can be manufactured, the illuminating device using the same, and the manufacturing method of a compound semiconductor element.

The compound semiconductor device of the present invention is formed on the substrate in a compound semiconductor device having a plurality of nanoscale columnar crystal structures formed by laminating at least an n-type layer and a p-type layer on a high-resistance substrate, A metal layer having a through-hole for allowing the columnar crystal structure to grow from the substrate; and the metal layer has the columnar crystal at a growth temperature of a base end portion of the columnar crystal structure. or not make crystals react with the material of the structure, making crystals form even metal compound and formed Ri of a metal material material crystallized columnar crystal structures do not adhere, the lower electrode and the metal layer characterized Rukoto used as.

The method for producing a compound semiconductor element of the present invention is a method for producing a compound semiconductor element having a plurality of nanoscale columnar crystal structures in which at least an n-type layer and a p-type layer are stacked on a high-resistance substrate. On the substrate, the growth temperature of the base end portion of the columnar crystal structure does not react with the material of the columnar crystal structure to form a crystal, or even if a crystal is formed, a metal compound is formed, and the crystal Ri of a metal material material of the columnar crystal structures do not adhere to ized formed, forming a metal layer Ru is used as a lower electrode, a step of drilling a through hole in the metal layer, exposed by the through-hole Crystallizing a material of the columnar crystal structure on the surface of the substrate, and growing at least the n-type layer and the p-type layer.

  According to the above configuration, a nanoscale columnar crystal structure called a nanocolumn or a nanorod formed by laminating at least an n-type layer and a p-type layer is formed on a high-resistance substrate including insulation. In the compound semiconductor device, a metal layer having high conductivity is laminated as a lower electrode on a substrate, and the columnar crystal structure is grown from a through-hole formed in the metal layer. However, when a compound semiconductor material such as Ga, N, In, or Al, which is a material of the columnar crystal structure, or an additive material such as Mg, Si, or Zn crystallizes in the plane direction on the metal layer. Since it becomes impossible to grow a columnar crystal structure with few crystal defects, the growth temperature of the columnar crystal structure protrudes from the through-hole, that is, while the base end portion of the columnar crystal structure grows. Then, it does not form a crystal by reacting with the material of the columnar crystal structure, or a metal compound is formed even if the crystal is formed, and the crystallized columnar crystal structure material does not adhere to the high melting point metal material. A metal layer is formed.

  Therefore, when forming a nanoscale columnar crystal structure on a high-resistance substrate, a metal layer with high conductivity can be used as the lower electrode instead of a GaN buffer layer as in the conventional example, and suitable for mass production. It is possible to realize an inexpensive process.

  Furthermore, in the compound semiconductor device of the present invention, the metal layer is made of a single metal of Ti, Zr, Hf, Cr, or Nb and one of those nitrides.

  According to the above configuration, these materials do not react with the GaN crystal at the growth temperature of 800 ° C. or higher which is the growth temperature of the n-type layer which is the base end portion of the columnar crystal structure, or metal nitrides even when reacted. And is a metal material to which GaN does not adhere at 700 ° C. or higher, and is easily available industrially.

  In the compound semiconductor device of the present invention, the substrate is made of one of sapphire, MgO, spinel, and lithium aluminite.

  According to the above configuration, these materials can form an insulating substrate on which the columnar crystal structure can be grown with good crystals, and further against blue light emitted from the InGaN / GaN light emitting layer. The substrate is transparent, the crystal axis and polarity of the nanocolumn LED can be easily controlled, and can be easily obtained industrially.

  Furthermore, the lighting device of the present invention is characterized by using the above-described compound semiconductor element.

  According to the above configuration, it is possible to realize a highly efficient lighting device that is low in manufacturing cost and excellent in reliability.

  In the method for producing a compound semiconductor device of the present invention, the through hole is formed using any one of an anodic oxidation method, a nanoimprint method, and a holographic exposure method.

  According to said structure, the drilling process of a through-hole can be performed more efficiently.

As described above, the compound semiconductor device and the manufacturing method thereof of the present invention include a plurality of nanoscale columnar crystal structures in which at least an n-type layer and a p-type layer are stacked on a high-resistance substrate including insulation. In the compound semiconductor device formed and a method for manufacturing the compound semiconductor device, a metal layer is formed on the substrate before the columnar crystal structure is grown, and the columnar crystal structure is formed from a through-hole formed in the metal layer. In the growth temperature of the base end portion of the columnar crystal structure, the metal layer does not react with the material of the columnar crystal structure, or does not form a crystal. formed, and formed Ri from the crystallized high melting point metal material material of the columnar crystal structures do not adhere was, Ru using the metal layer as a lower electrode.

  Therefore, in forming a nanoscale columnar crystal structure on a high-resistance substrate, a metal layer with high conductivity can be used as the lower electrode, and an inexpensive process suitable for mass production can be realized.

  Furthermore, in the compound semiconductor device of the present invention, as described above, the metal layer is made of a single metal of Ti, Zr, Hf, Cr, or Nb and one of their nitrides.

  Therefore, the above-mentioned conditions can be satisfied, and it can be easily obtained industrially.

  In the compound semiconductor device of the present invention, as described above, the substrate is made of one of sapphire, MgO, spinel, and lithium aluminite.

  Therefore, an insulating substrate capable of growing the columnar crystal structure with a good crystal can be formed, and the substrate is transparent to blue light emitted from the InGaN / GaN light emitting layer. In the LED, the crystal axis and polarity can be easily controlled, and can be easily obtained industrially.

  Furthermore, the illumination device of the present invention uses the compound semiconductor element as described above.

  Therefore, it is possible to realize a highly efficient lighting device that is low in manufacturing cost and excellent in reliability.

  In addition, as described above, in the method for producing a compound semiconductor device of the present invention, the through hole is formed using any one of an anodic oxidation method, a nanoimprint method, and a holographic exposure method.

  Therefore, the through hole can be drilled more efficiently.

[Embodiment 1]
FIG. 1 is a cross-sectional view schematically showing a manufacturing process of a light-emitting diode which is a compound semiconductor element according to an embodiment of the present invention. First, as shown in FIG. 1A, a TiN thin film 2 which is a high melting point metal layer is deposited on a sapphire substrate 1 by 100 nm and an Al thin film 3 by 800 nm using a magnetron sputtering apparatus. Next, the Al thin film 3 on the TiN thin film 2 is anodized to form an Al ₂ O ₃ nanoporous (porous) thin film 4 as shown in FIG.

The anodic oxidation step generally includes a first anodic oxidation and etching step and a second anodic oxidation and etching step. First, in the first anodic oxidation, the substrate 1 is immersed in an oxalic acid solution of 0.35 mol and 60 ° C., a clip connected to the anode of the power source is connected to the substrate 1 side, and the oxalic acid solution The negative electrode of the power source is connected to the immersed electrode and a voltage of 42V is applied. The end determination of the anodization is performed by monitoring the anodization current, and ends when the thickness of the Al thin film 3 is reduced by 200 nm. Next, in the first etching, the substrate is immersed in a solution obtained by adding chromium oxide (powder) to phosphoric acid at 60 ° C. for 3 minutes. Subsequently, the second anodic oxidation is performed under the same conditions as the first anodic oxidation, and the process ends when the monitor current density becomes 0.01 mA / cm ² or less. Thereafter, the second etching is performed in the same manner as the first etching. In this way, the fine holes 4a formed by the first anodic oxidation can be enlarged by the second anodic oxidation, so that the fine holes 4a have a uniform hole diameter suitable for nanocolumn formation. In the anodization process, the reaction is accelerated by irradiating a halogen lamp and performing etching by a photochemical reaction, and the process can be shortened.

Subsequently, as shown in FIG. 1 (c), the said _Al 2 _{O 3} porous thin film 4 as a mask material, the TiN thin film 2 of the base is etched by milling apparatus using Ar ions, the _Al 2 _{O 3} porous The porous pattern of the porous thin film 4 is transferred to the underlying TiN thin film 2. Subsequently, by wet etching with phosphoric acid at 60 ° C. for about 30 minutes, the Al ₂ O ₃ porous thin film 4 used as a mask material is removed as shown in FIG. The porous TiN thin film 5 with the underlying sapphire substrate 1 exposed can be formed.

  Next, the sapphire / porous TiN substrate is placed in a molecular beam epitaxy (MBE) apparatus, irradiated with RF nitrogen plasma for 10 minutes, and then heated to 800 ° C. to perform normal GaN nanocolumn growth. As shown in FIG. 1E, an n-type GaN layer 6 is grown by about 1000 nm. Here, when the n-type GaN layer 6 on the base end side of the nanocolumn is first grown, the n-type GaN layer 6 grows on the sapphire substrate 1 exposed in the microhole 4a. A GaN single crystal does not grow on the porous TiN thin film 5. This is because at 800 ° C. or higher, Ti and GaN do not form crystals, and the adhesion rate of GaN onto the porous TiN thin film 5 is extremely low.

  Thereafter, the growth temperature is lowered to 600 ° C., and as shown in FIG. 1F, a multiple quantum well layer 7 and a p-type GaN layer 8 made of n-type GaN / InGaN are formed to complete a GaN nanocolumn LED 11. . At this time, by adjusting the gas flow rate of the compound material, the p-type GaN layer 8 gradually increases in diameter as shown in FIG. 1 (f) and is brought into contact with the p-type GaN layer 8 of the adjacent nanocolumn. And planer structure.

  Here, by lowering the growth temperature from 800 ° C. to 600 ° C., Ti and GaN form crystals, and the adhesion rate on the porous TiN thin film 5 also increases, which is expanded to FIG. As shown, a multi-quantum well layer 7a and a p-type GaN layer 8a made of n-type GaN / InGaN are laminated on the porous TiN thin film 5 to form a GaN / InGaN single crystal laminated film 9. However, depending on the diameter expansion of the p-type GaN layer 8 and the height of the nanocolumn, the supply of the source gas to the base end side of the nanocolumn is small, and the growth of the GaN / InGaN single crystal multilayer film 9 is caused by the multiple quantum well layer 7. It is slightly more than that of the p-type GaN layer 8. Then, as shown by the arrows in FIG. 1 (g), all the GaN nanocolumn LEDs 11 formed on the chip are connected to each other through the porous TiN thin film 5 electrically connected to the n-type electrode layer in the chip. An n-type contact can be made.

  FIG. 2 is a schematic diagram for explaining an example of electrode formation on the GaN substrate 10 produced as described above. FIG. 2A is a plan view of a GaN substrate 10 having a planar p-type GaN layer 8 as shown in FIG. 1F, and the GaN nanocolumn LED 11 shown in FIG. It is formed on the entire surface of the substrate 10. 2B is applied to the GaN substrate 10 by photolithography, and the GaN nanocolumn LEDs 11 other than the mask 12 are removed by RIE etching, leaving only the underlying porous TiN thin film 5. Thus, as shown in FIG. 2C, a chip having the GaN nanocolumn LED 11 in the center and the porous TiN thin film 5 in the periphery is completed.

  With respect to the chip, as shown in FIG. 2D, a transparent conductive film 13 and a p-type pad electrode 14 are formed on the p-type GaN layer 8, and the porous TiN thin film serving as an n-type electrode layer is formed. An n-type pad electrode 15 is also formed on the periphery of 5, and wires 16 and 17 for leading out external electrodes are wire-bonded to each to complete a light emitting diode.

  FIG. 3 is a schematic cross-sectional view for explaining an example when the GaN substrate 10 is flip-chip mounted. A recess 31 is formed in the center of the ceramic package 30 used for mounting. A p-type wiring 38 and an n-type wiring 39 are patterned on the bottom 32 of the recess 31. These wirings 38 and 39 are packaged. It is taken out to the outside. On the wirings 38 and 39, the GaN substrate 10 is bump-bonded by Au bumps 36 and 37, respectively. Further, an Al thin film 34 is formed on the wall surface 33 of the recess 31 of the ceramic package 30 so as to reflect the light emitted from the nanocolumn light emitting element with a minimum loss, and the entire recess 31 is made of a translucent sealing resin. 35 is sealed.

  With this configuration, when forming the GaN nanocolumn LED 11 on the insulating sapphire substrate 1, the porous TiN thin film 5, which is a metal layer having high conductivity, is used instead of the GaN buffer layer as in the conventional example. It can be used as a lower electrode and can realize an inexpensive process suitable for mass production.

  In the above description, although the porous TiN thin film 5 made of a titanium nitride film is used as the metal layer serving as the lower electrode, the conductivity is high, and the base end portion of the nanocolumn (the n-type GaN layer 6 in FIG. 1) is formed. During growth, at the growth temperature (800 ° C. in FIG. 1), it reacts with compound semiconductor materials such as Ga, N, In, and Al, which are nanocolumn materials, and additive materials such as Mg, Si, and Zn. A high melting point metal material that does not form a crystal, forms a metal compound even when the crystal is formed, and does not adhere to the crystallized nanocolumn material may be used. As another embodiment of the present invention, Ti, Zr, Single metals of Hf, Cr, Nb and one of their nitrides can be used. These materials are metal materials that do not react with GaN crystals at 800 ° C or higher, or form metal nitrides even when reacted, and GaN does not adhere to them at 700 ° C or higher, and are industrially easy. And are suitable.

  In the above description, the sapphire substrate 1 is used as the substrate. However, MgO, spinel, lithium aluminumite, or the like can be used as another embodiment of the present invention. These materials can grow nanocolumns with good crystals, and are transparent to blue light emitted from the multiple quantum well layer (light emitting layer) 7 made of InGaN / GaN. It is easy to control the polarity and is easily available industrially and is suitable.

  Furthermore, when forming the porous thin film 4 shown in FIG. 1B, a mask 18 having a mesh pattern as shown in FIG. 2E may be used. In the portion covered with the mask 18, the fine holes 4a, and therefore the nanocolumns, are not formed, and the porous TiN thin film 5 serving as the lower electrode (n-type electrode layer) is left as it is. Therefore, the resistance of the lower electrode can be further reduced.

[Embodiment 2]
FIG. 4 is a cross-sectional view schematically showing a manufacturing process of a light-emitting diode which is a compound semiconductor element according to another embodiment of the present invention. The present embodiment is similar to the manufacturing process shown in FIG. It should be noted that in the present embodiment, any one of an anodic oxidation method, nanoimprint method, and holographic exposure method (in this example of FIG. 4, nanoimprint method) is used to form the fine holes 4a that are through holes. Is to be.

  That is, first, as shown in FIG. 2A, a Zr thin film 22 is deposited to 100 nm on an MgO substrate 21 using a magnetron sputtering apparatus, and a photoresist 23 is applied to 800 nm by spin coating. Next, using the nanoimprint technique, as shown in FIG. 2B, the photoresist 23 is etched to form a photoresist mask 24 having the fine holes 4a.

  Thereafter, as shown in FIG. 2C, the underlying Zr thin film 22 is etched by a milling apparatus using Ar ions using the photoresist mask 24 as a mask material, and the pattern of the photoresist mask 24 is changed to the underlying Zr thin film. 22 is transferred. Subsequently, as shown in FIG. 2D, the lower electrode layer 25 can be formed by removing the photoresist mask 24 using a normal lithography technique. Thereafter, a GaN nanocolumn LED can be realized by the method shown in FIG.

  By forming the fine holes 4a using such a mated mask, the arrangement of the fine holes 4a, and hence the GaN nanocolumn LEDs, that is, the arrangement pitch and arrangement pattern, and the column diameter can be arbitrarily set. Utilizing the advantages of GaN nanocolumn LEDs with few crystal defects, the generated light can be efficiently extracted to the outside, and the optical characteristics can be realized as intended by the designer, such as with the desired light distribution. be able to. For example, the light extraction efficiency can be improved by arranging the fine holes 4a so as to form a two-dimensional photonic crystal arrangement by the layout design of the nanoimprint mold.

  Further, by adjusting the column diameter of the GaN nanocolumn LED, light having a desired wavelength can be generated without using a phosphor for wavelength conversion. Moreover, GaN nanocolumn LEDs with multicolor emission can be realized on the same substrate, and by combining them, it is possible to produce a wide variety of colors, and at the same time, white light emission is possible. Can produce shades. For example, if three colors of R, G, and B are generated, it can be combined with white light, and if two colors of Y and B are generated, it can be combined with pseudo white light. Thus, a light-emitting diode adapted to white light can be realized, and the light-emitting diode is extremely suitable for a lighting device in combination with the low manufacturing cost and excellent reliability as described above.

  The present invention can be applied not only to a nitride semiconductor (GaN) but also to an oxide semiconductor. Further, the present invention can be applied not only to group III atoms and nitrogen atoms, but also to group II atoms and oxygen atoms and combinations thereof.

It is sectional drawing which shows typically the manufacturing process of the light emitting diode which is a compound semiconductor element which concerns on one Embodiment of this invention. It is a schematic diagram for demonstrating an example of electrode formation with respect to the GaN substrate produced as shown in FIG. It is typical sectional drawing for demonstrating an example in the case of flip-chip mounting the GaN board | substrate produced as shown in FIG. It is sectional drawing which shows typically the manufacturing process of the light emitting diode which is a compound semiconductor element which concerns on the other form of implementation of this invention.

Explanation of symbols

1 sapphire substrate 2 TiN thin film 3 Al thin film 4 Al ₂ O ₃ porous film 4a micropores 5 porous TiN film 6 n-type GaN layer 7 multi-quantum well layer 8 p-type GaN layer 10 GaN substrate 11 GaN nano-columns LED
12 mask 13 transparent conductive film 14 p-type pad electrode 15 n-type pad electrodes 16 and 17 wire 18 mask 21 MgO substrate 22 Zr thin film 23 photoresist 24 photoresist mask 25 lower electrode layer 30 ceramic package 31 recess 34 Al thin film 35 sealing Resin 36, 37 Au bump 38 p-type wiring 39 n-type wiring

Claims (6)

In a compound semiconductor device having a plurality of nanoscale columnar crystal structures in which at least an n-type layer and a p-type layer are stacked on a high-resistance substrate,
A metal layer formed on the substrate and having a through-hole for growing the columnar crystal structure from the substrate;
The metal layer reacts with the material of the columnar crystal structure at the growth temperature of the base end portion of the columnar crystal structure or does not form a crystal, or even if a crystal is formed, a metal compound is formed and crystallized. Ri metallic material a material is not adhered columnar crystal structure was formed, a compound semiconductor device according to claim Rukoto using the metal layer as a lower electrode.   2. The compound semiconductor device according to claim 1, wherein the metal layer is made of a single metal of Ti, Zr, Hf, Cr, or Nb and one of nitrides thereof.   3. The compound semiconductor device according to claim 1, wherein the substrate is made of one of sapphire, MgO, spinel and lithium aluminite.   The illuminating device using the compound semiconductor element of any one of the said Claims 1-3. In a method for manufacturing a compound semiconductor device having a plurality of nanoscale columnar crystal structures in which at least an n-type layer and a p-type layer are stacked on a high-resistance substrate,
On the substrate, the growth temperature of the base end portion of the columnar crystal structure does not react with the material of the columnar crystal structure to form a crystal, or even if a crystal is formed, a metal compound is formed and crystallized. Ri of a metal material material of the columnar crystal structures do not adhere to the forming, a step of forming a metal layer Ru is used as the lower electrode,
Drilling a through hole in the metal layer;
Crystallizing the material of the columnar crystal structure on the substrate surface exposed in the through-hole, and growing at least the n-type layer and the p-type layer. .   6. The method of manufacturing a compound semiconductor device according to claim 5, wherein the step of forming the through hole uses any one of an anodic oxidation method, a nanoimprint method, and a holographic exposure method.

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