JP2011258631A - Light-emitting diode element and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such a problem that a light-emitting element cannot be formed when graphite is used as a substrate on which a nitride semiconductor thin film of GaN, or the like, is formed because a GaN thin film becomes polycrystal and defects increase in the crystal.SOLUTION: On a graphite substrate 101 provided with an amorphous carbon layer 102, a c-axis orientation film of an AIN layer 103 is grown by an MOCVD method. A low temperature growth buffer layer 104 and a first n-type GaN layer 105 are then sequentially grown epitaxially on the AIN layer 103, and a mask layer 106 having an opening is formed on the first n-type GaN layer 105. Thereafter, a second n-type GaN layer 107, a multilayer quantum well layer 108 consisting of InGaN and GaN, a p-type GaN layer 109, and a p-type GaN contact layer 110 are sequentially grown epitaxially on the first n-type GaN layer 105 from the opening of the mask layer 106.

Description

  The present invention relates to a light emitting diode element composed of a nitride semiconductor.

  In recent years, intensive research and development have been conducted on semiconductor elements composed of nitride semiconductors typified by gallium nitride (GaN). Semiconductor elements made of aluminum nitride (AlN), GaN, indium nitride (InN) and mixed crystals thereof can emit light in a wide wavelength range from ultraviolet or blue to infrared by controlling the film composition. Can do. Patent Document 1 discloses a visible light emitting diode element using a columnar nitride semiconductor.

FIG. 8 shows a cross-sectional configuration of a light-emitting diode element made of a columnar nitride semiconductor according to a first conventional example. As shown in FIG. 8, the light emitting diode device of the first conventional example includes a buffer layer 20 made of GaN grown on the main surface of a substrate 10 and a columnar n-type GaN layer formed on the buffer layer 20 in large numbers. 31, a quantum well layer 33 made of In _x Ga _1-x N and GaN formed on the columnar n-type GaN layer 31, and a p-type GaN layer 35. Further, a transparent electrode 60 is formed on the p-type GaN layer 35, and an n-side electrode 50 is formed on the buffer layer 20.

  The light emitting diode element of the first conventional example uses columnar GaN to achieve higher luminance and higher light emission efficiency than a light emitting diode element using laminated film GaN.

  In the light emitting diode device as shown in the first conventional example, it is necessary that the crystal defects of the GaN layer be reduced as much as possible in order to suppress carrier recombination due to non-emissive transition caused by lattice defects and through defects. To do. This requires a single crystal substrate such as sapphire that lattice matches with the nitride semiconductor, leading to high costs.

  In order to realize further high luminance and high luminous efficiency of the light emitting diode element, it is necessary to increase the heat dissipation of the substrate. However, the thermal conductivity of single crystal substrates such as sapphire is insufficient.

  In order to solve these problems, Patent Document 2 discloses a method for producing a polycrystalline nitride semiconductor thin film on graphite by using a low-cost and high thermal conductivity graphite as a substrate and by pulse sputtering. ing.

JP 2005-228936 A JP 2009-200207 A

  However, since the GaN thin film produced on the graphite by the pulse sputtering method is a polycrystal, the thin film has many defects. Due to the defect, the GaN thin film is not suitable for a light emitting diode element. Furthermore, since the nitride semiconductor thin film formed by the pulse sputtering method is greatly damaged by the discharge plasma at the time of film formation, it is well known that the crystal of the thin film has a large number of defects. For this reason, it is very difficult to produce p-type GaN which is indispensable when producing a light-emitting diode element using the method of producing a nitride semiconductor by the pulse sputtering method disclosed in Patent Document 1. .

  The present invention solves the above-mentioned conventional problems, and uses a metal oxide chemical vapor deposition (MOCVD) method that is most suitable for the manufacture of semiconductor elements, using inexpensive graphite with high thermal conductivity as a substrate. Accordingly, an object of the present invention is to provide a low-cost and high-performance nitride light-emitting diode device.

In order to solve the conventional problems, a light emitting diode device of the present invention includes a graphite substrate, an amorphous carbon layer formed on the graphite substrate, and a c-axis orientation formed on the amorphous carbon layer by MOCVD. An AlN layer, a low-temperature growth buffer layer of GaN formed on the AlN layer, a first n-type GaN layer formed on the low-temperature buffer layer, and a first n-type GaN layer A mask layer having a plurality of openings, a second n-type GaN layer formed on the first n-type GaN layer in the opening of the mask layer, and on the second n-type GaN layer A formed multilayer quantum well layer made of In _x Ga _1-x N and GaN, a p-type GaN layer formed on the multilayer quantum well layer, and a p-type GaN contact formed on the p-type GaN layer Layer and The p-side electrode provided on the p-type GaN contact layer and the n-side electrode provided on the first n-type GaN layer, and the low temperature formed thereon with respect to the AlN layer A growth buffer layer, the first n-type GaN layer, the second n-type GaN layer, the multilayer quantum well layer, the p-type GaN layer, and the p-type GaN contact layer are epitaxially grown, and the second n-type The GaN layer, the multilayer quantum well layer, the p-type GaN layer, and the p-type GaN contact layer constitute a plurality of columnar structures, and the p-side electrode is the p-type GaN contact layer at the tip of the columnar structure. Are all cross-linked.

  With this configuration, a high-quality nitride semiconductor with few defects in which AlN and GaN are c-axis oriented using MOCVD can be realized on a graphite substrate. Therefore, a light emitting diode element made of a columnar nitride semiconductor can be directly manufactured on a graphite substrate.

  According to the light emitting diode device of the present invention, an amorphous carbon layer is provided on a graphite substrate, and an AlN c-axis alignment film is grown on the amorphous carbon layer by MOCVD, so that a high-quality columnar shape is directly formed on the graphite substrate. GaN can be manufactured, and a light-emitting diode element having excellent characteristics can be realized at low cost. In the following “Brief description of the drawings”, “SEM observation photograph” and “TEM observation photograph” mean “SEM observation image” and “TEM observation image”, respectively.

1 is a cross-sectional configuration diagram of a light-emitting diode element according to Embodiment 1 of the present invention. Cross-sectional block diagram of the order of the process of the manufacturing method of the light emitting diode element in Embodiment 1 of this invention (A) Surface SEM observation photograph when AlN is deposited on the graphite substrate not subjected to the oxidation treatment in Embodiment 1 of the present invention using the MOCVD method. (B) MOCVD on the graphite substrate subjected to the oxidation treatment. SEM observation photograph when AlN was deposited using the method (A) Cross-sectional TEM observation photograph near the interface between the graphite substrate and the AlN layer in Embodiment 1 of the present invention (b) Lattice image photograph by high resolution TEM near the interface between the graphite substrate and the AlN layer Schematic top view of mask layer in the first embodiment The graph which shows the photo-luminescence characteristic of the light emitting diode element produced on the graphite substrate in Embodiment 1 of this invention The graph which shows the IV characteristic of the light emitting diode element produced on the graphite board | substrate in Embodiment 1 of this invention. Cross-sectional configuration diagram of a conventional light emitting diode element

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is a cross-sectional configuration diagram of a light-emitting diode element according to the first embodiment. In FIG. 1, 101 indicates a graphite substrate. Reference numeral 102 denotes an amorphous carbon layer formed by amorphizing the surface of the graphite substrate 101 by oxygen ashing. Reference numeral 103 denotes an AlN layer formed on the amorphous carbon layer 102 by MOCVD.

  Reference numeral 104 denotes a low-temperature growth buffer layer of GaN formed on the AlN layer 103 by MOCVD. Reference numeral 105 denotes a first n-type GaN layer formed on the low temperature growth buffer layer 104. Reference numeral 106 denotes a mask layer formed on the first n-type GaN layer 106. Reference numeral 107 denotes a second n-type GaN layer 107 formed on the first n-type GaN layer 105 in the opening of the mask layer 106.

Reference numeral 108 denotes a multilayer quantum well layer made of In _x Ga _1-x N and GaN formed on the second n-type GaN layer 105. Reference numeral 109 denotes a p-type GaN layer formed on the multiple quantum well layer 108. Reference numeral 110 denotes a p-type GaN contact layer formed on the p-type GaN layer 109. 111 indicates a p-side electrode. Reference numeral 112 denotes an n-side electrode.

  The low temperature growth buffer layer 104, the first n-type GaN layer 105, the second n-type GaN layer 107, the multiple quantum well layer 108, the p-type GaN layer 109, and the p-type GaN contact layer 110 are arranged in this order as an AlN layer. 103 is formed by epitaxial growth.

  The second n-type GaN layer 107, the multilayer quantum well layer 108, the p-type GaN layer 109, and the p-type GaN contact layer 110 constitute a plurality of columnar structures.

  The p-side electrode 111 is electrically connected to all the p-type GaN contact layers 110 located at the tip of the columnar structure. As an example, the p-side electrode 111 is made of a transparent conductive film such as indium tin oxide (ITO) or zinc oxide (ZnO), or nickel (Ni) and gold (Au). An n-side electrode 112 is formed on the exposed surface of the first n-type GaN layer 105. As an example, the n-side electrode 112 is composed of a titanium (Ti) and aluminum (Al) laminated film.

  Hereinafter, a method for manufacturing the light emitting diode element will be described with reference to the drawings.

  2 (a) to 2 (g) are cross-sectional views showing respective steps in the method for manufacturing the light-emitting diode element according to the first embodiment.

In the first embodiment, the MOCVD method is used as a nitride semiconductor crystal growth method. Examples of the gallium source include trimethyl gallium (TMG). Examples of the aluminum source include trimethylaluminum (TMA). An example of the indium source is trimethylindium (TMI). Examples of the nitrogen source include ammonia (NH ₃ ). Examples of the raw material for the n-type dopant include silane (SiH ₄ ) containing silicon (Si). Examples of the raw material for the p-type dopant include cyclopentadienyl magnesium (CP ₂ Mg) containing magnesium (Mg).

  First, as shown in FIG. 2A, the surface of the graphite substrate 101 is made amorphous by oxidizing it using an oxygen ashing process. In this way, the amorphous carbon layer 102 is formed. Next, as shown in FIG. 2B, an AlN layer 103 is grown on the amorphous carbon layer 102 by using the MOCVD method at a temperature of about 960.degree. Further, as shown in FIG. 2C, a low temperature growth buffer layer 104 made of GaN is grown at a temperature of about 500.degree.

  As shown in FIG. 2D, a first n-type GaN layer 105 made of n-type GaN is grown at a high temperature of about 900 ° C. As shown in FIG. 2E, a mask layer 106 having a plurality of openings is formed on the first n-type GaN layer 105.

As shown in FIG. 2F, the second n-type GaN layer 107 made of n-type GaN at a high temperature of about 900 ° C. is formed on the first n-type GaN layer 105 exposed from each opening of the mask layer 106. In _x Ga _1-x N (preferably 0.01 ≦ x ≦ 0.20. As an example, x = 0.12) and a multiple quantum well layer 108 made of GaN, and a p-type GaN layer 109 made of p-type GaN. In addition, a p-type GaN contact layer 110 made of p ⁺ -type GaN is sequentially grown. As a result, a columnar structure composed of the n-type GaN layers 105 and 107, the multiple quantum well layer 108, and the p-type GaN layer 109 is formed.

  Finally, as shown in FIG. 2G, the p-side electrode 111 in contact with all the p-type GaN contact layers 110 located at the tip of the columnar structure is formed. An n-side electrode 112 is also formed on the first n-type GaN layer 105.

  In the first embodiment, the amorphous carbon layer 102 is provided by oxidizing the surface of the graphite substrate 101, and the AlN layer 103 is formed thereon by using the MOCVD method, so that it is very dense and c-axis oriented. An AlN layer 103 is formed. Therefore, even though a graphite substrate that is not a single crystal substrate is used, a high-quality GaN thin film with few penetration defects can be produced. Thereby, a light emitting diode element is produced on the graphite substrate.

Examples of the material of the mask layer 106 in the first embodiment are SiO ₂ , Si _x N _y , and Al ₂ O ₃ . These materials do not change at high temperatures of approximately 900 degrees. These materials can be formed using a general method such as a sputtering method or a chemical vapor deposition method.

Example 1
The following examples illustrate the invention in more detail.

  FIG. 3A shows an SEM observation image of the surface of AlN deposited by MOCVD on the graphite substrate 101 that has not been oxidized. FIG. 3B shows an SEM observation image of the surface of the AlN layer 103 having a thickness of 20 nm formed by MOCVD on the amorphous carbon layer 102 having a thickness of 20 nm formed on the graphite substrate 101 by oxidation. Indicates.

  As is clear from FIG. 3A, only microcrystals such as dendrites were deposited on the graphite substrate 101 that was not oxygen-treated. The AlN thin film was not formed on the graphite substrate 101.

  On the other hand, as is clear from FIG. 3B, a dense AlN thin film was formed on the graphite substrate 101 having the amorphous carbon layer 102 on the surface.

  4A shows an amorphous carbon layer 102 (corresponding to the “surface modification region” in FIG. 4A) formed on the graphite substrate 101, and an AlN layer having a thickness of 20 nm formed by MOCVD. The cross-sectional TEM observation photograph of the laminated body comprised from the GaN low-temperature growth buffer layer 104 of 103 and 1 micrometer is shown. FIG. 4B shows a lattice image near the interface between the amorphous carbon layer 102 and the AlN layer 103.

As is apparent from FIGS. 4A and 4B, an AlN layer 103 having a dense crystallinity is formed on the amorphous carbon layer 102. A low-temperature buffer layer 104 made of GaN having good crystallinity is grown on the AlN layer 103. The dislocation density determined from the cross-sectional TEM observation photograph was low, specifically 2 × 10 ⁹ cm ⁻² . It has been confirmed that the low temperature buffer layer 104 has substantially the same dislocation density as the GaN thin film grown on the sapphire substrate via the GaN low temperature growth buffer layer.

  It has been found that a nitride thin film having very high crystallinity can be formed by providing the amorphous carbon layer 102 on the surface of graphite which is a non-single crystal substrate.

The reason why the dense AlN thin film grows by forming the amorphous carbon layer 102 on the surface of the graphite substrate 101 is considered as follows. On the normal graphite surface, electrons are delocalized by π bonds consisting of sp ² hybrid orbitals of graphene. On the other hand, on the surface of the amorphous carbon layer 102 made amorphous by oxygen ashing, it is considered that not only sp ² orbits but also sp ³ orbitals exist because of π bonds broken everywhere.

Table 1 shows the adsorption energies of Al atoms and N atoms with respect to the carbon sp ² and sp ³ orbits determined by the first principle calculation.

As is apparent from Table 1, the adsorption energies of Al atoms and N atoms with respect to the sp ² orbital are both positive values. On the other hand, those for the sp ³ orbit are all negative values. This means that Al and N are easily adsorbed spontaneously with respect to the sp ³ orbit. From this, by forming an amorphous carbon layer on the surface of the graphite substrate by oxygen ashing, a large number of carbon sp ³ orbitals are formed, and nucleation is promoted in the initial stage of AlN growth. Thus, it is considered that a good thin film crystal has grown.

  Table 2 shows the half width of the (0002) peak obtained by the XRD rocking curve of GaN when amorphous carbon layers having thicknesses of 0, 20, 40, 60, and 80 nm were formed.

  When the amorphous carbon layer 102 has a thickness of 20 nm or more and 60 nm or less, the GaN thin film is c-axis oriented and has a good half width. When the amorphous carbon layer has a thickness of 80 nm, the amount of oxygen taken into the graphite thin film during oxygen ashing increases. Therefore, when AlN and GaN are subsequently grown by MOCVD, oxygen taken into the graphite substrate reacts with Al or Ga. This is thought to have hindered the formation of a steep interface. Therefore, the amorphous carbon layer 102 desirably has a thickness of 20 nm to 60 nm.

  Table 3 shows the film thickness of each layer in Example 1.

  Amorphous carbon layer 102 having a thickness shown in Table 3, AlN layer 103, GaN low-temperature growth buffer layer 104, first n-type GaN layer 105, mask layer 106, second n-type GaN layer 107, multiple quantum well Layer 108, p-type GaN layer 109, and p-type GaN contact layer 110 were sequentially grown.

The material of the mask layer 106 was SiO ₂ . As shown in FIG. 5, the mask layer 106 is
A plurality of circular openings 113 having a constant interval were provided. The diameter A of the opening 113 was 210 nm. A distance B between two adjacent openings 113 was 420 nm. A columnar structure having a diameter of 210 nm and an interval of 420 nm was obtained on the graphite substrate 101 using the mask layer 106. The columnar structure was composed of an n-type GaN layer, a multiple quantum well layer, and a p-type GaN layer.

The multiple quantum well layer 108 was formed by alternately laminating five periods of In _0.12 Ga _0.88 N having a thickness of 2.5 nm and GaN having a thickness of 8 nm.

  FIG. 6 shows the results of PL measurement of the columnar structure. The excitation light source at the time of PL measurement was a He—Cd laser.

  As is clear from FIG. 6, in Example 1, a clear emission peak from the multiple quantum well layer 108 was observed at a wavelength of 420 nm. The emission intensity of Example 1 was about 15% higher than that of Comparative Example 1.

  The p-side electrode 111 of Example 1 was a ZnO transparent conductive film formed by a liquid phase synthesis method. Hereinafter, a method for forming the ZnO transparent conductive film will be described.

Hexamethylenetetramine ((CH ₂ ) ₆ N ₄ ) having a concentration of 0.1 mol / L is dropped into a solution of zinc nitrate (ZnNO ₃ ) having a concentration of 0.1 mol / L, and the pH value is adjusted to 5 to 7 Adjusted between. Thereafter, a resist was applied and a laminated body in which only the p-type GaN contact layer 110 was exposed by photolithography was obtained. The laminate was immersed in the solution. The solution was allowed to stand for 2 to 6 hours while maintaining the temperature at 70 ° C. In this way, a ZnO transparent conductive film was grown on the p-type GaN contact layer 110. The thickness of the ZnO transparent conductive film was adjusted by the growth time. The growth rate was about 2.7 nm / min. A ZnO transparent conductive film having a thickness of 300 nm was grown. Thereafter, the resist was removed using acetone and dried.

As a result of the UV-visible transmittance measurement, the ZnO transparent electrode film prepared by the above method had a high transmittance of 95% or less in a wide wavelength range of 350 nm to 2.5 μm. As a result of the resistivity measurement by the four-terminal method, the ZnO transparent electrode had a relatively low resistivity of 1.2 × 10 ⁻² Ωcm. These results meant that the prepared ZnO transparent electrode was sufficiently usable as the p-side electrode of the light-emitting diode element.

  The n-side electrode 112 was formed by laminating Ti having a thickness of 10 nm and Al having a thickness of 100 nm. Then, the light emitting diode element of Example 1 was produced by isolate | separating into the size of 1 mm x 1 mm with a dicer. As Comparative Example 1, a light emitting diode device having a laminated film-like nitride semiconductor thin film was manufactured by omitting the step of forming the mask layer 106.

  FIG. 7 shows the IV characteristics of the light-emitting diode element of Example 1. As is apparent from FIG. 7, the light-emitting diode element of Example 1 exhibited good diode characteristics. The light emitting diode element of Example 1 started to light at a forward voltage of about 2.4 V and showed clear blue light emission.

  Table 4 shows the relative value of the emission intensity at λ = 420 nm when a voltage of 2.7 V is applied to the light emitting diode elements of Example 1 and Comparative Example 1.

  As shown in Table 4, the light emitting diode element of Example 1 had a light emission intensity 1.42 times that of the light emitting diode element of Comparative Example 1.

  As understood from these results, forming an amorphous carbon layer on the surface of the graphite substrate and subsequently providing an AlN layer by MOCVD makes it possible to produce a columnar GaN structure with good crystallinity. In this way, a high-performance blue light-emitting diode element can be realized at a low cost.

The multiple quantum well layer of Example 1 was obtained by alternately laminating In _x Ga _1-x N (x = 0.12) and GaN for five periods. However, x may be not less than 0.01 and not more than 0.20. The number of times of lamination (cycle) can also be 1 cycle (1 time) or more and 10 cycles (10 times or less).

The mask layer of Example 1 had a plurality of openings having a diameter of 210 nm and a spacing of 420 nm. However, those skilled in the art can appropriately select the diameter and interval so as to correspond to the emission wavelength of the multiple quantum well layer 108 determined by the composition of the In _x Ga _1-x N layer.

The light-emitting diode device according to the present invention has an AlN layer and a GaN layer with good crystallinity formed by MOCVD on a graphite substrate, and is useful as illumination, a display, and the like. The technology for forming a light-emitting diode element according to the present invention can be applied to applications such as high-frequency and power device FETs and other electronic devices.

The technical idea according to the present invention derived from the above disclosure is as follows.
1.
Graphite substrate (101),
An amorphous carbon layer (102) formed on the graphite substrate (101);
An AlN layer (103) formed on the amorphous carbon layer (102);
A first n-type nitride semiconductor layer (105) formed on the AlN layer (103);
A plurality of second n-type nitride semiconductor layers (107) formed on the first n-type nitride semiconductor layer (105), wherein each of the n-type nitride semiconductor layers (107) is columnar. Yes,
A quantum well layer (108) made of a nitride semiconductor formed on each of the second n-type nitride semiconductor layers (107),
A p-type nitride semiconductor layer (109) formed on the quantum well layer (108),
A p-side electrode (111) electrically connected to the p-type nitride semiconductor layer (109), and an n-side electrode (112) electrically connected to the first n-type nitride semiconductor layer (105) )
A method of manufacturing a light emitting diode device comprising:
The method
Oxygen ashing the surface of the graphite substrate (101) to form an amorphous carbon layer (102) on the surface of the graphite substrate (101);
Forming an AlN layer (103) on the amorphous carbon layer (102) by MOCVD (metal organic chemical vapor deposition);
Forming a first n-type nitride semiconductor layer (105) on the AlN layer (103);
Forming a mask layer (106) having a plurality of openings on the n-type nitride semiconductor layer (105);
Forming a plurality of second n-type nitride semiconductor layers (107) on portions of the n-type nitride semiconductor layer (105) exposed from the plurality of openings;
Forming a quantum well layer (108) made of a nitride semiconductor on each of the second n-type nitride semiconductor layers (107);
Forming a p-type nitride semiconductor layer (109) on the quantum well layer (108);
Forming a p-side electrode (111) on the p-type nitride semiconductor layer (109); and
Forming an n-side electrode (112) on the n-type nitride semiconductor layer (105);

2.
Item 2. The method according to Item 1, wherein the amorphous carbon layer (102) has a thickness of 20 nm to 60 nm.

3.
The method according to Item 1, further comprising a step of forming a buffer layer (104) made of a nitride semiconductor on the AlN layer (103) before forming the n-type nitride semiconductor layer (105).

4).
3. The method according to item 2, further comprising a step of forming a buffer layer (104) made of a nitride semiconductor on the AlN layer (103) before forming the n-type nitride semiconductor layer (105).

5).
Item 2. The method according to Item 1, wherein the p-type electrode (111) is a ZnO transparent conductive film.

6).
Item 5. The method according to Item 4, wherein the p-type electrode (111) is a ZnO transparent conductive film.

7).
Item 2. The method of Item 1, wherein the quantum well layer (108) comprises a multiple quantum well layer.

8).
Item 7. The method according to Item 6, wherein the quantum well layer (108) comprises a multiple quantum well layer.

9.
Graphite substrate (101),
An amorphous carbon layer (102) formed on the graphite substrate (101), and an AlN layer (103) formed on the amorphous carbon layer (102),
A semiconductor substrate comprising:

10.
Item 10. The semiconductor substrate according to Item 9, wherein the amorphous carbon layer (102) has a thickness of 20 nm to 60 nm.

11.
Graphite substrate (101),
An amorphous carbon layer (102) formed on the graphite substrate (101), and an AlN layer (103) formed on the amorphous carbon layer (102),
A method of manufacturing a semiconductor substrate comprising:
The method
Oxygen ashing the surface of the graphite substrate (101) to form an amorphous carbon layer (102) on the surface of the graphite substrate (101); and MOCVD (organometallic vapor phase) on the amorphous carbon layer (102) Forming an AlN layer (103) by a growth method),
In order.

12
Item 12. The method according to Item 11, wherein the amorphous carbon layer (102) has a thickness of 20 nm to 60 nm.

13.
Graphite substrate (101),
An amorphous carbon layer (102) formed on the graphite substrate (101);
An AlN layer (103) formed on the amorphous carbon layer (102);
A first n-type nitride semiconductor layer (105) formed on the AlN layer (103);
A plurality of second n-type nitride semiconductor layers (107) formed on the first n-type nitride semiconductor layer (105), wherein each of the n-type nitride semiconductor layers (107) is columnar. Yes,
A quantum well layer (108) made of a nitride semiconductor formed on each of the second n-type nitride semiconductor layers (107),
A p-type nitride semiconductor layer (109) formed on the quantum well layer (108),
A p-side electrode (111) electrically connected to the p-type nitride semiconductor layer (109), and an n-side electrode (112) electrically connected to the first n-type nitride semiconductor layer (105) )
A light emitting diode device comprising:

14
Item 14. The light-emitting diode element according to Item 13, wherein the amorphous carbon layer (102) has a thickness of 20 nm to 60 nm.

15.
Item 14. The light-emitting diode element according to Item 13, further comprising a buffer layer (104) made of a nitride semiconductor sandwiched between the AlN layer (103) and the n-type nitride semiconductor layer (105).

16.
Item 15. The light-emitting diode element according to Item 14, further comprising a buffer layer (104) made of a nitride semiconductor sandwiched between the AlN layer (103) and the n-type nitride semiconductor layer (105).

17.
Item 14. The light-emitting diode element according to Item 13, wherein the p-type electrode (111) is a ZnO transparent conductive film.

18.
Item 17. The light-emitting diode element according to Item 16, wherein the p-type electrode (111) is a ZnO transparent conductive film.

19.
Item 14. The light-emitting diode device according to Item 13, wherein the quantum well layer is a multiple quantum well layer.

20.
Item 19. The light-emitting diode device according to Item 18, wherein the quantum well layer is a multiple quantum well layer.

1.
A method of comprising a light-emitting diode comprising:
a graphite substrate (101),
an amorphous carbon layer (102) formed on the graphite substrate (101),
an AlN layer (103) formed on the amorphous carbon layer (102),
a first n-type nitride semiconductor layer (105) formed on the AlN layer (103),
a plural of second n-type nitride semiconductor layer (107), each of which is pole-shaped, formed on the first n-type nitride semiconductor layer (105),
a quantum well layer (108) formed on each of the plurality of second n-type nitride semiconductor layer (107)
a p-side nitride semiconductor layer (109) formed on the quantum well layer (108),
a p-side electrode (111) connected electrically to the p-type nitride semiconductor layer (109),
a n-side electrode (112) connected electrically to the first n-type nitride semiconductor layer (105),
the method comprising the following steps:
oxygen-ashing the surface of the graphite substrate (101) to form the amorphous carbon layer (102) on the surface of the graphite substrate (101),
forming the AlN layer (103) on the amorphous carbon layer (102) with MOCVD (Metal Organic Chemical Vapor Deposition),
forming the first n-type nitride semiconductor layer (105) on the AlN layer (103),
forming a mask layer (106) with a plurality of openings on the first n-type nitride semiconductor layer (105),
forming the plurality of second n-type nitride semiconductor layer (107) on the portions of the first n-type nitride semiconductor layer (105), which expose from the openings,
forming the quantum well layer (108) on the each of the plurality of second n-type nitride semiconductor layer (107),
forming the p-side nitride semiconductor layer (109) on the quantum well layer (108),
forming the p-side electrode (111) on the p-side nitride semiconductor layer (109), and
forming the n-side electrode (112) on the first n-type nitride semiconductor layer (105).

2.
A method of item 1, 10.the amorphous carbon layer (102) has a thickness of not less than 20nm and not more than 60nm.

3.
A method of item 1 further comprising a step of the forming a buffer layer (104) formed of a nitride semiconductor on the AlN layer (103).

Four.
A method of item 2 further comprising a step of the forming a buffer layer (104) formed of a nitride semiconductor on the AlN layer (103).

Five.
A method of item 1, etc.the p-side electrode (111) is formed of a ZnO transparent film.

6.
A method of item 4, etc.the p-side electrode (111) is formed of a ZnO transparent film.

7.
A method of item 1, etc.the quantum well layer (108) is formed of a multi-quantum well layer.

8.
A method of item 6, etc.the quantum well layer (108) is formed of a multi-quantum well layer.

9.
A semiconductor substrate comprising:
a graphite substrate (101),
an amorphous carbon layer (102) formed on the graphite substrate (101), and
an AlN layer (103) formed on the amorphous carbon layer (102).

Ten.
A semiconductor substrate of item 9, ... the amorphous carbon layer (102) has a thickness of not less than 20nm and not more than 60nm.

11.
A method of comprising a semiconductor substrate comprising:
a graphite substrate (101),
an amorphous carbon layer (102) formed on the graphite substrate (101), and
an AlN layer (103) formed on the amorphous carbon layer (102),
the method comprising the following steps in this order:
oxygen-ashing the surface of the graphite substrate (101) to form the amorphous carbon layer (102) on the surface of the graphite substrate (101), and
forming the AlN layer (103) on the amorphous carbon layer (102) with MOCVD (Metal Organic Chemical Vapor Deposition).

12.
A method of item 11, 10.the amorphous carbon layer (102) has a thickness of not less than 20nm and not more than 60nm.

13.
A light-emitting diode comprising:
a graphite substrate (101),
an amorphous carbon layer (102) formed on the graphite substrate (101),
an AlN layer (103) formed on the amorphous carbon layer (102),
a first n-type nitride semiconductor layer (105) formed on the AlN layer (103),
a plural of second n-type nitride semiconductor layer (107), each of which is pole-shaped, formed on the first n-type nitride semiconductor layer (105),
a quantum well layer (108) formed on each of the plurality of second n-type nitride semiconductor layer (107)
a p-side nitride semiconductor layer (109) formed on the quantum well layer (108),
a p-side electrode (111) connected electrically to the p-type nitride semiconductor layer (109),
a n-side electrode (112) connected electrically to the first n-type nitride semiconductor layer (105).

14.
A light-emitting diode of item 13, 10.the amorphous carbon layer (102) has a thickness of not less than 20nm and not more than 60nm.

15.
A light-emitting diode of item 13 further comprising a buffer layer (104) formed of a nitride semiconductor on the AlN layer (103).

16.
A light-emitting diode of item 14 further comprising a buffer layer (104) formed of a nitride semiconductor on the AlN layer (103).

17.
A light-emitting diode of item 13, 10.the p-side electrode (111) is formed of a ZnO transparent film.

18.
A light-emitting diode of item 16, wherein the p-side electrode (111) is formed of a ZnO transparent film.

19.
A light-emitting diode of item 13, 10.the quantum well layer (108) is formed of a multi-quantum well layer.

20.
A light-emitting diode of item 18, and the quantum well layer (108) is formed of a multi-quantum well layer.

10 Substrate 20 Buffer layer 31 Columnar n-type GaN
33 Quantum well 35 p-type GaN
41 transparent insulator layer 50 electrode pad 60 transparent electrode 70 electrode pad 101 graphite substrate 102 amorphous carbon layer 103 AlN layer 104 low temperature growth buffer layer 105 first n-type GaN layer 106 mask layer 107 second n-type GaN layer 108 multiple Quantum well layer 109 p-type GaN layer 110 p-type GaN contact layer 111 p-side electrode 112 n-side electrode 113 opening

Claims (3)

A graphite substrate;
An amorphous carbon layer formed on the graphite substrate;
A c-axis oriented AlN layer formed by MOCVD on the amorphous carbon layer;
A low temperature growth buffer layer of GaN formed on the AlN layer;
A first n-type GaN layer formed on the low-temperature buffer layer;
A mask layer having a plurality of openings formed on the first n-type GaN layer;
A second n-type GaN layer formed on the first n-type GaN layer in the opening of the mask layer;
A multilayer quantum well layer made of In _x Ga _1-x N and GaN formed on the second n-type GaN layer;
A p-type GaN layer formed on the multilayer quantum well layer;
A p-type GaN contact layer formed on the p-type GaN layer and a p-side electrode provided on the p-type GaN contact layer;
An n-side electrode provided on the first n-type GaN layer,
The low temperature growth buffer layer, the first n-type GaN layer, the second n-type GaN layer, the multilayer quantum well layer, the p-type GaN layer, and the p formed on the AlN layer. Type GaN contact layer grows epitaxially,
The second n-type GaN layer, the multilayer quantum well layer, the p-type GaN layer, and the p-type GaN contact layer constitute a plurality of columnar structures,
The p-side electrode bridges all of the p-type GaN contact layer at the tip of the columnar structure. The light emitting diode device according to claim 1, wherein the p-side electrode is a ZnO transparent conductive film formed by liquid phase synthesis. Providing an amorphous carbon layer on the graphite substrate;
Growing an AlN c-axis alignment film on the amorphous carbon layer by MOCVD;
Forming a low-temperature growth buffer layer of GaN on the AlN layer;
Forming a first n-type GaN layer on the low-temperature growth buffer layer, forming a mask layer having a plurality of openings on the first n-type GaN layer, and forming the openings in the mask layer Forming a second n-type GaN layer on the first n-type GaN layer;
Forming a multilayer quantum well layer composed of In _x Ga _1-x N and GaN on the second n-type GaN layer;
Forming a p-type GaN layer and a p-type GaN contact layer on the multiple quantum well layer;
Forming a p-side electrode on the p-type GaN contact layer;
Forming a n-side electrode on the first n-type GaN layer, and a method for manufacturing a light-emitting diode element comprising:
The low temperature growth buffer layer formed on the AlN layer, the first n-type GaN layer, the second n-type GaN layer, the multiple quantum well layer, the p-type GaN layer, and the p-type GaN The contact layer grows epitaxially,
The second n-type GaN layer, the multilayer quantum well layer, the p-type GaN layer, and the p-type GaN contact layer constitute a plurality of columnar structures,
The p-side electrode bridges all of the p-type GaN contact layer at the tip of the columnar structure;
A method for manufacturing a light-emitting diode element, wherein the amorphous carbon layer is formed by an oxidation treatment.

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