Light-emitting element and method for manufacturing light-emitting element

Abstract

The light-emitting element includes a substrate including amorphous glass, a first buffer layer, a second buffer layer, a gallium nitride layer, a laminate, a cathode, and an anode. The first buffer layer is located on the substrate and contains aluminum and oxygen. The second buffer layer is located on the first buffer layer and contains aluminum and nitrogen. The gallium nitride layer is located on the second buffer layer. The laminated body is located on the gallium nitride layer and comprises an n-type cladding layer, a p-type cladding layer and a light-emitting layer located between the n-type cladding layer and the p-type cladding layer. And the cathode and the anode are respectively positioned on the n-type coating layer and the p-type coating layer. The n-type cladding layer, the p-type cladding layer, and the light-emitting layer each contain a Group 13 element and a Group 15 element.

Description

Technical Field

[0001] One embodiment of the present invention relates to a semiconductor device exemplified in a light emitting device, a transistor, etc., and a method for manufacturing the same. For example, one embodiment of the present invention relates to a semiconductor device including a gallium nitride-based semiconductor and a method for manufacturing the same. Background Art

[0002] Representative examples of semiconductor elements include light-emitting elements and transistors. In recent years, semiconductor elements containing nitrides of group 13 elements such as gallium nitride (GaN) and indium nitride (InN) have been actively developed. In the past, such semiconductor elements could be made using silicon substrates and sapphire substrates. For example, Patent Documents 1 to 3 disclose light-emitting elements and transistors that can form a semiconductor layer containing a nitride of group 13 elements on a glass substrate.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2019-41113

[0006] Patent Document 2: Japanese Patent Application Publication No. 2018-168029

[0007] Patent Document 3: Japanese Patent Application Publication No. 2000-124140 Summary of the invention

[0008] Problems to be solved by the invention

[0009] One embodiment of the present invention provides a semiconductor element with a novel structure and a method for manufacturing the same. Alternatively, one embodiment of the present invention provides a light-emitting element or transistor containing a Group 13 element and a Group 15 element in a semiconductor layer and a method for manufacturing the same.

[0010] Means for solving problems

[0011] One embodiment of the present invention is a light-emitting element. The light-emitting element comprises a substrate comprising amorphous glass, a first buffer layer, a second buffer layer, a gallium nitride layer, a laminate, a cathode and an anode. The first buffer layer is located on the substrate and contains aluminum and oxygen. The second buffer layer is located on the first buffer layer and contains aluminum and nitrogen. The gallium nitride layer is located on the second buffer layer. The laminate is located on the gallium nitride layer and includes an n-type cladding layer, a p-type cladding layer and a light-emitting layer located between the n-type cladding layer and the p-type cladding layer. The cathode and the anode are located on the n-type cladding layer and the p-type cladding layer, respectively. The n-type cladding layer, the p-type cladding layer and the light-emitting layer each contain a Group 13 element and a Group 15 element.

[0012] One embodiment of the present invention is a method for manufacturing a light-emitting element. The manufacturing method includes the following steps: forming a first buffer layer on a substrate including amorphous glass; forming a second buffer layer on the first buffer layer; forming a gallium nitride layer on the second buffer layer by sputtering; forming a stack including an n-type cladding layer, a p-type cladding layer, and a light-emitting layer located between the n-type cladding layer and the p-type cladding layer on the gallium nitride layer by sputtering; and forming a cathode and an anode on each of the n-type cladding layer and the p-type cladding layer, wherein each of the n-type cladding layer, the p-type cladding layer, and the light-emitting layer contains a Group 13 element and a Group 15 element.

[0013] One embodiment of the present invention is a display device including a plurality of the above-mentioned light-emitting elements.

[0014] One embodiment of the present invention is a transistor. The transistor comprises a substrate comprising amorphous glass, a first buffer layer, a second buffer layer, an active layer comprising a Group 13 element and a Group 15 element, a gate insulating film, a gate electrode, and a first terminal and a second terminal. The first buffer layer is located on the substrate, and the second buffer layer is located on the first buffer layer. The active layer is located on the second buffer layer, and the gate insulating film is located on the active layer. The first terminal and the second terminal are located on the active layer and in contact with the active layer. The gate electrode is located on the active layer through the gate insulating film. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1A This is a schematic end view of a light emitting element according to one embodiment of the present invention.

[0016] Figure 1B This is a schematic end view of a light emitting element according to one embodiment of the present invention.

[0017] Figure 2 This is a diagram showing the relationship between lattice constants of components included in a light-emitting element according to one embodiment of the present invention.

[0018] Figure 3A This is a schematic end view showing a method for manufacturing a light emitting element according to one embodiment of the present invention.

[0019] Figure 3B This is a schematic end view showing a method for manufacturing a light emitting element according to one embodiment of the present invention.

[0020] Figure 3C This is a schematic end view showing a method for manufacturing a light emitting element according to one embodiment of the present invention.

[0021] Figure 4A This is a schematic end view showing a method for manufacturing a light emitting element according to one embodiment of the present invention.

[0022] Figure 4B This is a schematic end view showing a method for manufacturing a light emitting element according to one embodiment of the present invention.

[0023] Figure 4C This is a schematic end view showing a method for manufacturing a light emitting element according to one embodiment of the present invention.

[0024] Figure 5A This is a schematic end view of a transistor according to one embodiment of the present invention.

[0025] Figure 5B This is a schematic end view of a transistor according to one embodiment of the present invention. DETAILED DESCRIPTION

[0026] Hereinafter, various embodiments of the present invention will be described with reference to the drawings, etc. However, the present invention can be implemented in various forms within the scope not departing from the gist of the present invention, and the description of the embodiments illustrated below is not to be construed as being limited.

[0027] In order to make the description clearer, the drawings sometimes schematically show the width, thickness, shape, etc. of each part compared with the actual form, but it is always an example and does not limit the interpretation of the present invention. In this specification and each figure, the same symbol is marked for elements having the same function as that described in the figures shown, and sometimes repeated descriptions are omitted. This symbol can be used when collectively representing multiple identical or similar structures, and a hyphen and a natural number can be added after the symbol when representing these structures separately.

[0028] In the present specification and claims, when describing the configuration of another structure on a certain structure, when simply expressed as "on something", unless otherwise specified, it is defined to include both the case where another structure is configured directly on the certain structure in a manner of contacting the certain structure, and the case where another structure is configured above the certain structure via another structure.

[0029] In this specification and claims, the expression "a certain structure is exposed from another structure" means that a part of a certain structure is not covered by another structure, and the part not covered by the other structure also includes a part covered by another structure. In addition, the form represented by this expression also includes a form in which a certain structure is not in contact with another structure.

[0030] <First Embodiment>

[0031] In this embodiment, a light-emitting element which is one embodiment of the present invention is described. The light-emitting element is an inorganic light-emitting diode (LED) having a semiconductor layer containing a Group 13 element and a Group 15 element.

[0032] 1. Structure

[0033] Figure 1A FIG. 1 is a schematic end view of a light emitting element 100 according to one embodiment of the present invention. Figure 1A As shown, the light emitting element 100 has a substrate 102 made of amorphous glass, and two buffer layers (a first buffer layer 110 and a second buffer layer 112) are provided on the substrate 102. The light emitting element 100 further has a gallium nitride layer 120 in contact with the second buffer layer 112 on the second buffer layer 112, and has a stacked body on the gallium nitride layer 120, the stacked body including an n-type cladding layer 122, a p-type cladding layer 126, and a light emitting layer 124 sandwiched between the n-type cladding layer 122 and the p-type cladding layer 126. In addition, the light emitting element 100 has an anode 128 and a cathode 130 provided on the p-type cladding layer 126 and the gallium nitride layer 120, respectively. The first buffer layer 110 may be in direct contact with the substrate 102, or may be provided on the substrate 102 via an overcoat layer 104 of an arbitrary structure. By applying a potential difference greater than a light emission threshold voltage between the anode 128 and the cathode 130 , holes and electrons are injected from the anode 128 and the cathode 130 , respectively, and the holes and electrons are recombined in the light emitting layer 124 , thereby generating light emission.

[0034] The light emitting element 100 may further include a protective film 140 on the anode 128 and the cathode 130. In addition, the light emitting element 100 may include an undercoat layer 106 under the substrate 102. These configurations will be described below.

[0035] (1)Substrate

[0036] The substrate 102 is a structure that supports each structure provided thereon, and includes amorphous glass. It is preferred to use a substrate having a high strain point and high surface flatness as the substrate 102. For example, the strain point of the substrate 102 is preferably above 600°C. The substrate 102 may have a thickness that allows flexibility (e.g., 0.1 mm to 0.5 mm), or may have a thickness greater than that (e.g., 0.5 mm to 2 mm).

[0037] As an example, the substrate 102 is a glass substrate called alkali-free glass. In this case, the substrate 102 contains silicon dioxide, aluminum oxide, boron oxide, and alkaline earth metal oxides such as calcium oxide and barium oxide. The content of alkali metals such as sodium in the substrate 102 is preferably 0.1% or less.

[0038] (2) Topcoat and basecoat

[0039] The outer coating layer 104, which is an arbitrary structure, is provided on the substrate 102 in a manner of contacting the substrate 102. The outer coating layer 104 has a function of preventing the diffusion of impurities such as trace amounts of alkali metal ions contained in the substrate 102, and is a film or a stack of multiple films containing silicon-containing inorganic compounds such as silicon oxide and silicon nitride. The outer coating layer 104 is formed, for example, by a sputtering method or a chemical vapor deposition (CVD) method.

[0040] The undercoat layer 106 disposed under the substrate 102 and provided in contact with the substrate 102 is a film that has the function of inhibiting the detachment of water and the like from the substrate 102 under the high temperature conditions when manufacturing the light-emitting element 100, and preventing oxygen-containing impurities from being mixed into the gallium nitride layer 120 constituting the light-emitting element 100 and the semiconductor layers provided thereon, namely, the n-type cladding layer 122, the light-emitting layer 124, the p-type cladding layer 126, etc. In addition, it also has the function of preventing the substrate 102 from warping due to the difference in thermal expansion coefficient between the substrate 102 and the gallium nitride layer 120. The undercoat layer 106 having such a function is configured in such a way that its thermal expansion coefficient becomes between the thermal expansion coefficient of the substrate 102 and the thermal expansion coefficient of the gallium nitride layer 120. Specifically, the undercoat layer 106 is configured in such a way that the thermal expansion coefficient becomes higher than 4.0×10 -6 / ℃ and less than 5.0×10 -6 For example, a film containing aluminum nitride, a film containing aluminum oxide, or a laminate of these films can be used as the undercoat layer 106. The undercoat layer 106 can be formed by a sputtering method or the like.

[0041] (3) 1st buffer layer and 2nd buffer layer

[0042] The first buffer layer 110 and the second buffer layer 112 are structures that help promote the crystallization of the gallium nitride layer 120 disposed thereon. In addition, the first buffer layer 110 and the second buffer layer 112 are films that prevent the substrate 102 from deforming (warping) under high temperature conditions when manufacturing the light-emitting element 100 by improving the adhesion with the substrate 102, and prevent the layers disposed thereon from peeling off and cracking. Therefore, by using the first buffer layer 110 and the second buffer layer 112, cracks can be prevented from occurring in the gallium nitride layer 120 and the semiconductor layers disposed thereon, and the crystallinity of these layers can be improved without accompanying deformation of the substrate 102 and peeling off of the gallium nitride layer 120.

[0043] a1st buffer layer

[0044] The first buffer layer 110 is provided on the substrate 102 directly or via the outer coating layer 104. The first buffer layer 110 contains an inorganic compound containing aluminum and oxygen, specifically, aluminum oxide. The first buffer layer 110 may contain aluminum oxide (aluminum oxynitride) containing nitrogen in addition to aluminum and oxygen. For example, the composition of the first buffer layer 110 may be Alx O y (Formula 1) represents that y / x in Formula 1 may be greater than or equal to 1.4 and less than or equal to 1.6. Alternatively, the composition of the first buffer layer 110 may be Al x O y N z (Formula 2). In Formula 2, (2y+3z) / 3x can be greater than 0.9 and less than 1.1, and z / y can be greater than 0.05 and less than 0.2. By having the first buffer layer 110 contain aluminum oxide or nitrogen-containing aluminum oxide, a strong bond between the first buffer layer 110 and the aluminum oxide contained in the substrate 102 comprising amorphous glass can be formed. Therefore, the peeling between the substrate 102 and the first buffer layer 110 can be effectively suppressed. Furthermore, the composition of the first buffer layer 110 can be fixed in the film thickness direction, or the oxygen concentration can be reduced as the distance from the substrate 102 increases (that is, as it approaches the second buffer layer 112). In this way, by forming the first buffer layer 110 with a low oxygen concentration in the above, the oxygen concentration in the second buffer layer 112 in contact with the first buffer layer 110 can be reduced.

[0045] In order to make the second buffer layer formed on the first buffer layer 110 more effectively grow in the c-axis direction, it is preferred that the surface of the first buffer layer 110 has high flatness. In addition, in order to have high crystallinity and suppress defects such as peeling and cracks by reducing stress caused by the difference in thermal expansion coefficient with adjacent structures (substrate 102 and second buffer layer 112), it is preferred to form the first buffer layer 110 with a relatively thin film thickness. Specifically, the thickness of the first buffer layer 110 is preferably 50 nm or less, for example, the first buffer layer 110 is formed with a thickness of 2 nm or more and 50 nm or less.

[0046] b. Second buffer layer

[0047] The second buffer layer 112 is provided on the first buffer layer 110 so as to be in contact with the first buffer layer 110. The second buffer layer 112 contains an inorganic compound containing aluminum and nitrogen, such as aluminum nitride. For example, the composition of the second buffer layer 112 can be composed of Al x N y(Formula 3) indicates that x / y in Formula 3 can be greater than 0.9 and less than 1.1. The second buffer layer 112 may also contain oxygen, but its concentration (for example, the average concentration of oxygen in the second buffer layer 112) is lower than the oxygen concentration of the first buffer layer 110. The composition of the second buffer layer 112 may be fixed in the film thickness direction, or the nitrogen concentration may increase or decrease as the distance from the first buffer layer 110 increases (that is, as it approaches the gallium nitride layer 120). Alternatively, the nitrogen concentration may be changed in the film thickness direction in such a way that the ratio of x to y (x / y) in Formula 3 approaches 1 as the distance from the first buffer layer 110 increases. On the upper surface of the second buffer layer 112 in contact with the gallium nitride layer 120, it is preferred that the composition of the second buffer layer 112 is substantially AlN (that is, x and y are the same or substantially the same).

[0048] Similar to the first buffer layer 110, the second buffer layer 112 preferably has a high surface flatness in order to more effectively grow the gallium nitride layer 120 formed on the second buffer layer 112 in the c-axis direction. In addition, in order to have high crystallinity and suppress the occurrence of defects such as cracks by reducing stress caused by the difference in thermal expansion coefficient with adjacent structures (the first buffer layer 110 and the gallium nitride layer 120), the second buffer layer 112 is preferably formed with a thickness of, for example, 20 nm or more and 100 nm or less.

[0049] As described above, since the second buffer layer 112 can contain aluminum nitride, it can have a hexagonal closest structure, a face-centered cubic structure, or a structure based on these structures. Among them, the hexagonal closest structure or a structure based thereon includes a crystal structure in which the c-axis is not orthogonal to the a-axis and the b-axis. Therefore, with respect to this structure, the second buffer layer 112 is oriented along the (0001) direction, i.e., the c-axis, relative to its surface. In addition, the second buffer layer 112 having a face-centered cubic structure or a structure based thereon is oriented along the (111) direction relative to its surface. Therefore, the c-axis of the second buffer layer 112 is oriented in a direction perpendicular or substantially perpendicular to the surface on which the second buffer layer 112 is provided (i.e., the upper surface of the first buffer layer 110). As described later, the second buffer layer 112 and the gallium nitride layer 120, n-type cladding layer 122, light-emitting layer 124, and p-type cladding layer 126 disposed thereon contain semiconductors containing Group 13 and Group 15 elements, such as gallium nitride. However, it is known that gallium nitride forms a hexagonal closest-packed structure and grows crystals along the c-axis in a manner that minimizes its surface energy. Therefore, by forming the gallium nitride layer 120 on the second buffer layer 112, not only the crystal growth of the gallium nitride layer 120 is promoted, but also the crystal growth of the semiconductor layer formed thereon in the c-axis direction is promoted. As a result, the crystallinity of these layers is improved, and excellent characteristics as a light-emitting element can be obtained.

[0050] c Thermal expansion coefficient of the first buffer layer and the second buffer layer

[0051] The thermal expansion coefficients of the first buffer layer 110 and the second buffer layer 112 having the above-mentioned structure are both between the thermal expansion coefficient of the substrate 102 and the thermal expansion coefficient of the gallium nitride layer 120. Specifically, it is known that the thermal expansion coefficient of the substrate 102 including amorphous glass is 3.5×10 -6 / ℃~3.9×10 -6 / °C, the expansion coefficient of the gallium nitride contained in the gallium nitride layer 120 in the in-plane direction (a direction parallel to the upper surface of the substrate 102, the a-axis direction. The same applies hereinafter) is 5.6×10 -6 / °C. On the other hand, the thermal expansion coefficient of the first buffer layer 110 in the in-plane direction depends on the composition and is 3.5×10 -6 / ℃ and above 5.6×10 -6 / °C or less. Similarly, the thermal expansion coefficient of the second buffer layer 112 in the in-plane direction also depends on its composition and is 3.6×10 -6 / ℃ and above 4.6×10 -6 / °C or less. Therefore, for the light emitting element 100, the thermal expansion coefficient in the in-plane direction can be changed (increased) stepwise from the substrate 102 toward the gallium nitride layer 120, and there is no large difference in thermal expansion coefficient between adjacent components. As a result, no large stress is generated under high temperature conditions when manufacturing the light emitting element 100, and peeling between adjacent components and the generation of cracks in each layer can be effectively prevented.

[0052] d Lattice constants of the first and second buffer layers

[0053] Since amorphous glass is different from crystalline glass (such as quartz) and does not have a clear crystal structure, the lattice constant cannot be generally defined, but it can be considered that the crystal structure of its main component, silicon oxide, affects the crystallinity of the first buffer layer 110 provided on the substrate 102. Therefore, in this specification, the value of 0.491nm calculated from the broad peak near 22° in the X-ray diffraction of amorphous glass is used as the lattice constant in the a-axis direction of the substrate 102. It is known that the lattice constant in the a-axis direction of gallium nitride contained in the gallium nitride layer 120 is 0.318nm. In contrast, the lattice constant in the a-axis direction of the first buffer layer 110 and the second buffer layer 112 having the above-mentioned structure depends on the composition, and the former is greater than 0.355nm and less than 0.480nm, and the latter is greater than 0.300nm and less than 0.330nm.

[0054] So, if Figure 2 The relationship between the lattice constants of the substrate 102, the first buffer layer 110, the second buffer layer 112, and the gallium nitride layer 120 is schematically shown. Figure 2As can be understood, in the light emitting element 100, the lattice constant in the a-axis direction is gradually reduced in the order of the substrate 102, the first buffer layer 110, the second buffer layer 112, and the gallium nitride layer 120. Therefore, the difference (Δ1) in the lattice constant in the a-axis direction between the first buffer layer 110 containing aluminum oxide and the gallium nitride layer 120 containing gallium nitride is smaller than the difference (Δ2) in the lattice constant in the a-axis direction between the substrate 102 containing amorphous glass and the gallium nitride layer 120. In addition, the difference (Δ3) in the lattice constant in the a-axis direction between the second buffer layer 112 containing aluminum nitride and the gallium nitride layer 120 is smaller than the difference (Δ2) in the lattice constant in the a-axis direction between the substrate 102 and the gallium nitride layer 120, and smaller than the difference (Δ1) in the lattice constant in the a-axis direction between the first buffer layer 110 and the gallium nitride layer 120.

[0055] Since the difference Δ3 in the lattice constant in the a-axis direction is small between the second buffer layer 112 and the gallium nitride layer 120, the crystal structure of the gallium nitride layer 120 formed on the second buffer layer 112 is easily affected by the second buffer layer 112. Therefore, when the second buffer layer 112 is highly oriented along the c-axis, the gallium nitride layer 120 also effectively promotes crystallization in the c-axis direction, but when the crystallinity of the second buffer layer 112 is low, the gallium nitride layer 120 cannot be fully crystallized, which causes a decrease in the crystallite size.

[0056] In addition, if Figure 2 As understood, when the difference Δ2 between the lattice constant of the substrate 102 and the lattice constant of the second buffer layer 112 is large and the second buffer layer is formed directly on the substrate 102, the crystal growth of the second buffer layer 112 is hindered due to the large lattice constant difference. However, by providing the first buffer layer 110 having a lattice constant between the substrate 102 and the second buffer layer 112, the mismatch in the lattice constant between the substrate 102 and the second buffer layer 112 can be alleviated, so that by forming the second buffer layer 112 on the first buffer layer 110, the crystallization of the second buffer layer 112 can be promoted. As a result, the second buffer layer 112 with improved crystallinity can be obtained, and by forming the gallium nitride layer 120 thereon, the crystallinity of the gallium nitride layer 120 in the c-axis direction can be improved. As a result, the crystallinity of the semiconductor layer provided on the gallium nitride layer 120 can also be improved, so that the light-emitting element 100 with excellent characteristics can be provided.

[0057] (4) Gallium Nitride Layer

[0058] The gallium nitride layer 120 contains gallium nitride. Gallium nitride is given p-type or n-type conductivity by adding a dopant, but the gallium nitride layer 120 may also be an undoped gallium nitride layer containing no dopant. Alternatively, the gallium nitride layer 120 may also include n-type gallium nitride containing a dopant that imparts n-type conductivity (such as silicon and germanium), or p-type gallium nitride containing a dopant that imparts p-type conductivity (such as magnesium, zinc, cadmium, and beryllium).

[0059] (5) n-type cladding layer, light-emitting layer, p-type cladding layer

[0060] The n-type cladding layer 122, the light-emitting layer 124, and the p-type cladding layer 126 are formed by recombination of holes and electrons injected from the anode 128 and the cathode 130, respectively, to emit visible light. The n-type cladding layer 122, the light-emitting layer 124, and the p-type cladding layer 126 may each have a single-layer structure or a stacked structure in which a plurality of layers are stacked. Figure 1A In the example shown, the n-type cladding layer 122, the light-emitting layer 124, and the p-type cladding layer 126 are stacked in this order from the substrate 102 side, but the semiconductor layers may be formed in the reverse order. In this case, the gallium nitride layer 120 is formed to include undoped gallium nitride or p-type gallium nitride, and the p-type cladding layer 126, the light-emitting layer 124, and the n-type cladding layer 122 are formed thereon.

[0061] The n-type cladding layer 122, the light-emitting layer 124, and the p-type cladding layer 126 are semiconductor layers containing elements of Group 13 and Group 15, respectively. Specifically, these layers contain semiconductors containing aluminum, gallium and / or indium as well as nitrogen, phosphorus and / or arsenic. Typical semiconductors include gallium-based materials. For example, gallium nitride, aluminum gallium nitride (AlGaN), indium gallium nitride (InGaN) and other gallium nitride-based materials, gallium phosphide (GaP), aluminum gallium indium phosphide (AlGaInP) and other gallium phosphide-based materials can be exemplified. The n-type cladding layer 122 and the p-type cladding layer 126 may further contain the above-mentioned dopants. By adding dopants, the valence electrons of each layer can be controlled, and the band gap can also be controlled. Furthermore, the gallium nitride layer 120 and the layer disposed in contact therewith (in Figure 1A In the example shown, the composition of the n-type cladding layer 122 may also be the same.

[0062] The light emitting layer 124 may be, for example, a single-layer structure of indium gallium nitride, or may have a quantum well structure. The so-called quantum well structure is a structure formed by alternately stacking a plurality of thin films having different band gaps and a thickness in the range of 1 to 5 nm, and examples thereof include an alternating stack of indium gallium nitride and gallium nitride, an alternating stack of indium gallium arsenide phosphide (GaInAsP) and indium phosphide (InP), an alternating stack of aluminum indium arsenide (AlInAs) and indium gallium arsenide (InGaAs), and the like.

[0063] (6) Anode and cathode

[0064] The anode 128 and the cathode 130 inject holes and electrons into the p-type cladding layer 126 and the n-type cladding layer 122, respectively. As the anode 128, for example, a metal such as palladium, gold, an alloy of these metals, or a thin film of a conductive oxide that transmits visible light such as indium-tin mixed oxide (ITO) and indium-zinc mixed oxide (IZO) can be used. As the cathode 130, a metal such as aluminum, titanium, gold, silver or indium, or an alloy of these metals can be used. Both the anode 128 and the cathode 130 may have a single-layer structure, or may be a stack of multiple films having different compositions.

[0065] (7) Protective film

[0066] The protective film 140 is used to prevent impurities such as oxygen and water from entering the light emitting element 100, and can be composed of one or more films containing silicon-containing inorganic compounds such as silicon oxide and silicon nitride. The protective film 140 is provided with openings for exposing the anode 128 and the cathode 130, and wiring (not shown) is electrically connected to the anode 128 and the cathode 130 by using these openings.

[0067] As described above, in the light emitting element 100, the first buffer layer 110 and the second buffer layer 112 are stacked on the substrate 102 made of amorphous glass, and the gallium nitride layer 120 is provided thereon. Since the substrate 102 and the first buffer layer 110 contain aluminum oxide, a strong bond can be obtained therebetween. In addition, since the thermal expansion coefficient increases stepwise from the first buffer layer 110 to the gallium nitride layer 120, there is no large difference in thermal expansion coefficient between adjacent structures, so that peeling and cracking can be prevented from occurring under high temperature conditions.

[0068] In addition, since the first buffer layer 110 having the lattice constant between the substrate 102 and the second buffer layer 112 is provided between the substrate 102 and the second buffer layer 112, which have a large lattice constant difference, the large lattice mismatch between the substrate 102 and the second buffer layer 112 can be alleviated. Therefore, by providing the second buffer layer 112 on the first buffer layer 110 having a high bonding force with the substrate 102, the crystallinity of the second buffer layer 112 can be greatly improved compared to when the second buffer layer 112 is directly provided on the substrate 102. As a result, the crystallinity of the n-type cladding layer 122, the light-emitting layer 124, and the p-type cladding layer 126, which are responsible for the function of the light-emitting element 100, is improved, and a light-emitting element with excellent characteristics can be provided.

[0069] In addition, since the aluminum oxide, aluminum oxynitride, and aluminum nitride contained in the first buffer layer 110 and the second buffer layer 112 have high resistance to various etchants used in the photolithography process, they will not disappear or be damaged in the manufacturing process of the light-emitting element 100 described later. Therefore, the light-emitting element 100 with high reliability can be manufactured using various conventional devices for manufacturing semiconductor devices.

[0070] 2. Modifications

[0071] The structure of the light emitting element 100 is not limited to the above structure. Specifically, three or more buffer layers may be provided between the substrate 102 and the gallium nitride layer 120. Figure 1B As shown, in addition to the first buffer layer 110 and the second buffer layer 112, a third buffer layer 114 may be provided on the second buffer layer 112, and a fourth buffer layer 116 may be provided on the third buffer layer 114. Adjacent buffer layers are provided in contact with each other.

[0072] The third buffer layer 114 and the fourth buffer layer 116 may have the same configuration as the first buffer layer 110 and the second buffer layer 112. Alternatively, each of the first buffer layer 110 to the fourth buffer layer 116 may contain aluminum oxide, aluminum oxynitride, or aluminum nitride, and the oxygen concentration may decrease and the nitrogen concentration may increase in the order of the first buffer layer 110 to the fourth buffer layer 116. In this case, it is preferred that the fourth buffer layer 116 contain aluminum nitride.

[0073] Even in such a modified example, the lattice mismatch between the buffer layer in contact with the gallium nitride layer 120 and the substrate 102 can be alleviated, and the difference in thermal expansion coefficient between adjacent structures can be reduced. Therefore, the gallium nitride layer 120 with high crystallinity can be formed while suppressing the occurrence of peeling and cracking.

[0074] <Second Embodiment>

[0075] In this embodiment, a method for manufacturing the light emitting element 100 is described. The description of the same or similar configurations as those described in the first embodiment may be omitted.

[0076] (1) Formation of topcoat and primer

[0077] First, if Figure 3AAs shown, an outer coating 104 and an undercoat 106 are formed on the upper and lower sides of the substrate 102, respectively. There is no limitation on the size of the substrate 102, and a large amorphous glass substrate called a sample glass may be used as the substrate 102. For example, an amorphous glass substrate having a size of 600 mm × 720 mm, a size of 730 mm × 920 mm, a size of 600 mm × 1850 mm, or a size above that of 3.5 generation glass, a size of 730 mm × 920 mm, a size of 6.5 generation glass, or a size of 1500 mm × 1850 mm, or a size above that of 6.5 generation glass may be used. Therefore, a plurality of light-emitting elements 100 may be manufactured using one substrate 102. This helps to reduce the manufacturing cost of the light-emitting element 100. The outer coating 104 and the undercoat 106 may be formed by a CVD method and a sputtering method. Furthermore, the outer coating 104 and the undercoat 106 are of arbitrary configurations, so one or both of them may not be formed.

[0078] (2) Formation of the first buffer layer

[0079] Next, a first buffer layer 110 ( Figure 3B ). The first buffer layer 110 can be formed by a sputtering method. In the case where the first buffer layer 110 contains aluminum oxide, for example, aluminum or aluminum oxide can be used as a target, and oxygen free radicals can be irradiated in reactive sputtering using a mixed gas of argon and oxygen to form the first buffer layer 110. Alternatively, an aluminum oxide target can be sputtered with argon, and the obtained first buffer layer 110 can be treated with oxygen free radicals. Alternatively, the substrate 102 can be irradiated with oxygen plasma to form an oxygen-excess layer on the surface of the substrate 102, an aluminum thin film is formed thereon by sputtering an aluminum target, and then the aluminum thin film is converted into an aluminum oxide film by heating (annealing), thereby forming the first buffer layer 110. Alternatively, an aluminum thin film or an aluminum thin film containing aluminum oxide is formed on the substrate 102, respectively, by sputtering an aluminum target using argon or a mixed gas of argon and oxygen, and then the aluminum is oxidized by oxygen plasma or oxygen free radical treatment, thereby forming the first buffer layer 110.

[0080] In the case where the first buffer layer 110 contains nitrogen-containing aluminum oxide, the first buffer layer 110 can be formed by reactive sputtering using a mixed gas of argon, oxygen and nitrogen, for example, using an aluminum target or an aluminum oxide target. At this time, the obtained first buffer layer 110 can also be subjected to oxygen radical treatment and / or nitrogen radical treatment. Alternatively, the first buffer layer 110 can be formed by reactive sputtering using a mixed gas of argon and nitrogen using an aluminum oxide target. Alternatively, the first buffer layer 110 can be formed by sputtering an oxynitride aluminum target using argon. Alternatively, the first buffer layer 110 can be formed by irradiating the substrate 102 with nitrogen dioxide plasma to oxynitride the surface of the substrate 102, then forming an aluminum thin film by sputtering an aluminum target, and then annealing to oxynitride the aluminum. Alternatively, an aluminum thin film can be formed by sputtering an aluminum target with argon, and then oxynitriding the aluminum thin film using oxygen and nitrogen plasma. Alternatively, the first buffer layer 110 may be formed by performing oxygen radical treatment and nitrogen radical irradiation while sputtering an aluminum target, an aluminum oxynitride target, or an aluminum oxide target with argon.

[0081] As described above, the first buffer layer 110 can be configured so that the oxygen concentration decreases as the distance from the substrate 102 increases. As a result, aluminum oxide closer to the stoichiometric ratio can be formed on the upper surface of the first buffer layer 110. In this case, for example, in reactive sputtering using a mixed gas of argon and oxygen, the oxygen partial pressure can be reduced as the film grows.

[0082] After forming the first buffer layer 110 , the density of the layer can be increased by promoting crystallization through annealing. The temperature at this time can be appropriately selected from the range of, for example, 500° C. to 700° C. inclusive.

[0083] (3) Formation of the Second Buffer Layer

[0084] Next, a second buffer layer 112 is formed on the first buffer layer 110 ( Figure 3B ). The second buffer layer 112 can also be formed by a sputtering method. For example, the second buffer layer 112 can be formed by sputtering an aluminum nitride target with argon. Alternatively, the second buffer layer 112 can be formed by reactively sputtering an aluminum target or an aluminum nitride target using a mixed gas of argon and nitrogen. At this time, the obtained second buffer layer 112 can also be further treated with nitrogen radicals. Alternatively, the second buffer layer 112 can also be formed by irradiating nitrogen radicals while sputtering an aluminum target or an aluminum nitride target with argon.

[0085] As described above, the nitrogen concentration can be changed in the thickness direction also in the second buffer layer 112. For example, the nitrogen concentration can be controlled by controlling the nitrogen partial pressure in reactive sputtering, or the nitrogen concentration on the surface of the second buffer layer 112 can be increased by nitrogen radical treatment.

[0086] The density of the layer can also be increased by annealing the second buffer layer 112 to promote crystallization, similarly to the first buffer layer 110. The temperature at this time can be appropriately selected from the range of 500°C or more and 700°C or less, for example.

[0087] Furthermore, it is preferred that the first buffer layer 110 and the second buffer layer 112 are formed continuously in the same chamber, or preferably formed in another chamber while maintaining a vacuum state without returning to the atmospheric state. Thus, it is possible to prevent impurities from being mixed into the interface between the first buffer layer 110 and the second buffer layer 112, and it is possible to more effectively promote the crystallization of the second buffer layer 112.

[0088] (4) Formation of GaN layer, n-type cladding layer, light-emitting layer, and p-type cladding layer

[0089] Next, a gallium nitride layer 120 is formed on the second buffer layer 112, and semiconductor layers, namely, an n-type cladding layer 122, a light-emitting layer 124, and a p-type cladding layer 126 are sequentially formed thereon ( Figure 3C ). Each of these layers can be formed by sputtering. For example, these layers can be formed by sputtering a semiconductor target such as gallium nitride with argon in the presence of plasma. When a dopant is contained in the layer, a target containing the dopant can be used. Alternatively, a gallium nitride target and a target for the dopant can be sputtered at the same time. In addition, by using an indium gallium nitride target and a gallium nitride target, a light-emitting layer 124 consisting of an indium gallium nitride film and a gallium nitride film alternately stacked can be formed. Alternatively, when the light-emitting layer 124 is an indium gallium nitride film, a gallium nitride target and an indium target are sputtered simultaneously, and by sputtering a gallium nitride target when a gallium nitride film is formed, a light-emitting layer 124 consisting of an indium gallium nitride film and a gallium nitride film alternately stacked can be formed.

[0090] Next, the n-type cladding layer 122 to the p-type cladding layer 126 are patterned. Figure 4A As shown in the figure, a plurality of stacked bodies including an n-type cladding layer 122, a light-emitting layer 124, and a p-type cladding layer 126 are arranged in an island shape on the gallium nitride layer 120. Since each stacked body constitutes one light-emitting element 100, through this method, a plurality of light-emitting elements 100 sharing the gallium nitride layer 120 can be formed on one substrate 102. Since pattern processing can be performed by a known photolithography method, a detailed description thereof will be omitted.

[0091] Then, the anode 128 and the cathode 130 are formed on the p-type cladding layer 126 and the n-type cladding layer 122, respectively ( Figure 4B). The anode 128 and the cathode 130 can be formed by vacuum evaporation, electron beam evaporation, CVD, sputtering, etc. When the protective film 140 is provided, one or more films containing a silicon-containing inorganic compound can be formed by CVD or sputtering to cover the anode 128 and the cathode 130, and then the protective film 140 is etched to expose a portion of the anode 128 and the cathode 130. Therefore, the protective film 140 is also formed on the side of the substrate 102 ( Figure 4C ).

[0092] Then, by following Figure 4C The dotted line cuts through the substrate 102, and the Figure 1A The light emitting element 100 is shown.

[0093] As described above, the first buffer layer 110 to the p-type cladding layer 126 can all be formed by sputtering. Therefore, the temperature during film formation is room temperature to a temperature lower than 600° C., typically 100° C. to 400° C. Therefore, by using an inexpensive substrate 102 made of amorphous glass, a plurality of light-emitting elements 100 can be manufactured.

[0094] Furthermore, the gallium nitride layer 120 to the p-type cladding layer 126 are formed on the second buffer layer 112. Therefore, even without using the vapor phase epitaxial growth conventionally used to form the inorganic semiconductor layer, the semiconductor particles ejected by sputtering the semiconductor target can be effectively c-axis oriented by being excited by the second buffer layer 112 while being deposited to form each layer. As a result, high temperature is not required when forming the first buffer layer 110 to the p-type cladding layer 126, each layer can have high crystallinity, and the light-emitting element 100 can show excellent characteristics as an LED.

[0095] <Third Embodiment>

[0096] In this embodiment, a transistor according to one embodiment of the present invention is described. The description of the same or similar configurations as those described in the first and second embodiments may be omitted.

[0097] 1. High Electron Mobility Field Effect Transistor

[0098] As an example of a transistor according to one embodiment of the present invention, Figure 5A, a schematic end view of a high electron mobility field effect transistor 150 is shown. The transistor 150 has a substrate 102, and includes a first buffer layer 110 and a second buffer layer 112 on the substrate 102, and an active layer (also called an electron transit layer) 152 on the second buffer layer 112. The active layer 152 corresponds to the gallium nitride layer 120 of the light-emitting element 100 described in the first embodiment. The transistor 150 further includes an electron supply layer 158 on the active layer 152, and a pair of terminals (a first terminal 154 and a second terminal 156) located on the active layer 152 and electrically connected to the active layer 152 and the electron supply layer 158. The first terminal 154 and the second terminal 156 may also be in contact with the active layer 152, and although not shown in the figure, they may also be connected to the active layer 152 via the electron supply layer 158. The transistor 150 further includes a gate electrode 162, which is in direct contact with the electron supply layer 158 or is provided on the electron supply layer 158 via an arbitrary structure, namely, a gate insulating film 160. These structures are described below, but since the structures of the substrate 102, the overcoat layer 104, the undercoat layer 106, the first buffer layer 110, and the second buffer layer 112 are the same as those of the first embodiment, the description thereof is omitted.

[0099] (1) Active layer and electron supply layer

[0100] By stacking the active layer 152 and the electron supply layer 158, a path for source / drain current is formed when the transistor 150 is driven. The active layer 152 and the electron supply layer 158 contain group 13 elements and group 15 elements. For example, the active layer 152 and the electron supply layer 158 may contain undoped gallium nitride and n-type aluminum gallium nitride, respectively. Alternatively, the active layer 152 and the electron supply layer 158 may also contain undoped gallium arsenide (GaAs) and n-type aluminum gallium arsenide (AlGaAs), respectively. The active layer 152 is disposed on the second buffer layer 112 in contact with the second buffer layer 112 by sputtering. Therefore, film formation at a high temperature as required for epitaxial growth using MOCVD is not required, and the active layer 152 and the electron supply layer 158 can be formed even when a substrate 102 containing amorphous glass is used. In addition, the active layer 152 and the electron supply layer 158 promote crystallization in the c-axis direction through the second buffer layer 112 acting as its substrate. In addition, as described in the first embodiment, since the second buffer layer 112 is not directly disposed on the substrate 102 having a large lattice mismatch, but is disposed on the first buffer layer 110 for alleviating the lattice mismatch, the c-axis orientation is high. Therefore, since the second buffer layer 112 also has a high c-axis orientation, even if the active layer 152 and the electron supply layer 158 are formed by sputtering, a high c-axis orientation can be achieved in these layers. As a result, a transistor having a high field mobility can be provided.

[0101] (2) First terminal, second terminal, gate insulating film, and gate electrode

[0102] The first terminal 154, the second terminal 156 and the gate electrode 162 contain metals such as aluminum, gold, silver, tantalum, molybdenum, titanium, copper, or alloys containing one or more of the above metals. The gate insulating film 160 of any structure contains, for example, silicon oxide and silicon nitride, silicon-containing inorganic compounds, or so-called high-K materials such as hafnium silicate, zirconium silicate, hafnium oxide, zirconium oxide, etc. There is no limitation on the method of forming these structures, and vacuum evaporation, electron beam evaporation, CVD, and sputtering can be appropriately used. Among them, by using sputtering and electron beam evaporation with fast film forming speed, the first terminal 154, the second terminal 156, the gate insulating film 160 and the gate electrode 162 can be formed efficiently.

[0103] 2. Metal Insulation Film Field Effect Transistor

[0104] The transistor involved in this embodiment may also be a so-called metal insulating film field effect transistor (MISFET). Figure 5B As in the transistor 170 shown in FIG. 1 , the electron supply layer 158 may be omitted and the active layer 152 may be formed by stacking a first active layer 152-1 including a p-type gallium nitride layer and a second active layer 152-2 located on the first active layer 152-1 and including i-type or n-type gallium nitride. The second active layer 152-2 may be separately provided between the first active layer 152-1 and the first terminal 154 and between the first active layer 152-1 and the second terminal 156, respectively, in such a manner that a source region and a drain region are formed on the first active layer 152-1.

[0105] In the transistor 170, the active layer 152 that influences its characteristics is also provided on the second buffer layer 112, and the second buffer layer 112 is provided on the first buffer layer 110 for alleviating the lattice constant mismatch between the substrate 102 and the second buffer layer 112. Therefore, the c-axis orientation of the active layer 152 can be promoted on the second buffer layer 112 whose c-axis orientation is improved by the first buffer layer 110, and as a result, the active layer 152 has high crystallinity. As a result, the transistor 170 can have high field mobility.

[0106] The above-mentioned embodiments as embodiments of the present invention can be implemented by appropriate combination within the scope of non-contradiction. In addition, based on the display device of each embodiment, those skilled in the art can appropriately add, delete or change the design of the components, or add, omit or change the conditions of the process, and these changes are included in the scope of the present invention as long as they have the main purpose of the present invention.

[0107] Even if there are other effects that are different from the effects brought about by the forms of the above-mentioned embodiments, for the effects that can be clarified from the description of this specification or the effects that are easily predicted by those skilled in the art, they should of course be understood as the effects brought about by the present invention.

[0108] Explanation of symbols

[0109] 100: light emitting element, 102: substrate, 104: outer coating, 106: base coating, 110: first buffer layer, 112: second buffer layer, 114: third buffer layer, 116: fourth buffer layer, 120: gallium nitride layer, 122: n-type cladding layer, 124: light emitting layer, 126: p-type cladding layer, 128: anode, 130: cathode, 140: protective film, 150: transistor, 152: active layer, 152-1: first active layer, 152-2: second active layer, 154: first terminal, 156: second terminal, 158: electron supply layer, 160: gate insulating film, 162: gate electrode, 170: transistor.

Claims

1. A light-emitting element, comprising: A substrate comprising amorphous glass, a first buffer layer located on the substrate and containing aluminum and oxygen, a second buffer layer located on the first buffer layer and containing aluminum and nitrogen, The gallium nitride layer on the second buffer layer, A stacked body located on the gallium nitride layer and comprising an n-type cladding layer, a p-type cladding layer, and a light-emitting layer located between the n-type cladding layer and the p-type cladding layer, and a cathode and an anode located on the n-type cladding layer and the p-type cladding layer, respectively; in, The n-type cladding layer, the p-type cladding layer, and the light-emitting layer each contain a Group 13 element and a Group 15 element.

2. The light-emitting element according to claim 1, wherein In the in-plane direction, the thermal expansion coefficient of the first buffer layer is between the thermal expansion coefficients of the substrate and the gallium nitride layer. A difference in lattice constant between the first buffer layer and the gallium nitride layer in the a-axis direction is smaller than a difference in lattice constant between the substrate and the gallium nitride layer in the a-axis direction.

3. The light-emitting element according to claim 2, wherein The thermal expansion coefficient of the first buffer layer in the in-plane direction is 3.5×10 -6 / ℃ and above 5.6×10 -6 / ℃ below, The lattice constant of the first buffer layer in the a-axis direction is greater than or equal to 0.355 nm and less than or equal to 0.480 nm.

4. The light-emitting element according to claim 2, wherein In the in-plane direction, the thermal expansion coefficient of the second buffer layer is between the thermal expansion coefficients of the substrate and the gallium nitride layer. The difference in lattice constant between the second buffer layer and the gallium nitride layer in the a-axis direction is smaller than the difference in lattice constant between the substrate and the gallium nitride layer in the a-axis direction, and is smaller than the difference in lattice constant between the first buffer layer and the gallium nitride layer in the a-axis direction.

5. The light emitting element according to claim 4, wherein The thermal expansion coefficient of the second buffer layer in the in-plane direction is 3.6×10 -6 / ℃ and above 4.6×10 -6 / ℃ below, The lattice constant of the second buffer layer in the a-axis direction is greater than or equal to 0.300 nm and less than or equal to 0.330 nm.

6. The light-emitting element according to claim 1, wherein The first buffer layer further contains nitrogen.

7. The light-emitting element according to claim 6, wherein The oxygen concentration of the first buffer layer decreases as the distance from the substrate increases.

8. The light-emitting element according to claim 1, wherein In the second buffer layer, the atomic ratio of nitrogen to aluminum approaches 1 as the distance from the first buffer layer increases.

9. The light-emitting element according to claim 1, wherein A primer layer containing aluminum nitride and / or aluminum oxide is further provided under the substrate.

10. The light emitting element according to claim 1, wherein The gallium nitride layer is in direct contact with the second buffer layer.

11. A method for manufacturing a light emitting element, comprising the following steps: forming a first buffer layer on a substrate including amorphous glass, forming a second buffer layer on the first buffer layer, forming a gallium nitride layer on the second buffer layer by sputtering, forming a stacked body on the gallium nitride layer by a sputtering method, the stacked body comprising an n-type cladding layer, a p-type cladding layer, and a light-emitting layer located between the n-type cladding layer and the p-type cladding layer, and forming a cathode and an anode on each of the n-type cladding layer and the p-type cladding layer; in, The n-type cladding layer, the p-type cladding layer, and the light-emitting layer each contain a Group 13 element and a Group 15 element.

12. The manufacturing method according to claim 11, wherein: In the in-plane direction, the thermal expansion coefficient of the first buffer layer is between the thermal expansion coefficients of the substrate and the gallium nitride layer. A difference in lattice constant between the first buffer layer and the gallium nitride layer in the a-axis direction is smaller than a difference in lattice constant between the substrate and the gallium nitride layer in the a-axis direction.

13. The manufacturing method according to claim 12, wherein: The thermal expansion coefficient of the first buffer layer in the in-plane direction is 3.5×10 -6 / ℃ and above 5.6×10 -6 / ℃ below, The lattice constant of the first buffer layer in the a-axis direction is greater than or equal to 0.355 nm and less than or equal to 0.480 nm.

14. The manufacturing method according to claim 12, wherein: In the in-plane direction, the thermal expansion coefficient of the second buffer layer is between the thermal expansion coefficients of the substrate and the gallium nitride layer. The difference in lattice constant between the second buffer layer and the gallium nitride layer in the a-axis direction is smaller than the difference in lattice constant between the substrate and the gallium nitride layer in the a-axis direction, and is smaller than the difference in lattice constant between the first buffer layer and the gallium nitride layer in the a-axis direction.

15. The manufacturing method according to claim 14, wherein: The thermal expansion coefficient of the second buffer layer in the in-plane direction is 3.6×10 -6 / ℃ and above 4.6×10 -6 / ℃ below, The lattice constant of the second buffer layer in the a-axis direction is greater than or equal to 0.300 nm and less than or equal to 0.330 nm.

16. The manufacturing method according to claim 11, wherein: The first buffer layer further contains nitrogen.

17. The manufacturing method according to claim 16, wherein: The oxygen concentration of the first buffer layer decreases as the distance from the substrate increases.

18. The manufacturing method according to claim 11, wherein: In the second buffer layer, the atomic ratio of nitrogen to aluminum approaches 1 as the distance from the first buffer layer increases.

19. The manufacturing method according to claim 11, wherein: The method further comprises the step of forming an undercoat layer containing aluminum nitride and / or aluminum oxide under the substrate.

20. The manufacturing method according to claim 11, wherein: The gallium nitride layer is in direct contact with the second buffer layer.

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