HK1148869A - Semiconductor light-emitting device and method for manufacturing the same - Google Patents

Description

Semiconductor light emitting device and method for manufacturing semiconductor light emitting device

Technical Field

The present invention relates to a semiconductor light emitting device and a method for manufacturing the semiconductor light emitting device.

Background

A semiconductor light emitting device such as a Light Emitting Diode (LED) has, for example, the following structure: in this structure, an n-type conductivity type first compound semiconductor layer 11, an active layer 12, and a p-type conductivity type second compound semiconductor layer 13 are sequentially stacked on a substrate 10. In addition, a first electrode (n-side electrode) 15 is provided on the substrate or on the exposed portion 11A of the first compound semiconductor layer 11, and a second electrode (p-side electrode) 114 is provided on top of the second compound semiconductor layer 13. Such semiconductor light emitting devices can be classified into two types: one type of semiconductor light-emitting device is a semiconductor light-emitting device in which light from the active layer 12 is emitted through the second compound semiconductor layer 13; another type of semiconductor light emitting device is disclosed in, for example, WO2003/007390, in which light from an active layer 12 is emitted through a first compound semiconductor layer 11 (referred to as "bottom emission type" for simplicity).

In general, as shown in fig. 5, a conventional bottom-emission type semiconductor light-emitting device often uses a reflective electrode as the second electrode 114, which reflects visible light from the active layer 12 in order to maintain high emission efficiency. In this case, the second electrode 114 needs to have an electron density sufficient to reflect visible light emitted from the active layer 12, and the second electrode 114 is composed of, for example, a metal such as silver (Ag), aluminum (Al), or the like. However, the second electrode made of such a metal is liable to cause electromigration (electrical migration) during the manufacturing process of the semiconductor light emitting device or during the operation of the semiconductor light emitting device, and to cause significant deterioration due to oxidation or the like. Therefore, a coating layer 100 composed of, for example, TiW is often formed to cover the second electrode. Further, other elements of the semiconductor light emitting device shown in fig. 5 will be described in detail in embodiment 1 described later.

However, in order to cover the second electrode 114 with the overcoat layer 100, it is necessary to use various processes, for example, to form the overcoat layer 100 based on a physical vapor deposition method (PVD method) and to pattern the overcoat layer 100 by a photolithography technique and an etching technique. Thus, the manufacturing cost of the semiconductor light emitting device is inevitably increased.

Disclosure of Invention

Accordingly, an object of the present invention is to provide a semiconductor light emitting device including a second electrode exhibiting stable behavior during the manufacturing process of the semiconductor light emitting device or during the operation of the semiconductor light emitting device, and to provide a semiconductor light emitting device manufacturing method.

In order to achieve the above object, a semiconductor light emitting device of the present invention includes: (A) a first compound semiconductor layer formed on the first substrate,it is of n-type conductivity; (B) an active layer formed on the first compound semiconductor layer and composed of a compound semiconductor; (C) a second compound semiconductor layer which is formed on the active layer and is of p-type conductivity; (D) a first electrode electrically connected to the first compound semiconductor layer; and (E) a second electrode formed on the second compound semiconductor layer. Wherein the second electrode is made of titanium oxide and has a thickness of 4 × 10²¹/cm³The above electron concentration and reflects light emitted from the active layer.

The semiconductor light emitting device of the present invention may take the form of: wherein the semiconductor layer is doped with niobium (Nb), tantalum (Ta) or vanadium (V). In other words, the semiconductor light emitting device may take the form of: wherein the doping impurity of the second electrode is at least one atom selected from the group consisting of niobium (Nb), tantalum (Ta) and vanadium (V).

In addition, the semiconductor light emitting device of the present invention including the above-described preferred forms may be configured such that: the compound semiconductor for forming the first compound semiconductor layer, the active layer and the second compound semiconductor layer is Al_XGa_YIn_1-X-YN(0≤X≤1，0≤Y≤1，0≤X+Y≤1)。

Further, the semiconductor light emitting device of the present invention including the above-described preferred forms and configurations is preferably configured such that: the crystal structure of titanium oxide is a rutile (rutile) structure.

Further, the semiconductor light emitting device of the present invention including the above-described preferred forms and configurations is preferably configured such that: the top surface of the second compound semiconductor layer on which the second electrode is formed has a (0001) plane (also referred to as "C plane"). In this manner, since the top surface of the second compound semiconductor layer has a C-plane, high lattice matching with the second electrode can be achieved depending on the compound semiconductor constituting the compound semiconductor layer.

In order to achieve the above object, a method for manufacturing a semiconductor light emitting device of the present invention includes at least the steps of: (a) by sequentially laminating an n-type conductivity type first compound semiconductor layer, an active layer and a p-type conductivity type first compound semiconductor layer on a substrateA conductive second compound semiconductor layer forming a light emitting portion; and (b) next, forming a second electrode on the second compound semiconductor layer. Wherein the compound semiconductor for forming the first compound semiconductor layer, the active layer and the second compound semiconductor layer is Al_XGa_YIn_1-X-YN (X is more than or equal to 0 and less than or equal to 1, Y is more than or equal to 0 and less than or equal to 1, and X + Y is more than or equal to 0 and less than or equal to 1); and in the step (b), on the top surface having the (0001) plane of the second compound semiconductor layer, a second electrode made of titanium oxide having a rutile crystal structure is impurity-doped so that the electron concentration is 4 × 10²¹/cm³The above state is obtained by epitaxial growth.

The semiconductor light emitting device manufacturing method of the present invention may take the form of: wherein the impurities are niobium (Nb), tantalum (Ta) or vanadium (V). In other words, the method may take the form of: wherein the doping impurity of the second electrode is at least one atom selected from the group consisting of niobium (Nb), tantalum (Ta) and vanadium (V). In addition, according to circumstances, after the second electrode is formed, an impurity may be implanted in the second electrode by, for example, an ion implantation method from the viewpoint of adding the impurity.

In the method for manufacturing a semiconductor light emitting device of the present invention including the above preferred forms, the second electrode is preferably formed based on a pulsed laser deposition method (PLD method) which is one of physical vapor deposition methods, but the method is not limited thereto, and the second electrode may be formed on the basis of another method such as a molecular beam epitaxy method (MBE method) or a sputtering method.

In addition, in the semiconductor light emitting device or the manufacturing method thereof of the present invention including the above-described preferred forms and configurations, the material for constituting the second electrode preferably has a characteristic that conductivity increases with an increase in temperature, that is, a characteristic similar to a metal. In addition, in order to judge whether the characteristic is similar to a metal, in addition to the conductivity, the density of states of a substance may be measured on the basis of an X-ray photoelectron spectroscopy method (XPS method) to judge whether a Fermi edge (Fermi edge) is present.

In addition, the semiconductor light emitting device or the method for manufacturing the same of the present invention including the above preferred forms and configurations preferably has the following forms: wherein in the second electrode, a plasma frequency ω represented by the following expression (1) is 425nm or less.

ω＝{(n_e·e²)/(ε₀·m_e)}^1/2 (1)

Here, n is_eIs the electron density, e is the basic charge,. epsilon₀Is the vacuum dielectric constant, m_eIs the static mass of the electrons.

In addition, the semiconductor light emitting device or the manufacturing method thereof of the present invention including the above-described preferred forms and configurations is preferably configured such that: light emitted from the active layer is emitted outward through the first compound semiconductor layer. That is, the semiconductor light emitting device is preferably of a bottom emission type.

In the semiconductor light emitting device of the present invention including the above-described preferred forms and configurations or the method of manufacturing the semiconductor light emitting device of the present invention including the above-described preferred forms and configurations (hereinafter may be collectively referred to as "the present invention"), as the compound semiconductor, not only GaN-based compound semiconductors (including AlGaN mixed crystals or AlGaInN mixed crystals, and GaInN mixed crystals), but also InN-based compound semiconductors and AlN-based compound semiconductors may be used, as described above. In addition, as a formation method (deposition method) of these semiconductor layers, a metal organic chemical vapor deposition method (MOCVD method), an MBE method, and a hydride vapor deposition method in which transport or reaction is assisted by halogen can be used. Examples of the n-type impurity added to these compound semiconductor layers include silicon (Si), selenium (Se), germanium (Ge), tin (Sn), carbon (C), and titanium (Ti). Examples of p-type impurities include zinc (Zn), magnesium (Mg), beryllium (Be), cadmium (Cd), calcium (Ca), barium (Ba), and oxygen (O).

Substrates that can be used as substrates in the present invention include sapphire substrates, GaAs substrates, GaN substrates, SiC substrates, alumina substrates, ZnS substrates, ZnO substrates, AlN substrates, LiMgO substrates, LiGaO substrates₂Substrate and MgAl₂O₄A substrate, an InP substrate, a Si substrate, a Ga substrate, and these substrates each including an underlayer and a buffer layer formed on a surface (main surface). In the present invention, the semiconductor light emitting device is first provided on the substrate, but such a form may be used as a final form of the semiconductor light emitting device: a form in which the semiconductor light emitting device is formed on the substrate, or a form in which the substrate is removed.

In the semiconductor light emitting device of the present invention including the above-described preferred form and configuration or the semiconductor light emitting device manufacturing method of the present invention including the above-described preferred form and configuration (hereinafter may be collectively referred to as "semiconductor light emitting device of the present invention or the like"), as for a material constituting the first electrode, the first electrode may be composed of: titanium (Ti); or a titanium alloy such as TiW or TiMo (e.g., TiW layer, Ti layer/Ni layer/Au layer, etc.); or aluminum (Al), aluminum alloys, AuGe/Ni/Au, etc. In addition, when the electrode has a multilayer structure, the material shown before "/" is provided on the substrate side. The first electrode and the second electrode may be provided with a contact portion (pad portion) including a multilayer metal layer having a laminated configuration such as a Ti layer/Pt layer/Au layer [ for example, [ an adhesive layer (Ti layer, Cr layer, or the like) ]/[ a barrier metal layer (Pt layer, Ti layer, TiW layer, Mo layer, or the like) ]/[ a metal layer having good compatibility at the time of mounting (for example, Au layer) ], as necessary. The first electrode and the contact portion (pad portion) can be formed by any one of the following methods: various PVD methods such as a vacuum evaporation deposition method, a sputtering method, and the like; various chemical vapor deposition methods (CVD methods); and a plating method.

Specifically, for example, a Light Emitting Diode (LED), an edge-emitting semiconductor laser, or a surface-emitting laser device (vertical cavity laser, VCSEL) can be configured using the semiconductor light emitting device of the present invention or the like.

In the semiconductor light-emitting device and the like of the present invention, the second electrode reflects light emitted from the active layer, but the phrase "second electrode reflects. The light reflectance of the second electrode can be determined by comparing the relative reflected light intensity with the dielectric multilayer film as a reference having a light reflectance of 100% in theory. The electron concentration of the second electrode can be determined on the basis of Hall measurements (Van der Pauw method).

In the present invention, since the second electrode is made of titanium oxide having a high electron density, not only high conductivity but also high light reflectance can be achieved. Therefore, the emission efficiency of the semiconductor light emitting device can be significantly improved. In addition, since the second electrode is composed of titanium oxide, there occurs no problem of deterioration due to oxidation, and since titanium oxide is a very stable substance, electromigration does not occur. Therefore, it is not necessary to cover the second electrode with a cladding layer, and thus it is possible to attempt to simplify the manufacturing process of the semiconductor light emitting device and to reduce the manufacturing cost of the semiconductor light emitting device.

Drawings

Fig. 1(a) is a schematic layout view of elements of the semiconductor light emitting device of embodiment 1, and fig. 1(B) is a schematic sectional view of the semiconductor light emitting device of embodiment 1 taken along an arrow B-B in fig. 1 (a).

Fig. 2 is a graph showing the relationship between the electron concentration and the plasma frequency expressed in terms of wavelength.

Fig. 3(a) and 3(B) are partial end views of a substrate or the like for explaining a method for manufacturing the semiconductor light emitting device of embodiment 1.

Fig. 4(a) and 4(B) are partial end views of a substrate and the like for explaining a method for manufacturing the semiconductor light emitting device of embodiment 1, following fig. 3 (B).

Fig. 5 is a schematic cross-sectional view of a conventional semiconductor light emitting device.

Detailed Description

Although the present invention will be described below on the basis of embodiments with reference to the drawings, the second electrode of the present invention is considered before the description.

It is known to dope titanium oxide with pentavalent niobium (Nb) or tantalum (Ta), i.e., by forming Ti_1-zA_zO₂(A is a pentavalent impurity) and a high conductivity equivalent to that of ITO can be obtained (see, for example, T.Hitotsugi, A.Ueda, Y.Furubayashi, Y.Hirose, S.Nomura, T.Shimada, T.Hasegawa, Jpn.J.Appl.Phys.46, L86 (2007); N.Yamada, T.Hitotsugi, N.L.Kuong, Y.Furubayashi, Y.Hirose, T.Shimada, T.Hasegawa, Jpn.J.Phys.46, 5275 (2007); T.Hitotsugi, Y.Furubayashi, A.Ueda, K.Itashi, K.Inna, Y.Hirose, G.Kinoda, Y.Yamatoto, Yatsyashi, T.25210, Shimada, T.Shimada, T.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.R.A, T.R.R.R.R.R.R. Here, assuming no free electron tourism on the basis of Drude's electron theory, the plasma frequency (ω) called "plasmon (plasma)" can be determined according to expression (1) (see, for example, "Introduction to Solid State Physics" by c.kittel, 7 th edition, page 304 (1998)).

ω＝{(n_e·e²)/(ε₀·m_e)}^1/2 (1)

Here, n is_eIs the electron density, e is the basic charge,. epsilon₀Is the vacuum dielectric constant, m_eIs the static mass of the electrons.

Plasmons are quantized electronic vibrations, and light with lower energy than it is theoretically totally reflected. Therefore, the electron concentration in the titanium oxide can be increased byAbove the plasma frequency to fully reflect light in the visible region. In titanium oxide, for example, the activation rate of impurities such as Nb and Ta is said to be about 80%. Thus, by doping 5 × 10²¹/cm³Becomes 4X 10 in electron concentration (carrier concentration)²¹/cm³And light up to about 423nm can be completely reflected (refer to fig. 2). In addition, in fig. 2, the abscissa represents the electron concentration, and the ordinate represents the plasma frequency converted into the wavelength. Of course, higher plasma frequencies can be achieved by doping with higher concentrations of impurities.

In addition, since titanium oxide is a very stable substance, the second electrode made of titanium oxide has very strong resistance to processing, heat, and electric resistance. Further, rutile type titanium oxide (titanium dioxide; titanium (IV) oxide) is known to be stable in air, and titanium oxide having a rutile structure (may be referred to as "rutile type TiO)₂") undergoes heteroepitaxial growth on the C-plane of GaN (see, e.g., t.hitotsugi, y.hirose, j.kasai, y.furubayashi, m.ohtani, k.nakajima, t.chilow, t.shimada, t.hasegawa, jpn.j.appl.phys.44, L1503 (2005)). Therefore, the heteroepitaxial growth of the second electrode on the C-plane of the second compound semiconductor layer can provide an electrically good interface at the interface between the compound semiconductor layer and the second electrode without occurrence of an energy level at the interface due to defects or the like.

Example 1

Embodiment 1 relates to a semiconductor light emitting device of the present invention and a method for manufacturing the same.

The semiconductor light emitting device of embodiment 1 includes a Light Emitting Diode (LED), and as shown in fig. 1(a), which is a schematic layout diagram of respective elements, and fig. 1(B), which is a schematic sectional view taken along an arrow B-B in fig. 1(a), there are provided: (A) an n-type conductivity first compound semiconductor layer 11; (B) an active layer 12 formed on the first compound semiconductor layer 11 and composed of a compound semiconductor; (C) a second compound semiconductor layer 13 which is formed on the active layer 12 and is of p-type conductivity; (D) a first electrode 15 electrically connected to the first compound semiconductor layer 11; and (E) a second electrode 14 formed on the second compound semiconductor layer 13.

In addition, the second electrode 14 is made of titanium oxide, specifically, titanium oxide having a rutile crystal structure, and has a size of 4 × 10²¹/cm³The above electron concentration, and reflects light emitted from the active layer 12. That is, the semiconductor light emitting device of embodiment 1 is of a bottom emission type in which light emitted from the active layer 12 is emitted outward through the first compound semiconductor layer 11. Here, in the second electrode 14, titanium oxide (rutile type TiO)₂) Doped with niobium (Nb) or tantalum (Ta). The value of the electron concentration determined in the second electrode 14 based on Hall measurement (Van der Pauw method) is 4X 10²¹/cm³. Therefore, in the second electrode 14, the plasma frequency (ω) represented by the above expression (1) is 425nm or less. Material for constituting the second electrode 14 (rutile type TiO doped with Nb or Ta)₂) Has a characteristic that conductivity increases with an increase in temperature, i.e., a characteristic similar to that of metal.

Here, the substrate 10 includes a substrate 10A composed of, for example, sapphire, and an underlayer 10B formed on the substrate 10A and composed of GaN. The compound semiconductor constituting the first compound semiconductor layer 11, the active layer 12, and the second compound semiconductor layer 13 is made of Al_XGa_YIn_1-X-YN (0. ltoreq. X.ltoreq.1, 0. ltoreq. Y.ltoreq.1, 0. ltoreq. X + Y. ltoreq.1), and more specifically, a GaN-based compound semiconductor. That is, the first compound semiconductor layer 11 is composed of GaN (GaN: Si) doped with Si, and the active layer 12 is composed of an InGaN layer (well layer) and a GaN layer (barrier layer) and has a multiple quantum well structure. In addition, the second compound semiconductor layer 13 is composed of GaN (GaN: Mg) doped with Mg. In addition, the light emitting portion is configured by a laminated structure in which the first compound semiconductor layer 11, the active layer 12, and the second compound semiconductor layer 12 are laminated together. Further, the top surface of the second compound semiconductor layer 13 on which the second electrode 14 is formed has a (0001) plane, and the (0001) plane is a C plane.

In addition, the first electrode 15 is provided on a portion 11A of the first compound semiconductor layer 11, the portion 11A being exposed by partially removing (etching) the second compound semiconductor layer 13 and the active layer 12. When a current flows from the second electrode 14 to the first compound semiconductor layer 11 and the first electrode 15 through the active layer 12 located directly below the remaining second compound semiconductor layer 13, the quantum well structure of the active layer 12 is excited by the current injection in the active layer 12, and a light-emitting state is formed over the entire surface. In addition, fig. 1(a) shows only some elements of the light emitting diode.

Further, in the light emitting diode of embodiment 1, a first contact portion (first pad portion) 18A is formed on the first electrode 15 and extends from the first opening 17A provided in the insulating layer 16 to the top of the insulating layer 16, and a second contact portion (second pad portion) 18B is formed on the second electrode 14 and extends from the second opening 17B provided in the insulating layer 16 to the top of the insulating layer 16. As a material constituting the insulating layer 16, the following examples can be cited: SiO 2_XBase material, SiN_XBase material, SiO_XN_YBase material, Ta₂O₅、ZrO₂AlN and Al₂O₃。

Hereinafter, a method for manufacturing the semiconductor light emitting device of example 1 will be described with reference to fig. 3(a) and 3(B) and partial sectional views of fig. 4(a) and 4(B) showing a substrate and the like.

[ step 100]

First, the substrate 10A composed of sapphire was transported to an MOCVD apparatus and cleaned in a carrier gas containing hydrogen at a substrate temperature of 1050 ℃ for 10 minutes, and then the substrate temperature was lowered to 500 ℃. Then, on the basis of the MOCVD method, crystal growth is performed on the surface of the substrate 10A to obtain an underlayer 10B composed of GaN by supplying trimethyl gallium (TMG) gas as a gallium source material while supplying ammonia gas as a nitrogen source material, and then supply of TMG gas is stopped.

[ step 110]

Next, an n-type conductivity first compound semiconductor layer 11, an active layer 12, and a p-type conductivity second compound semiconductor layer 13 are sequentially stacked on the substrate 10 to form a light emitting portion.

Specifically, on the basis of the MOCVD method, the substrate temperature was raised to 1020 ℃, and then supply of monosilane (SiH) was started at normal pressure₄) The gas is used as a silicon raw material to cause crystal growth of the first compound semiconductor layer 11 on the underlayer 10B, and the first compound semiconductor layer 11 is composed of GaN (GaN: Si) doped with Si, and is of n-type conductivity and has a thickness of 3 μm. In addition, the doping concentration is about 5 × 10¹⁸/cm³。

Then, the supply of TMG gas and SiH gas is stopped₄Gas, and the substrate temperature was reduced to 750 ℃. Then, Triethylgallium (TEG) gas and Trimethylindium (TMI) gas were used and supplied by valve switching to perform crystal growth to obtain the active layer 12 composed of InGaN and GaN and having a multiple quantum well structure.

For example, In a light emitting diode having an emission wavelength of 400nm, a multiple quantum well structure (e.g., including 2 well layers) composed of InGaN and GaN (having thicknesses of 2.5nm and 7.5nm, respectively) having an In ratio of about 9% may be formed. In addition, In a blue light emitting diode emitting light having a wavelength of 460nm ± 10nm, a multiple quantum well structure (e.g., including 15 well layers) composed of InGaN and GaN (having thicknesses of 2.5nm and 7.5nm, respectively) having an In ratio of about 15% may be formed. In addition, In a green light emitting diode having an emission wavelength of 520nm + -10 nm, a multiple quantum well structure (e.g., including 9 well layers) composed of InGaN and GaN (having thicknesses of 2.5nm and 15nm, respectively) having an In ratio of about 23% may be formed.

After the active layer 12 was formed, the supply of the TEG gas and the TMI gas was stopped, the carrier gas was changed from nitrogen to hydrogen, the substrate temperature was raised to 850 ℃, and the supply of the TMG gas and the magnesium dicocene (Cp) gas was started₂MG) gas to cause crystal growth of the second compound semiconductor layer 13 on the active layer 12, the second compound semiconductor layer 13 being composed of GaN (GaN: MG) doped with MGAnd has a thickness of 100 nm. In addition, the doping concentration is about 5 × 10¹⁹/cm³. Then, supply of TMG gas and Cp is stopped₂MG gas, and lowering the substrate temperature to room temperature, thereby completing crystal growth.

[ step 120]

After the crystal growth was completed as described above, the p-type impurity (p-type dopant) was activated by annealing at about 800 ℃ for 10 minutes in a nitrogen atmosphere.

[ step 130]

Then, Ti is deposited on the second compound semiconductor layer on the basis of the PLD method_1-zA_zO₂(A is a pentavalent impurity, specifically Nb or Ta) as the second electrode (p-side electrode) 14. Specifically, the second electrode 14 is deposited under the conditions shown in table 1 below, for example. Next, TiO constituting the peroxide second electrode 14 can be formed by, for example, performing reduction annealing at 400 ℃ for 5 minutes in a hydrogen atmosphere_X(X > 2) conversion to TiO₂. In this case, the impurity concentration is a value: so that the carrier concentration is 4X 10²¹/cm³In order to allow the second electrode 14 to reflect light emitted from the active layer 12. For example, as described above, in the case of Nb or Ta, since in TiO₂The rate of electrical activation in (1) is about 80%, and thus the dose can be about 5X 10²¹/cm³The above. In general, TiO is assumed₂The electric activation rate of the impurity is alpha, the dosage of the impurity can be 4X 10²¹×(1/α)/cm³The above. Further, rutile type TiO is known₂Since the GaN is grown heteroepitaxially on the C-plane, a good interface can be easily obtained.

[ Table 1]

A laser light source: KrF excimer laser (wavelength: 248nm)

Strength: 2J/cm²2Hz

Target material: TiO 2₂Sintered body of powder

(adding Nb)₂O₅Or Ta₂O₅To dope Nb or Ta)

Distance between the target and the second compound semiconductor layer: about 50mm

Process gas: o is₂

Substrate temperature: 250 deg.C

[ step 140]

Then, the first compound semiconductor layer 11 is partially exposed. Specifically, on the basis of the photolithography technique and the dry etching technique, the portion 11A of the first compound semiconductor layer 11 is exposed by partially removing the second electrode 14, the second compound semiconductor layer 13, and the active layer 12 (see fig. 3 (a)). Then, on the basis of a lift off method, the first electrode 15 is formed on the exposed portion of the first compound semiconductor layer 11. Specifically, a resist layer is formed on the entire surface, and an opening is formed in the resist layer on the portion of the first compound semiconductor layer where the first electrode 15 is to be formed. Then, a metal layer (e.g., Ti layer) for constituting the first electrode 15 is deposited on the entire surface by a sputtering method, and then the first electrode 15 can be formed by removing the resist layer (see fig. 3 (B)).

[ step 150]

Then, at least the exposed portion of the first compound semiconductor layer 11, the exposed portion of the active layer 12, the exposed portion of the second compound semiconductor layer 13, and a portion of the second electrode 14 are covered with an insulating layer 16 (see fig. 4 (a)). As a method for forming the insulating layer 16, for example, a PVD method such as a vacuum evaporation deposition method or a sputtering method, or a CVD method can be used. Then, on the basis of the photolithography technique and the dry etching technique, a first opening 17A and a second opening 17B are formed in a portion of the insulating layer 16 located on the first electrode 15 and a portion of the insulating layer 16 located on the second electrode 14, respectively (see fig. 4 (B)). Next, a first contact portion (first pad portion) 18A extending from the first electrode 15 to the top of the insulating layer 16 through the first opening 17A is formed, and simultaneously a second contact portion (second pad portion) 18B extending from the second electrode 14 to the top of the insulating layer 16 through the second opening 17B is formed. In addition, each of the first contact portion (first pad portion) 18A and the second contact portion (second pad portion) 18B includes, for example, a Ti layer/Pt layer formed by a vacuum evaporation deposition method and an Au layer formed on the Ti layer/Pt layer by a plating method. Then, a chip is formed by dicing to obtain the semiconductor light emitting device (light emitting diode) shown in fig. 1(a) and 1 (B). Further, various semiconductor light emitting devices (specifically, light emitting diodes) of a bullet type and a surface mounting type can be formed by resin molding or encapsulation.

In embodiment 1, the second electrode 14 is composed of titanium oxide doped with impurities and having a high electron density, and therefore not only high conductivity but also high light reflectance can be achieved. Therefore, the emission efficiency of the semiconductor light emitting device can be significantly improved. In addition, since the second electrode 14 is composed of titanium oxide, deterioration due to oxidation does not occur, and electromigration does not occur. Therefore, unlike the conventional art, the second electrode 14 does not need to be covered with a cladding layer, and thus it is possible to attempt to simplify the manufacturing process of the semiconductor light emitting device and to reduce the manufacturing cost of the semiconductor light emitting device. In addition, since the impurity-doped titanium oxide has a high work function, a low schottky barrier is formed between the second electrode 14 and the p-type conductivity type second compound semiconductor layer 13, and thus a good ohmic connection can be obtained as an electrical connection between the second electrode 14 and the second compound semiconductor layer 13.

Although the present invention has been described above on the basis of preferred embodiments, the present invention is not limited to this embodiment. The configuration and structure of the semiconductor light emitting device, the material for constituting the semiconductor light emitting device, and the manufacturing conditions and various numerical values of the semiconductor light emitting device described in the embodiments are exemplary, and may be appropriately modified. For example, in the semiconductor light emitting device described in embodiment 1, the form formed on the substrate is described as the final form of the semiconductor light emitting device, but alternatively, a structure may be formed in which: in this structure, the first electrode 15 is formed on the first compound semiconductor layer 11 exposed by polishing or etching the substrate. In addition, by using a substrate having conductivity, the first compound semiconductor layer or the like can be formed on a main surface (front surface) of the substrate, and the first electrode 15 can be formed on a back surface of the substrate.

Claims (14)

1. A semiconductor light emitting device, comprising:

A) a first compound semiconductor layer of n-type conductivity;

B) an active layer formed on the first compound semiconductor layer and composed of a compound semiconductor;

C) a second compound semiconductor layer which is formed on the active layer and is of p-type conductivity;

D) a first electrode electrically connected to the first compound semiconductor layer; and

E) a second electrode formed on the second compound semiconductor layer,

wherein the second electrode is made of titanium oxide and has a thickness of 4 x 10²¹/cm³The above electron concentration, and reflects light emitted from the active layer.

2. The semiconductor light emitting device of claim 1, wherein the second electrode is doped with niobium or tantalum.

3. The semiconductor light-emitting device according to claim 1, wherein the compound semiconductor for constituting the first compound semiconductor layer, the active layer, and the second compound semiconductor layer is Al_XGa_YIn_1-X-YN, where 0. ltoreq. X.ltoreq.1, 0. ltoreq. Y.ltoreq.1 and 0. ltoreq. X + Y.ltoreq.1.

4. The semiconductor light-emitting device according to claim 1, wherein a crystal structure of the titanium oxide is a rutile structure.

5. The semiconductor light-emitting device according to claim 1, wherein a top surface of the second compound semiconductor layer on which the second electrode is formed has a (0001) plane.

6. The semiconductor light-emitting device according to claim 1, wherein a material for constituting the second electrode has a property that conductivity increases with an increase in temperature.

7. The semiconductor light-emitting device according to claim 1, wherein in the second electrode, a plasma frequency ω represented by the following expression (1) is 425nm or less:

ω＝{(n_e·e²)/(ε₀·m_e)}^1/2 (1)

here, n is_eIs the electron density, e is the basic charge,. epsilon₀Is the vacuum dielectric constant, m_eIs electronicA static mass.

8. The semiconductor light-emitting device according to claim 1, wherein light emitted from the active layer is emitted outward through the first compound semiconductor layer.

9. A method of fabricating a semiconductor light emitting device, comprising at least the steps of:

a) forming a light emitting portion by sequentially laminating an n-type conductivity type first compound semiconductor layer, an active layer, and a p-type conductivity type second compound semiconductor layer on a substrate; and

b) next, a second electrode is formed on the second compound semiconductor layer,

wherein the compound semiconductor for constituting the first compound semiconductor layer, the active layer and the second compound semiconductor layer is Al_XGa_YIn_1-X-YN, where 0. ltoreq. X.ltoreq.1, 0. ltoreq. Y.ltoreq.1 and 0. ltoreq. X + Y.ltoreq.1; and is

In the step b), the second electrode made of titanium oxide having a rutile crystal structure is impurity-doped so that the electron concentration is 4 × 10 on the top surface having a (0001) plane of the second compound semiconductor layer²¹/cm³The above state is obtained by epitaxial growth.

10. The method for manufacturing a semiconductor light-emitting device according to claim 9, wherein the impurity is niobium or tantalum.

11. The manufacturing method of a semiconductor light emitting device according to claim 9, wherein the second electrode is formed on the basis of a pulsed laser deposition method.

12. The manufacturing method of a semiconductor light emitting device according to claim 9, wherein a material for constituting the second electrode has a property that conductivity increases with an increase in temperature.

13. The manufacturing method of a semiconductor light-emitting device according to claim 9, wherein in the second electrode, a plasma frequency ω represented by the following expression (1) is 425nm or less:

ω＝{(n_e·e²)/(ε₀·m_e)}^1/2 (1)

here, n is_eIs the electron density, e is the basic charge,. epsilon₀Is the vacuum dielectric constant, m_eIs the static mass of the electrons.

14. The manufacturing method of a semiconductor light-emitting device according to claim 9, wherein light emitted from the active layer is emitted outward through the first compound semiconductor layer.