JP4030534B2 - Compound semiconductor light emitting device and manufacturing method thereof - Google Patents

Description

  The present invention provides an n-type and p-type ohmic electrode provided in contact with the surface of an n-type group III nitride semiconductor layer or p-type boron phosphide-based semiconductor layer for constituting a compound semiconductor light emitting device, respectively, The present invention relates to a technique for easily obtaining a pn junction type compound semiconductor light-emitting element by using the same material regardless of the conductivity type of a semiconductor layer.

Conventionally, for example, a group III nitride semiconductor represented by a general formula Al _x Ga _y In _z N (0 ≦ x, y, z ≦ 1, x + y + z = 1) has been used for short-wavelength visible light in a blue band or a green band. It is used as a material for constituting a compound semiconductor light emitting device that emits light (see, for example, Patent Document 1). Taking gallium nitride (chemical formula: GaN) as an example, a group III nitride semiconductor generally exhibits n-type conduction in a state in which impurities for controlling the conduction type are not intentionally added, that is, in an undoped state. (For example, see Patent Document 2). Therefore, conventionally, an n-type group III nitride semiconductor that can be easily formed is used as, for example, an n-type clad layer in a compound semiconductor light emitting device (see, for example, Non-Patent Document 1). . In a conventional compound semiconductor light emitting device having an n-type group III nitride semiconductor layer as a cladding layer, the n-type ohmic electrode (negative electrode) is made of, for example, titanium (element symbol: Ti) or an alloy thereof. (For example, refer to Patent Document 3).

In a conventional pn junction type compound semiconductor short wavelength light emitting device including an n-type cladding layer made of a group III nitride semiconductor, the p-type cladding layer is complicated as described later (see paragraph 0006). In general, it is also composed of a group III nitride semiconductor (for example, see Non-Patent Document 1). For example, a so-called doped p-type Al _x Ga _y N (0 ≦ x, y ≦ 1, x + y = 1) layer to which magnesium (element symbol: Mg) is intentionally added is used as a p-type cladding layer and a pn junction type double An example of forming a compound semiconductor light emitting device having a hetero (DH) junction structure is disclosed (for example, see Non-Patent Document 1). In constituting a compound semiconductor light emitting device, a p-type ohmic electrode (positive electrode) is made of, for example, nickel (element symbol: Ni) or gold (element symbol: Au) (for example, Patent Documents). 4 and 5). In a conventional compound semiconductor light emitting device including an n-type and p-type group III nitride semiconductor layer, as described above, n-type or p-type may be formed from different materials depending on the conductivity type of the group III nitride semiconductor layer. In the conventional example, the ohmic electrode is constructed.

  On the other hand, monomeric boron phosphide (BP) is said to provide an undoped, low-resistance p-type conductive layer without doping impurities (see, for example, Non-Patent Document 2). ). For this reason, an example in which a p-type boron phosphide layer is used as a contact layer to form a laser diode (abbreviation: LD) is disclosed (for example, see Patent Document 6). A conventional LD is configured by providing a p-type ohmic electrode made of gold (Au) / zinc (element symbol: Zn) on a contact layer made of a p-type boron phosphide layer added with magnesium (Mg) ( For example, see Patent Document 6.) Further, in the prior art, an example in which a p-type ohmic electrode is formed from a single aluminum (Al) is known for a p-type boron phosphide layer (see, for example, Non-Patent Document 3).

Japanese Patent Publication No.55-3834 JP-A 61-7671 JP 7-45867 A JP-A-6-151968 JP 7-106633 A Japanese Patent Laid-Open No. 10-242567 Akazaki Isao, "III-V compound semiconductor", May 20, 1994, first edition, published by Baifukan Co., Ltd., Chapter 13 T.A. UDAGAWA et al., 5th International Conference on Nitride Semiconductors (ICNS-5) Technical Digest, May 25-30, 2003, p.431 K. Shono et al., J. Crystal Growth, 24/25, 1974 (Netherlands), p. 193.

  In the prior art in which a pn junction type compound semiconductor device is configured using a p-type group III nitride semiconductor layer, the first problem is that the low-resistance p-type group III nitride semiconductor layer itself is simple. There are things that cannot be obtained. That is, in order to obtain a low-resistance p-type group III nitride semiconductor layer, it is necessary to add impurities such as Mg at least during vapor phase growth of the same layer, and the film forming process itself is complicated. Next, it is necessary to perform heat treatment for removing hydrogen that has penetrated into the group III nitride semiconductor layer doped with Mg during vapor phase growth (see, for example, JP-A-5-183189).

  In a compound semiconductor light emitting device having a conventional configuration in which an ohmic electrode is disposed on an n-type and p-type group III nitride semiconductor layer, the n-type and p-type ohmic electrodes are each formed of different materials. That is, in order to form the n-type and p-type ohmic electrodes, each requires a separate process, which is complicated, and a compound semiconductor light emitting device has not been easily constructed. One effective technical means for solving such a conventional problem is that a p-type semiconductor layer provided with a p-type ohmic electrode is made of a semiconductor material that can be easily formed, and then formed from the same material. And forming a p-type ohmic electrode. In the present invention, a boron phosphide-based semiconductor layer capable of easily forming a low-resistance p-type layer is utilized, and both n-type and p-type ohmic electrodes can be formed in a single process, so that compound semiconductor light emission can be easily performed. Technical means for obtaining the device are provided.

In order to solve the above problems, the present invention has the following configuration.
(1) a crystal substrate, an n-type group III nitride semiconductor layer provided on one surface of the crystal substrate, a light-emitting layer made of an n-type or p-type compound semiconductor, boron (element symbol: B) and phosphorus A p-type boron phosphide-based semiconductor layer made of a boron phosphide-based semiconductor containing (element symbol: P) as a constituent element, each of an n-type group III nitride semiconductor layer and a p-type boron phosphide-based semiconductor layer In a compound semiconductor light emitting device in which an n-type or p-type ohmic electrode is provided in contact with the surface of the n-type, the portion of the n-type ohmic electrode that contacts the n-type group III nitride semiconductor layer And a portion of the p-type ohmic electrode that is in contact with the p-type boron phosphide-based semiconductor layer is made of the same metal material.

(2) The compound as described in (1) above, wherein the same metal material is an alloy containing aluminum (element symbol: Al) and a group I element having an element periodicity in common. Semiconductor light emitting device.
(3) The compound semiconductor light-emitting element according to (1), wherein the same metal material is commonly an alloy containing aluminum (Al) and a group II element having an element periodicity. .
(4) The compound semiconductor light-emitting device according to (1), wherein the same metal material is an alloy containing aluminum (Al) and a lanthanum (element symbol: La) group element in common. element.
(5) The compound semiconductor light-emitting element according to (1), wherein the same metal material is an alloy containing aluminum (Al) and silicon (element symbol: Si) in common.
(6) The compound semiconductor light-emitting element according to (1), wherein the same metal material is commonly titanium (element symbol: Ti) or an alloy thereof.

(7) a crystal substrate, an n-type group III nitride semiconductor layer provided on one surface of the crystal substrate, a light-emitting layer made of an n-type or p-type compound semiconductor, boron (element symbol: B) and phosphorus A p-type boron phosphide-based semiconductor layer made of a boron phosphide-based semiconductor containing (element symbol: P) as a constituent element, each of an n-type group III nitride semiconductor layer and a p-type boron phosphide-based semiconductor layer In the method of manufacturing a compound semiconductor light emitting device in which an n-type or p-type ohmic electrode is provided in contact with the surface of the n-type group III nitride semiconductor layer of the n-type ohmic electrode, A method of manufacturing a compound semiconductor light-emitting element, wherein the contacting portion and the portion of the p-type ohmic electrode that contacts the p-type boron phosphide-based semiconductor layer are made of the same metal material in common. .
(8) An alloy containing aluminum (Al) and a group I element having an element periodicity, an alloy containing aluminum (Al) and a group II element having an element periodicity, aluminum (Al ) And a lanthanum (La) group element, an alloy containing aluminum (Al) and silicon (Si), titanium (Ti), or an alloy of titanium (Ti). The manufacturing method of the compound semiconductor light-emitting device of description.

  According to the present invention, the p-type ohmic electrode provided in contact with the surface of the p-type boron phosphide-based semiconductor layer and the n-type ohmic electrode provided on the surface of the n-type Group III nitride semiconductor layer are made of the same material. Therefore, a short wavelength LED with a low forward voltage can be easily supplied.

The boron phosphide-based semiconductor according to the present invention includes boron (B) and phosphorus (P) as constituent elements, for example, B _α Al _β Ga _γ In _1-α-β-γ P _1-δ As _δ. (0 <α ≦ 1, 0 ≦ β <1, 0 ≦ γ <1, 0 <α + β + γ ≦ 1, 0 ≦ δ <1). In addition, for example, B _α Al _β Ga _γ In _1-α-β-γ P _1-δ N _δ (0 <α ≦ 1, 0 ≦ β <1, 0 ≦ γ <1, 0 <α + β + γ ≦ 1, 0 ≦ δ <1). For example, monomeric boron phosphide (BP), boron phosphide / gallium / indium (composition formula B _α Ga _γ In _1-α-γ P: 0 <α ≦ 1, 0 ≦ γ <1), boron phosphide nitride (compositional formula _{BP 1-δ N δ: 0} ≦ δ <1) is or arsenide phosphide boron (formula _{B α P 1-δ As δ} ) mixed crystal containing a plurality of group V elements such as . In particular, the composition ratio (α or 1-δ) of boron and phosphorus is suitably 0.50 (= 50%) or more. If the composition ratio of boron and phosphorus is less than 0.5, a low-resistance p-type boron phosphide-based semiconductor layer cannot be obtained easily and stably.

A p-type boron phosphide-based semiconductor layer for providing a p-type ohmic electrode can be formed by a halogen method, a hydride method, or a MOCVD (metal organic chemical vapor deposition) method. It can also be formed by molecular beam epitaxy (see J. Solid State Chem., 133 (1997), pages 269-272). For example, the p-type monomeric boron phosphide layer can be formed by MOCVD using triethylboron (molecular formula: (C ₂ H ₅ ) ₃ B) and phosphine (molecular formula: PH ₃ ) as raw materials. As the formation temperature of the p-type BP layer, a temperature of 1000 ° C. to 1200 ° C. is suitable. The raw material supply ratio (= PH ₃ / (C ₂ H ₅ ) ₃ B) at the time of formation is suitably 10-50. A so-called undoped BP layer in which impurities are not intentionally added is effective in avoiding the modification of other layers due to the diffusion of impurities. A boron phosphide-based semiconductor layer having a large forbidden band width can be formed by precisely controlling the formation rate in addition to the formation temperature and the V / III ratio (see Japanese Patent Application No. 2002-158282).

In particular, a p-type boron phosphide-based semiconductor layer having a forbidden band width at room temperature of 2.8 electron volts (unit: eV) to 5.4 eV can be preferably used. More preferably, the p-type boron phosphide-based semiconductor layer having a wide band gap of 2.8 eV to 3.2 eV is in a compound semiconductor light emitting device, such as a p-type cladding layer. It can be used as a barrier layer having a barrier action. In addition, the wide band gap p-type boron phosphide-based semiconductor layer is formed using gallium nitride indium (composition formula Ga _X In _1-X : 0 ≦ X ≦ 1) or gallium nitride phosphide (composition formula GaN _1-Y P _Y : It is suitable for constituting a window layer for transmitting visible light such as blue light or green light from the light emitting layer composed of 0 ≦ Y ≦ 1) to the outside of the light emitting element. When the forbidden band width exceeds 5 eV, the barrier difference from the light emitting layer becomes large, which is disadvantageous for obtaining a compound semiconductor light emitting device having a low forward voltage or low threshold voltage.

For example, the p-type cladding layer can be suitably formed from a low-resistance boron phosphide layer having a carrier concentration at room temperature of 1 × 10 ¹⁹ cm ⁻³ or more and a resistivity of 5 × 10 ⁻² Ω · cm or less. . The layer thickness of the p-type boron phosphide constituting the p-type cladding layer is suitably 500 nanometers (nm) or more and 5000 nm or less. When the p-type ohmic electrode is provided in contact with the p-type cladding layer and the p-type cladding layer is unnecessarily thin, the device driving current supplied via the ohmic electrode is transmitted to the entire light emitting layer. This is inconvenient because it cannot diffuse evenly and flatly. In the present invention, the p-type ohmic electrode is a positive (+, positive) electrode provided in contact with the surface of the p-type boron phosphide-based semiconductor layer. On the other hand, the n-type ohmic electrode is a negative (−, negative) electrode provided in contact with the surface of the n-type group III nitride semiconductor layer in the present invention.

The n-type group III nitride semiconductor layer of the present invention is represented by, for example, the general formula Al _α Ga _β In _γ N (where 0 ≦ α, β, γ ≦ 1, and α + β + γ = 1). N-type conductive layer. In addition, for example, the general formula Al _α Ga _β In _γ N _1-δ M _δ (0 ≦ α, β, γ ≦ 1, and α + β + γ = 1. M is a group V different from nitrogen. An n-type conductive layer containing a plurality of Group V elements represented by 0 <δ <1. These n-type group III nitride semiconductor layers can be vapor-phase grown on a crystal substrate made of sapphire (α-Al ₂ O ₃ ) by, for example, MOCVD. In addition, silicon single crystal (silicon), cubic 3C crystal type, hexagonal 2H, 4H and 6H crystal type silicon carbide (chemical formula: SiC), perovskite crystal type oxide crystal, and the like can be used for the substrate. As for the group III nitride semiconductor layer, an n-type conductive layer can be originally obtained even in an undoped state in which no impurity is added (see, for example, Japanese Patent Laid-Open No. 61-7671). Therefore, in the pn junction type compound semiconductor light emitting device, if the n-type junction layer is composed of an n-type group III nitride semiconductor layer, it is advantageous to obtain a light-emitting device easily. Furthermore, if the n-type group III nitride semiconductor layer and the p-type boron phosphide layer are grown by the same means, it can contribute to the construction of a compound semiconductor light emitting device more easily.

  According to the results of intensive studies by the present inventors, for p-type boron phosphide-based semiconductors, a p-type ohmic electrode can be formed from a metal material having a small work function. In addition, for an n-type group III nitride semiconductor, if the work function is small, an n-type ohmic electrode tends to be easily formed. This suggests that the experiment results of the present inventor can simultaneously form n-type and p-type ohmic electrodes from the same material in common with the n-type group III nitride semiconductor and p-type boron phosphide. . Among the metal materials that can be used in common for the n-type group III nitride semiconductor layer and the p-type boron phosphide-based semiconductor layer, an aluminum alloy containing a group I element is preferable. For example, an aluminum alloy containing lithium (element symbol: Li). For example, an aluminum / lithium (Al / Li) alloy. Further, it is an aluminum alloy containing a Group II element. In particular, an aluminum / lithium / zinc (Al / Li / Zn) alloy and an aluminum / copper (Al / Cu) alloy are used.

In addition, it is preferable that the same metal material is an alloy containing aluminum (Al) and a lanthanum (La) group element, that is, a lanthanide element. The lanthanoid element refers to an element from lanthanum (La) having an atomic number of 57 to lutetium having an atomic number of 71 (element symbol: Lu), cerium (Ce; atomic number 58), praseodymium (Pr; atomic number 59). ), Neodymium (Nd; atomic number 60), holmium (Ho; atomic number 67), and the like. In particular, in the present invention, an alloy of aluminum (Al) and lanthanum (La), for example, LaAl _{2 is} used. This is because, among lanthanoids, lanthanum provides good ohmic contact with an n-type group III nitride semiconductor. In addition, it is easy to obtain ohmic contact with the p-type boron phosphide-based semiconductor layer and has excellent adhesion with the semiconductor layer, so that a strongly deposited ohmic electrode can be formed. Further, since LaAl ₂ can be deposited using a normal resistance heating type vacuum vapor deposition means, there is an advantage that n-type and p-type ohmic electrodes can be easily formed.

  Also, as an alloy containing aluminum (Al) and silicon (element symbol: Si), n-type and p-type ohmic electrodes can be formed simultaneously from the same material, which is convenient. Examples of the aluminum alloy containing silicon include an aluminum (Al) / silicon (Si) binary alloy and an aluminum (Al) / silicon (Si) / titanium (Ti) ternary alloy. In the alloy of aluminum and silicon, the weight content of silicon is preferably 10% or more and 50% or less. An alloy mainly composed of aluminum whose weight content of silicon is less than 10% is inconvenient for stabilizing a migration-resistant ohmic electrode. On the other hand, an aluminum / silicon alloy having a silicon weight content exceeding 50% does not lead to stable formation of an n-type ohmic electrode having good contact particularly with respect to an n-type group III nitride semiconductor. In the Al.Si-based multi-component alloy, it is preferable that the alloy is an element having a work function equal to or lower than that of aluminum and silicon. For example, an aluminum / lanthanum / silicon (Al / La / Si) alloy which is a ternary alloy with lanthanum (work function = 3.3 eV) can be exemplified. Since an aluminum alloy generally has a melting point that is not so high, there is an advantage that it can be easily formed by a resistance heating type vacuum vapor deposition means.

  When titanium (Ti) or an alloy thereof is used, an n-type ohmic electrode can be formed on the n-type group III nitride semiconductor and a p-type ohmic electrode can be formed on the p-type boron phosphide-based semiconductor at the same time. The element that forms an alloy with Ti preferably has a work function of 4.5 eV or less. Further, an alloy with an element having a low melting point gives convenience that it can be deposited by an ordinary resistance heating type vacuum deposition means. As a suitable Ti alloy, a Ti · Al alloy which is an alloy with aluminum (work function = 4.3 eV, melting point = 660 ° C.) can be exemplified. In the Ti · Al alloy, the aluminum content is preferably 50% by weight or less. Since the work function of silicon (= 4.0 eV) is larger than the work function of Ti (= 3.9 eV), both the n-type and p-type having low contact resistance are obtained from Ti / Si alloys having a large Si content. The ohmic electrode cannot be constructed stably. The n-type and p-type ohmic electrodes do not necessarily need to be composed of only a Ti film or an alloy film thereof, and may be composed of a multilayer structure in which other metal films are further stacked. For example, an electrode can be comprised from the multilayer structure of Ti * Al alloy film / molybdenum (element symbol: Mo) film / gold (Au) film. An electrode having a multilayer structure can also be configured by using a platinum (element symbol: Pt) film instead of the Mo film. Even in the multilayer electrode, there is no change in the necessity of configuring the portion contacting the n-type and p-type semiconductor layers as Ti or an alloy film thereof.

  In order to form the n-type and p-type ohmic electrodes simultaneously, first, for example, a titanium-aluminum (Ti.Al) alloy film is formed on the surfaces of the n-type group III nitride semiconductor layer and the p-type boron phosphide-based semiconductor layer. Is deposited by conventional vacuum deposition means. Next, using a known photolithography technique, patterning is performed so that an ohmic electrode having a desired shape is arranged at a suitable position. It is preferable that the ohmic electrode has an n-type or p-type semiconductor layer having a shape capable of diffusing a device driving current in a plane over a wide range, and capable of forming an equipotential distribution in each semiconductor layer. . Next, an unnecessary Ti / Al alloy film is removed by means such as a wet etching method or a plasma dry etching method. As a result, it is possible to form n-type and p-type ohmic electrodes having a desired shape, limited to desired positions on the surface of each semiconductor layer.

  The metal and alloy materials according to the present invention have the effect of simultaneously providing a p-type or n-type ohmic electrode on the surface of each of the p-type boron phosphide-based semiconductor layer and the n-type group III nitride semiconductor layer. .

  The present invention will be specifically described by taking as an example a compound semiconductor LED in which both n-type and p-type ohmic electrodes are composed of titanium (Ti).

  FIG. 1 schematically shows a cross-sectional structure of a laminated structure 110 used for manufacturing the LED 100 having a double hetero (DH) junction structure. FIG. 2 schematically shows a planar structure of the LED 100.

The stacked structure 110 includes an undoped n-type gallium nitride (GaN) clad layer 102 and an n-type gallium nitride on an insulating (0001) -sapphire (α-Al ₂ O ₃ ) single crystal substrate 101. A light emitting layer 103 made of indium (Ga _0.90 In _0.10 N) and an upper cladding layer 104 made of undoped p-type monomer boron phosphide (BP) were sequentially deposited.

The lower cladding layer 102 was formed at 1100 ° C. by means of trimethylgallium (molecular formula: (CH ₃ ) ₃ Ga) / NH ₃ / H ₂ reaction system normal pressure (substantially atmospheric pressure) metal organic vapor phase epitaxy (MOVPE). The layer thickness was about 3 μm. The light emitting layer 103 was composed of a multiphase structure layer composed of a plurality of phases having different indium compositions. The average indium composition was 0.10 (= 10%). The layer thickness of the light emitting layer 103 was about 10 nm. The undoped p-type BP layer 104 uses atmospheric pressure MOVPE means using triethylboron (molecular formula: (C ₂ H ₅ ) ₃ B) as a boron (B) source and phosphine (molecular formula: PH ₃ ) as a phosphorus source. Formed. The p-type BP layer 104 was formed at 1025 ° C. The constituent layers 102 to 104 of the laminated structure 110 were formed by the same vapor phase growth means as described above.

The carrier (hole) concentration of the undoped p-type BP layer 104 forming the upper cladding layer 104 was 2 × 10 ¹⁹ cm ⁻³ and the layer thickness was about 600 nm. The resistivity of the same layer 104 at room temperature was 5 × 10 ⁻² Ω · cm. Further, since the forbidden band width at room temperature of the p-type BP layer 104 was about 3.2 eV, a p-type cladding layer that also serves as a window layer for transmitting light emitted from the light-emitting layer 103 to the outside was used.

  The stacked structure 110 is processed by a plasma dry etching method using a halogen-based mixed gas containing chlorine, and the p-type BP layer 104 and the light emitting layer 103 are limited to a region where the n-type ohmic electrode 105 is to be formed. It was selectively removed by etching. As a result, the surface of the n-type lower cladding layer 102 was exposed (see FIG. 2). Next, the surface of the n-type GaN layer 102 exposed in the region where the n-type ohmic electrode 105 is to be formed and the surface of the p-type BP layer are simultaneously applied to titanium (Ti ) A film was deposited. Thereafter, the Ti film deposited using a known photolithography technique was selectively patterned and etched to form n-type and p-type ohmic electrodes 105 and 106 having desired shapes in desired regions.

  Both element driving currents were passed in the forward direction between n-type and p-type ohmic electrodes 105 and 106 made of Ti, and the light emission characteristics of the LED 100 were confirmed. The central wavelength of light emission was about 430 nm. The half width of the emission spectrum was 190 millielectron volts (meV). The luminance in a chip state before the resin mold measured using a general integrating sphere was 11 millicandelas (mcd). In addition, since both the n-type and p-type ohmic electrodes 105 and 106 are made of Ti having excellent ohmic contact with the n-type GaN layer 102 and the p-type BP layer 104, the forward voltage (Vf) is 3. It was a low value of 1 V (forward current 20 mA). In addition, the upper clad layer 104 on the light emitting layer 103 is composed of a p-type BP layer having a wide forbidden band width and a low resistance that can be easily obtained, so that it is effective for diffusing the element driving current over a wide range of the light emitting layer 103. It became. For this reason, the LED which can bring about blue light emission of the substantially uniform intensity | strength from the substantially whole surface of the light emission area | region was provided.

The present invention will be described in detail by taking as an example a compound semiconductor LED having n-type and p-type ohmic electrodes made of lanthanum aluminum (LaAl ₂ ).

An upper cladding layer 104 made of a p-type boron phosphide / gallium (B _0.98 Ga _0.02 P) layer was deposited on the light emitting layer 103 described in Example 1 by MOVPE. The carrier concentration of the B _0.98 Ga _0.02 P layer was about 8 × 10 ¹⁸ cm ⁻³ and the layer thickness was about 500 nm. After the plasma etching process described in Example 1 is performed on the laminated structure 110, n-type and p-type ohmic electrodes made of LaAl ₂ alloy are formed instead of Ti in Example 1, and an LED is manufactured. did. Both ohmic electrodes were formed by laminating a LaAl ₂ alloy film by a general vacuum vapor deposition means and subsequently a Ti film on the LaAl ₂ alloy film. Thereafter, the deposited LaAl ₂ alloy film and Ti film were processed into a desired shape using a known photolithography technique and etching technique.

Both device driving currents were passed in the forward direction between n-type and p-type ohmic electrodes composed of LaAl ₂ to confirm the light emission characteristics of the LEDs. The central wavelength of light emission was about 430 nm. The half width of the emission spectrum was 190 meV. The luminance in a chip state before resin molding measured using a general integrating sphere was about 11 mcd. Further, the forward voltage (Vf) was 3.3 V (when the forward current was 20 mA). In addition, the upper clad layer on the light emitting layer is composed of a p-type BP layer having a wide forbidden band width and a low resistance that can be easily obtained, so that it is effective for diffusing the element driving current over a wide range of the light emitting layer. . For this reason, the LED which can bring about blue light emission of substantially uniform intensity | strength from the whole surface of the light emission area | region was provided. Moreover, since both the n-type and p-type ohmic electrodes are made of the same LaAl ₂ alloy, a high-brightness LED can be easily constructed.

  Both n-type and p-type ohmic electrodes are made of an aluminum / lithium (Al / Li) alloy (weight composition: Al: 95%, Li: 2.5%, Cu: 1.5%, Mg: 1%). The present invention will be described in detail by taking a compound semiconductor LED as an example.

  The p-type BP layer is limited to a region where the n-type ohmic electrode 105 is to be formed by processing the laminated structure 110 described in Example 1 by a plasma dry etching method using a halogen-based mixed gas containing chlorine. 104 and the light emitting layer 103 were selectively removed by etching. As a result, the surface of the n-type lower cladding layer 102 was exposed (see FIG. 2). Next, the surface of the n-type GaN layer 102 exposed to the region where the n-type ohmic electrode 105 is to be formed and the surface of the p-type BP layer are simultaneously formed on the surface of aluminum. A lithium alloy (Al.Li) film was deposited. Thereafter, the Al / Li film deposited by using a known photolithography technique was selectively patterned and etched to form n-type and p-type ohmic electrodes 105 and 106 having desired shapes in desired regions.

Both device driving currents were passed in the forward direction between the n-type and p-type ohmic electrodes 105 and 106 made of Al·Li, and the light emission characteristics of the LED 100 were confirmed. The central wavelength of light emission was about 430 nm. The half width of the emission spectrum was 190 millielectron volts (meV). The luminance in a chip state before the resin mold measured using a general integrating sphere was 10 millicandelas (mcd). When both the n-type and p-type ohmic electrodes 105 and 106 are made of Al·Li, the ohmic contact with respect to the n-type GaN layer 102 is compared with the Ti and LaAl ₂ of the first and second embodiments. And it became a little inferior. On the other hand, the ohmic contact with the p-type BP layer 104 is superior to that of LaAl ₂ for Al·Li. For this reason, the forward voltage (Vf) was 3.3 V (when the forward current was 20 mA). In addition, the upper clad layer 104 on the light emitting layer 103 is composed of a p-type BP layer having a wide forbidden band width and a low resistance that can be easily obtained, so that it is effective for diffusing the element driving current in a wide range of the light emitting layer. It became. For this reason, the LED which can bring about blue light emission of substantially uniform intensity | strength from the whole surface of the light emission area | region was provided. Moreover, since both the n-type and p-type ohmic electrodes are made of the same Al / Li alloy, a high-brightness LED can be easily constructed.

  The present invention is exemplified by a compound semiconductor LED in which both n-type and p-type ohmic electrodes are made of an aluminum-magnesium (Al.Mg) alloy (weight composition; Al composition: 97%, magnesium composition: 3%). This will be specifically described.

  The p-type BP layer is limited to a region where the n-type ohmic electrode 105 is to be formed by processing the laminated structure 110 described in Example 1 by a plasma dry etching method using a halogen-based mixed gas containing chlorine. 104 and the light emitting layer 103 were selectively removed by etching. As a result, the surface of the n-type lower cladding layer 102 was exposed (see FIG. 2). Next, the surface of the n-type GaN layer 102 exposed to the region where the n-type ohmic electrode 105 is to be formed and the surface of the p-type BP layer are simultaneously formed on the surface of aluminum. A magnesium alloy (Al · Mg) film was deposited. Thereafter, the Al / Mg film deposited using a known photolithography technique was selectively patterned and etched to form n-type and p-type ohmic electrodes 105 and 106 having desired shapes in desired regions.

Both device driving currents were passed in the forward direction between the n-type and p-type ohmic electrodes 105 and 106 made of Al · Mg, and the light emission characteristics of the LED 100 were confirmed. The central wavelength of light emission was about 430 nm. The half width of the emission spectrum was 190 millielectron volts (meV). The luminance in a chip state before the resin mold measured using a general integrating sphere was 10 millicandelas (mcd). The ohmic contact property of the Al · Mg n-type GaN layer 102 was inferior to that of Ti and LaAl _{2 in} Examples 1 and 2. On the other hand, ohmic contact with the p-type BP layer 104 was superior to Ti, LaAl ₂ , and Al·Li. For this reason, the forward voltage (Vf) was 3.2 V (when the forward current was 20 mA). In addition, the upper clad layer 104 on the light emitting layer 103 is composed of a p-type BP layer having a wide forbidden band width and a low resistance that can be easily obtained, so that it is effective for diffusing the element driving current in a wide range of the light emitting layer. It became. For this reason, the LED which can bring about blue light emission of substantially uniform intensity | strength from the whole surface of the light emission area | region was provided. Moreover, since both the n-type and p-type ohmic electrodes are made of the same Al / Mg alloy, a high-brightness LED can be easily constructed.

  The present invention is concretely exemplified by a compound semiconductor LED in which both n-type and p-type ohmic electrodes are composed of an aluminum-silicon (Al.Si) alloy (weight composition; Al: 99%, silicon: 1%). Explained.

  The p-type BP layer is limited to a region where the n-type ohmic electrode 105 is to be formed by processing the laminated structure 110 described in Example 1 by a plasma dry etching method using a halogen-based mixed gas containing chlorine. 104 and the light emitting layer 103 were selectively removed by etching. As a result, the surface of the n-type lower cladding layer 102 was exposed (see FIG. 2). Next, the surface of the n-type GaN layer 102 exposed to the region where the n-type ohmic electrode 105 is to be formed and the surface of the p-type BP layer are simultaneously formed on the surface of aluminum. A silicon alloy (Al.Si) film was deposited. Thereafter, the Al / Si film deposited by using a known photolithography technique was selectively patterned and etched to form n-type and p-type ohmic electrodes 105 and 106 having desired shapes in desired regions.

Both device driving currents were passed in the forward direction between n-type and p-type ohmic electrodes 105 and 106 made of Al · Si, and the light emission characteristics of the LED 100 were confirmed. The central wavelength of light emission was about 430 nm. The half width of the emission spectrum was 190 millielectron volts (meV). The luminance in a chip state before the resin mold measured using a general integrating sphere was 10 millicandelas (mcd). The ohmic contact property for the Al · Si n-type GaN layer 102 was equivalent to that of the Ti and LaAl ₂ of Examples 1 and 2. On the other hand, the ohmic contact with the p-type BP layer 104 was slightly inferior to Ti, LaAl ₂ , Al·Li, and Al · Mg. For this reason, the forward voltage (Vf) was 3.2 V (when the forward current was 20 mA). In addition, the upper clad layer 104 on the light emitting layer 103 is composed of a p-type BP layer having a wide forbidden band width and a low resistance that can be easily obtained. It became. For this reason, the LED which can bring about blue light emission of substantially uniform intensity | strength from the whole surface of the light emission area | region was provided. Moreover, since both the n-type and p-type ohmic electrodes are made of the same Al / Si alloy, a high-brightness LED can be easily constructed.

FIG. 2 is a schematic cross-sectional view of an LED of Example 1. 2 is a schematic plan view of the LED of Example 1. FIG.

Explanation of symbols

100 LED
DESCRIPTION OF SYMBOLS 110 Laminated structure 101 Sapphire substrate 102 N-type lower clad layer 103 Light emitting layer 104 P-type upper clad layer 105 N-type ohmic electrode 106 P-type ohmic electrode

Claims (2)

A crystal substrate, an n-type group III nitride semiconductor layer provided on one surface of the crystal substrate, a light-emitting layer made of an n-type or p-type compound semiconductor, boron (element symbol: B), and phosphorus (element symbol) : P) as a constituent element and a p-type boron phosphide-based semiconductor layer made of a boron phosphide-based semiconductor, and on each surface of the n-type group III nitride semiconductor layer and the p-type boron phosphide-based semiconductor layer. In a compound semiconductor light emitting device provided with either an n-type or p-type ohmic electrode in contact with the n-type group III nitride semiconductor layer of the n-type ohmic electrode, p A compound semiconductor light-emitting device characterized in that a portion of the ohmic electrode in contact with the p-type boron phosphide-based semiconductor layer is made of dialuminum lanthanum (composition formula: LaAl ₂ ) in common . A crystal substrate, an n-type group III nitride semiconductor layer provided on one surface of the crystal substrate, a light-emitting layer made of an n-type or p-type compound semiconductor, boron (element symbol: B), and phosphorus (element symbol) : P) as a constituent element and a p-type boron phosphide-based semiconductor layer made of a boron phosphide-based semiconductor, and on each surface of the n-type group III nitride semiconductor layer and the p-type boron phosphide-based semiconductor layer. In a method for manufacturing a compound semiconductor light emitting device in which an n-type or p-type ohmic electrode is provided in contact with the n-type group III nitride semiconductor layer of the n-type ohmic electrode And a portion of the p-type ohmic electrode that contacts the p-type boron phosphide-based semiconductor layer described above in common, ₂ A method for producing a compound semiconductor light emitting device, comprising:

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