KR20050106489A - Ohmic electrode structure, compound semiconductor light-emitting device having the same, and led lamp - Google Patents

Abstract

An Ohmic electrode structure comprising a p-conductivity-type boron phosphide-based semiconductor layer containing boron and phosphorus as constitutional elements and having a surface; and an electrode disposed on said surface of said semiconductor layer and having an Ohmic contact with said semiconductor layer, wherein at least a surface portion of said electrode which is in contact with said semiconductor layer is formed from a lanthanide element or a lanthanide element-containing alloy. A compound semiconductor light- emitting device comprising a light-emitting layer formed of a compound semiconductor may advantageously comprise the Ohmic electrode structure.

Description

OHMIC ELECTRODE STRUCTURE, COMPOUND SEMICONDUCTOR LIGHT-EMITTING DEVICE HAVING THE SAME, AND LED LAMP}

Cross Reference of Related Application

This application claims 35 U.S.C. 35 U.S.C. of the date of filing of US Provisional Serial No. 60 / 458,950, filed April 1, 2003, filed under § 111 (b). An application filed under § 111 (a) of 35 U.S.C. claiming benefits under §119 (e) (1).

The present invention relates to a p-type ohmic electrode structure provided on the surface of a p-conductive boron phosphide-based semiconductor layer to obtain ohmic contact with a layer, and a compound semiconductor device employing the p-type ohmic electrode structure. In particular, the present invention relates to a technique for producing a compound semiconductor light emitting device.

Conventionally, a technique for producing a boron phosphide-based semiconductor device such as a light emitting diode (abbreviated as LED) from boron phosphide (formula: BP), which is a type of group III-V compound semiconductor, and a mixed crystal thereof has been disclosed (for example, the United States) Patent 6,069,021). For example, the p-conductive monomer boron phosphide (BP) layer is used to serve as a barrier layer constituting a light emitting part having a pn-double hetero (DH) junction structure [for example, Japanese Patent Laid-Open See publication 2-288388. The boron phosphide-based semiconductor light emitting diode is composed of, for example, a p-type cladding layer formed of a boron phosphide layer and a p-type ohmic electrode provided on the surface of the p-type cladding layer. In one conventional case, the p-type ohmic electrode provided on the p-type boron phosphide layer is formed of aluminum (Al). See, eg, K. Shohno et al., J. Crystal Growth, vol. 24/25, 1974 (Netherlands), p. 193].

Boron phosphide is known to provide one of the n-conducting and p-conducting low resistance semiconductor layers even when no impurities are intentionally added [K. Shohno et al., J. Crystal Growth, vol. 24/25, 1974 (Netherlands), p. 193]. Thus, the ohmic electrode can be formed on a conductive boron phosphide layer such as a clad layer or a contact layer. In a conventional compound semiconductor light emitting device having a p-type boron phosphide layer doped with magnesium (element symbol: Mg) serving as a contact layer, the ohmic contact electrode is made of gold (element symbol: Au) -zinc (element symbol: Zn) (See, for example, Japanese Patent Laid-Open No. 2-288388).

However, when the above-described metal type is used, formation of an ohmic electrode exhibiting excellent ohmic contact with p-type boron phosphide has not been successfully achieved. Therefore, the input resistance when passing the current supplied to drive the light emitting device (i.e., the device operating current) disadvantageously increases, resulting in a problem that the high forward voltage Vf appears in the LED. In addition, the high input resistance has a problem in manufacturing a laser diode LD having a low threshold voltage Vth.

1 is a graph showing the current-voltage characteristics of the material of the present invention and the conventional material.

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

3 is a schematic cross-sectional view of the LED of Example 2. FIG.

4 is a schematic plan view of the LED of Example 2. FIG.

It is an object of the present invention to provide a p-type ohmic electrode structure which provides excellent ohmic contact of a p-type ohmic electrode on the surface of a p-type boron phosphide-based semiconductor layer containing boron (B) and phosphorus (P) as components. It is. The term "p-type ohmic electrode" refers to a positive electrode provided on a p-type semiconductor layer. Another object of the present invention to provide a compound semiconductor light emitting device having a p-type ohmic electrode having an electrode structure according to the present invention.

In order to achieve the above object, the present invention provides the following contents.

(1) a p-conductive boron phosphide-based semiconductor layer containing boron and phosphorus as constituent elements and having a surface; And

An electrode disposed on the surface of the semiconductor layer and in ohmic contact with the semiconductor layer; At least a surface portion of the electrode in contact with the semiconductor layer is formed of a lanthanide element or a lanthanide element-containing alloy.

(2) In the above (1),

And the surface portion of the electrode in contact with the surface of the semiconductor layer is formed of an alloy composed of lanthanum and an element having a work function of 4.5 eV or less.

(3) As for (1) or (2),

And the surface portion of the electrode in contact with the surface of the semiconductor layer is formed of an alloy consisting of lanthanum and aluminum.

(4) As for (1) or (2),

And the surface portion of the electrode in contact with the surface of the semiconductor layer is formed of an alloy consisting of lanthanum and silicon.

(5) In any one of said (1)-(4),

The electrode includes a bottom layer of a lanthanide element or a lanthanide element-containing alloy in contact with the semiconductor layer, an intermediate layer of at least one of titanium, molybdenum and platinum in the bottom layer, and an upper layer of gold or aluminum in the intermediate layer. Ohmic electrode structure, characterized in that.

(6) A compound semiconductor device comprising the ohmic electrode structure according to any one of (1) to (5) above.

The p-conductive boron phosphide-based semiconductor layer is a compound semiconductor, characterized in that it is formed of p-type monomer boron phosphide which is not doped and intentionally added with impurities and has a comprehensive bandgap between 2.8 eV and 5.4 eV at room temperature. device.

(7) A compound semiconductor light emitting device comprising the compound semiconductor device according to (6) above.

(8) a crystalline substrate formed of an insulating or conductive crystal;

A light emitting layer formed of a compound semiconductor formed on the crystalline substrate;

A p-conductive boron phosphide-based semiconductor layer containing boron and phosphorus as constituent elements and formed in the light emitting layer, comprising: a p-conductive boron phosphide-based semiconductor layer having a surface; And

A compound semiconductor light emitting device comprising a p-conductive ohmic electrode formed in contact with the surface of the p-conductive boron phosphide semiconductor layer and in ohmic contact with the surface,

And at least a surface portion of the p-conductive ohmic electrode in contact with the surface of the p-conductive boron phosphide based semiconductor layer is formed of a lanthanide element or a lanthanide element-containing alloy.

(9) As for (8),

The p-conducting boron phosphide-based semiconductor layer is 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) or _{B α Al β Ga γ In 1} -α-β-γ P 1-δ N δ (0 <α≤1, 0≤β <1, A compound semiconductor light-emitting device, which is formed of 0 ≦ γ <1, 0 <α + β + γ ≦ 1, 0 ≦ δ <1).

(10) As for (8),

The p-conductive boron phosphide-based semiconductor layer is a monomer boron phosphide (BP), indium boron phosphide (formula: B _α Ga _γ In _{1 -α-γ} P: 0 <α≤1, 0≤γ <1) or A compound semiconductor light-emitting device, comprising: a mixed crystal compound containing a plurality of Group V elements in addition to boron and phosphorus;

(11) As for (10),

The p-conductive boron phosphide-based semiconductor layer is formed of boron nitride phosphide (formula: BP _{1 -δ} N _δ : 0≤δ <1) or boron arsenide phosphide (formula: BP _{1 -δ} As _δ ) Compound semiconductor light emitting device.

(12) any one of (8) to (11) above,

And the surface portion of the electrode in contact with the surface of the p-conductive boron phosphide-based semiconductor layer is formed of an alloy composed of lanthanum and an element having a work function of 4.5 eV or less.

(13) In any one of said (8)-(12),

And the surface portion of the electrode in contact with the surface of the p-conductive boron phosphide-based semiconductor layer is formed of an alloy consisting of lanthanum and aluminum.

(14) The method according to any one of (8) to (12) above,

And the surface portion of the electrode in contact with the surface of the p-conductive boron phosphide-based semiconductor layer is formed of an alloy consisting of lanthanum and silicon.

(15) In any one of said (8)-(14),

The compound semiconductor layer is formed of a III-V compound semiconductor, characterized in that the compound semiconductor light emitting device.

(16) any one of (8) to (15) above,

The compound semiconductor layer may be indium gallium nitride being formed by: _{-: -::} (0≤y≤1 formula _y P _y GaN ₁₎ (the composition formula In _x Ga _{1 x} N 0≤x≤1) nitride or gallium phosphide A compound semiconductor light emitting device characterized by the above-mentioned.

(17) In any one of (8)-(16),

The surface portion of the electrode in contact with the surface of the p-conductive boron phosphide-based semiconductor layer is formed of a lanthanide element or a lanthanide element-containing alloy, and has a pad electrode portion and a pad electrode portion for bonding as a planar shape. A compound semiconductor light-emitting device having a net-like portion extending from the.

(18) any one of (7) to (17) above,

The p-conductive boron phosphide-based semiconductor layer is not doped, no impurities are intentionally added, and is formed of a p-type monomer boron having a comprehensive bandgap of 2.8 eV to 5.4 eV at room temperature. Compound semiconductor light emitting device.

(19) An LED lamp using the compound semiconductor element according to any one of the above (8) to (18).

The present invention relates to an electrode structure for providing excellent ohmic contact with respect to a p-type boron phosphide based semiconductor layer.

In the present invention, the term "boron phosphide semiconductor" denotes a compound semiconductor containing boron (element symbol: B) and phosphorus (element symbol: P) as constituent elements. Specific examples include 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) and _{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). Examples include monomer boron phosphide (BP), gallium boron phosphide (formula: B _α Ga _γ In _{1 -α-γ} P: 0 <α ≦ 1, 0 ≦ _γ <1) and boron nitride phosphide (formula: BP _And a mixed compound containing a plurality of Group V element species such as _1-δ Nδ: 0 ≦ _δ <1) and boron phosphide (formula: BP _{1 -δ} As _δ ). The composition ratio (1-δ) of the lower limit of phosphorus (P) is preferably 0.50 or more, more preferably 0.75 or more, for example, in the case of BP _{1 -δ} N _δ , BP _{1 -δ} As _δ and the like.

The p-type boron phosphide-based semiconductor layer provided with the p-type ohmic electrode may be formed by halogen method, hydride method or MOCVD (metal-organic chemical vapor deposition). Alternatively, the semiconductor layer can be grown in the vapor phase through molecular beam epitaxy [J. Solid State Chem., 133 (1997), p. 269-272]. Specifically, the p-type monomer boron phosphide layer may be formed by MOVCD using triethyl boron [molecular formula: (C ₂ H ₅ ) ₃ B] and phosphine (molecular formula: PH ₃ ) as raw materials. The p-type BP layer is preferably formed at 1,000 ° C. to 1200 ° C., and the raw material feed ratio [= PH ₃ / (C ₂ H ₅ ) ₃ B] during layer formation is preferably controlled to 10 to 50. The BP layer, in which no impurities are intentionally added, ie, the undoped BP layer, effectively prevents deterioration of other component layers caused by diffusion of impurities. By strictly controlling the formation temperature and the V / III ratio as well as the formation speed, a boron phosphide-based semiconductor layer having an optical band gap can be formed (see Unexamined Japanese Patent Publication No. 2002-158282).

Particularly preferably, a p-type boron phosphide-based semiconductor layer having a bandgap of 2.8 eV to 5.4 eV at room temperature is used. More preferably, the p-type boron phosphide-based semiconductor layer having a bandgap as wide as 2.8 eV to 3.2 eV may be used as a barrier layer having a barrier action, for example, a p-type cladding layer included in a compound semiconductor light emitting device. have. The optical band gap p-type boron phosphide-based semiconductor layer is indium gallium nitride (compositional _{formula: Ga x In 1-x N} : 0≤x≤1) nitride or gallium phosphide (compositional _{formula: GaN 1 - y P y:} 0≤y≤ A window layer for transmitting visible light (blue, green, etc.) emitted from the light ray layer formed by 1) to the outside of the light emitting element is appropriately formed. If the bandgap exceeds 5.4 eV, the barrier height for the light emitting layer is increased, which is disadvantageous for manufacturing a compound semiconductor light emitting device having a low forward voltage or a low threshold voltage. For example, the p-type cladding layer is appropriately formed from a low-resistance boron phosphide layer having a carrier concentration of 1 × 10 ¹⁹ cm ⁻³ or more and resistivity of 5 × 10 ⁻² Pa · cm or less at room temperature. It is preferable that the thickness of the p-type boron phosphide layer which comprises a p-type cladding layer is controlled to 500 nm or more and 5,000 nm or less. In the structure of the p-type ohmic electrode formed to make contact with the p-type cladding layer, in the p-type cladding layer which is too thin, the device operating current supplied through the ohmic electrode cannot uniformly spread on the entire surface of the light emitting layer. Inappropriate

No particular limitation is imposed on the compound semiconductor device employing this p-type boron phosphide-based semiconductor layer. However, a typical example is a boron phosphide-based semiconductor LED. In particular, the boron phosphide-based semiconductor layer is preferably gallium indium as described above (composition _{formula: Ga x In 1-x N} : 0≤x≤1) nitride or gallium phosphide (compositional formula: GaN _{1 - y} P _y: It is used in combination with a light emitting layer formed of 0 ≦ y ≦ 1). In addition, the boron phosphide-based semiconductor layer can be used in compound semiconductor light emitting devices such as laser diodes (LD).

In the present invention, the bottom surface of the p-type ohmic electrode in contact with the surface of the p-type boron phosphide-based semiconductor layer serving as a cladding layer, a contact layer for forming an electrode, or a similar layer is a lanthanide element layer or a lanthanide element-containing alloy. Formed into layers.

The term "lanthanide element" refers to a group of elements, including lanthanum (La, 57 atoms) to lutetium (Lu, 71 atoms) (JA Duffy, "Inorganic Chemistry", Hirokawa Shoten, April 15, 1971 Publication, 5th edition, p. 262). Elements such as cerium (Ce, number of atoms: 58), praseodymium (Pr, number of atoms: 59), neodymium (Nd, number of atoms: 60), and holmium (Ho, number of atoms: 67) are collectively referred to as "lanthanoids ( lanthanoids "(see page 263 in" Inorganic Chemistry "). In particular, in the present invention, since the lanthanum and the lanthanum alloy provide excellent ohmic contact properties with respect to the p-type boron phosphide-based semiconductor layer, the bottom portion of the p-type ohmic electrode is preferably lanthanum (La) or lanthanum. It is formed of an alloy. In addition, lanthanum (La) or lanthanum alloy among the lanthanum provides the best bonding properties with respect to the boron phosphide-based semiconductor layer, so that the bottom portion can be firmly bonded to the layer.

An alloy formed of lanthanum and a material having a work function of 4.5 eV or less is preferably used to form the p-type ohmic electrode bottom portion in contact with the surface of the p-type boron phosphide-based semiconductor layer. When the alloy has a work function of more than 4.5 eV, the barrier height for the p-type boron phosphide-based semiconductor layer increases sharply, which is disadvantageous for the manufacture of the p-type ohmic electrode. For those with a large work function, alloys of lanthanum and materials with high melting points are advantageous for forming p-type ohmic electrodes with good heat resistance. Therefore, high melting point alloys are more preferable than lanthanum alloys with small work function and low melting point gallium (work function = 4.0 eV, melting point = 29.8 ° C.) or indium (work function = 3.8 eV, melting point = 156 ° C.). For example, the bottom portion exhibiting good ohmic contact is suitably from an alloy of lanthanum and aluminum (work function: 4.3 eV, melting point: 660 ° C.) or an alloy of lanthanum and silicon (work function: 4.0 eV, melting point: 1,414 ° C.). Can be formed.

It is preferable that content of aluminum (Al) or silicon (Si) is 1 mass% or more and less than 50 mass% with respect to mass%. The lanthanum alloy film may be formed using a means such as vacuum deposition, electron beam deposition, or high frequency sputtering. The bottom portion having a desired planar shape, such as a circle or a square, may be formed by patterning the alloy film through known photolithography techniques. Examples of the alloy include lanthanum telluride (formula: La ₂ Te ₃ ), which is an alloy of lanthanum and tellurium (element symbol: Te, work function = 4.3 eV, melting point = 450 ° C), or lanthanum and nickel (element symbol: Ni, It further includes a lanthanum nickel (composition formula: LaNi ₅ ) alloy which is an alloy with a work function of 4.5 eV and a melting point of 1,453 ° C.

The properties of the p-type ohmic electrode having the bottom portion formed of lanthanum or lanthanum alloy according to the present invention can be investigated through, for example, a current-voltage (IV) characteristic profile generally used. For example, FIG. 1 shows the IV characteristic profile of a p-type ohmic electrode formed of a lanthanum-aluminum alloy (Formula LaAl ₂ ) in comparison with that of a conventional electrode. IV characteristics were measured between p-type ohmic electrodes arranged at intervals of 350 mu m. In each measurement, a p-type boron phosphide layer having the same electrical resistance was used. Therefore, low resistance represents low contact resistance. As shown in Fig. 1, under a given applied voltage, the LaAl ₂ electrode according to the present invention is formed of an aluminum (Al), gold (Au) -zinc (Zn) alloy or a gold (Au) -beryllium (Be) alloy. Many current flows can be achieved as compared to ohmic electrodes. Thus, a p-type ohmic electrode having a low contact resistance can be manufactured.

In order to obtain excellent contact between the ohmic electrode and the p-type boron phosphide-based semiconductor layer, it is preferable that the p-type ohmic electrode, especially its bottom portion, is formed of a continuous film without fine pores. Accordingly, the bottom portion is preferably formed of a lanthanum-containing film having a thickness of 100 nm or more, more preferably 100 nm or more, and most preferably 300 nm.

By stacking another metal film on the surface of the bottom portion, an ohmic electrode having a multilayer structure can be produced. For example, in a preferable embodiment, the bottom portion of the titanium (Ti) film and the gold (Au) film formed of a lanthanum (La) (95 mass%)-aluminum (Al) (5 mass%) alloy film having a thickness of 120 nm Stacked sequentially (circular planar shape) to form a p-type ohmic electrode of a three-layer structure. When a p-type ohmic electrode having a stacking layer structure is manufactured, it is preferable that the uppermost layer is formed of gold (Au) or aluminum (Al) to facilitate bonding. In addition, the intermediate layer included in the p-type ohmic electrode having a three-layer structure and sandwiched on the bottom and top layers may be formed of a transition metal such as platinum (Pt) or titanium or molybdenum (Mo).

Through the use of the p-type ohmic electrode of the structure according to the present invention, a compound semiconductor light emitting device exhibiting excellent electrical characteristics can be provided. For example, an LED indicative of low forward voltage Vf may be provided. The low Vf visible light emitting LED has, for example, a stacking structure constituting a sapphire substrate / n type gallium nitride (GaN) clad layer / n type gallium indium nitride (GaInN) light emitting layer / p type boron phosphide (BP) clad layer. It can be formed by use, and the p-type ohmic electrode formed of the lanthanum-aluminum alloy film is provided on the surface of the p-type BP clad layer. In the LED having a chip size of 300 µm to 350 µm, the bottom portion of the p-type ohmic electrode preferably has a diameter of 90 µm to 150 µm, for example. When a Ga _x In _{1 - x} N (0 <X <1) layer of a multiphase structure including a plurality of gallium indium regions having different indium composition ratios (= 1-X) is used, it has higher emission intensity. A compound semiconductor light emitting element can be manufactured effectively (Japanese Patent No. 3090057).

For example, an effective means for producing a planar large LED having a length of one side of 500 mu m or more is to arrange a p-type ohmic electrode over a wide range of the surface of the p-type boron phosphide-based semiconductor layer. The ohmic electrode is advantageous for the manufacture of LEDs having a high luminous intensity and a large luminous area since the device operating current can be spread over a wide range of the surface of the luminous layer. The ohmic electrode is preferably formed in a shape in which the device operating current can be uniformly diffused. For example, a p-type ohmic electrode formed of a lanthanum-aluminum alloy is disposed on the surface of the p-type boron phosphide mixed layer provided on the light emitting layer so that the p-type ohmic electrode exhibits a lattice or network in electrical contact. Alternatively, the p-type ohmic electrode is radially from the bottom to the periphery of the chip, while maintaining the bottom of the lanthanum-silicon alloy provided for contacting the surface of the p-type boron phosphide-based semiconductor layer, and the electrical conduction between the bottom and the electrode is maintained. Or a portion extending into a branch shape. Alternatively, the p-type ohmic electrode is made of a plurality of concentric lanthanum-aluminum alloy film sublayers electrically connected with a pad electrode disposed in the center of the p-type boron phosphide-based semiconductor layer. In the pad electrode for wire bonding according to any of the p-type ohmic electrodes, when the bottom surface of the pad electrode is formed of a material having a high ohmic contact resistance with respect to the p-type boron phosphide-based semiconductor layer, the pad is directly under the base layer. The flow of the device operating current up to the bottom of the electrode can be prevented by a short circuit, and advantageously the device operating current can be spread over a large area of the light emitting area open to the outside to properly allow transmission of the light emission.

In order to form a desired planar p-type ohmic electrode, the entire surface of the p-type boron phosphide-based semiconductor layer is covered with a lanthanum-aluminum alloy film using conventional means such as, for example, vacuum deposition or electron beam deposition. do. The alloy film is then patterned into the desired shape through conventional photolithography techniques. The alloy film is preferably patterned into a shape capable of realizing an equipotential distribution in the p-type boron phosphide semiconductor layer. Unnecessary portions of the alloy film are then removed by means of a wet etching method or a plasma dry etching method using a halogen gas (for example, chlorine gas (molecular formula: Cl ₂ )). Wet etching of lanthanoid-based alloys is carried out by using acid mixtures containing glacial acetic acid (eg, glacial acetic acid-hydrogen peroxide mixture) [von Guenter Petzow (Gentaro Matsumura translation), "Mental Etching Technique" AGNE, September 10 , 1977, 1st edition, 1st printing, p. 91].

An electrode having a bottom portion in contact with the surface of a p-type boron phosphide-based semiconductor layer and formed of a lanthanide element or an alloy containing the element provides a p-type ohmic electrode exhibiting excellent ohmic characteristics with respect to the p-type boron phosphide-based semiconductor layer. can do.

A p-type ohmic electrode having a bottom portion in contact with the surface of a p-type boron phosphide-based semiconductor layer and formed of a lanthanide element or an alloy containing the element can diffuse the device operating current over a wide portion of the light emitting region.

EXAMPLE

<First Embodiment>

The present invention will be described in detail by employing, as an example, a compound semiconductor LED manufactured by providing a p-type ohmic electrode formed of a lanthanum-aluminum alloy (LaAl ₂ ) on the surface of a p-type boron phosphide semiconductor layer.

2 schematically illustrates a cross-sectional view of a stacking structure used to fabricate an LED 100 of a double-hetero (DH) junction structure. The stacking structure includes a lower cladding layer 102 formed of undoped n-type boron phosphide (BP) on a phosphorus (P) -doped n-type (111) -silicon (Si) single crystal substrate (10); an n-type gallium indium nitride _{(Ga 0 .90 In 0 .10 N} ) light emitting layer 103 has a multi-layer quantum well structure including a well layer (103a) and gallium five units consisting of a (GaN), the barrier layer (103b) ; And an upper clad layer 104 formed of undoped p-type boron phosphide was deposited sequentially.

The undoped n-type and p-type boron phosphide layers 102 and 104 are composed of triethyl boron [molecular formula: (C ₂ H ₅ ) ₃ B] as the boron (B) source and phosphine (molecular formula: PH ₃ ) as the personnel. It was formed via means of atmospheric (nearly atmospheric) organo-metal vapor phase epitaxy (M0VPE) used. The n type boron phosphide layer 102 and the p type boron phosphide layer 104 were formed at 925 degreeC and 1,025 degreeC, respectively. The light emitting layer 103 is trimethyl gallium [molecular formula: (CH ₃ ) ₃ Ga] / NH ₃ / H ₂ It was formed through atmospheric MOCVD means at 800 ° C. by use of a reaction system. The above-described gallium indium nitride layer serving as the well layer 103a has a multiphase structure including a plurality of indium gallium nitride phases having different indium composition ratios. The average composition ratio of indium (In) was 0.10 (= 10%). The thicknesses of the well layer 103a and the barrier layer 103b were adjusted to 5 nm and 10 nm, respectively.

The carrier (hole) concentration and thickness of the undoped p-type boron phosphide layer 104 serving as the upper clad layer 104 were adjusted to 2 × 10 ¹⁹ cm ⁻³ and 720 nm, respectively. The layer 104 had a resistivity of 5 × 10 ⁻² Pa · cm at room temperature. Since the p-type boron phosphide layer 104 has a bandgap of 3.2 eV at room temperature, the layer 104 also serves as a window layer for transmitting light emitted from the light emitting layer 103 to the outside. Used as layer.

The lanthanum-aluminum (LaAl ₂ ) alloy film 105, titanium (Ti) on the entire surface of the p-type boron phosphide layer 104 serving as the p-type upper cladding layer through conventional vacuum deposition and electron beam deposition The film 106 and the gold (Au) film 107 were deposited. Then, only in the region providing the pad electrode 108 for bonding, in order to leave the above-described triple layer electrode in the bottom portion formed of the LaAl ₂ alloy film 105, selectively through the use of conventional photolithography techniques. Patterning was performed. Then, by using an acid mixture such as a glacial acetic acid-sulfuric acid solution, the LaAl ₂ alloy film and other sublayers in the region except for the region serving as the pad electrode 108 are removed by etching, thereby forming the p-type boron phosphide layer 104. The surface of was exposed. After removing the photoresist, selective patterning was performed to provide a lattice groove for cutting the structure into chips. Thereafter, the p-type boron phosphide-based layer 104 was selectively removed by plasma dry etching using a halogen-based mixture containing chlorine only in the patterned region.

On the other hand, on the entire back surface of the silicon single crystal substrate 101, a gold (Au) film was deposited by means of a conventional vacuum deposition method to form an n-type ohmic electrode (sub electrode) 109. The structure is cleaved along the above-described stripe-shaped cutting grooves having a line width of 50 μm provided in a direction parallel to the <110> crystal direction perpendicular to the (111) -crystal plane of the Si single crystal substrate 101. A square LED chip having a length of one side of 350 µm is provided.

In the present invention, the bottom portion of the p-type ohmic electrode is formed of a lanthanum-aluminum (LaAl ₂ ) alloy film 105 having excellent adhesion with respect to the p-type boron phosphide layer serving as the upper clad layer 104. Thus, a p-type ohmic electrode 108 can be formed that does not peel off from the p-type boron phosphide layer 104 during wire bonding and also serves as a pad electrode.

The light emission characteristic of each LED chip 100 was confirmed by flowing a device operating current of 20 mA in the forward direction between the p-type ohmic electrode 108 and the n-type ohmic electrode 109. The LED l00 emitted blue light having an emission center wavelength of 440 nm, and the half peak full width observed in the emission spectrum was 210 meV. The brightness of the LED chip before the resin-mold determined through the conventional photometer was 11 mcd. The bottom portion of the p-type ohmic electrode 105 is LaAl _{2 having} low contact resistance with respect to the p-type boron phosphide layer. Since it was formed of an alloy film, the forward voltage Vf at a forward current of 20 mA was as low as 3.1 V and the reverse voltage at a reverse current of 10 μm was as high as 9.5 V. Furthermore, a p-type ohmic electrode comprising a lanthanum-aluminum alloy film of low contact resistance is formed to form an upper clad layer from a low-resistance undoped p-type boron phosphide layer at high carrier concentration and to make ohmic contact with the surface of the p-type boron phosphide. As a result, the light emission caused by the element operating current is provided from almost the entire part of the light emitting area other than the projecting area of the pad electrode.

Second Embodiment

The present invention will be described in detail by way of example of a compound semiconductor LED produced by providing a p-type ohmic electrode formed of a lanthanum-silicon alloy on the surface of a p-type gallium phosphide mixed crystal layer. The basic structure of the compound semiconductor light emitting element of the second embodiment is the same as that of the LED of the first embodiment, and the same sublayer is denoted by the same reference numeral used in the first embodiment. 3 is a cross-sectional view of the device of the second embodiment and FIG. 4 is a plan view of the device of the second embodiment.

An undoped p-type gallium boron phosphide mixed crystal (B _0.98 Ga _0.02 P) layer 204 was deposited on the light emitting layer 103 described in the first embodiment described above. B _{0.98 0 .02} Ga P layer 204 is a (C ₂ H ₅₎ was formed in the _{3B / (CH 3) 3 Ga} / PH 3 based 850 ℃ by a pressure reduction by using the MOCVD method. The layer thickness was adjusted to 340 nm. B _0.98 Ga carrier concentration and the resistivity of the _{0 .02} P layer 204 is shown as a 8 × 10 ¹⁸ ㎝ ^-3 and 8 × 1O ^-2 Ω and ㎝ at each temperature.

Then a p-type B _0.98 Ga _.02 P ₀ on the entire surface of the layer (2O4), lanthanum-silicon (La-Si) alloy film 205 was deposited through a conventional vacuum deposition method. The thickness of the La-Si alloy film 205 was adjusted to 540 nm. Subsequently, patterning was carried out through the use of conventional photolithography techniques and plasma etching techniques. Thereafter, through plasma dry etching, an unnecessary portion of the alloy film is removed to provide a circle 205 (diameter: 150 mu m) in the center of the LED chip 200, as shown in FIG. a Si alloy was patterned to provide a p-type Ga _{0.98 0 .02} B so as to contact the surface of the P layer reticular around circle 210. The intermediate layer 206 and the gold film 207 were formed on the provided circular portion to form the pad electrode 208.

On the entire back surface of the silicon single crystal substrate 101, a gold (Au) (99 mass%)-antimony (Sb) (1 mass%) alloy film 209 was deposited through a conventional vacuum deposition method.

The patterned La-Si alloy film and gold deposited film are then sintered at 450 ° C. for 10 minutes under hydrogen flow while the film remains in contact with the stacking structure, improving ohmic contact. Thus, the p-type ohmic electrode 205 formed of La-Si was provided on the surface of the p-type B _0.98 sGa _0.02 P layer 204 and the Au ohmic electrode was formed on the back surface of the silicon single crystal substrate 101. The Au film constituting the n-type ohmic electrode 209 was adjusted to 2 mu m.

Then, cutting is performed along the cutting line provided during the etching of the La-Si alloy film described above to manufacture individual LED chips. Cutting grooves are provided in parallel to the [1.-1.0] and [-1.-1.0] crystal directions of the Si single crystal substrate 101 to fabricate individual LED chips of rectangular shape having side lengths of 500 μm and 600 μm. do. The center wavelength of emitted light when the forward current of 20 mA is flowed between the p-type and n-type ohmic electrodes 205 and 209 of each large-scale LED chip 200 is 440 nm. In the light emitting form of the near region, the light emission intensity was uniform in all parts of the light emitting region except for the pad electrode region disposed at the center of the chip 200. Since the device operating current of the p-type Ga _{0.98 0 .02} B was placed with the p-type ohmic electrode in the same way that can be widely diffused uniformly on the P layer, the light emission was obtained. The forward voltage when the forward current was 20 mA was 3.4 V, and the reverse voltage when the reverse current was 10 mA was 8.3 V.

According to the present invention, the p-type ohmic electrode provided to obtain ohmic contact on the surface of the p-type boron phosphide-based semiconductor layer is formed from an lanthanide element or an alloy film containing a lanthanide element, and an electrode of low contact resistance is formed. Can be utilized to efficiently utilize the device operating current supplied for light emission. Therefore, a compound semiconductor light emitting device can be produced that obtains high light emission intensity. In addition, a high brightness LED lamp can be manufactured by connecting a conducting wire to the compound semiconductor light emitting device according to the present invention and molding the assembly with a resin.

Claims (19)

A p-conductive boron phosphide-based semiconductor layer containing boron and phosphorus as constituent elements and having a surface; And An electrode disposed on the surface of the semiconductor layer and in ohmic contact with the semiconductor layer; At least a surface portion of the electrode in contact with the semiconductor layer is formed of a lanthanide element or a lanthanide element-containing alloy. The method of claim 1, And the surface portion of the electrode in contact with the surface of the semiconductor layer is formed of an alloy composed of lanthanum and an element having a work function of 4.5 eV or less. The method according to claim 1 or 2, And the surface portion of the electrode in contact with the surface of the semiconductor layer is formed of an alloy consisting of lanthanum and aluminum. The method according to claim 1 or 2, And the surface portion of the electrode in contact with the surface of the semiconductor layer is formed of an alloy consisting of lanthanum and silicon. The method according to any one of claims 1 to 4, The electrode includes a bottom layer of a lanthanide element or a lanthanide element-containing alloy in contact with the semiconductor layer, an intermediate layer of at least one of titanium, molybdenum and platinum in the bottom layer, and an upper layer of gold or aluminum in the intermediate layer. Ohmic electrode structure, characterized in that. A compound semiconductor device comprising the ohmic electrode structure according to any one of claims 1 to 5, Wherein the p-conductive boron phosphide-based semiconductor layer is formed of p-type monomer boron phosphide which is not doped and is not deliberately added with impurities, and has a comprehensive bandgap between 2.8 eV and 5.4 eV at room temperature. Semiconductor device. A compound semiconductor light emitting device comprising the compound semiconductor device according to claim 6. A crystalline substrate formed of an insulating or conductive crystal; A light emitting layer made of a compound semiconductor formed on the crystalline substrate; A p-conductive boron phosphide-based semiconductor layer containing boron and phosphorus as constituent elements and formed in the light emitting layer, comprising: a p-conductive boron phosphide-based semiconductor layer having a surface; And A compound semiconductor light emitting device comprising a p-conductive ohmic electrode formed in contact with the surface of the p-conductive boron phosphide semiconductor layer and in ohmic contact with the surface, And at least a surface portion of the p-conductive ohmic electrode in contact with the surface of the p-conductive boron phosphide based semiconductor layer is formed of a lanthanide element or a lanthanide element-containing alloy. The method of claim 8, The p-conducting boron phosphide-based semiconductor layer is 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) or B _α Al _β Ga _γ In _{1 -α-β-γ} P _{1 -δ} N _δ (0 <α≤1, 0≤β <1, A compound semiconductor light-emitting device, which is formed of 0 ≦ γ <1, 0 <α + β + γ ≦ 1, 0 ≦ δ <1). The method of claim 8, The p-conductive boron phosphide-based semiconductor layer is a monomer boron phosphide (BP), indium boron phosphide (formula: B _α Ga _γ In _{1 -α-γ} P: 0 <α≤1, 0≤γ <1) or A compound semiconductor light-emitting device, which is formed of a mixed crystal compound containing a plurality of Group V elements in addition to boron and phosphorus. The method of claim 10, The p-conductive boron phosphide-based semiconductor layer is formed of boron nitride phosphide (formula: BP _{1 -δ} N _δ : 0≤δ <1) or boron arsenide phosphide (formula: BP _{1 -δ} As _δ ) Compound semiconductor light emitting device. The method according to any one of claims 8 to 11, And said surface portion of said electrode in contact with said surface of said p-conductive boron phosphide-based semiconductor layer is formed of an alloy composed of lanthanum and an element having a work function of 4.5 eV or less. The method according to any one of claims 8 to 12, And the surface portion of the electrode in contact with the surface of the p-conductive boron phosphide-based semiconductor layer is formed of an alloy consisting of lanthanum and aluminum.  The method according to any one of claims 8 to 12, And the surface portion of the electrode in contact with the surface of the p-conductive boron phosphide-based semiconductor layer is formed of an alloy consisting of lanthanum and silicon. The method according to any one of claims 8 to 14, The compound semiconductor layer is formed of a III-V compound semiconductor, characterized in that the compound semiconductor light emitting device. The method according to any one of claims 8 to 15, The compound semiconductor layer may be indium gallium nitride being formed by: _{-: -::} (0≤y≤1 formula _y P _y GaN ₁₎ (the composition formula In _x Ga _{1 x} N 0≤x≤1) nitride or gallium phosphide A compound semiconductor light emitting device characterized by the above-mentioned. The method according to any one of claims 8 to 16, The surface portion of the electrode in contact with the surface of the p-conductive boron phosphide-based semiconductor layer is formed of a lanthanide element or a lanthanide element-containing alloy, and has a pad electrode portion and a pad electrode portion for bonding as a planar shape. A compound semiconductor light emitting device, characterized in that it has a net-like portion extending in the. The method according to any one of claims 7 to 17, The p-conductive boron phosphide-based semiconductor layer is not doped, no impurities are intentionally added and is formed of a p-type monomer boron having a bandgap of 2.8 eV to 5.4 eV at room temperature. Semiconductor light emitting device. The LED lamp using the said compound semiconductor element in any one of Claims 8-18.