JP3772708B2 - Multicolor light emitting lamp and light source - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a technique for forming a multicolor light emitting lamp (lamp) capable of emitting multiple colors having different wavelengths using a plurality of light emitting diodes (LEDs).
[0002]
[Prior art]
Conventionally, for example, light emitting diodes (LEDs) that can emit each of the three primary colors of light, red light (R), green light (G), and blue light (B), are arranged adjacent to each other, and RGB type multicolor A technique for forming a (multi-color) light-emitting lamp is known. For example, an LED (blue LED) that emits blue band light having an emission wavelength of 450 nanometers (nm), a green LED that emits green band light of around 525 nm, and a red band having a wavelength of approximately 600 nm to 700 nm. There is a technology example in which a red LED that emits light is integrated to constitute an RGB type multi-color light emitting lamp (“Display Technology” (published on September 25, 1998, Kyoritsu Publishing Co., Ltd., 2nd edition), 100-101 pages).
[0003]
Conventionally, a multicolor light emitting lamp is a Ga _X In _1-X N-based blue light emitting layer made of a III-V group compound semiconductor such as gallium nitride indium (Ga _X In _1-X N: 0 ≦ X ≦ 1). (Refer to Japanese Patent Publication No. 55-3834) ("Group III nitride semiconductor" (December 8, 1999, published by Bafukan Co., Ltd., pages 252-254). There are Ga _X In _1-X N green LEDs or homo (homogeneous) junction type GaP green LEDs having a light emitting layer of gallium phosphide (GaP) ((1) above-mentioned “Group III nitride”) Pp. 249-252, and (2) "III-V compound semiconductor" (May 20, 1994, first published by Bafukan Co., Ltd.), pages 253-261). Is a mixed crystal of aluminum arsenide and gallium ( _{l X Ga 1-X As:} 0 <X <1) , or aluminum phosphide, Gallim indium _{((Al X Ga 1-X} ) Y In 1-Y P: 0 ≦ X ≦ 1,0 <Y <1) There is an LED having a light emitting layer of a III-V group compound semiconductor such as Tetsuji Teramoto, “Introduction to Semiconductor Devices” (published March 30, 1995, Baifukan Co., Ltd., pages 116 to 118).
[0004]
In addition, it is also known that white light can be obtained by, for example, color mixing of blue band light and yellow band light in a complementary color relationship (“Light Pencil-Applied Optics for Optical Engineers” (1989). (See page 51, New Technology Communications, Inc., published on June 20, 2010.) Yellow LEDs suitable for combination with blue LEDs include gallium arsenide (GaAs ₁₎ having an emission wavelength of about 590 nm. _{-Z P Z: 0 <Z <} 1) homo having a light emitting layer junction GaAsP-based LED and aluminum phosphide, gallium indium mixed crystal _{((Al X Ga 1-X} ) Y In 1-Y P: 0 ≦ Hetero (heterogeneous) junction type LED can be used (X.ltoreq.1, 0 <Y <1, and generally Y.apprxeq.0.5) (see J. Crystal Growth, 221 (2000), pages 652-656).
[0005]
The gallium indium nitride (Ga _X In _1-X N (0 ≦ X ≦ 1)) LED constituting the multicolor light emitting lamp is made of electrically insulating sapphire (α-Al ₂ O ₃ single crystal) as a substrate material. Generally, it is configured (see “Group III nitride semiconductor” above, pages 243 to 252). Since the current (drive current) for driving the LED cannot flow through the insulating crystal substrate, both the positive and negative electrodes are installed on the same surface side of the substrate. On the other hand, homozygous GaP-based or homozygous GaAs _1-Z P Z based LED is the conductivity of the gallium phosphide (GaP) by utilizing a single crystal or gallium arsenide (GaAs) single crystal is constituted, Only electrodes having either positive or negative polarity are arranged on the surface side (see “Overview of Semiconductor Devices”, 117 above).
[0006]
[Problems to be solved by the invention]
All are composed of RGB three-color integrated white lamp using conventional Ga _X In _1-X N (0 ≦ X ≦ 1) blue LED, green LED and red LED with insulating crystal as substrate. If it is going to be, since it becomes the structure by which the electrode of both positive and negative polarity is arrange | positioned on the surface of each LED, the connection (bonding) according to polarity to the electrode of both polarities is needed, and it is complicated. If the polarity of the electrodes to be connected can be unified to either positive or negative by using a conductive substrate, in particular, the same conductive substrate, the complexity of the connection can be avoided.
[0007]
Recently, a technique for constructing a blue LED using a boron-containing group III-V compound semiconductor layer and a light emitting layer made of a group III-V compound semiconductor provided on a conductive silicon single crystal (silicon) has been disclosed. (See US Pat. No. 6,069,021). If a blue LED using a conductive substrate having the same conductivity as that used to construct a green or red LED is used, the conventional multi-color light-emitting lamp can be simplified by avoiding the complexity of the conventional wiring operation. Can be configured.
[0008]
Turned, GaP-based or GaAs _1-Z P Z based LED constituting a multicolor light-emitting lamp together with the Ga _X In _1-X N-based blue LED has a structure of the homo (homo) junction. Therefore, the emission intensity of the GaP-based or GaAs _1-Z P Z based LED _{is, Ga X In 1-X N} (0 ≦ X ≦ 1) double hetero (DH) lower in comparison to the junction LED, luminous strength Has not led to a balanced multicolor light emitting lamp. A heterojunction structure that can exhibit a “confinement” effect on a carrier that generates light emission or radiative recombination is expected to produce higher intensity light emission.
[0009]
The present invention provides a technique for constructing a multicolor light emitting lamp using a blue LED having a configuration capable of avoiding complicated wiring. In particular, the present invention provides a technique for forming a multicolor light emitting lamp with a heterojunction GaP-based LED that can emit green light with high intensity. In addition, for example, when a multi-color light emitting lamp is composed of a blue LED and a yellow LED, a blue LED that does not require complicated connection, and a heterojunction GaAs _{1-Z PZ} system that emits light with high emission intensity. A technique for constructing a multicolor light emitting lamp from a yellow LED is provided. Moreover, the light source comprised from the multicolor light emission lamp concerning this invention is provided.
[0010]
[Means for Solving the Problems]
That is, the present invention provides a multicolor light emitting lamp having the features described in the following items (1) to (5).
(1) a low-temperature buffer layer made of an amorphous or polycrystalline III-V compound semiconductor containing boron (B) (boron-containing III-V compound semiconductor) provided on the surface of a conductive substrate; A barrier layer made of a boron phosphide (BP) group III-V compound semiconductor containing boron (B) and phosphorus (P) provided on the low-temperature buffer layer; and III- provided on the barrier layer A light emitting layer composed of a V group compound semiconductor and a blue light emitting diode (LED) that emits blue band light is provided. Color light-emitting lamp.
(2) Heterojunction type that emits yellowish light comprising a light emitting layer provided on a substrate and an upper barrier layer made of a boron phosphide-based III-V compound semiconductor layer provided on the light emitting layer The multicolor light-emitting lamp described in (1) above, comprising a yellow LED.
(3) Heterojunction type that emits green band light comprising a light emitting layer provided on a substrate and an upper barrier layer made of a boron phosphide-based III-V compound semiconductor layer provided on the light emitting layer The multicolor light-emitting lamp described in (1) or (2) above, comprising a green LED.
(4) Heterojunction type that emits red band light comprising a light emitting layer provided on a substrate and an upper barrier layer made of a boron phosphide-based III-V compound semiconductor layer provided on the light emitting layer The multicolor light-emitting lamp according to any one of (1) to (3), wherein the multicolor light-emitting lamp includes a red LED.
(5) The multicolor light-emitting lamp according to any one of (1) to (4), wherein the substrate is made of a single crystal of the same conductivity type.
[0011]
The present invention also provides
(6) A light source using the multicolor light-emitting lamp described in any one of (1) to (5) above.
It is.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 schematically illustrates a cross-sectional structure of a blue LED 1A according to the first embodiment of the present invention. If an n-type or p-type conductive single crystal is used for the substrate 101, an ohmic back electrode 106 can be installed on the back surface of the substrate 101, and thus the blue LED 1A can be simply configured. A single crystal material suitable for the conductive substrate 101 includes silicon single crystal (silicon), gallium phosphide (GaP), gallium arsenide (GaAs), silicon carbide (SiC), or boron phosphide (BP) (▲ 1 ▼ J. Electrochem. Soc., 120 (1973), pp. 802 to 806, and (2) US Pat. No. 5,042,043). In particular, a low resistivity (resistivity) conductive single crystal substrate having a resistivity of 10 milliohms (mΩ) or less, more preferably 1 mΩ or less can contribute to an LED having a low forward voltage (so-called Vf). .
[0013]
A buffer layer 102 is formed on the single crystal substrate 101 to form a lower barrier layer 103 made of a boron-containing III-V compound semiconductor and having excellent crystallinity. For example, the buffer layer 102 may have a general formula 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). It can be suitably configured from a boron phosphide-based semiconductor represented by ≦ 1, 0 ≦ δ <1). Further, for example, the general formula 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), and a boron phosphide-based semiconductor containing nitrogen (N). Preferably, it is composed of a binary crystal or a ternary mixed crystal that has a small number of constituent elements and can be easily constructed. For example, monomeric boron phosphide (BP), aluminum phosphide / boron mixed crystal (B _α Al _β P: 0 <α ≦ 1, α + β = 1), boron phosphide / gallium mixed crystal (B _α Ga _δ P) : 0 <α ≦ 1, α + δ = 1), or a boron phosphide / indium mixed crystal (B _α In _{1- α} P: 0 <α ≦ 1).
[0014]
In particular, a buffer layer (low temperature buffer layer) 102 made of an amorphous or polycrystalline boron-containing group III-V compound semiconductor layer formed at a low temperature alleviates lattice mismatch between the substrate 101 and the lower barrier layer 103. Thus, the lower barrier layer 103 having a small crystal defect density such as misfit dislocation is exhibited (see the above-mentioned US Pat. No. 6,029,021). Further, when the low-temperature buffer layer 102 is composed of a boron-containing group III-V compound semiconductor containing an element (constituent element) constituting the boron-containing group III-V compound semiconductor forming the lower barrier layer 103, “growth of the constituent element” There is an advantage that the formation of a continuous lower barrier layer 103 is promoted by the action of “nucleus”. For example, an amorphous or polycrystalline B _α Al _β Ga _γ In _{1- α - β - γ} P _{1- δ} As _δ layer (0 <α ≦ 1, 0 ≦ β <1, 0 ≦ γ <1, 0 <Α + β + γ ≦ 1, 0 ≦ δ <1) is about 250 ° C. to 750 ° C. according to MOCVD method (Inst. Phys. Conf. Ser., No. 129 (see IOP Publishing Ltd., 1993), pages 157 to 162). (See US Pat. No. 6,194,744). At a low temperature of about 500 ° C. or lower, a boron-containing group III-V compound semiconductor layer mainly composed of amorphous is easily obtained. In a higher temperature range of about 500 ° C. to 750 ° C., a boron-containing group III-V compound semiconductor layer mainly composed of polycrystal is obtained. The amorphous low-temperature buffer layer 102 in the as-grown state is usually converted to a polycrystalline layer when exposed to a higher temperature environment of 750 ° C. to about 1200 ° C. Whether the buffer layer 102 is an amorphous layer or a polycrystalline layer is known from, for example, analysis of a diffraction image by a general X-ray diffraction method or electron beam diffraction method. The layer thickness of the amorphous layer or polycrystalline layer constituting the low-temperature buffer layer 102 is desirably about 1 nm to 100 nm, and more desirably 2 nm to 50 nm.
[0015]
A lower barrier layer 103 made of a boron-containing III-V compound semiconductor is provided on the buffer layer 102. The lower barrier layer 103 serving as a base layer (deposited layer) of the light emitting layer 104 is composed of boron phosphide (BP) having a band gap of 3.0 ± 0.2 eV at room temperature as a base material. The boron phosphide (BP) -based III-V group compound semiconductor layer containing boron (B) and phosphorus (P) can be suitably configured. For example, at room temperature, which is a mixed crystal of monomeric boron phosphide having a band gap of 3.0 eV at room temperature and gallium phosphide (GaP: room temperature band gap≈2.3 eV). The lower barrier layer 103 can be preferably formed from a gallium nitride phosphide mixed crystal (B _0.50 Ga _0.50 P) having a forbidden band width of about 2.7 eV. A boron phosphide layer having a high forbidden band width at room temperature can be formed by setting both the growth rate and the supply ratio of raw materials within a prescribed range. The growth rate is preferably 2 nm or more and 30 nm or less per minute. In addition to the growth rate, when the supply ratio of the group V source material to the group III material (so-called V / III ratio) is preferably set in the range of 15 to 60, it has a high forbidden bandwidth at room temperature. A boron phosphide layer can be formed. The forbidden band width is obtained, for example, from the light energy dependence of the imaginary part (ε ₂ = 2 · n · k) of the complex dielectric constant obtained from the refractive index (= n) and the extinction coefficient (= k).
[0016]
The lower barrier layer 103 made of a boron-containing III-V compound semiconductor layer lattice-matched to the buffer layer 102 at the bonding interface with the buffer layer 102 and lattice-matched to the light-emitting layer 104 on the surface on the light-emitting layer 104 side It is possible to contribute to providing a high-quality light-emitting layer 104 having a low crystal defect density such as misfit dislocation and stacking fault. The lower barrier layer 103 lattice-matched to both the buffer layer 102 and the light emitting layer 104 is, for example, a boron-containing group III-V compound semiconductor layer having a gradient in the composition of the group III or group V constituent elements. It can be configured (see Japanese Patent Laid-Open No. 2000-22211). The compositional gradient of the constituent elements can be applied in any manner that increases or decreases uniformly, stepwise, or non-linearly in the increasing direction of the layer thickness. For example, on a buffer layer 102 made of a boron phosphide / gallium mixed crystal (B _0.02 Ga _0.98 P) lattice-matched to the silicon substrate 101, gallium nitride indium (Ga _0.90 In _0.10 N: Boron phosphide / gallium composition gradient in which the boron composition ratio (= X) is linearly increased from 0.02 to 0.98 toward the bonding surface with the light emitting layer 104 having a lattice constant ≈4.557 Å) It can be composed of layers (B _α Ga _δ P: α = 0.02 → 0.98, correspondingly δ = 0.98 → 0.02).
[0017]
The light emitting layer 104 is made of, for example, a group III-V compound semiconductor such as gallium nitride indium (Ga _X In _1-X N: 0 ≦ X ≦ 1) that can emit blue-band short-wavelength visible light (the above-mentioned) (See Japanese Patent Publication No. 55-3834). Further, it can be composed of gallium nitride phosphide (GaN _1-X P _X : 0 ≦ X ≦ 1) (see Appl. Phys. Lett., 60 (20) (1992), pages 2540 to 2542). Further, it can be composed of gallium arsenide nitride (GaN _1-X As _X : 0 ≦ X ≦ 1). The light emitting layer 104 may be formed of a single or multi quantum well structure in which these III-V compound semiconductor layers are well layers.
[0018]
When the upper barrier layer 105 is provided on the light emitting layer 104, a double hetero (DH) structure type light emitting portion can be configured. The upper barrier layer 105 includes the above-described monomeric boron phosphide having a forbidden band width of 3.0 ± 0.2 eV at room temperature, and a boron phosphide (BP) system based on the boron phosphide. It can consist of a III-V compound semiconductor. Moreover, gallium nitride (GaN) or aluminum gallium nitride mixed crystal _{(Al X Ga 1-X N} : 0 <X <1) can be made of III-V compound semiconductor such as.
[0019]
In the double heterojunction (DH) structure type LED 1A according to the present invention, for example, an ohmic surface electrode 106 is provided on the upper barrier layer 105, and an ohmic back electrode 107 is disposed on the back surface of the substrate 101. And configure. When the upper barrier layer 105 is made of a boron-containing III-V group compound semiconductor, the p-type ohmic electrode can be made of, for example, a gold / zinc (Au / Zn) alloy, a gold / beryllium (Au / Be) alloy, or the like. Further, an n-type ohmic electrode can be formed from a gold alloy such as a gold / germanium (Au / Ge) alloy, a gold / indium (Au / In) alloy, and a gold / tin (Au / Sn) alloy. In order to form an electrode that exhibits good ohmic contact, the surface electrode 106 may be provided on a highly conductive contact layer. From the boron-containing group III-V compound semiconductor layer having a high forbidden band according to the present invention, a contact layer for the surface ohmic electrode 106 that also serves as a window layer that transmits light emitted in the extraction direction can be suitably configured.
[0020]
An example of a cross-sectional structure of the heterojunction yellow LED 2A according to the second embodiment of the present invention is schematically illustrated in FIG. In FIG. 2, the same components as those described in FIG. 1 are denoted by the same reference numerals.
[0021]
The heterojunction yellow LED 2 </ b> A includes an n-type or p-type conductive gallium arsenide (GaAs) single crystal as a substrate 101. The intermediate between the substrate 101 and the light emitting layer 104, to relax the lattice mismatch between the substrate 101 and the light emitting layer 104, for example, providing a composition gradient layer 108 composed of GaAs _1-Z P Z. A light-emitting layer 104 with good crystallinity can be obtained by taking measures to alleviate this lattice mismatch.
[0022]
The light emitting layer 104 is made of, for example, n-type or p-type gallium arsenide phosphide (GaAs _1-Z P _Z ). In particular, from GaAs _1-Z P _Z containing nitrogen (N) as an isoelectronic impurity, a light emitting layer 104 that is convenient for providing high intensity light emission can be formed. For example, from GaAs _0.25 P _0.75 having an arsenic (As) composition ratio (= 1-Z) of approximately 0.25, a light emitting layer that emits yellowish light having a wavelength of about 580 nm can be formed.
[0023]
The heterojunction yellow LED 2A according to the present invention is characterized in that an upper barrier layer 105 made of a boron-containing III-V group compound semiconductor is provided on the light emitting layer 104. The upper barrier layer 105 is composed of a monomeric boron phosphide (BP) having a forbidden band width of 3.0 ± 0.2 eV at room temperature or a boron phosphide (BP) -based III-III based thereon. A group V compound semiconductor can be particularly preferably configured. Further, the upper barrier layer 105 made of such a boron-containing group III-V compound semiconductor having a high forbidden band width can also act as a light-emitting transmission layer (window layer) suitable for transmitting light to the outside. Therefore, the heterojunction type yellow LED 2A with high emission intensity is brought about by the “confinement” effect of the carrier exhibited by the upper barrier layer 105 and the effect of efficiently transmitting the emitted light to the outside.
[0024]
In particular, an upper barrier layer 105 made of a boron phosphide-based III-V group compound semiconductor mainly composed of amorphous material formed at a relatively low temperature of 250 ° C. or higher and 750 ° C. or lower is heterojunctioned on the light emitting layer 104. According to the means, there is an effect of suppressing thermal deterioration of the light emitting layer 104 due to heat. That is, since the crystallinity of the light-emitting layer 104 can be maintained well, the light-emitting layer 104 that provides high-intensity light emission can be provided.
[0025]
An example of a cross-sectional structure of a heterojunction green LED 3A according to the third embodiment of the present invention is schematically illustrated in FIG. In FIG. 3, the same components as those described in FIG. 1 or 2 are denoted by the same reference numerals.
[0026]
The green LED 3 </ b> A includes an n-type or p-type conductive gallium phosphide (GaP) single crystal as a substrate 101. An n-type or p-type first gallium phosphide (GaP) layer 109 is provided on the substrate 101 by, for example, a liquid phase epitaxial (LPE) growth method. On the first GaP layer 109, for example, a second GaP layer 110 having a conductivity type opposite to that of the first GaP layer 109 is provided by an LPE method. The first and second GaP layers 109 and 110 constitute a pn junction type light emitting unit. For example, if the second GaP layer 110 is made of GaP to which nitrogen (N) is added as an isoelectronic impurity, a light emitting layer that provides high intensity light emission is provided.
[0027]
A heterojunction green LED 3A according to the present invention is a heterojunction junction LED in which an upper barrier layer 105 made of a boron phosphide III-V compound semiconductor is provided on a second GaP layer 110 serving as a light emitting layer. It is characterized by being. The heterojunction structure can be formed by providing the upper barrier layer 105 on the light emitting layer. The upper barrier layer 105 is a monomeric boron phosphide (BP) having a forbidden band width of 3.0 ± 0.2 eV at room temperature or a boron phosphide-based III-V group compound based thereon. It can be particularly preferably configured from a semiconductor. Further, the upper barrier layer 105 made of a boron phosphide-based III-V group compound semiconductor having such a high forbidden band exhibits a function of confining carriers in the light emitting layer and is suitable for transmitting light to the outside. Also acts as a transmission layer (window layer). For this reason, it can contribute to bringing about heterojunction type green LED3A of high luminous intensity.
[0028]
In particular, means for heterojunction the upper barrier layer 105 made of a boron phosphide-based III-V group compound semiconductor mainly composed of amorphous formed at a relatively low temperature of 250 ° C. or higher and 750 ° C. or lower on the light emitting layer. According to the above, there is an effect in suppressing the thermal degradation of the light emitting layer due to heat. That is, since the crystallinity of the light emitting layer can be maintained satisfactorily, there is an effect in providing a light emitting layer that provides high intensity light emission.
[0029]
The heterojunction red LED 4A according to the fourth embodiment of the present invention can be composed of a GaP LED having the cross-sectional structure illustrated in FIG. In FIG. 4, the same components as those described in FIGS. 1 to 3 are denoted by the same reference numerals.
[0030]
In the heterojunction GaP red LED 4A, the light emitting layer 104 can be configured as a p-type GaP layer to which, for example, both zinc (Zn) and oxygen (O) are added. The heterojunction type red LED 4A is formed from a boron phosphide-based III-V compound semiconductor having a conductivity type opposite to that of the light emitting layer 104 on the light emitting layer 104 obtained by vapor phase growth means such as LPE method or MOCVD method. The upper barrier layer 105 can be provided. The upper barrier layer 105 that forms a heterojunction with the light-emitting layer 104 is composed of the above-described monomeric boron phosphide (BP) having a forbidden band width of 3.0 ± 0.2 eV at room temperature or phosphorus based on it. A boron fluoride III-V compound semiconductor can be particularly suitably configured. In addition, the upper barrier layer 105 made of a boron phosphide-based III-V group compound semiconductor having such a high forbidden band exhibits the effect of confining carriers in the light emitting layer 104 and is suitable for transmitting light emission to the outside. It also acts as a light-emitting transmission layer (window layer). For this reason, it can contribute to bringing about heterojunction type red LED4A of high luminous intensity.
[0031]
In particular, an upper barrier layer 105 made of a boron phosphide-based III-V group compound semiconductor mainly composed of amorphous material formed at a relatively low temperature of 250 ° C. or higher and 750 ° C. or lower is heterojunctioned on the light emitting layer 104. According to the means, there is an effect of suppressing thermal deterioration of the light emitting layer 104 due to heat. That is, since the crystallinity of the light emitting layer 104 can be maintained satisfactorily, there is an effect in providing the light emitting layer 104 that provides high intensity light emission.
[0032]
The heterozygous red LED, for example, aluminum phosphide, gallium indium mixed crystal: emitting _{((Al X Ga 1-X} ) Y In 1-Y P 0 <X <1,0 <Y <1) It can be composed of an aluminum phosphide-gallium-indium (AlGaInP) LED as a layer (see J. Crystal Growth, 221 (2000), pages 652-656 above). The AlGaInP mixed crystal LED has an advantage that light emission with higher intensity can be obtained as compared with the GaP red LED. In particular, an ohmic electrode dispersion type AlGaInP based mixed crystal LED in which surface electrodes are dispersed on an upper barrier layer can transmit device driving current almost uniformly over the entire surface of the light emitting layer, so that high-intensity red light is emitted. (See J. Crystal Growth, 221 (2000) above).
[0033]
When the blue LED and the heterojunction yellow, green, and red LEDs 1A to 4A are composed of the conductive substrate 101 having the same conductivity type, the ohmic electrode 107 having the same polarity is formed on the back surface of the substrate 101. Can be laid. Therefore, the multicolor light-emitting lamp can be simply configured by being grounded to a pedestal having a common polarity. Moreover, the polarity of the surface electrode 106 of LED can also be unified, and a multicolor light emission lamp can be simply comprised only by the connection operation to the surface electrode of any one polarity. As a good example of the fifth embodiment of the present invention, a blue LED 1A using a boron (B) -doped p-type silicon single crystal (silicon) as a substrate 101, and a zinc (Zn) -doped p-type gallium phosphide (GaP) single crystal. Example of configuring a multicolor light emitting lamp by assembling a heterojunction green LED 3A having a substrate 101 and a heterojunction red LED 4A having a zinc (Zn) -doped p-type gallium arsenide (GaAs) single crystal as a substrate Is mentioned. Further, for example, a blue LED 1A using phosphorus (P) or antimony (Sb) -doped n-type silicon as a substrate 101 and a heterojunction yellow LED 2A using silicon (Si) -added n-type gallium arsenide as a substrate 101 are assembled. Thus, a multicolor light emitting lamp is constructed. In other words, if a so-called so-called n-side-up type LED or p-side-up type LED is used, a conventional multi-color light emitting lamp can be obtained simply by avoiding the conventional complicated wiring operation. be able to.
[0034]
The multicolor light emitting lamp 10 according to the present invention can be constituted by the following steps. As illustrated in FIG. 5, for example, an n-side-up blue LED 1A and a heterojunction yellow LED 2A are formed on a metal coating 16 plated with a metal such as silver (Ag) or aluminum (Al) on a pedestal 15. Secure with conductive bonding material. Thus, the back electrode 14 provided on the back surface of the conductive substrate 11 used for configuring the LEDs 1A and 2A is electrically connected to the pedestal 15. Further, for example, the surface electrode 13 installed on the upper barrier layer 12 of each LED 1 </ b> A, 2 </ b> A is connected to terminals 17, 18 attached to the base 15. When there is an extreme difference in light emission luminance, a dedicated terminal 17, 18 is provided for each LED 1A, 2A, and the current flowing through each LED 1A, 2A is individually adjusted to adjust the luminance. Then, color mixing is achieved conveniently and the multicolor light-emitting lamp 10 can be obtained easily.
[0035]
Further, a light source can be configured by assembling the multicolor light emitting lamps 10 according to the present invention. For example, a constant voltage drive type white light source can be configured by electrically connecting a plurality of white lamps 10 in parallel. In addition, a constant current drive type multicolor light source can be configured by electrically connecting multicolor light emitting lamps in series. Since these multicolor light sources require less power for lighting than conventional incandescent fluorescent light sources, they can be used particularly effectively as low power consumption and long-life multicolor light sources. For example, it can be used as a light source for room illumination. For example, it can be used as a multicolor light source for outdoor display or indirect illumination.
[0036]
【Example】
(First embodiment)
Silicon illustrate the present invention and a blue LED and GaAs _1-Z P _Z based multicolor light-emitting lamp which is constructed by combining the yellow LED as an example of the substrate.
[0037]
A schematic cross-sectional view of the multicolor light emitting lamp 20 according to the first embodiment is shown in FIG. The multi-color light emitting lamp 20 is configured by assembling one blue LED 1A and two yellow LEDs 2A in order to balance the emission intensity of blue band light and yellow band light.
[0038]
In the blue LED 1A, the layered structure in which the functional layers described in the items (2) to (5) are sequentially stacked on the substrate 101 described in the following item (1) is combined with the items (6) to (7). The n-side-up type LED which arrange | positioned and comprised the ohmic surface and back surface electrode as described in 1 was used.
(1) Boron (B) doped p-type (111) -Si single crystal substrate 101
(2) Triethyl boron ((C ₂ H ₅ ) ₃ B) / phosphine (PH ₃ ) / hydrogen (H ₂ ) system grown at 350 ° C. by atmospheric pressure MOCVD, with a layer thickness of 5 nm. Buffer layer 102 made of boron (BP)
(3) Using the above MOCVD vapor phase growth means, p-type boron phosphide (mainly p-type boron phosphide) doped from magnesium (Mg) at 850 ° C. and consisting mainly of {110} crystal planes arranged substantially parallel to the surface of the substrate 101. BP) lower barrier layer 103 (carrier concentration≈4 × 10 ¹⁸ cm ⁻³ , layer thickness≈700 nm)
(4) Light-emitting layer 104 mainly composed of cubic n-type Ga _0.94 In _0.06 N layer (lattice constant = 4.538Å) (carrier concentration≈3 × 10 ¹⁷ cm ⁻³ , layer thickness≈180 nm)
(5) An upper barrier made of an amorphous n-type boron phosphide (BP) layer grown at 400 ° C. by the MOCVD reaction system and having a forbidden band width of 3.1 eV at room temperature. Layer 105 (carrier concentration≈8 × 10 ¹⁶ cm ⁻³ , layer thickness≈480 nm)
(6) Ohmic surface electrode 106 made of a gold / germanium (Au · Ge) circular electrode (diameter = 120 μm) disposed in the center of the upper barrier layer 105
(7) Ohmic back electrode 107 made of aluminum (Al) provided on substantially the entire back surface of the p-type Si substrate 101.
[0039]
Moreover, LED which exhibits the characteristic as described in the following (a)-(d) term was utilized for blue-type LED1A.
(A) Emission center wavelength: 430 nm
(B) Luminance: 6 millicandela (mcd)
(C) Forward voltage: 3 volts (V) (forward current = 20 mA (mA))
(D) Reverse voltage: 8 V (reverse current = 10 μA)
[0040]
The yellow LED 2A has a laminated structure in which the functional layers described in the items (2) to (4) are sequentially laminated on the substrate 101 described in the following item (1), and the items (5) and (6). The n-side-up type LED in which the ohmic front and back electrodes described in 1 are arranged is used.
(1) Zinc (Zn) doped p-type (100) -GaAs single crystal substrate 101
(2) Zn-doped p-type GaAs _{1-Z PZ} composition gradient layer grown at 720 ° C. by gallium (Ga) / arsine (AsH ₃ ) / hydrogen (H ₂ ) hydride vapor phase epitaxy (VPE) method (Carrier concentration≈1 × 10 ¹⁸ cm ⁻³ , layer thickness = 15 μm) 108
(3) Silicon (Si) -doped n-type GaAs _0.25 P _0.75 light emitting layer 104 grown at 720 ° C. using nitrogen (N) as an isoelectronic impurity by using the hydride VPE means.
(4) Grown at 400 ° C. by (C ₂ H ₅ ) ₃ B / PH ₃ / H ₂ MOCVD reaction system, n-type mainly composed of amorphous material having a forbidden band width of 2.7 eV at room temperature Upper barrier layer 105 composed of a boron arsenide phosphide (BP _0.95 As _0.05 ) layer (carrier concentration≈4 × 10 ¹⁸ cm ⁻³ , layer thickness≈750 nm)
(5) Ohmic surface electrode 106 made of a gold / germanium (Au · Ge) circular electrode (diameter = 120 μm) disposed in the center of the upper barrier layer 105
(6) Ohmic back electrode 107 made of gold / zinc (Au / Zn) provided on substantially the entire back surface of the p-type GaAs substrate 101
[0041]
Moreover, LED which exhibits the characteristic as described in the following (a)-(d) term was utilized for 2A of yellow LED.
(A) Emission center wavelength: 580 nm
(B) Luminance: 3 millicandela (mcd)
(C) Forward voltage: 2 volts (V) (forward current = 20 mA (mA))
(D) Reverse voltage: 5 V (reverse current = 10 μA)
[0042]
The multicolor light emitting lamp 20 in which the square blue LED 1A and the yellow LED 2A each having a side of 300 μm were assembled was formed through the steps described in the following (A) to (C).
(A) Step of fixing the p-type back electrodes 107 of the LEDs 1A and 2A to the common base 15 by using, for example, a chip-on-board means using a conductive adhesive (B) LED 1A A process of individually connecting each of the 2A n-type surface electrodes 106 to the two terminals 17 and 18 electrically insulated from the base 15 by wedge bonding means or ball bonding means. ]
Since the multicolor light emitting lamp 20 is configured by individually connecting the LEDs 1A and 2A, it can be used as a blue single light lamp. Alternatively, it can be used as a lamp that emits a single light of a yellow band. In addition, if a blue LED 1A and a yellow LED 2A are energized simultaneously, a multicolor lamp that can be used as a white lamp is provided.
[0044]
(Second embodiment)
The present invention will be described in detail by taking as an example the case of constructing an RGB type multicolor light emitting lamp including a blue LED having a silicon substrate.
[0045]
The structure of the multicolor light emitting lamp 30 according to the second embodiment is shown in a schematic cross-sectional view of FIG. The RGB type multicolor light emitting lamp 30 is configured by combining the blue LED 1A described in the first embodiment, the heterojunction type GaP green LED 3A, and the heterojunction type AlGaAs red LED 4A.
[0046]
The blue LED 1A is formed by laminating the functional layers described in the items (2) to (5) in order on the substrate 101 described in the item (1) below, (6) to (7) The ohmic front and back electrodes described in 1 were arranged. The p-side-up blue LED 1A according to the second embodiment includes a double hetero (DH) junction type LED having the same light emission characteristics as the first embodiment and the n-side-up blue LED 1A. Using.
(1) Phosphorus (P) doped n-type (100) -Si single crystal substrate 101
(2) Triethyl boron ((C ₂ H ₅ ) ₃ B) / phosphine (PH ₃ ) / hydrogen (H ₂ ) substrate grown at 400 ° C. by atmospheric pressure MOCVD method, substrate 101 having a layer thickness of 15 nm Buffer layer 102 made of n-type boron phosphide / indium mixed crystal (B _0.33 In _0.67 P) lattice-matched to the Si single crystal (lattice constant≈5.431４３) constituting
(3) Using the above-described MOCVD vapor phase growth means, silicon (Si) is doped at 850 ° C., and the n-type boron phosphide mainly composed of {110} crystal planes arranged substantially parallel to the surface of the substrate 101 Lower barrier layer 103 (carrier concentration≈1 × 10 ¹⁸ cm ⁻³ , layer thickness≈560 nm) composed of an indium (B _X In _1-X P: X = 0.33 → 0.98) composition gradient layer. The boron (B) composition ratio (= X) of the boron phosphide / indium (B _X In _1-X P) composition gradient layer is set to X = 0.33 at the bonding interface with the buffer layer 102 and bonded to the light emitting layer 104. 0.98 at the surface to be used.
(4) Luminescent layer 104 mainly composed of cubic n-type Ga _0.90 In _0.10 N (lattice constant≈4.557Å) layer (carrier concentration≈4 × 10 ¹⁷ cm ⁻³ , layer thickness≈150 nm)
(5) Magnesium (Mg) -doped p-type boron phosphide / indium (B) mainly composed of amorphous material, grown at 400 ° C. by the MOCVD reaction system and having a band gap at room temperature of 3.1 eV. _0.98 In _0.02 P: lattice constant≈4.557Å) upper barrier layer 105 (carrier concentration≈2 × 10 ¹⁹ cm ⁻³ , layer thickness≈400 nm)
(6) Ohmic surface electrode 106 made of a gold / zinc (Au / Zn) circular electrode (diameter = 130 μm) disposed in the center of the upper barrier layer 105
(7) Ohmic back electrode 107 made of aluminum (Al) provided on substantially the entire back surface of the n-type Si substrate 101.
[0047]
As a heterojunction type GaP-based green LED 3A, a laminated structure in which the functional layers described in the items (2) and (3) are sequentially stacked on the substrate 101 described in the item (1) below, (4) and A p-side-up single hetero (SH) junction type LED configured by arranging the ohmic front and back electrodes described in the section (5) was used.
(1) Silicon (Si) doped n-type (100) 2 ° off-GaP single crystal substrate 101
(2) Nitrogen (N) 6 as an isoelectronic trap grown at 800 ° C. by a general liquid phase epitaxial (LPE) method (see “III-V compound semiconductor” above, pages 253 to 256). Light emitting layer 104 made of silicon (Si) -doped n-type GaP added at an atomic concentration of × 10 ¹⁸ cm ⁻³
(3) Upper barrier made of amorphous p-type boron phosphide (BP) layer grown at 380 ° C. by the above MOCVD reaction system and having a forbidden band width of 3.0 eV at room temperature Layer 105 (carrier concentration≈3 × 10 ¹⁹ cm ⁻³ , layer thickness≈400 nm)
(4) Ohmic surface electrode 106 made of a gold / beryllium (Au · Be) circular electrode (diameter = 110 μm) disposed in the center of the upper barrier layer 105
(5) Ohmic back electrode 107 made of gold / germanium alloy (Au 95 wt% / Ge 5 wt%) provided on substantially the entire back surface of the n-type GaP substrate 101.
[0048]
Moreover, LED which exhibits the characteristic as described in the following (a)-(d) term was utilized for heterojunction type GaP green type LED3A.
(A) Emission center wavelength: 555 nm
(B) Luminance: 5 millicandela (mcd)
(C) Forward voltage: 2 volts (V) (forward current = 20 mA (mA))
(D) Reverse voltage: 5 V (reverse current = 10 μA)
[0049]
The heterojunction red LED 4A includes an n-type aluminum arsenide / gallium (AlGaAs) light-emitting layer 104 and a p-type boron phosphide (BP) using a silicon (Si) -doped n-type (100) -Si single crystal as a substrate 101. A pn junction type LED with an upper barrier layer 105 made of a layer was used. The main characteristics of the p-side-up red LED 4A are described below.
(A) Emission center wavelength: 660 nm
(B) Luminance: 8 milli candela (mcd)
(C) Forward voltage: 2 volts (V) (forward current = 20 mA (mA)
(D) Reverse voltage: 5 V (reverse current = 10 μA)
[0050]
A square blue LED 1A having a side of about 250 μm, a heterojunction green LED 3A, and a heterojunction red LED 4A are assembled through the following steps (A) to (C) to obtain RGB multicolor A light emitting lamp 30 was constructed.
(A) Step of fixing the n-type back electrodes 107 of the LEDs 1A, 3A, 4A to the common base 15 by using, for example, a chip-on-board means using a conductive adhesive (B ) The p-type surface electrodes 106 of the LEDs 1A, 3A, and 4A are individually connected to the three terminals 17 to 19 that are electrically insulated from the pedestal 15 by wedge bonding means or ball bonding means. Process to do [0051]
Since the multicolor light emitting lamp 30 is configured by individually connecting the LEDs 1A, 3A, and 4A, it can be used as a single light lamp of a blue band, a green band, or a red band. In particular, since the lamp 30 of the second embodiment uses a heterojunction type GaP-based LED 3A using a boron-containing III-V group semiconductor layer, it can be used as a lamp that emits a single light of a high-brightness green band. It was available. . Further, since the LEDs 1A, 3A, and 4A are individually connected, the forward currents flowing through the LEDs can be individually adjusted, so that mixed color light of each of the RGB emission colors can be generated. Moreover, the RGB type multicolor light-emitting lamp 30 capable of emitting white light is provided by simultaneously lighting the LEDs 1A, 3A, and 4A.
[0052]
(Third embodiment)
The contents of the present invention will be described by taking as an example the case where the RGB type multicolor light emitting lamps 30 described in the second embodiment are assembled to form a light source.
[0053]
The light source 40 according to the present invention is configured, for example, by regularly arranging the plan view of the RGB type multicolor light emitting lamp 30 at regular intervals as schematically shown in FIG. If wiring that allows the forward current to be individually controlled through the terminals 18 of the lamps 30 arranged is provided, chromaticity can be adjusted, and a multicolor lamp for display (display) use or the like can be configured.
[0054]
【The invention's effect】
According to the present invention, a heterojunction type light emitting device having a boron phosphide-based III-V compound semiconductor layer as a barrier layer, for example, a heterojunction type GaP green LED, or a heterojunction type GaAs _1-Z P _Since the multi-color light-emitting lamp and the light source are configured using the _Z- based LED, for example, an RGB mixed color multi-color light-emitting lamp that provides high-intensity light emission can be provided.
[0055]
Further, according to the present invention, a light emitting element that emits blue band light, for example, a boron-containing III-V compound semiconductor layer, which is configured by using a conductive substrate material and providing an electrode on the back surface of the substrate is provided. Since the multi-color light emitting lamp and the light source are configured using the blue LED, a high-intensity multi-color light emitting lamp and the light source can be provided with an easy connection (bonding) operation.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of a blue LED according to the present invention.
FIG. 2 is a schematic cross-sectional view of a heterojunction yellow LED according to the present invention.
FIG. 3 is a schematic sectional view of a heterojunction green LED according to the present invention.
FIG. 4 is a schematic cross-sectional view of a heterojunction red LED according to the present invention.
FIG. 5 is a schematic cross-sectional view of a multicolor light emitting lamp according to the present invention.
FIG. 6 is a schematic cross-sectional view of a multicolor light emitting lamp according to the first embodiment.
FIG. 7 is a schematic sectional view of a multicolor light emitting lamp according to a second embodiment.
FIG. 8 is a plan view showing a configuration of a light source using a multicolor light emitting lamp according to a third embodiment.
[Explanation of symbols]
1A, 2A, 3A, 4A LED
10, 20, 30 Multicolor light emitting lamp 40 Light source 11 Substrate 12 Upper barrier layer 13 Front electrode 14 Back electrode 15 Base 16 Metal coating 17, 18, 19 Terminal 101 Single crystal substrate 102 Buffer layer 103 Lower barrier layer 104 Light emitting layer 105 Upper part Barrier layer 106 Front electrode 107 Back electrode 108 Composition gradient layer 109 First GaP layer 110 Second GaP layer

Claims (5)

A low-temperature buffer layer made of an amorphous or polycrystalline III-V group compound semiconductor containing boron (B) (boron-containing group III-V compound semiconductor) provided on a conductive substrate surface; A barrier layer made of a boron phosphide (BP) group III-V compound semiconductor containing boron (B) and phosphorus (P) provided on the layer, and a group III-V compound provided on the barrier layer A blue light emitting diode (LED) that emits blue band light comprising a light emitting layer made of a semiconductor, a light emitting layer provided on a substrate, and a boron phosphide-based III- provided on the light emitting layer A multicolor light emitting lamp comprising a heterojunction yellow LED that emits yellowish light comprising an upper barrier layer made of a group V compound semiconductor layer . A low-temperature buffer layer made of an amorphous or polycrystalline III-V group compound semiconductor containing boron (B) (boron-containing group III-V compound semiconductor) provided on a conductive substrate surface; A barrier layer made of a boron phosphide (BP) group III-V compound semiconductor containing boron (B) and phosphorus (P) provided on the layer, and a group III-V compound provided on the barrier layer A blue light emitting diode (LED) that emits blue band light comprising a light emitting layer made of a semiconductor, a light emitting layer provided on a substrate, and a boron phosphide-based III- provided on the light emitting layer A multicolor light-emitting lamp including a heterojunction green LED that emits green band light including an upper barrier layer made of a group V compound semiconductor layer . A low-temperature buffer layer made of an amorphous or polycrystalline III-V group compound semiconductor containing boron (B) (boron-containing group III-V compound semiconductor) provided on a conductive substrate surface; A barrier layer made of a boron phosphide (BP) group III-V compound semiconductor containing boron (B) and phosphorus (P) provided on the layer, and a group III-V compound provided on the barrier layer A blue light emitting diode (LED) that emits blue band light comprising a light emitting layer made of a semiconductor, a light emitting layer provided on a substrate, and a boron phosphide-based III- provided on the light emitting layer A multicolor light-emitting lamp including a heterojunction red LED that emits red band light including an upper barrier layer made of a group V compound semiconductor layer . 4. The multicolor light-emitting lamp according to claim 1 , wherein the substrate is made of a single crystal having the same conductivity type. A light source using the multicolor light-emitting lamp according to claim 1 .

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