USOO7479731B2
(12) United States Patent (10) Patent No.: US 7479,731 B2 Udagawa (45) Date of Patent: Jan. 20, 2009
(54) MULTICOLOR LIGHT-EMITTING LAMP (58) Field of Classification Search ...... 313/409 AND LIGHT SOURCE See application file for complete search history. (75) Inventor: Takashi Udagawa, Chichibu (JP) (56) References Cited (73) Assignee: Showa Denko K.K., Tokyo (JP) U.S. PATENT DOCUMENTS 4.322,735 A 3/1982 Sadamasa et al...... 257/89 (*) Notice: Subject to any disclaimer, the term of this 4,929,866 A * 5, 1990 Murata et al...... 313,500 patent is extended or adjusted under 35 5,005,057 A 4/1991 Izumiya et al. U.S.C. 154(b) by 206 days. 5,042,043 A 8, 1991 Hatano et al. 5,324.962 A 6/1994 Komoto et al. 21) Appl. No.: 10/486,985 (21) App 9 (Continued) (22) PCT Filed: Aug. 16, 2002 FOREIGN PATENT DOCUMENTS (86). PCT No.: PCT/UP02/08317 DE 19734034 A1 2, 1998 S371 (c)(1), (Continued) (2), (4) Date: Feb. 18, 2004 Primary Examiner Sikha Roy (87) PCT Pub. No.: WO03/017387 Assistant Examiner Natalie KWalford (74) Attorney, Agent, or Firm Sughrue Mion, PLLC PCT Pub. Date: Feb. 27, 2003 (57) ABSTRACT (65) Prior Publication Data The present invention provides a technique for fabricating a US 2004/O183089 A1 Sep. 23, 2004 multicolor light-emitting lamp by using a blue LED having a structure capable of avoiding cumbersome bonding. In par Related U.S. Application Data ticular, the present invention provides a technique for fabri (60) Provisional application No. 60/323,088, filed on Sep. cating a multicolor light-emitting lamp by using a hetero 19, 2001. junction type GaP-base LED capable of emitting high intensity green light in combination. Also, for example, in (30) Foreign Application Priority Data fabricating a multicolor light-emitting lamp from the blue Aug. 20, 2001 (JP) ...... 2001-24.8455 LED and the yellow LED, the present invention provides a technique for fabricating a multicolor light-emitting lamp (51) Int. Cl. from a blue LED requiring no cumbersome bonding and a HOL L/62 (2006.01) hetero-junction type GaAS2P-base yellow LED of emitting HOI 63/04 (2006.01) light having high light emission intensity. (52) U.S. Cl...... 313/499; 313/500; 313/501; 313/483 15 Claims, 4 Drawing Sheets
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U.S. PATENT DOCUMENTS GB 2316226 A 2, 1998 JP 54-33748 A 3, 1979 5,375,043 A * 12/1994 Tokunaga ...... 362/601 p. 2-288388 11, 1990 5,886,367 A 3/1999 Udagawa JP 4-209584 7, 1992 6,069,021 A * 5/2000 Terashima et al...... 257/13 JP 5-283744 A 10, 1993 6,110,757 A 8/2000 Udagawa JP 10-562O2 2, 1998 6,220,722 B1* 4/2001 Begemann ...... 362.231 10-242567 9, 1998 6,936,863 B2 * 8/2005 Udagawa et al...... 438/47 7,030.003 B2 * 4/2006 Udagawa ...... 438/604 JP 2000-12896. A 1, 2000 JP 2000-584.51 2, 2000 FOREIGN PATENT DOCUMENTS EP 395392 A2 10, 1990 * cited by examiner U.S. Patent Jan. 20, 2009 Sheet 1 of 4 US 7479,731 B2 Fig. 1 N-106
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18 4A o oooooooo oo o o o US 7,479,731 B2 1. 2 MULTICOLOR LIGHT-EMITTING LAMP single crystal) as the Substrate material (see, III Zoku AND LIGHT SOURCE Chikkabutsu Handotai (Group III Nitride Semiconductor), pages 243 to 252, Supra). Since a current (operating current) This application claims benefit of Provisional Application for driving the LED cannot be passed through the insulating No. 60/323,088 filed Sep.19, 2001, the disclosure of which is 5 crystal Substrate, both of positive and negative electrodes are incorporated herein by reference. disposed in the same surface side of the substrate. On the TECHNICAL FIELD other hand, the homo-junction type GaP-base or homo-junc tion type GaAS2P-base LED is fabricated by using an The present invention relates to a technique for fabricating 10 electrically conducting gallium phosphide (GaP) single crys a multicolor light-emitting lamp which uses a plurality of tal or gallium arsenide (GaAs) single crystal and therefore, light-emitting diodes (LED) and can emit multiple colors only one electrode having either positive polarity or negative different in the wavelength. polarity is disposed in the surface side (see, Handotai Device BACKGROUND ART Gairon (Outline of Semiconductor Device), page 117, supra). 15 In any case, when an RGB three color integration-type A technique of fabricating an RGB-type multicolor light white lamp is fabricated by using conventional Gan N emitting lamp by adjacently disposing light-emitting diodes (0sXs 1)-base blue, green and red LEDs each comprising an (LED) capable of emitting each color of red light (R), green insulating crystal Substrate, both electrodes of positive polar light (G) and blue light (B) which are the three primary colors ity and negative polarity are disposed on the Surface of each oflight has been heretofore known. For example, a technique LED, therefore, wire bonding to electrodes of one polarity of fabricating an RGB-type multicolor light-emitting lamp by and wire bonding to electrodes of another polarity must be integrating an LED (blue LED) of emitting blue band light separately performed and this is cumbersome. If the polarity having a light emission wavelength of 450 nm, a green LED of the electrodes to be bonded can be unified to either positive of emitting green band light having a light emission wave 25 length of around 525 nm and a red LED of emitting redband or negative by making use of an electrically conducting Sub light having a light emission wavelength of approximately strate, particularly an electrically conducting Substrate hav from 600 to 700 nm is known (see, Display Gijutsu (Display ing the same conductivity, the cumbersome bonding can be Technique), 1st ed., 2nd imp., pages 100 to 101, Kyoritsu avoided. Shuppan (Sep. 25, 1998)). 30 In recent years, a technique of fabricating a blue LED by Conventionally, a multicolor light-emitting lamp is fabri using a boron-containing group III-V compound semicon cated by using a Gan N-base blue LED (see, JP-B-55 ductor layer and a light-emitting layer composed of a group 3834) where the light-emitting layer is composed of a group III-V compound semiconductor, which are provided on an III-V compound semiconductor Such as gallium indium electrically conducting silicon single crystal (silicon), is dis nitride (Galin N: 0s)xs1) (see, III Zoku Chikkabutsu 35 closed (see, U.S. Pat. No. 6,069,021). If a blue LED using an Handotai (Group III Nitride Semiconductor), pages 252 to electrically conducting Substrate having the same conductiv 254, Baifukan (Dec. 8, 1999)). For the green LED, a Ga ity as the substrate used for the fabrication of a green or red In N green LED or a homo-junction type GaP green LED, LED is used, an RGB-type multicolor light-emitting lamp can which has gallium phosphide as a light-emitting layer, is used be readily fabricated without incurring cumbersome bonding (see, (1) III Zoku Chikkabutsu Handotai (Group III Nitride 40 operation as in conventional techniques. Semiconductor), pages 249 to 252, supra, and (2) III-V Zoku Kagobutsu Handotai (Group III-V Compound Semiconduc On the other hand, the GaP-base or GaAsP-base LED tor), 1st ed., pages 253 to 261, Baifukan (May 20, 1994)). For constituting the multicolor light-emitting lamp together with the red LED, an LED having a light-emitting layer composed the Gal-In-N-base blue LED has a homo-junction type of a group III-V compound semiconductor Such as aluminum 45 structure. Therefore, the light emission intensity of the GaP gallium arsenide mixed crystal (AlGaAS: 0indium phosphide ((AlGa). In-P: In N (0sXs 1) double hetero (DH)-junction type LED, OsXs 1, 0DISCLOSURE OF THE INVENTION DESCRIPTION OF NUMERICAL REFERENCES More specifically, the present invention provides a multi 1A, 2A, 3A4A LED color light-emitting lamp having the characteristics described 10, 20, 30 multicolor light-emitting lamp in the following (1) to (5): 40 light source (1) a multicolor light-emitting lamp fabricated by dispos 10 11 substrate ing a plurality of LEDs in combination, wherein a blue light 12 upper barrier layer emitting diode (LED) of emitting blue band light is disposed 13 surface electrode and the blue light-emitting diode comprises a low-tempera 14 back-surface electrode ture buffer layer composed of an amorphous or polycrystal 15 pad line boron-containing group III-V compound semiconductor 15 16 metal film and provided on an electrically conducting Substrate surface, 17, 18, 19 terminal a barrier layer composed of a boron phosphide (BP)-base 101 single crystal substrate group III-V compound semiconductor containing boron (B) 102 buffer layer and phosphorus (P) and provided on the low-temperature 103 lower barrier layer buffer layer, and a light-emitting layer composed of a group 104 light-emitting layer III-V compound semiconductor and provided on the barrier 105 upper barrier layer layer; 106 surface electrode (2) the multicolor light-emitting lamp as described in (1) 107 back-surface electrode above, wherein a hetero-junction type yellow LED of emit 108 compositional gradient layer ting yellow band light is disposed and the yellow LED com 25 109 first GaPlayer prises a light-emitting layer provided on a Substrate and an 110 second GaPlayer upper barrier layer composed of a boron phosphide-base group III-V compound semiconductor layer and provided on BEST MODE FOR CARRYING OUT THE the light-emitting layer, INVENTION (3) the multicolor light-emitting lamp as described in (1) or 30 (2) above, wherein a hetero-junction type green LED of emit FIG. 1 is a view schematically showing the cross-sectional ting green band light is disposed and the green LED com structure of a blue LED1A according to the first embodiment prises a light-emitting layer provided on a Substrate and an of the present invention. When an electrically conducting upper barrier layer composed of a boron phosphide-base single crystal having an n-type or p-type conductivity is used group III-V compound semiconductor layer and provided on 35 for the substrate 101, an ohmic back-surface electrode 106 the light-emitting layer, can be disposed on the back surface of the substrate 101 and (4) the multicolor light-emitting lamp as described in any therefore, a blue LED1A can be readily fabricated. Examples one of (1) to (3) above, wherein a hetero-junction type red of the single crystal material which is suitably used as the LED of emitting red band light is disposed and the red LED electrically conducting substrate 101 include semiconductor comprises a light-emitting layer provided on a Substrate and 40 single crystals such as silicon single crystal (silicon), gallium an upper barrier layer composed of a boron phosphide-base phosphide (GaP), gallium arsenide (GaAs), silicon carbide group III-V compound semiconductor layer and provided on (SiC) and boron phosphide (BP) (see, (1) J. Electrochem. the light-emitting layer, and Soc., 120, pages 802 to 806 (1973), and (2) U.S. Pat. No. (5) the multicolor light-emitting lamp as described in any 5,042,043). In particular, an electrically conducting single one of (1) to (4) above, wherein the substrate is formed of a 45 crystal Substrate having a low specific resistance (resistivity) single crystal having the same conduction type. of 10 m2 cm or less, preferably 1 mS2 cm or less, can con The present invention also provides: tribute toward providing an LED having a low forward volt (6) a light source using the multicolor light-emitting lamp age (so-called Vf). described in any one of (1) to (5) above. On the single crystal substrate 101, a buffer layer 102 50 composed of a boron-containing group III-V compound BRIEF DESCRIPTION OF DRAWINGS semiconductor is provided for forming a lower barrier layer 103 having excellent crystallinity. The buffer layer 102 can be FIG. 1 is a schematic sectional view of a blue LED accord Suitably composed of, for example, a boron phosphide-base ing to the present invention. semiconductor represented by the formula B.AlGa, 55 In-P-Ass (wherein 00.98 and being amorphous is readily obtained. In the high temperature correspondingly thereto 6-0.98->0.02) where the boron region of approximately from 500 to 750° C., a boron-con 25 composition ratio (=O) is linearly increased from 0.02 to 0.98 taining group III-V compound semiconductor layer mainly from the junction face with the buffer layer 102 toward the comprising polycrystalline is obtained. A low-temperature junction face with the light-emitting layer 104 composed of buffer layer 102 which is amorphous in the as-grown state is, gallium indium nitride (Gao. In N: lattice constant about when exposed to a high temperature environment of 750 to 4.557 A). about 1200° C., usually converted into a polycrystalline 30 The light-emitting layer 104 is composed of for example, layer. Whether the buffer layer 102 is an amorphous layer or a group III-V compound semiconductor Such as gallium a polycrystalline layer can be known, for example, by the indium nitride (Gan N: 0s)xS 1), which can emit short analysis of a diffraction pattern according to general X-ray wavelength visible light in the blue band (see, JP-B-55-3834. diffraction or electron beam diffraction method. The layer Supra). The light-emitting layer 104 can also be composed of thickness of the amorphous or polycrystalline layer constitut 35 gallium nitride phosphide (GaN. P. OsXs 1) (see, Appl. ing the low-temperature buffer layer 102 is preferably from Phys. Lett., 60 (20), pages 2540 to 2542 (1992)). Further about 1 nm to 100 nm, more preferably from 2 to 50 nm. more, the light-emitting layer 104 can be composed of gal On the buffer layer 102, a lower barrier layer 103 com lium nitride arsenide (GaNAS: 0s)xs 1). The light-emit posed of a boron-containing group III-V compound semicon ting layer 104 can be constructed by a single- or multi ductor is provided. The lower barrier layer 103 as an under 40 quantum well structure having the above-described group lying layer (a layer on which a light-emitting layer 104 is III-V compound semiconductor layer as the well layer. deposited) of a light-emitting layer 104 is preferably com When an upper barrier layer 105 is provided on the light posed of a boron phosphide (BP)-base group III-V compound emitting layer 104, a double hetero (DH) structure type light semiconductor layer containing boron (B) and phosphorus emitting part can be constructed. The upper barrier layer 105 (P), which is formed by using a boron phosphide (BP) having 45 can be composed of the above-described monomer boron a band gap at room temperature of 3.0+0.2 eV as a matrix phosphide (boron monophosphide) having a band gap at material. For example, the lower barrier layer 103 can be room temperature of 3.0+0.2 eV or a boron phosphide (BP)- Suitably composed of a boron gallium phosphide mixed crys base group III-V compound semiconductor using this boron tal (BosGasoP) having a band gap at room temperature of monophosphide as a matrix component. The upper barrier about 2.7 eV, which is a mixed crystal of monomer boron 50 layer 105 can also be composed of a group III-V compound phosphide (boron monophosphide) having a band gap at semiconductor Such as gallium nitride (GaN) or aluminum room temperature of 3.0 eV and gallium phosphide (GaP. gallium nitride mixed crystal (Al-GalN: 0phosphine (PH)/hydrogen (H). and a hetero-junction type yellow LED 2A using a silicon (3) A lower barrier layer 103 (carrier concentration: about (Si)-doped n-type gallium arsenide as the substrate 101. In 4x10" cm, layer thickness: about 700 nm) composed of other words, when LEDs unified to either so-called n-side up p-type boron phosphide (BP) mainly comprising (110) crys type or p-side up type are used, a multicolor light-emitting tal planes oriented almost in parallel on the surface of the lamp can be readily obtained while avoiding a cumbersome 50 bonding operation as in conventional techniques. substrate 101, which was doped with magnesium (Mg) at The multicolor light-emitting lamp 10 according to the 850° C. using the above-described MOCVD gas phase present invention can be fabricated through the following growth method. steps. As shown in FIG. 5, for example, an n-side up type blue (4) A light-emitting layer 104 (carrier concentration: about LED1A and a hetero-junction type yellow LED2A are fixed 55 3x10'7 cm, layer thickness: about 180 nm) mainly com to a metal film 16 on a pad 15 plated with a metal such as silver posed of a cubic n-type Gao InooN layer (lattice constant: (Ag) or aluminum (Al), using an electrically conducting 4.538 A). adhesive material. Back-surface electrodes 14 provided on (5) An upper barrier layer 105 (carrier concentration: about respective back Surfaces of electrically conducting Substrates 8x10" cm, layer thickness: about 480 nm) composed of an 11 used for fabricating LEDs 1A and 2A are electrically 60 n-type boron phosphide (BP) layer with the major part being connected to the pad 15. Also, surface electrodes 13 disposed, amorphous, having a bandgap at room temperature of 3.1 eV. for example, on respective upper barrier layers 12 of LEDs which was grown at 400° C. by the above-described MOCVD 1A and 2A are connected to terminals 17 and 18 attached to reaction system. the pad 15. In the case of causing an excessively large differ (6) An ohmic Surface electrode 106 composed of a gold.g- ence in luminous emission intensity, terminals 17 and 18 65 ermanium (Au.Ge) circular electrode (diameter: 120 um), exclusive to respective LEDs 1A and 2A may be individually which was disposed in the center of the upper barrier layer provided to employ a mechanism capable of adjusting the 105. US 7,479,731 B2 11 12 (7) An ohmic back-surface electrode 107 composed of Example 2 aluminum (Al), which was provided almost throughout the back surface of the p-type Si substrate 101. The present invention is described in detail below by refer The blue LED 1A used was an LED exhibiting the follow ring to the case of fabricating an RGB-type multicolor light ing properties (a) to (d): emitting lamp containing a blue LED using a silicon Sub (a) Light emission center wavelength: 430 nm. Strate. (b) Luminance: 6 millicandela (mcd) (c) Forward voltage: 3 volt (V) (forward current: 20 milli FIG. 7 is a schematic sectional view showing the construc ampere (mA)) tion of the multicolor light-emitting lamp 30 according to 10 Example 2. The RGB-type multicolor light-emitting lamp 30 (d) Reverse voltage: 8 V (reverse current: 10 LA) was fabricated by combining the blue LED 1A described in The yellow LED 2A used was an n-side up type LED Example 1, a hetero-junction type GaP green LED 3A and a fabricated by disposing ohmic Surface and back-Surface elec trodes described in (5) and (6) below on a stacked layer hetero-junction type AlGaAs red LED 4A. structure where functional layers described in (2) to (4) below The blue LED 1A was fabricated by disposing ohmic sur were stacked in sequence on a substrate 101 described in (1) 15 face and back-surface electrodes described in (6) and (7) below. below on a stacked layer structure where functional layers (1) A zinc (Zn)-doped p-type (100)-GaAs single crystal described in (2) to (5) below were stacked in sequence on a Substrate 101. substrate 101 described in (1) below. The p-side up type blue (2) A Zn-doped p-type GaAsP compositional gradient LED 1A of Example 2 was a double hetero (DH)-junction layer (carrier concentration: about 1x10" cm, layer thick type LED exhibiting the same light emitting properties as the ness: 15um) 108 grown at 720° C. by a hydride vapor phase n-side up type blue LED 1A of Example 1. epitaxy (VPE) method using a system of gallium (Ga)/arsine (1) A phosphorus (P)-doped n-type (100)-Si single crystal (ASH)/hydrogen (H2). Substrate 101. (3) A silicon (Si)-doped n-type GaAsPozs light-emit 25 (2) A buffer layer 102 composed of an n-type boron indium ting layer 104, which was grown at 720° C. by using the phosphide mixed crystal (Bo Ino,P) lattice-matching with above-described hydride VPE means and doped with nitro the Sisingle crystal (lattice constant: about 5.431 A) consti gen (N) as an isoelectronic impurity. tuting the substrate 101, which was grown to a layer thickness (4) An upper barrier layer 105 (carrier concentration: about of 15 nm at 400° C. by an atmospheric pressure MOCVD 4x10" cm, layer thickness: about 750 nm) composed of an 30 method using a system of triethylboran ((CHS),B)/phos n-type boron phosphide arsenide (BPosAsolos) layer with phine (PH)/hydrogen (H). the major part being amorphous, having a band gap at room (3) A lower barrier layer 103 (carrier concentration: about temperature of 2.7 eV, which was grown at 400° C. by the 1x10" cm, layer thickness: about 560 nm) composed of an MOCVD using a reaction system of (CHs).B/PH/(H). n-type boron indium phosphide (B-In-P: X=0.33->0.98) (5) An ohmic surface electrode 106 composed of a gold.g- 35 mainly comprising (110) crystal planes oriented almost in ermanium (Au.Ge) circular electrode (diameter: 120 um), parallel on the surface of the substrate 101, which was doped which was disposed in the center of the upper barrier layer with silicon (Si) at 850° C. using the above-described 105. MOCVD vapor phase growth means. The boron (B) compo (6) An ohmic back-surface electrode 107 composed of sition ratio (X) in the boron indium phosphide (B-In-P) gold.Zinc (Au.Zn), which was provided almost throughout 40 compositional gradient layer was set to X=0.33 at the junction the back surface of the p-type GaAs substrate 101. interface with the buffer layer 102 and X=0.98 on the surface The yellow LED 2A used was an LED exhibiting the fol joined with the light-emitting layer 104. lowing properties (a) to (d). (4) A light-emitting layer 104 (carrier concentration: about (a) Light emission center wavelength: 580 nm 4x10'7 cm, layer thickness: about 150 nm) mainly com (b) Luminance: 3 millicandela (mcd) 45 posed of a cubic n-type Gao Ino, N layer (lattice constant: (c) Forward voltage: 2 volt (V) (forward current: 20 mA) 4.557 A). (d) Reverse voltage: 5 V (reverse current: 10 LA) (5) An upper barrier layer 105 (carrier concentration: about The multicolor light-emitting lamp 20 obtained by assem 2x10" cm, layer thickness: about 400 nm) composed of a magnesium (Mg)-doped p-type boron indium phosphide bling the blue LED1A and the yellow LED2A each having a 50 square shape with a one-side length of 300 um was fabricated (BoosInoo,P. lattice constant: about 4.557 A) layer with the through the following steps (A) to (B): major part being amorphous, having a band gap at room (A) a step of fixing respective p-type back-Surface elec temperature of 3.1 eV, which was grown at 400° C. by the trodes 107 of LEDs 1A and 2A to a metal film 16 on a above-described MOCVD reaction system. common pad 15 using, for example, an electrically conduct 55 (6) An ohmic surface electrode 106 composed of a gold.Z- ing adhesive material by chip-on-board means, and inc (Au.Zn) circular electrode (diameter: 130 um), which was (B) a step of individually bonding n-type surface electrodes disposed in the center of the upper barrier layer 105. 106 of LED1A and 2A to two terminals 17 and 18 electrically (7) An ohmic back-surface electrode 107 composed of insulated from the pad 15, by wedge bonding means or ball aluminum (Al), which was provided almost throughout the bonding means. 60 back surface of the n-type Si substrate 101. The multicolor light-emitting lamp 20 was fabricated by The hetero-junction type GaP-base green LED 3A used individually applying bonding to LEDs 1A and 2A and there was a p-side up type single hetero (SH)-junction type LED fore, can be used as a blue single light lamp or as a lamp fabricated by disposing ohmic Surface and back-Surface elec emitting single light in the yellow band. When a current is trodes described in (4) and (5) below on a stacked layer passed to the blue LED 1A and the yellow LED 2A at the 65 structure where functional layers described in (2) and (3) same time, a multicolor lamp which can be used as a white were stacked in sequence on a substrate 101 described in (1) lamp is provided. below. US 7,479,731 B2 13 14 (1) A silicon (Si)-doped n-type (100) 2 off-GaP single an RGB-type multicolor light-emitting lamp 30 capable of crystal substrate 101. emitting white light can be provided. (2) A light-emitting layer composed of silicon (Si)-doped n-type GaP, which was grown at 800° C. by a general liquid Example 3 phase epitaxy (LPE) method (see, III-V Zoku Kagobutsu 5 Handotai (Group III-V compound Semiconductor), pages The present invention is described below by referring to the 253 to 256, supra) and doped with nitrogen (N) as an isoelec case of constructing a light source by assembling the RGB tronic trap to an atomic concentration of 6x10" cm. type multicolor light-emitting lamps 30 described in Example (3) An upper barrier layer 105 (carrier concentration: about 2. 3x10" cm, layer thickness: about 400 nm) composed of a 10 FIG. 8 is a plan view showing the light source 40 according p-type boron phosphide (BP) layer with the major part being to the present invention, which is fabricated, for example, by amorphous, having a bandgap at room temperature of 3.0 eV. regularly arraying the RGB type multicolor light-emitting which was grown at 380° C. by the above-described MOCVD lamps 30 at equal intervals. By applying wiring capable of reaction system. passing a forward current under control to individual termi (4) An ohmic surface electrode 106 composed of a gold 15 nals 18 of lamps 30 arrayed, the chromaticity can be adjusted .beryllium (Au. Be) circular electrode (diameter: 110 um), and a multicolor lamp for use in display and the like can be which was disposed in the center of the upper barrier layer fabricated. 105. (5) An ohmic back-surface electrode 107 composed of a INDUSTRIAL APPLICABILITY gold...germanium alloy (Au: 95 wt %, Ge: 5 wt %), which was provided almost throughout the back surface of the n-type According to the present invention, a multicolor light GaP Substrate 101. emitting lamp or a light source is fabricated by using a hetero The hetero-junction type GaP green LED 3A used was an junction type light-emitting device having a boron phos LED exhibiting the following properties (a) to (d). phide-base group III-V compound semiconductor layer as a 25 barrier layer, for example, a hetero-junction type GaP-base (a) Light emission center wavelength: 555 nm. green LED or a hetero-junction type GaAS2P-base LED, (b) Luminance: 5 millicandela (mcd) so that, for example, an RGB mixed color-type multicolor (c) Forward voltage: 2 volt (V) (forward current: 20 milli light-emitting lamp of giving high-intensity light emission ampere (mA)) can be provided. (d) Reverse voltage: 5 V (reverse current: 10 LA) 30 Furthermore, according to the present invention, a multi The hetero-junction type red LED 4A used was a pn color light-emitting lamp or a light Source is fabricated by junction type LED using a silicon (Si)-doped n-type (100)-Si using a light-emitting device of emitting blue band light, single crystal as the Substrate 101 and having a light-emitting where an electrically conducting Substrate is used and an layer 104 composed of an n-type aluminum gallium arsenide electrode is provided on the back surface of the substrate, for (AlGaAs) and an upper barrier layer 105 composed of a 35 example, a blue LED having a boron-containing group III-V p-type boron phosphide (BP) layer. The main properties of compound semiconductor layer, so that a high-intensity mul the p-side up type red LED 4A are shown below. ticolor light emitting lamp or light source can be provided by (a) Light emission center wavelength: 660 nm. an easy bonding operation. (b) Luminance: 8 millicandela (mcd) The invention claimed is: (c) Forward voltage: 2 volt (V) (forward current: 20 milli 40 1. A multicolor light-emitting lamp fabricated by disposing ampere (mA)) a plurality of LEDs by combining at least a blue light emitting (d) Reverse voltage: 5 V (reverse current: 10 LA) diode (LED), a green LED and a red LED, An RGB-type multicolor light-emitting lamp 30 was fab wherein the blue LED comprises a low-temperature buffer ricated by assembling the blue LED 1A, the hetero-junction layer composed of an amorphous or polycrystalline type green LED 3A and the hetero-junction type red LED 4A 45 boron-containing group III-V compound semiconductor each having a square shape with a one-side length of about and provided on an electrically conducting Substrate 250 um, through the following steps (A) to (B): Surface, a lower barrier layer composed of a boron phos (A) a step of fixing respective n-type back-Surface elec phide (BP)-base group III-V compound semiconductor trodes 107 of LEDs 1A, 3A and 4A to a metal film 16 on a containing boron (B) and phosphorus (P) and provided common pad 15 using, for example, an electrically conduct 50 on the low-temperature buffer layer, a light-emitting ing adhesive material by chip-on-board means, and layer composed of a group III-V compound semicon (B) a step of individually bonding p-type surface electrodes ductor and provided on the lower barrier layer, and an 106 of LEDs 1A, 3A and 4A to three terminals 17 to 19 upper barrier layer composed of a boron phosphide-base electrically insulated from the pad 15, by wedge bonding group III-V compound semiconductor formed on the means or ball bonding means. 55 light emitting layer, The multicolor light-emitting lamp 30 is fabricated by wherein the green LED is a hetero-junction type LED of individually applying bonding to LEDs 1A, 3A and 4A and emitting green band light and comprises a light-emitting therefore, can be used also as a single light lamp of blue band, layer provided on a single crystal Substrate and an upper green band or redband. In particular, the lamp 30 of Example barrier layer composed of a boron phosphide-base group 2 uses a hetero-junction type GaP-base LED 3A having a 60 III-V compound semiconductor layer and provided on boron-containing group III-V semiconductor layer and there the light-emitting layer, fore, can be used also as a lamp of emitting high-luminance wherein the red LED is a hetero-junction type LED of single light of green band. In addition, LEDs 1A, 3A and 4A emitting red band light and comprises a light-emitting are individually applied with bonding and therefore, the for layer provided on a single crystal Substrate and an upper ward current passing to each LED can be individually con 65 barrier layer composed of a boron phosphide-base group trolled and mixed color light of RGB can be generated. Fur III-V compound semiconductor layer and provided on thermore, by lighting LEDs 1A, 3A and 4A at the same time, the light-emitting layer, US 7,479,731 B2 15 16 wherein each of the LEDs for providing the multicolor 9. The multicolor light-emitting lamp according to claim 1, light emitting lamp is formed on an upper Surface of a wherein the light-emitting layer of said blue LED is a GalnN single crystal Substrate having the same conduction light-emitting layer, and said multicolor light-emitting lamp type, comprises agreen light emitting diode including a GaPlight wherein a back-Surface ohmic electrode having a first emitting layer and a red light emitting diode including a GalP polarity is provided on a lower Surface of the single light-emitting layer. crystal substrate of each of the LED, and wherein a front-Surface ohmic electrode having a second 10. The multicolor light-emitting lamp according to claim polarity opposite to said first polarity is provided on a 1, further comprising a metal film disposed on a conductive side of each of the LEDs opposite the back-surface 10 pad, and wherein the back-Surface ohmic electrodes of each ohmic electrode. of said blue LED, said green LED and said red LED are fixed 2. The multicolor light-emitting lamp according to claim 1, to said metal film So as to electrically connect respective wherein a hetero-junction type yellow LED of emitting yel back-surface ohmic electrodes of said first polarity to one low band light is disposed and the yellow LED comprises a another. light-emitting layer provided on a single crystal Substrate 15 11. The multicolor light-emitting lamp according to claim having the same conduction type as that of the blue LED and 1, wherein the front-surface ohmic electrodes are provided on an upper barrier layer composed of a boron phosphide-base respective upper barrier layers of each of said blue LED, said group III-V compound semiconductor layer and provided on green LED and said red LED. the light-emitting layer. 12. The multicolor light-emitting lamp according to claim 3. A light source comprising a multicolor light-emitting 1, wherein the color light emitting diodes other than the blue lamp according to claim 1 or 2. LED have a single hetero-junction structure, and the blue 4. A light source comprising a multicolor light-emitting LED has a double hetero-junction structure. lamp according to claim 1. 13. The multicolor light-emitting lamp according to claim 5. A light source comprising a multicolor light-emitting 2, wherein the yellow LED has a single hetero-junction struc lamp according to claim 2. 25 6. The multicolor light-emitting lamp according to claim 2, ture, and the blue LED has a double hetero-junction structure. comprising a yellow light emitting diode including a GaAsP 14. The multicolor light-emitting lamp according to claim light-emitting layer. 1, wherein the green LED has a single hetero-junction struc 7. The multicolor light-emitting lamp according to claim 1, ture, and the blue LED has a double hetero-junction structure. comprising a green LED including a GalPlight-emitting layer 30 15. The multicolor light-emitting lamp according to claim and a red LED including a AlGaAs light-emitting layer. 1, wherein the red LED has a single hetero-junction structure, 8. The multicolor light-emitting lamp according to claim 1, and the blue LED has a double hetero-junction structure. comprising a green LED including a GalPlight-emitting layer and a red LED including a GaP light-emitting layer.