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 ), 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 (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 -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 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: 0

DISCLOSURE 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 (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: 0