EXHIBIT 1027
`
`Shuji Nakamura, Takahashi Mukai and Masayuki Senoh, Candela-class
`high-brightness InGaN/AlGaN double heterostructure blue-light-
`emitting diodes Appl. Phys. Lett. 64 (13) 1687-89 (Mar. 28 1994)
`
`(“Candela”)
`
`

`
`InGaN/AIGaN double-heterostructure
`
`high-brightness
`Candela-class
`blue-light-emitting
`Shuji Nakamura, Takashi Mukai, and Masayuki Senoh
`D.epartment of Research and Development, Nichia Chemical Industries, Ltd., 491 Oka, Kaminaka, Anan,
`Tokushima 774, Japan
`(Received 2 December 1993; accepted for publication 5 January 1994)
`(DH) blue-light-emitting
`Candela-class high-brightness
`InGaN/AIGaN
`double-heterostructure
`diodes (LEDs) with the luminous intensity over 1 cd were fabricated. As an active layer, a Zn-doped
`InGaN layer was used for the DH LEDs. The typical output power was 1500 /.LW and the external
`quantum efficiency was as high as 2.7% at a forward current of 20 mA at room temperature. The
`peak wavelength and the full width at half-maximum of the electroluminescence were 450 and 70
`nm, respectively. This value of luminous intensity was the highest ever reported for blue LEDs.
`
`Recently, there has been much progress in wide-band-
`gap II-VI compound semiconductor
`research, in which
`the
`first blue-green’ and blue injection
`laser diodes (LDs)’ as
`well as high-efficiency blue-light-emitting
`diodes (LEDs)~
`have been demonstrated. For the application
`to blue light-
`emitting devices,
`there are promising materials, such as
`wide-band-gap nitride semiconductors, which have great
`physical hardness, extremely
`large heterojunction offsets,
`high thermal conductivity, and high melting temperature.4 In
`this area, there has recently been great progress in the crystal
`quality, p-type control, and growth method of GaN films?p6
`For practical applications
`to short-wavelength optical de-
`vices, such as LDs, a double heterostructure is indispensable
`for
`III-V nitrides. The
`ternary
`III-V semiconductor com-
`pound, InGaN,
`is one candidate as the active layer for the
`blue emission because its band gap varies from 1.95 to 3.40
`eV, depending on the indium mole fraction. Up to now, not
`much research has been performed on InGaN growth.7-g Re-
`cently, relatively high-quality
`InGaN films were obtained by
`Yoshimoto et aZ.,’ at a high growth temperature (800 “C) and
`a high indium source flow rate ratio. The present authors
`discovered
`that the crystal quality of InGaN
`films grown
`on GaN films was greatly improved in comparison with that
`on a sapphire substrate, and the band-edge (BE) emission
`of
`InGaN became much stronger
`in photoluminescence
`(PL) measurements.” Thus, the first successful InGaN/GaN
`DH blue LEDs were fabricated using the above-mentioned
`InGaN films.‘r On the other hand, Zn doping into GaN has
`been intensively
`investigated to obtain blue emission centers
`for the application
`to blue LEDs by many researchers be-
`cause strong blue emissions have been obtained by Zn dop-
`ing into GaN.“-r5 However, there are no reports on Zn dop-
`ing into InGaN.
`In this letter, the InGaN/AlGaN DH blue
`LED which has a Zn-doped InGaN layer as an active layer is
`described for the frrst time.
`InGaN films were grown by the two-flow metalorganic
`chemical vapor deposition (MOCVD) method. Details of the
`two-tlow MOCVD are described in other articles.‘6”7 The
`growth was conducted at atmospheric pressure. Sapphire
`with (0001) orientation (C face), two inches in diameter, was
`used as a substrate. Trimethylgallium
`(TMG),
`trimethylalu-
`minum (TM&,
`trimethylindium
`(TMI), monosilane (SiH,),
`
`diethylzinc
`(CpzMgj,
`magnesium
`bis-cyclopentadienyl
`(DEZ), and ammonia (NH,) were used as Ga, Al, In, Si, Mg,
`Zn, and N sources, respectively. First,
`the substrate was
`heated to 1050 “C in a’stream of hydrogen. Then, the sub-
`strate temperature was lowered to 510 “C to grow the GaN
`buffer layer. The thickness of the GaN buffer layer was about
`300 A. Next,
`the substrate temperature was elevated
`to
`1020 “C to grow GaN films. During the deposition, the flow
`rates of NH,, TMG, and SiH4 (10 ppm SiH,
`in Ha) in the
`main flow were maintained at 4.0 //min, 30 pmollmin, and
`4 nmol/min, respectively. The flow rates of H, and N, in the
`subflow were both maintained at 10 //min. The Si-doped
`GaN films were grown
`for 60 min. The thickness of the
`Si-doped GaN film was approximately 4 ,um. After GaN
`growth, a Si-doped Al,,,Gao,,N
`layer was grown
`to the
`thickness of 0.15 pm by flowing TMA and TMG. After Si-
`doped Al,,,Ga,.,N
`growth,
`the temperature was decreased
`to 800 “C, and the Zn-doped In0,0,Gao.94N layer was grown
`for 15 min. During
`the Ino,o,Gao,g4N deposition,
`the flow
`rates of TMI, TEG, and NH,
`in the main flow were main-
`tained at 17 pm/min, 1.0 ,umol/min, and 4.0 /‘/min, respec-
`tively. The Zn-doped InGaN films were grown by introduc-
`ing DEZ at the flow rate of 10 nmol/min. The thickness of
`the Zn-doped InGaN layer was about 500 A. After
`the Zn-
`doped
`InGaN growth,
`the
`temperature was
`increased to
`1020 “C to grow Mg-doped p-type Alo,,,Ga,a,N
`and GaN
`layers by introducing TMA, TMG, and CpaMg gases. The
`thicknesses of the Mg-doped p-type Alo,r,Gao,,,N and GaN
`layers were 0.15 and 0.5 pm, respectively. A p-type GaN
`layer was grown as the contact layer of a p-type electrode in
`order to improve Ohmic contact. After the growth, Na ambi-
`ent thermal annealing was performed
`to obtain a highly
`p-type GaN layer at a temperature of 700 OC.r8 With
`this
`thermal annealing technique, the entire area of the as-grown
`p-type GaN layer uniformly becomes a highly p-type GaN
`layer.” Fabrication of LED chips was accomplished as fol-
`lows. The surface of the p-type GaN layer was partially
`etched until
`the n-type GaN
`layer was exposed. Next, a
`Ni/Au contact was evaporated onto the p-type GaN layer and
`a Ti/Al contact onto the n-type GaN layer. The wafer was cut
`into a rectangular shape. These chips were set on the lead
`frame, and were then molded. The characteristics of LEDs
`
`Appl. Phys. Lett. 64 (13), 28 March 1994
`
`0003-6951/94/64(13)/l
`
`687/3/$6.00
`
`0 1994 American
`
`Institute of Physics
`
`1687
`
`Downloaded 29 Nov 2007 to 132.178.126.155. Redistribution subject to AIP license or copyright; see http://apl.aip.org/apl/copyright.jsp
`
`Kingbright Elec. Co. Ltd., Kingbright Corp., SunLED Corp.,
`Kingbright Co. LLC, SunLED Co. LLC and Sunscreen Co. Ltd.
`Exhibit - 1027 Page 1
`
`

`
`p-Electrode
`/
`
`FIG. 1. The structure of
`LED.
`
`the InGaN/AlGaN double-heterostructure blue
`
`were measured under dc-biased conditions at room tempera-
`ture. Figure 1 shows the structure of the InGaN/AlGaN DH
`LEDS.
`Figure 2 shows the electroluminescence (EL) spectra of
`the InGaN/AlGaN DH LEDs at forward currents of 10, 20,
`30, and 40 mA. The peak wavelength is 450 run and the fulI
`width at half-maximum (FWHM) of the peak emission is 70
`nm at each current. The peak wavelength and the FWHM are
`almost constant under these dc-biased conditions. In the PL
`measurements, Zn-related emission energy obtained with Zn
`doping into InGaN was about 0.5 eV lower than the BE
`emission energy of InGaN depending on the indium mole
`fraction. Therefore, the energy level of Zn in InGaN is al-
`most the same as that of Cd in InGaN, and the peak position
`of EL of DH LEDs depends on the indium mole fraction of
`InGaN.lg Zn doping into InGaN films will be described in
`other articles in detail. The output power is shown as a func-
`tion of the forward current in Fig. 3. The output power in-
`creases sublinearly up to 40 mA as a function of the forward
`current. The output powers of the InGaN/AlGaN DH LBDs
`are 800 pW at 10 mA, 1500 ,uW at 20 mALand 2500 ,uW at
`40 mA. The external quantum efficiency is 2.7% at 20 mA. A
`typical on-axis luminous
`intensity of DH LEDs with 15”
`
`G+ e 100
`,h ‘G; 80
`Ei 3 6o
`a *$ 40
`72 20
`d
`
`300
`
`o_ E
`
`I -I
`
`500 600 700 800
`400
`Wavelength (run)
`
`.
`
`.
`
`?& ‘;~~-&-r-L;
`
`I
`
`I/
`
`,
`
`I
`
`/
`
`-1
`
`I
`
`0
`
`OOI
`Forward Current $A)
`
`50
`
`FIG. 3. The output power of the InGaN/AlGaN double-heterostructure blue
`LED as a function of the forward current.
`
`cone viewing angle is 1.2 cd at 20 mA. This luminous inten-
`sity is the highest value ever reported for blue LEDs. A typi-
`cal example of the current-voltage (1-V) characteristics of
`InGaN/AlGaN DH LEDs is shown in Fig. 4. It is shown that
`the. forward voltage is 3.6 V at 20 mA. This forward voltage
`is the lowest value ever reported for III-V nitride LEDs. In
`previous reports on InGaN/GaN DH LEDs, the forward volt-
`age was as high as about 10 V and the output power was not
`so high (about 125 pW).‘r
`In the previous study, electron
`beam irradiation instead of thermal annealing was performed
`for as-grown InGaN/GaN epilayers in order to obtain a
`highly p-type GaN layer. It is considered that the forward
`voltage was as high as 10 V and the output power was not so
`high because the entire area of the p
`layer was not uniformly
`changed into a highly p-type GaN layer by electron beam
`irradiation. By thermal annealing, the entire area of as-grown
`high-resistivity p-type GaN layer can be uniformly changed
`into a low-resistivity p-type GaN layerr
`InGaN/
`In
`summary, candela-class high-brightness
`AlGaN DH blue LEDs with the luminous intensity over 1 cd
`were fabricated for the first time. The output power was 1500
`,uW and the external quantum efficiency was as high as 2.7%
`at a forward current of 20 mA at room temperature. The peak
`wavelength and the FWHM of the EL were 450 and 70 nm,
`respectively. This value of luminous intensity was the high-
`
`X: 2Vidiv.
`
`InGaN/AlGaN
`the
`FIG. 2. Electroluminescence spectra of
`heterostmcture blue LED under different dc currents.
`
`double-
`
`I-V
`FIG. 4. ‘Qpical
`heterostructure blue LED.
`
`characteristic of
`
`the
`
`InGaN/AlGaN
`
`double-
`
`1688
`
`Appl. Phys. Lelt., Vol. 64, No. 13, 28 March 1994
`
`Nakamura, Mukai, and Senoh
`
`Downloaded 29 Nov 2007 to 132.178.126.155. Redistribution subject to AIP license or copyright; see http://apl.aip.org/apl/copyright.jsp
`
`Kingbright Elec. Co. Ltd., Kingbright Corp., SunLED Corp.,
`Kingbright Co. LLC, SunLED Co. LLC and Sunscreen Co. Ltd.
`Exhibit - 1027 Page 2
`
`

`
`est ever reported for blue LEDs. Using these high-brightness
`blue LEDs, high-brightness
`full-color
`indicators and flat
`panel displays will be developed in the near future.
`
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`Appl. Phys. Let-t., Vol. 64, No. 13, 28 March 1994
`
`Nakamura, Mukai, and Senoh
`
`1689
`
`Downloaded 29 Nov 2007 to 132.178.126.155. Redistribution subject to AIP license or copyright; see http://apl.aip.org/apl/copyright.jsp
`
`Kingbright Elec. Co. Ltd., Kingbright Corp., SunLED Corp.,
`Kingbright Co. LLC, SunLED Co. LLC and Sunscreen Co. Ltd.
`Exhibit - 1027 Page 3