Blue 1

1

2
OUTLINE
1. Introduction 2. Blue LED (1) III-V
Nitrides based Devices (2) SiC based Devices
(3) II-VI ZnSe based Devices (4) Organic
Compounds(Polymer)based Devices (5) Others 3.
Blue LD (1) II-VI Compounds based Devices
(2) III-V Nitrides based Devices 4.
Applications 5. Summary

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1. INTRODUCTION
(1) Motivation

4
1. INTRODUCTION

• (1) Motivation
• Full Color
• Display
• High Density
• Optical Storage
• Others

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1. INTRODUCTION
(2) Materials and growth technologies ?
Wide Band Gap and Direct Band

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Emission properties of visible Light-Emitting
Diodes
Led Peak Device
Ext. Quantum Performance type
wavelength structure efficiency()
lumens(watt) GaAsP 700 nm HJ
0.2 0.15 AlGaAs
650 nm DH 16.0
8.0 AlInGaP 620 nm DH
6.0 20.0 AlInGaP 585 nm
DH 5.0 20.0
AlInGaP 570 nm DH 1.0
6.0 GaP 555 nm
HJ 0.1 0.6 InGaN
514 nm DH 2.6
7.0 ZnTeSe 512 nm DH
5.3 18.0 ZnCdSe 489
nm DH 1.3
1.7 SiC 470 nm HJ
0.03 0.04 InGaN 450 nm
DH 3.8 3.6
HJ Homojunction
DH Double heterostructure

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????????????
The publications of nitride research over
the world has grown up rapidly since mid-1990 due
to important electronic and opto-electronic
applications of nitrides.
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1. INTRODUCTION
? Suitable Substrate Matching of
lattice thermal conductivity ? High
Quality Crystal Growth Technology
Epitaxy Growth by MOCVD,
MBE

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1. INTRODUCTION

• (3) Device Structure
• Dopants ---- P type and N type
• Homojunction
• ? Double Hetrojunction
• ? QW and/or SL Structures
• Ohmic Contacts

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2. Blue LED

• 2-1 III-V Nitrides based Blue LED
• (1) Fundamental Properties of Nitrides
• Crystal structure
• Wurtzite ?-AlN ?-GaN ?-InN
• Zincblende ?-AlN ?-GaN ?-InN

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2-1 III-V Nitrides based Blue LED

• ? Bandgap
• AlN Eg 6.28 eV
• GaN Eg 3.39 eV Direct
• InN Eg 1.95 eV Bandgap
• AlGaN Eg 6.28 3.39 eV
• InGaN Eg 3.39 1.95 eV

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2-1 III-V Nitrides based Blue LED

• The materials (GaN) have the potential
• for covering the entire visible spectrum from
• the UV ( 200 nm) to the RED ( 600nm).

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2-1 III-V Nitrides based Blue LED

• ? Electrical Properties (Undoped)
• AlN Insulator (donor, acceptor, defect levels
• all lie within the
  bandgap deep)
• GaN n 4 x 1016cm-3 , ?n 600 cm2/v.s (300K)
• InN n 1018 cm-3
• N Type VN defects in donor state with binding
• energies of 1eV, 40 meV and 10 meV in
• AlN, GaN and InN respectively.

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2-1 III-V Nitrides based Blue LED
(2) Historical Review 1907 AlN was
synthesized(One of the first reported
III-V compounds) F.Fichter Z.
Anorg 1937 GaN crystal structure was reported
J.V.Lirman
H.S.Zhdanov 1959 GaN optical properties was
reported
H.G.Grimmeiss H Koelmans 1969 GaN epitaxial
layers (on Sapphire substrates by CVD)
H.P.Marusk J.J.Tietjen

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2-1 III-V Nitrides based Blue LED
1971 GaN bulk needles R. Dingle,
et.al. Blue-emiting m-i-n junction (the
first Blue LED)
J.Pankov, et.al. GaN, AlN
hetroepitaxial growth by MOCVD
H.M.Manasevit et.al.
1975 AlN by reactive MBE S.Yoshita,
et.al. 1982 Alx Ga1-x N by MBE
S.Yoshita, et.al. 1986 GaN by MOMBE
S.Zembatsu T.Sasaki Low temperature
AlN buffer layer (quality of epitaxial
films improved greatly)
H.Amano et al.

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2-1 III-V Nitrides based Blue LED
1989 P-type GaN layer growth (GaNMg,
annealing or LEEBI) H.Amano et al. 1991
high performance blue LED
S. Nakamura, et.al.
1994 LED products (gt1cd) Nichia Chemical
Co. 1997 LED products (475nm, 1.1cd)
HP 1998 LED products Cree,
Sony 1999 LED products (3 million/month)
Rhom Co.

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2-1 III-V Nitrides based Blue LED
(3) Main Issues ? Substrate Sapphire
lattice mismatch 16, thermal mismatch 34 ,
by buffer layer AIN (25 50 nm) 6H SiC
lattice mismatch 3.5, thermal mismatch
25 GaAs, Si .......

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Comparison of the relevant III-V Nitride material
properties with perspective substrate materials
Substrate Lattice
thermal Coefficients of material
parameters conductivity
thermal expansion GaN a
3.189 Å 1.3 W/cm.K 5.59 ?
10-6 /K c 5.185 Å
3.17 ?
10-6 /K AlN a 3.112 Å
2.0 W/cm.K 4.2 ? 10-6 /K
c 4.982 Å
5.3 ? 10-6 /K 6H-SiC
a 3.08 Å 4.9 W/cm.K
4.2 ? 10-6 /K c
15.12 Å
4.68 ? 10-6 /K Sapphire a 4.758
Å 0.5 W/cm.K 7.5 ? 10-6 /K
c 12.99 Å
8.5 ? 10-6
/K ZnO a 3.252 Å
2.9 ? 10-6 /K
c 5.213 Å
4.75 ? 10-6 /K Si
a 5.4301 Å 1.5 W/cm.K
3.59 ? 10-6 /K GaAs
a 5.6533 Å 0.5 W/cm.K 6
? 10-6 /K 3C-SiC a 4.36 Å
4.9 W/cm.K MgO
a 4.216 Å 1.3 W/cm.K
10.5 ? 10-6 /K

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2-1 III-V Nitrides based Blue LED
? Epitaxy growth MOCVD downward
subflow of the He and N2 MBE plasma based
sources ? P type - doping Mg doping
with low energy electron-beam irradiation
Thermal annealing at 700?C under N2 ambient
? Light emitting mechanism ?
Hetrostructure and QW structure

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GaN????
A. ?????, ??????
10mm
lt1100gt
B. GaN????
SiO2
C. GaN????
D. GaN????
????GaN??????,??????106/cm2
E. ???GaN? ?,???? ???
21
?????????

• ??????????????,?????1010/cm2???lt106/cm2
• ???????????????????????,???lt1016/cm2,????P?????
  
• ??HVPE???????(Hydride Vapor Phase
  Epitaxy)???????GaN????,?????????????
• ??GaN?????????,?????GaN?????????????????
• GaN ??????,????????,???????????

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2-1 III-V Nitrides based Blue LED

• (4) Typical results
• Nichia Chemical Co. of Japan
• Dec.,1993 ?450nm, I 10 mA, ?3.8, P1mW
• 1994 I 20 mA, ?2.7, P1.5mW
• I 40 mA, P2.5mW
• Cree Research, NC. U.S.A.
• (SiC)1-x (GaN)x / SiC P
  0.85 mW

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2-1 III-V Nitrides based Blue LED

• Nichia Chemical Industries (Tokushima, Japan)
  Jan.1996. LFW. Blue SQW LED ( InGaN/AlGaN )
• emissions span from Blue to Yellow
• ? 450nm, ?? 20nm (FWHM), I 20
  mA,
• ? 9.1, P 5mW
• ? 520nm, ?? 30nm (FWHM), I 20 mA,
  
• ? 6.3, P 3mW
• ? 590nm, ?? 50nm (FWHM), I 20 mA,
• ? 1, P 1mW
• ? 106 Hrs, Unit price 25 ? 0.80
  
• ( Red LED
  0.050.10)

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2-2 SiC based Blue LED

• (1) Fundamental Properties of SiC
• Crystal structure ---- Polytypism
• Zincblende
• ?-SiC
• 3C SiC
• Wurtzite
• ?-SiC
• 2H SiC,
• 4H SiC,
• 6H SiC ...

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2-2 SiC based Blue LED

• Features
• Wide bandgap (indirect), Large Si-C bonding
  energy make it resistant to chemical attack and
  radiation, and ensure its stability at high
  temperature.
• High thermal conductivity and high electron
  saturation velocity make it ideal for high power
  operation.
• High quality substrates, easy to be doped to
  NP type.

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Comparison of important semiconductor properties
Si
GaAs 3C-SiC 6H-SiC GaN Diamond Band Gap(eV)(300K)
1.12 1.43 2.2 2.9 3.39
5.5 Dielectric Constant 11.8 12.8 9.7
10 9 5.5 Max. Op. Temp. (K)
600? 760? 1200 1580
1400 Melting point (K) 1690 1510
sublimes gt2100 phase change Physical
Stability Good Fair Excellent
Good Very G. e mobility RT(cm2/Vs) 1440
8500 1000 600 900 2200 h mobility
RT(cm2/Vs) 600 400 40 40
150? 1600 Breakdown V.(106/V cm) 0.3 0.4
4 4 5? 10 Thermal
Cond.(W/cm) 1.5 0.5 5 5
1.3 20 Sat. e drif.Vel. (107cm/s) 1
2 2 2 2.7 2.7

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2-2 SiC based Blue LED

• Main Light-producing Mechanisms
• Electroluminesce across the entire visible
  spectrum by the addition of various impurities
• B, Ga, Be, Sc, Al ......
• Donor-to-Acceptor(DA) pair recombination
• 480nm
• Bound exciton recom. at localized Al center
• 455nm
• Free exciton recombination.
• 425nm

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Main Light-producing Mechanisms

3C-SiC
?????? ?SiC???? 1.6H-SiC (Be) 2.6H-SiC
(B) 3.6H-SiC (Sc) 4.4H-SiC (Sc) 5.6H-SiC (Al)

4h-SiC
6H-SiC
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2-2 SiC based Blue LED
(2) Historical Review 1969 First SiC blue LED
by LPE R.Brander R.Sutton 1978 SiC substrate
crystal growth by thermal
decomposition
V.I.Levin, et.al. 1979 SiC substrate crystal
growth by sublimation and epxitaxial
growth by LPE M.Ikeda,et.al. 1981
SiC growth from a carbon-enriched silicon melt

Y.M.Tairov and R.Tsverkov 1980 low
atmospheric pressure CVD, MBE, GSMBE 1983 SiC
film grown on Si substrates S.Nishino,
et.al. 1992 Commercial SiC blue LED(470nm) Cree
Reaearch

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2-2 SiC based Blue LED

• (3) Main Issues
• Substrate
• Ohmic contact
• SiC etching ------ by RIE
• Doping ------ by Ion Implantation

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SiC ????????????
??
????(?/ cm2) N? 3C-SiC Au/Ta
2 ? 10-3 Au/W
8 ? 10-4
Au/Ti 1 ? 10-3
Au/Ni 2 ? 10-3
W 8
? 10-2 N? 6H-SiC Al/W 1
? 10-4 Ni, Cr
3 ? 10-4 P? 6H-SiC Al/W - Au/W/Al
2 ? 10-4

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???????????
???? ???? (nm/min ) ???? ???
E - Mode
SiCSi CHF390O2 75 171
21 CBrF390O2 38
61 21 SF635O2 53
101 126 SF690O2 40
111 12
H - Mode SiCAl SF6
1700 101 151
SF6 500
51 101

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2-2 SiC based Blue LED
(4) Typical results
Cree Research, NC. U.S.A.
Siements AG, Sanyo, Sharp... SiC Blue LED
? 470 nm I 20mA ( V3.0V) , ? 0.03,
P 18.3 ?W , ?? 69 nm I
50mA , P 50 ?W. ? ? 104 Hrs,
unit cost 18 Cents ?

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2-3 II-VI ZnSe based Blue LED

• Materials
• ZnSe and its trinary and/or quaternary compounds
• Device Structure ----- Green-Blue LED
• DH Structure on ZnSe Substrates

Metal electrode
HgSe
ZnTeSe
P-TYPE ZnSe
ZnTeSe active region
N-TYPE ZnSe
Metal electrode
ZnSe Substrate
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2-3 II-VI ZnSe based Blue LED

• Typical Results
• June 1994 Eagle-Picher Industries (Miami, OK)
• With North Carolina State
  University
• 
  (Raleigh,NC)
• p-ZnSe--ZnTeSe-- n-ZnSe
• ? 512nm, ? 5.3, I 10mA, P 1.3 mW
• p-ZnSe--ZnCdSe-- n-ZnSe
• ? 489nm, ? 1.3, I 10mA, P 0.33 mW

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2-4 Organic compounds based LED
Organic Light Emitting Diode --- OLED
Vapor-deposited devices Polymer based
devices(spin-coated) (1) Materials
Mq3 TAD PP. PVC
...

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2-4 Organic compounds based LED

• (2) Features
• easy to fabricate,
• low cost,
• light weight,
• flexible...

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2-4 Organic compounds based LED
(3) Milestones 1987 First demonstration of EL in
organic film
C.W.Tang, et.al. 1990 Green LED
R.H.Friend, et.al. 1991
Read LED A.J.Heeger,
et.al. 1992 Blue LED
D.Clery, et.al. 1993 Bright blue
LED Jilin University 1994 ? gt
104 Hrs. C.W.Tang, et.al.

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2-4 Organic compounds based LED

• (4) Main Issues
• Spectrum Content --- Changing OLED color
• by adjusting the bandgap of organic
• compounds in terms of changing dopands
• and composition.
• Quantum Efficiency --- By improve electrodes,
• materials quality... ? 0.01 ? 4
• Lifetime and reliability a few minutes?104 hrs

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2-4 Organic compounds based LED
(5) Typical results and Novel approaches
OLED Structure Color Peak
wavelength Brightness ITO/PVK-TPB/PBD/Alq/Al
Blue 455 nm 2300
cd/m2 ITO/PVK/TAZ/Alq/MGAg Blue
410 nm 700 cd/m2 ITO/PVK-
Perylene/MgAg Blue 450 nm
1700 cd/m2 ITO/ TBD/TAZ/Alq/ MgAg
Blue 464 nm 3700
cd/m2 ITO/PMMATPDAlq/MgAg Green 525
nm 920 cd/m2 ITO/PMP/ Alq/ MgAg
Green 525 nm 1000
cd/m2 ITO/PPV/Ca
Green 530 nm 500
cd/m2 ITO/PPV/PBD/Ca Green
530 nm 500 cd/m2 ITO/TPD/Znq2/M
gAg Yellow 568 nm
16200 cd/m2 ITO/T6/TBS/Alq/MgAg Green
525 nm 2000
cd/m2 ITO/TAD/EuPBD/ Alq/ MgAg Red
617 nm 10 cd/m2 ITO/TPD/EuPBD/
Alq/ MgAg Red 614 nm 2400
cd/m2

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2-4 Organic compounds based LED

• ? Color-changeable LED By changing
  bias voltage can obtain from orange to green.
• Optical micro-cavity LED
• Organic compounds LD

Electroluminescent organic thin film
could be used in large low - cost display
if uniformity and efficiency are improved
and lifetime issues are overcome.
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2-5 Blue LED fabricated by other materials
(1) ZnS Eg 3.66 eV Direct Band gap Blue
lighting Deep level recombination centers Tm
? ? 480nm, Tb ? ? 491 nm Pr ? ? 495 nm
(2) Porous Silicon

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3. Blue LD
A comprision of ZnSe and GaN Blue LD -1996

II-VI ZnSe III-V GaN Crystal
structure Zincblend
Wurtzite n doping max. (cm-3) Cl 3?1020
Si 2?1020 p doping max. (cm-3)
N 2?1019 Mg 2?1019 d/a
0.25/GaAs
16/Al2O3 ,3.5/SiC QW/barrier
ZnCdSe/ZnSe In0.2Ga0.8N/In0.05Ga0.95N Device
defect density 1?105 cm-3 1?107-
1?1010 cm-3 ? (nm)
460 420 Jth
350 mA/cm2
8.7 A/cm2 Lifetime 100 hrs.
CW(RT) pulse (RT)

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3-1 II-VI ZnSe based Blue LD
(1) Fundamental Properties of ZnSe Eg
2.67 eV Direct Bandgap ZnSe is nearly
lattice matched to GaAs Pseudomophic ternary
and lattice matched quaternary alloys provide
sufficient carrier and optical confinement for
SCH laser operation.

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3-1 II-VI ZnSe based Blue LD
(2) Historical Review 1970s Fundamental
materials research 1980s
Nonequilibrium epitaxial growth ( MBE...) 1972
Electron beam pumping ZnSe/ZnS and ZnSe/GaAs
sample_at_95K produced 452nm stimulated
emission with J8A/cm2 ,6A/cm2 resp.
O.V.Bogdankevich, et.al. 1991 1stelectrically
pumped ZnCdSe/ZnSe LD_at_77K under pulsed
operation M.A.Haase, et.al.(3M
Corp.)
H.Jeon, et.al. (Brown-Purdue Univ.) 1992 RT
Pulsed operation of LD 1993 RT CW operation
? from seconds to an hour.
N.Nakayama, et.al.
Salokatve, et.al. 1994 RT CW operation ? gt 3
hours 1996 RT CW operation ? gt 100 hours

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3-1 II-VI ZnSe based Blue LD

• (3) Main Issues
• P type - doping
• Ohmic contacts
• Hetrostructure and QW structures
• Lifetime

(4) Typical Results
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3-2 III-V Nitrides based Blue LD
(1) Historical Review 1971 Optically pumped
stimulated emission from GaN

R. Dingle, et.al. 1990 Optical properties of
nitride QWs M.A.Khan, et.al. 1991 Vertical
cavity lasing (SEL) M.A.Khan,
et.al. 18 periods AlGaN/GaN superlattice
quart-? mirror (R80 _at_442nm, R95
_at_375nm) M.A.Khan, et.al. 1993 Al0.1Ga0.9N/GaN
SCH LD Ith down to 1/12 of the HJ

H.Amano, et.al. 1996 Bluish-purple LD ?
410 nm (Pulse) Nichia 1999 LD Products ?
400 nm, 10000hrs. 5000 ? 2000

Nichia

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GaN Based Injection LD
? (nm) Jth(KA/cm2) V(v)
CW/P. Pout(mW) ? NICHIA 403.7 4
5 CW 20 104 hrs TOSHIBA
417.5 10.6 18 Pulse
4 days CREE 404, 423 20.2 27
CW/P. 2.4 15s./16h. FUJITSU 405 - 425
12 22 Pulse 80 5 hrs UCSB
419 12.7 23 Pulse 17
6 hrs SONY 417.5 9.5 20
Pulse 65 XEROX 422 - 423 25
Pulse 10

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3-2 III-V Nitrides based Blue LD

• (2) Main Issues
• large series resistance of AlGaN
• P type materials
• Increase G in active layer ( short cavity in
  SEL )
• Etching of the mirror by R-FABE
• (
  for SCH edge-emitting LD)
• (3) Typical results
• ?
  403.7 nm P 20 mW
• Active
  layer InGaN/GaN MQW
• 
  Cladding layer
• 
  P-Al0.14Ga0.86N/GaN MD- SLS
• 
  Doping n - Si, p - Mg.
• ?
  60?C 700hrs, 50?C 1000hrs
• 
  40?C 3000hrs, 20?C 104hrs

P-Al0.14Ga0.86N/GaN MD- SLS
P- GaN
P-Al0.2Ga0.8N
P-Al0.14Ga0.86N/GaN
N- GaN
P-Al0.14Ga0.86N/GaN MD- SLS
50
GaN??LD(MQW)
????MQW,??ELOG??????????
51
4. APPLICATIONS

• (1) Optoelectronics Area
• LED, LD, PD
• Full color flat-panel displays
• Optical storage
• Illumination
• Laser printing
• Undersea optical communication
• Military applications (high sensitivity, low
• noise UV photodetector)
• Mark lighting --- traffic signs, vehicle
• exterior and dash lighting)
• Medical analysis instruments
• Agriculture --- speed up photosynthesis

52
???????????????
?????
?????????
???
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4. APPLICATIONS

• (2) Electronics, Electricity Area and others
• JFET, MESFET, MOS FET,
• Bipolar transistor, Rectifier
• High temperature devices
• GaN MESFET T400?C, SiC MESFET T850 ?C
• High power devices
• Nonvolatile MOS circuitry
• Piezoelectric devices ( GaN, AlN )
• High temperature Gas sensors
• SiC MOS Device, 800 ?C H2, 700 ?C CH4
  (Methane)
• Radiation hard system
• Cold cathode source

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4. APPLICATIONS

• (3) Illumination --- Replacing the light
  Bulb ?!!!
• White LED Nichia
• VF 3.6 - 4.0 v ( IF 20 mA )
• IR 50 ? A ( VR 5 v )
• IV 0.3 - 0.6 -1.0 cd ( IF 20 mA )
• Incandescent bulbs turn about 5 of their
  power into light.
• Nowadays white LEDs provide 10 efficiency.
• To make efficient room lighting, whitw LEDs
  efficiency must exceed 25, which is
  theoretically achievable.

55
4. APPLICATIONS
(3) Illumination --- Replacing the light
Bulb ?!!! Issues Cost ?! How From
1 to 0.1?

56
LED??????????

• ??????40W,LED10W?
• ????????1???,LED5-10??
• ????????????, LED??????,?????
  LED????????????????,???????????????

57
4. APPLICATIONS
Compression of Bulbs to LEDs for Traffic Lights
light Bulbs
LEDs Power
consumpation Red 70 W
Red 10 W Yellow
70 W Yellow 20 W
Green 70 W Green
35 W Replace
interval 6 - 12 months
5 - 10 years
Failure mode Sudden total failure
Gradual intensity decrease
Visibility Use color filter, reflect
sunlight Direct

58
????LED???
?. ?????????????LED?????????,??,??,??????????????
???,??????,??????????????LED???????????,??????????
????????????LED?? ?. ??????LED??LED??????,????????
???????????????????,??,??,????????????????,??????
?????????????,???????? ?. ????????????LED????,????
????????????????????????????,??????,??????????????
??????

59
4. APPLICATIONS
White LED Blue/Purple LED Phosphor

60
LD????DVD????

• VCD???LD??780nm,GaAlAs,??640MB?
• DVD???LD??630nm,InGaAlP,????2.5GB?
• ???DVD???LD??415nm,????17.5GB,?????VCD?100-150ms?
  ??20-40ns?
• ?????350nm??LD???,????25GB?

61
???????DVD
DVD???LD
??650nm ???????? 4.7Gb ??415nm ????????
18Gb
62
5. SUMMARY
(1) Rising of the third Generation Semiconductor


Panel Displays
DVD Optical storage

The Third generation Semiconductor
Others
Illumination




High power High temp. Electronics
UV detector Military
63
5. SUMMARY
(1) Rising of The third Generation
Semiconductor LED GaN vs.
SiC LD GaN vs. ZnSe
IF ?peak
Brightness Pout ?
(mA) (nm) (mcd) (?W) ()
SiC 20 470 20
20 0.04 ZnCdSe/ZnSe 10 489
700 327 1.3 InGaN/GaN 20
450 2500 5000 9.1

64
5. SUMMARY

• (2) Current Status of Domestic Institutions
• GaN ????,???????,??,??
• SiC, GaN ????
• ZnSe ????????,?????,??
• ZnS ????????
• Porous Silicon ????
• Organic Materials LED ????