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Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 1
The Race for Gallium Nitride
Blue Lasers:
Scott Corzine October 24, 2014
A Tribute to Shuji Nakamura
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 2
Outline
• Motivation
• Challenges
• Accomplishments
• What’s Happened
Recently
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 3
Key Markets for Blue Lasers
DVDs Laser Printers Color Displays
Requirements:
Good Beam Quality
Read: 1-2 mW
Write: 15-30 mW 5-10 mW 1-10 W
Advantages:
3-Fold Increase in
Storage Density
Lower NA allows
Simpler Optics
Efficient, Compact, High
Power Blue Light Source
High Efficiency
410 nm or less 450 nm, 520 nm
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 4
Basic Components of a Semiconductor Laser
Substrate
Epi Layers • P Cladding • I Active • N Cladding
• Lateral Processing
• Mirror Facets
Optical Cavity
Electrical Connection
• P Contact
• N Contact
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 5
Epi Material Requirements
• Active Layer: direct bandgap semiconductor
in the desired wavelength range
• Cladding Layers: compatible higher-bandgap
semiconductors – large bandgap differences to confine electrons
– large index differences to confine photons
• Substrate: must be suitable for epitaxial growth – lattice-matched to desired epi materials
– compatible crystal structure (zinc blende, wurtzite, etc.)
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 6
Epi Material Requirements
• Active Layer: direct bandgap semiconductor
in the desired wavelength range
• Cladding Layers: compatible higher-bandgap
semiconductors – large bandgap differences to confine electrons
– large index differences to confine photons
• Substrate: must be suitable for epitaxial growth – lattice-matched to desired epi materials
– compatible crystal structure (zinc blende, wurtzite, etc.)
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 7
He
Ne
Ar
Kr
Xe
Rn
F
Cl
Br
I
At
O
S
Se
Te
Po
N
P
As
Sb
Bi
C
Si
Ge
Sn
Pb
B
Al
Ga
In
Tl
Zn
Cd
Hg
Cu
Ag
Au
2
10
18
36
54
86
9
17
35
53
85
8
16
34
52
84
7
15
33
51
83
6
14
32
50
82
5
13
31
49
81
30
48
80
29
47
80
VII VI V IV III
II
I
VIII
• • •
Periodic Table
• S
ma
ller
Ato
m
• S
ma
ller
La
ttic
e C
on
sta
nt
• S
ho
rte
r W
ave
len
gth
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 8
III-V and II-VI Compounds
BN
BP
BAs
BSb
AlN
AlP
AlAs
AlSb
GaN
GaP
GaAs
GaSb
InN
InP
InAs
InSb
III-V Materials
II-VI Materials
HgO
HgS
HgSe
HgTe
ZnO
ZnS
ZnSe
ZnTe
CdO
CdS
CdSe
CdTe
MgO
MgS
MgSe
MgTe
Short
Wavelength
Long
Wavelength
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 9
400 600 800 1000 1200 1400 1600 1800
Lasing Wavelengths of Common Semiconductor Materials
InP
AlGaAs
InGaP 620-690 nm
700-1100 nm
1200-1600 nm
• Telecom, Datacom
Wavelength (nm)
InGaAs InGaAsP InP
InGaAs GaAs AlGaAs
InGaP AlInGaP AlInP
• DVDs, Laser Printers
• CDs, Laser Printers, Datacom
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 10
350 400 450 500 550 600 650
Different Options for Blue Lasers
2f-GaAs
ZnSe
GaN 390-440 nm
480-550 nm
400-500 nm
• Bulky, Complex External Optics
Wavelength (nm)
InGaAs GaAs AlGaAs
ZnCdSe ZnSSe ZnMgSSe
InGaN GaN AlGaN
• Lattice-Mismatched System
• Short Lifetimes (<1000 hrs)
• Not Blue Enough
InN GaN
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 11
Epi Material Requirements
• Active Layer: direct bandgap semiconductor
in the desired wavelength range
• Cladding Layers: compatible higher-bandgap
semiconductors – large bandgap differences to confine electrons
– large index differences to confine photons
• Substrate: must be suitable for epitaxial growth – lattice-matched to desired epi materials
– compatible crystal structure (zinc blende, wurtzite, etc.)
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 12
Role of Cladding Layers
P
N
ΔEc
e–
h+
Δn
active
ba
rrie
r
cla
dd
ing
index profile
mode profile
Ileak ~ exp[-ΔEc /kT ]
Electron Confinement
Optical Confinement
want large ΔEc
• smaller Ith
• better over T
want large Δn
• maximize Γ
• reduce substrate leakage
Γ = energy in active
total energy
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 13
Common Lattice-Matched Systems
AlAs
GaAs
InP
InAs
AlP
GaP
AlGaAs
InGaAsP
AlInGaP
0
0.5
1
1.5
2
2.5
5.4 5.5 5.6 5.7 5.8 5.9 6 6.1
Ban
dgap
(eV
)
Lattice Constant (Å)
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 14
AlInGaN Material System
GaN
InN
AlN
?
1
2
3
4
5
6
7
3 3.1 3.2 3.3 3.4 3.5 3.6
-4 -2 0 2 4 6 8 10 12B
and
gap
(eV
)
Lattice Constant (Å)
Strain (%)
Lattice mismatch limits:
• Al and In compositions
• Epi layer thickness
InGaN (In < ~20%)
AlGaN (Al < ~20%)
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 15
Conduction Band Offsets ΔEc Material
GaAs/AlAs
InGaAsP/InP (1.55µm)
InGaAsP/InP (1.3µm)
InGaP/AlInP
InGaN/GaN (xIn=10%)
InGaN/GaN (xIn=20%)
GaN/AlGaN (xAl=10%)
GaN/AlGaN (xAl=20%)
440 meV
220 meV
160 meV
260 meV
100 meV
200 meV
100 meV
200 meV
(estimates do not take into account strain and quantum effects) (GaN numbers assume 50% conduction band offset)
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 16
One Method to Reduce Leakage
P N
active
ba
rrie
r
cla
dd
ing
active
ba
rrie
r
cla
dd
ing
e– e– P N
Electron
Blocking Layer
After
Shuji Nakamura
P-AlGaN (x=0.05) 5000 Å
P-GaN 1000 Å
AlGaN (x=0.2) 200 Å
InGaN(x=0.2) MQW 360 Å
N-GaN 1000 Å
N-AlGaN (x=0.05) 5000 Å
Example
Epi Design
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 17
Index Differences Δn Material
GaAs/AlAs
InGaAsP/InP (1.55µm)
InGaAsP/InP (1.3µm)
InGaP/AlInP
GaN/AlGaN (xAl=10%)
GaN/AlGaN (xAl=20%)
GaN/AlN
0.6
0.4
0.3
0.4
0.06
0.12
0.44
AlxGa1-xN index @ 400nm, x < 0.3 ~ 2.54 - 0.6x
(from Brunner et. al., JAP, 82 (10), p5090, 1997)
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 18
0
0.001
0.002
0.003
0.004
0.005
2.46
2.5
2.54
-0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6
Mod
e S
hap
e (G
/nm
)In
dex
Pro
file
z (mm)
GaN AlGaN AlGaN
x = 0.05
x = 0.1
x = 0.15
Typical Cladding:
x = 0.07-0.1
d = 0.4-0.6 mm
l= 410 nm
GaN/AlGaN Waveguide Modes: Effect of Cladding Composition
Guide =
0.25µm
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 19
Epi Material Requirements
• Active Layer: direct bandgap semiconductor
in the desired wavelength range
• Cladding Layers: compatible higher-bandgap
semiconductors – large bandgap differences to confine electrons
– large index differences to confine photons
• Substrate: must be suitable for epitaxial growth – lattice-matched to desired epi materials
– compatible crystal structure (zinc blende, wurtzite, etc.)
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 20
Common Material Systems
AlAs
GaAs
InP
InAs
AlP
GaP
AlGaAs
InGaAsP
AlInGaP
GaAs Substrate
InP Substrate
0
0.5
1
1.5
2
2.5
5.4 5.5 5.6 5.7 5.8 5.9 6 6.1
Ban
dgap
(eV
)
Lattice Constant (Å)
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 21
1
2
3
4
5
6
7
2.6 2.8 3 3.2 3.4 3.6
-15 -10 -5 0 5 10B
and
gap
(eV
)
Lattice Constant (Å)
Strain (%)
Substrate Options for GaN
GaN
InN Sapphire SiC
AlN Buffer Layer
Required
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 22
GaN on Sapphire
Carrier Recombination,
Scattering, Reliability?
Sapphire
Substrate
GaN or AlN
Buffer Layer
(Low Temp)
GaN
(High Temp)
Dislocation Density
~ 109 - 1010 cm-2 TEM image from
D. Basile, HP Labs
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 23
SiC vs Sapphire GaN Laser on SiC
• Conductive Substrate Allows:
Vertical Current Flow
Single Top Contact
• 10x Better Thermal Conductivity
• High Quality Cleaved Facets
• But, Substrates are Expensive
GaN Laser on Sapphire
• Insulating Substrate Requires:
Two Top Contacts
• Poor Thermal Conductivity
• Poor Cleaved Facets
• But, Best Devices Still Made
on Cheap Sapphire Substrates
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 24
Cavity Requirements
• Vertical Waveguiding: large index differences
• Lateral Waveguiding: must be able to process
the epi materials – gain-guided (metal patterning)
– stripe and ridge waveguides (etching)
• Low Scattering Losses: smooth surfaces/interfaces
• Optical Feedback: crystal facets or distributed
reflectors – smooth cleaved facets
– smooth etched facets
– etched periodic gratings (regrowth)
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 25
Cavity Requirements
• Vertical Waveguiding: large index differences
• Lateral Waveguiding: must be able to process
the epi materials – gain-guided (metal patterning)
– stripe and ridge waveguides (etching)
• Low Scattering Losses: smooth surfaces/interfaces
• Optical Feedback: crystal facets or distributed
reflectors – smooth cleaved facets
– smooth etched facets
– etched periodic gratings (regrowth)
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 26
Types of Lateral Guides
Gain-Guided Stripe Ridge
Metal Stripe
• No Etching
Simple to Make
• Poor Confinement
High Threshold
Low Efficiency
Deep Mesa etched
past Active
• Good Confinement
Low Threshold
Multi-Mode
• Poor Heat Flow
Shallow Mesa etched
into Upper Cladding
• Controlled Confinement
Low Threshold
Single-Mode
• Good Heat Flow
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 27
Sidewall Etching Examples
Youtsey, et al. Appl. Phys. Lett. 71, 2151 (1997)
Dry Etching Using
Cl2/H2/Ar ICP (~ 0.7 µm/min)
2 µm 2 µm
Shul, et al. Appl. Phys. Lett. 69, 1119 (1996)
Wet (PEC) Etching Using
KOH under UV light (~ 0.3 µm/min)
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 28
Nakamura, et al. Appl. Phys. Lett. 73, 832 (1998)
Ridge Laser for Single-Mode
Mesa Height and Width Control
Lateral Mode Structure typical width ~ 3-5µm
Etched Mesa Effective Index Step
Current Confinement active guide
guide cladding
cladding contact
contact
neff2 neff2 neff1
2 µm
Etched sidewalls can be
a source of scattering
70 mW
100 mW
3 µm
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 29
Cavity Requirements
• Vertical Waveguiding: large index differences
• Lateral Waveguiding: must be able to process
the epi materials – gain-guided (metal patterning)
– stripe and ridge waveguides (etching)
• Low Scattering Losses: smooth surfaces/interfaces
• Optical Feedback: crystal facets or distributed
reflectors – smooth cleaved facets
– smooth etched facets
– etched periodic gratings (regrowth)
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 30
Cavity Loss Mechanisms
L
Internal Losses: •Absorption
• Scattering
Mirror Losses
xieP
~
Internal Loss
)(cm -1
i
RLm
1ln
1
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 31
Internal Cavity Losses i Material
GaAs/AlAs
InGaAsP/InP
InGaN/AlGaN
35-50 cm-1
3-10 cm-1
Sources of Internal Loss
• Absorption
Free Carriers in Doped Layers
Absorption Tails in “Transparent” Layers
• Scattering
Dislocations
Rough Sidewalls
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 32
Measured AlGaN Absorption Curves
Brunner, et al. J. Appl. Phys. 82, 5090 (1997)
Large
Absorption Tails
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 33
Cavity Requirements
• Vertical Waveguiding: large index differences
• Lateral Waveguiding: must be able to process
the epi materials – gain-guided (metal patterning)
– stripe and ridge waveguides (etching)
• Low Scattering Losses: smooth surfaces/interfaces
• Optical Feedback: crystal facets or distributed
reflectors – smooth cleaved facets
– smooth etched facets
– etched periodic gratings (regrowth)
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 34
Cleaving GaN on Sapphire
m-face Cleavage Planes
of Sapphire
Sapphire
GaN
~2.4° 3 µm
)1021(
)0011(
Stocker, et al. Appl. Phys. Lett. 73, 1925 (1998)
16 nm roughness
R ~ 4%
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 35
Cleaving GaN on SiC
1 µm
High Quality
Cleaved Facets
Are Readily
Obtained
Doverspike, et al. SPIE ’98, 3284, 82 (1998)
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 36
Other Types of Mirrors
Dry-Etched Facets 3rd-Order Gratings
Hofstetter, et al. Appl. Phys. Lett. 73, 2158 (1998)
Abare, et al. Appl. Phys. Lett. 73, 3887 (1998)
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 37
Performance Requirements
• High Optical Gain: small effective masses – low threshold current
– high differential gain
• High P- and N-Doping: shallow donor and
acceptor levels – low voltage operation
• low series resistance
• good ohmic contacts
• Robust, Reliable Materials: low impurity and
defect concentrations – long lifetime
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 38
Performance Requirements
• High Optical Gain: small effective masses – low threshold current
– high differential gain
• High P- and N-Doping: shallow donor and
acceptor levels – low voltage operation
• low series resistance
• good ohmic contacts
• Robust, Reliable Materials: low impurity and
defect concentrations – long lifetime
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 39
Relevant Gain Parameters
Material
GaAs/AlAs
InGaAsP/InP
InGaN/AlGaN
~1019
1-2 x 1018
mC
0.15-0.2
0.04-0.07
mHH
0.8-1.6
0.35-0.6
tr (ns) Material
GaAs/AlAs
InGaAsP/InP
InGaN/AlGaN
2-3
2-3
Jtr (A/cm2)
200-500
50-100
Ntr (cm-3)
Large Effective Masses Takes Lots of
Carriers to Get Gain
dg/dN (cm2)
0.5-2 x 10-16
2-5 x 10-16
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 40
Gain vs Current Density (Theory)
Example Design:
If R = 18%, L= 500µm
m ~ 35 cm-1
Yeo, et al. J. Appl. Phys. 84, 1813 (1998) Current Density (kA/cm2)
Modal
Gai
n, G
g (
cm-1
)
1 0.5 1.5 2 2.5 3 0
nw = 1
nw = 2
nw = 3
nw = 4
0
20
40
60
80
100
120
140
(50Å)
In0.2Ga0.8N/GaN MQW
If i = 0 cm-1
Jth ~ 1 kA/cm2
nw ~ 1 or 2
If i = 40 cm-1
Jth ~ 2 kA/cm2
nw ~ 2, 3, or 4
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 41
Other Issues for Gain in InGaN QWs
Very Unusual:
Broad Low Energy Gain Spectrum
Song, et al. Appl. Phys. Lett. 72, 1418 (1998)
• Indium Clustering? – localized transitions?
– quantum dot effects?
• Free Electron-Hole Pair or
Exciton Transitions?
• Piezoelectric Field is Strong
in Strained InGaN – is gain affected?
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 42
Performance Requirements
• High Optical Gain: small effective masses – low threshold current
– high differential gain
• High P- and N-Doping: shallow donor and
acceptor levels – low voltage operation
• low series resistance
• good ohmic contacts
• Robust, Reliable Materials: low impurity and
defect concentrations – long lifetime
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 43
Voltage Drops in Laser Structure
Rn-contact Rn-AlGaN/GaN
Rspread (n-GaN)
Vlaser = Vdiode + I ( R)
GaN
AlGaN
Metal
Active
Rp-contact
Rp-AlGaN/GaN
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 44
Dopant Materials P-Type Dopants Material
GaAs
GaN
AlGaN
Si 5.8 ~3x1018
Se 5.8 ~1019
Si 12-17 ~1019
Si 15-20 ~1019
N-Type Dopants
Element Eact (meV) Cmax (cm-3)
C 26 ~1020
Zn 30.7 ~1019
Mg 28.4 ~1019
Be 28 ~1019
Mg 170-200 ~1018
Mg + 4·x[%] ~1017
Element Eact (meV) Cmax (cm-3)
r (p-GaN) ~ 1-2 Wcm 0.1-0.2 V/µm @ 1 kA/cm2
r (p-AlGaN) ~ 10-20 Wcm 1-2 V/µm @ 1 kA/cm2
r (n-GaN/AlGaN) < 0.01 Wcm
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 45
Ohmic Contacts
P-Contacts Material
GaAs
GaN
N-Contacts
Metal rc (W-cm2)
AuZn 10-5-10-6
Ni/Au 10-2-10-3
Pt/Ni/Au 5x10-4
Pd/Au 4x10-4
Ta/Ti 3x10-5
Au/Ge/Ni 10-5-10-6
Ti/Al 10-5-10-6
Pd/Al 10-5
Ti/Ag 5x10-5
Ti/TiN 4x10-6
Metal rc (W-cm2)
rc = 10-3 W-cm2 1 V @ 1 kA/cm2
recently
reported
Want rc < 10- 4 W-cm2
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 46
Example: Voltage Drops @ 10kA/cm2
0.1 Wcm (0.5µm)
0.05V
Vlaser = 3V + 16.15V
~ 19V
GaN
AlGaN
Metal
Active
10-3 W-cm2 10V
10 Wcm (0.5µm)
5V
10-5 W-cm2 0.1V
0.01 Wcm (100µm) 1V (assuming conduction x-section comparable
to laser stripe dimensions)
(assuming current crowding comparable
to laser stripe width)
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 47
Performance Requirements
• High Optical Gain: small effective masses – low threshold current
– high differential gain
• High P- and N-Doping: shallow donor and
acceptor levels – low voltage operation
• low series resistance
• good ohmic contacts
• Robust, Reliable Materials: low impurity and
defect concentrations – long lifetime
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 48
Degradation Mechanisms Material
AlGaAs
GaN
• Oxygen Contamination is a Source of
Nonradiative Recombination which can
Limit Device Lifetimes
• Laser Facet Damage
• High Dislocation Densities are a Major
Concern. However:
(1) Defect Propagation is Slower than in GaAs (but more temperature dependent)
(2) Defect Recombination Rates are Slow
• Laser Facet Damage?
Reliability Issues
For Long Lifetime, Still Desirable to Minimize Defect Density
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 49
Epitaxial Lateral Overgrowth (ELOG)
Vertical Dislocation Threads
Can’t Follow Lateral
Growth
Nam, et al. Appl. Phys. Lett. 71, 2638 (1997)
Lateral
Growth
The Result:
Nearly Defect-Free Material!
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 50
Highlights of Challenges for GaN Laser Research
• Lattice Mismatched System – limits range of cladding layer compositions and thicknesses
– difficult to create good electron and photon confinement
• Lack of Suitable Substrate – high dislocation densities
• reliability concerns
• large scattering losses
– high quality cleaved facets are difficult to make
• Large Effective Masses (in Both Conduction and Valence Bands)
– high carrier and current densities required for optical gain
– low differential gain (due to asymmetry in band structure)
• Large Acceptor Activation Energy – high p-type doping difficult (especially in AlGaN)
• high series resistance
• hard to make good p-ohmic contacts
– high voltage operation
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 51
First GaN Blue Laser - Dec‘95
(Nichia)
Nakamura, et al. Jpn. J. Appl. Phys., 35, L74 (1996)
1μs pulse width
1ms rep rate
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 52
Nichia’s Early Laser Structure
c-face Sapphire
Substrate
RIE-Etched
Facets
InGaN MQW
Active
Ridge Waveguide
Nakamura, et al. IEEE J. STQE, 3, 712 (1997)
Nakamura, et al. Jpn. J. Appl. Phys., 35, L74 (1996)
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 53
Who’s Got Blue? (circa 1998) Operation Company
Nichia
Meijo University
Toshiba
Cree
Fujitsu
UCSB
Sony
Xerox
Hewlett Packard
SDL
Pioneer
RT, CW: 6000 hr
RT, Pulsed
RT, Pulsed
RT, quasi-CW: 30 sec
250K, quasi-CW: 1 sec
RT, Pulsed
RT, quasi-CW: 1 sec
RT, Pulsed
RT, Pulsed
RT, Pulsed
RT, Pulsed
RT = Room Temperature
CW = Continuous Wave
Entry Date (CW)
Dec-95 (Nov-96)
Jun-96
Sep-96
Jun-97 (Jan-98)
Jul-97 (Oct-98)
Sep-97
Oct-97 (Jul-98)
Oct-97
Nov-97
Feb-98
Aug-98
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 54
Typical Commercial Laser Performance
CD Players, DVD Players, Laser Printers
Threshold Current, Ith :
Threshold Voltage, Vth :
Output Power, Pout :
20-50 mA
2-3 V
5-30 mW
0.1-1 mA
1.6-2 V
1-2 W
High Performance/Specialty Applications
Threshold Current, Ith :
Threshold Voltage, Vth :
Output Power, Pout :
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 55
0
500
1000
1500
2000
0
2
4
6
8
10
12
14
16
Ith (mA)
Jth (kA/cm2)
Th
resh
old
Cu
rren
t (m
A)
Jth (k
A/cm
2)
CW
1996 1997 1998
Nichia’s Amazing Progress
16 mA!
1.2 kA/cm2
Nichia
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 56
Nichia’s Blue Laser (circa 1998)
• l : ~ 410 nm
• Ith : ~ 50 mA
• Jth : 3-5 kA/cm2
• Vth : ~ 5 V
• Pout : > 30 mW
CW
Nakamura, et al. Jpn. J. Appl. Phys., 37, L1020 (1998)
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 57
0
200
400
600
800
1000
1200
1400
1600
0
2
4
6
8
10
12
14
16
Th
resh
old
Cu
rren
t (m
A)
Jth (k
A/cm
2)
1997 1998
= CW
Other “quasi-CW” Players
Cree
Sony Fujitsu
CW lifetimes all < 1 min
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 58
Cree’s Blue Laser (circa 1998) Pulsed
CW • SiC Substrate
• Stripe Waveguide
• Cleaved Facets
• Wavelength : 408 nm 425 nm
• Lowest Ith : 107 mA 600 mA
• Lowest Jth : 7.1 kA/cm2 25 kA/cm2
• Lowest Vth : 15.7 V 25 V
• Pmax : 2.4 mW 1.2 mW
Pulsed CW
Doverspike, et al. SPIE ‘98, 3284, 82 (1998)
Bulman, et al. LEOS ‘98, FI2 (1998)
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 59
Fujitsu’s Blue Laser (circa 1998) Pulsed
CW
• Wavelength : 406 nm 406 nm
• Lowest Ith : 300 mA 380 mA
• Lowest Jth : 9.5 kA/cm2 12 kA/cm2
• Lowest Vth : 12.5 V 12.6 V
• Pmax : > 20 mW > 0.2 mW
• SiC Substrate
• Ridge Waveguide
• Cleaved Facets
Pulsed CW
Soejima, et al. Jpn. J. Appl. Phys., 37, L1205 (1998)
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 60
UCSB’s Blue Laser (circa 1998)
• c-face & a-face Sapphire Substrate
• Gain-Guided Waveguide
• RIE-Etched & Cleaved Facets
Pulsed
• Wavelength : 422 nm
• Lowest Ith : 650 mA
• Lowest Jth : 9.2 kA/cm2
• Lowest Vth : 19 V
• Pmax : 67 mW
Pulsed
A.C. Abare, M.P. Mack, et al. IEEE JSTQE, 4, 505 (1998)
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 61
Sony’s Blue Laser (circa 1998) Pulsed CW
• c-face Sapphire Substrate
• Ridge Waveguide
• Cleaved Facets
• Wavelength : 411 nm 411 nm
• Lowest Ith : 280 mA 466 mA
• Lowest Jth : 7 kA/cm2 11.7 kA/cm2
• Lowest Vth : 11.8 V 11.5 V
• Pmax : > 5 mW > 5 mW
Pulsed CW
Kobayashi, et al. Electron. Lett., 34, 1494 (1998)
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 62
Xerox’s Blue Laser (circa 1998)
• c-face Sapphire Substrate
• Gain-Guided Waveguide
• CAIBE-Etched Facets
Pulsed
• Wavelength : 419 nm
• Lowest Ith : 740 mA
• Lowest Jth : 20 kA/cm2
• Lowest Vth : 19 V
• Pmax : ~ 50 mW
Pulsed
David P. Bour, et al. IEEE JSTQE, 4, 498 (1998)
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 63
0
10
20
30
40
50
0 0.2 0.4 0.6 0.8 1
Current (A)
Forw
ard
Volt
age (
V)
0
20
40
60
80
100
Lig
ht
Ou
tpu
t p
er f
acet
(mW
)
HP’s Blue Laser (circa 1998)
p-contact (Ni/Au)
p-GaN
p-AlGaN
p-GaN QW(n-GaInN/n-GaInN)
n-GaN
n-AlGaN n-GaN
Buffer(AlN)
Sapphire (0001)
n-contact (Ti/Al)
RIE etched wall
Cleaved facet
• c-face Sapphire Substrate
• Ridge Waveguide
• Cleaved Facets
Pulsed
• Wavelength : 415 nm
• Lowest Ith : 300 mA
• Lowest Jth : 16 kA/cm2
• Lowest Vth : 14 V
• Pmax : ~ 100 mW
Pulsed
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 64
0.0001
0.001
0.01
0.1
1
10
100
1000
104
0
5
10
15
20
25
30
35
40
RT
-CW
Lif
etim
e (h
ou
rs) T
hresh
old
Vo
ltage (V
)
1996 1997 1998
Nichia’s Amazing Progress II
V Drop
CW
stripe
LD
ridge
LD
c-face
sapph
thick
ELOG
extrapolates to
> 10 kHrs!
Si-doping
in MQW
MD-SLS
cladding
&
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 65
Nichia RT-CW Lifetime Data
> 6000 Hrs
Lifetime
Nakamura, et al. Science, 281, 956 (1998)
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 66
Evolution of Nichia’s Substrate
• Free Standing GaN Substrate
+
• ELOG with Thick Buffer • Sapphire Substrate
Polished
Off
LT Buffer
ELOG + Sapphire Removal
10-20µm
80-150µm
c-face
“Defect-Free” Regions
Epi Layers
80µm LP-MOCVD
or
150µm HVPE
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 67
0
100
200
300
400
500
0
10
20
30
40
50
CW
Po
wer
/Fac
et (
mW
)Q
uan
tum
Efficien
cy (%
)
1997 1998
Nichia’s Amazing Progress III
RIE etched
mirrors
cleaved
facets
420 mW!
ELOG sub
“GaN” sub
uncoated/HR
stripe widths = 3 or 4 µm
in all cases
AP
growth
LP
growth
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 68
Nichia High Power Blue Laser
420 mW with
11% WP Eff.
Nakamura, et al. Jpn. J. Appl. Phys., 37, L627 (1998)
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 69
Summary of Best Results (circa 1998)
Ith (mA) Company
Nichia
Cree
Sony
Fujitsu
Toshiba
Xerox
HP
SDL
Pioneer
Meijo
UCSB
16
600
466
380
(P and are per facet)
Vth (V)
4.3
15.7
11.5
12.5
20
16
14
35
16
19
107
280
300
530
600
300
820
290
650
CW Pulsed
Jth (kA/cm2)
1.2
25
11.7
12
7.1
7
9.5
10.6
16
16
8.5
41
2.9
9.2
CW Pulsed
P (mW)
420
1.2
5
0.2
ext (%)
8
49
20
0.7
5
4.2
235
280
80
50
100
150
35
67
39
0.3
CW Pulsed CW Pulsed
Lifetime
6000 hrs
30 sec
1 sec
1 sec
RT-CW
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 70
Date Wed, 13 Jan 1999 103425 +1728
From shuji NAKAMURA <[email protected]>
Subject commercialization of violet laser diodes
Announcement of a start of sample shipments of InGaN-based
violet laser diodes
We announced a commercilization of first InGaN-based violet
laser diodes through Japanese Nikkei Sangyo news paper
yesterday on January 12, 1999. The charactersistics of the
violet laser diodes are an output power of 5 mW, an emission
wavelength of 400 nm, an operating current of 40 mA and an
operating voltage of 5V. The lifetime of the laser diodes is
more than10,000 hours at room temperature. If you were
interested in testing our laser diodes, please check URL
http//www1a.mesh.ne.jp/nichia/index-e.htm. Just for your
information.
Sincerely yours,
Shuji Nakamura
-----------------------------
Shuji Nakamura
R & D Department
Nichia Chemical Industries Ltd.
491, Oka, Kaminaka, Anan
Tokushima 774, Japan
Phone +81-884-23-7787
Fax +81-884-23-1802
e-mail (Office) [email protected]
------------------------------
Nichia Announces Commercial Sampling of
Blue Laser Diodes - Jan 12, 1999 E-mail sent out
by Nakamura: Nichia’s Web Page:
]
V I O L E T L A S E R D I O D E
N i c h i a a n n o u n c e s t o r e l e a s e s a m p l e s h i p m e n t o f V I O L E T L A S E R D I O D E .
S P E C I F I C A T I O N
T y p e N o . N L H V 5 0 0
W a v e L e n g t h 4 0 0 ( n m )
O u t p u t P o w e r 5 ( m W )
P a c k a g e s i z e & p h i ; 5 . 6 c a n t y p e
C O N T A C T
T O K Y O T E C H N I C A L C E N T E R N I C H I A C H E M I C A L I N D U S T R I E S , L T D .
T E L : + 8 1 - 3 - 3 4 5 6 - 3 7 4 6 F A X : + 8 1 - 3 - 5 4 4 0 - 7 5 1 6 E - m a i l : h s h i m i z u @ t o k y o . n i c h i a . c o . j p
[ H O M E ] [ C O M P A N Y P R O F I L E ] [ H I G H B R I G H T N E S S L E D s ] [ U L T R A G L O W ] [ I R V I C O N ] [ R E F E R E N C E
C o p y r i g h t © 1 9 9 8 , 1 9 9 9 N i c h i a C h e m i c a l I n d u s t r i e s , L t d .
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 71
Fast-Forward 5 Years… Sony At Photonics West 2004:
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 72
Progress in the U.S.
Xerox Blue Laser in 2001
M. Kneissl et al., IEEE Jour. Sel. Topics in Quantum Electronics 7, 188 (2001).
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 73
DVD Market
“Blu-ray Disc” Standard
27GB
12 cm disc
single-sided
single-layer
(conventional DVDs = 4.7GB)
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 74
What Happened to Nakamura?
January 30, 2004…the Japanese court ruled in favor of Nakamura
over Nichia in a lawsuit quoting that:
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 75
Fast-Forward 10 Years…
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 76
Shuji wins the Nobel Prize in 2014…
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers
Isamu Akasaki
Hiroshi Amano
Shuji Nakamura
77
share the Nobel Prize
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 78
Tetsuya Takeuchi Part of Agilent Labs Blue Laser Team (led by Rick Schneider)
Now a Professor at Meijo University
In 1973, Professor Akasaki embarked upon the
previously unexplored challenge of using nitride
semiconductors to create a p-n junction-type high-
performance blue luminescent device.
However, the issues were even more difficult than
predicted, resulting in many challenges and
setbacks. In the last half of the 1970s, many
researchers abandoned the "unexplored
semiconductor" research.
Feeling like he was "walking alone in a
wasteland", Professor Akasaki worked on gallium
nitride (GaN) crystal growth day and night.
One day, he saw a tiny crystal under his
fluorescent microscope that gave off cobalt blue
light, and became convinced of the major
possibilities of GaN.
Isamu Akasaki
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 79
I joined Professor Isamu Akasaki's group
in 1982 as an undergraduate student.
In 1985, I developed low-temperature
deposited buffer layers for the growth of
group III nitride semiconductor films on
a sapphire substrate, which led to the
realization of group-III-nitride
semiconductor based light-emitting
diodes and laser diodes.
In 1989, I succeeded in growing p-type
GaN and fabricating a p-n-junction-type
GaN-based UV/blue light-emitting diode
for the first time in the world.
Hiroshi Amano
Scott Corzine
Scott Corzine The Race for GaN Blue Lasers 80
“It also makes me happy to see that my
dream of LED lighting has become a
reality,” Nakamura said in a statement a
press conference this morning.
Nakamura also said he did not
anticipate developing the blue LED
from the outset of his research but
rather started with the goal of simply
getting a Ph.D.
“My dream was to get a Ph.D. At that
time, in Japan, by submitting several
scientific papers, you can get a Ph.D…
you don’t have to go to university … so
at the time, my dream was to publish
five scientific papers, not blue LED,”
Nakamura said.
Shuji Nakamura