michael shur and asif khan - ecse @ rensselaer technology michael shur 1 and asif khan 2 ......

1http://nina.ecse.rpi.edu/shur/

GaN Technology

Michael Shur 1 and Asif Khan 21 Rensselaer Polytechnic Institute, Troy, USA

http://nina.ecse.rpi.edu/shur/2 Department of EE, USC, SC 12110, USA

UV LED growth, Courtesy of SET, Inc.


Outline• Nitride materials system• Materials growth• Device fabrication• Nitride based electronics• Nitride-based LEDs• To explore further


AlInGaN Materials System

2.6 2.8 3.0 3.2 3.4 3.6 3.8 4.0

1

2

3

4

5

6

7

o

InN

GaN

AlN

6H- S

iC

ZnO

sapp

hir e

(O s

u bla

tt ice

)

Ban

d G

ap E

nerg

y (e

V)

Lattice Constant a (A)

Old valuefor InN


Nitride Advantages for Electronic Devices

Properties Advantages•High mobility•High saturation velocity•High sheet carrier concentration•High breakdown field

High power

Heat handling capability•Decent thermal conductivity•Growth on SiC substrate

•Chemical inertness•Good ohmic contacts•No micropipes

Reliability

InsulatedGate

•SiO2/AlGaN and SiO2/GaN good quality interfaces


Figure of Meritfor high frequency/high power

CFOM =χε oµvsEB

2

χε oµvs EB2( )silicon

0

200

400

Si GaAs 6H-SiC

4H-SiC GaN

Com

bine

d Fi

gure

of M

erit

χ is thermal conductivityEB is breakdown fieldµ is low field mobilityvs is saturation velocityεo is dielectric constant


SEMICONDUCTOR MATERIALS SYSTEMS FOR LIGHT EMITTERS

InSbInAsGeGaSbSiInPGaAsCdTeAlSbCdSeInNAlAsZnTeGaPSiC(3C)CdOAlPCdSZnSeSiC(6H)SiC(4H)ZnOGaNZnSCAlN

0 1 2 3 4 5 6 7

Wavelength (nm)2000 800 600 500 400 300 200

Band Gap Energy (eV)

1E-5

1E-4

1E-3

0.01

0.1

1

Rel

ativ

e E

y e S

e nsi

tivity


Energy gaps of nitrides compared with spectral sensitivity

of human eye

InN

GaN

AlN

0 1 2 3 4 5 6 7Energy Gap (eV)

Wavelength (?m)12 0.20.5 0.30.40.8

Rel

ativ

e ey

e re

spon

se


Problems to Solve

• Aging• Substrates• Current slump• Cost• Yield• Manufacturability


Basic parameters of InN, GaN, and AlN at 300 K

Parameter Units GaN AlN InN Lattice constant, c Ǻ 5.186 4.982 5.693 Lattice constant, a Ǻ 3.189 3.112 3.533

Band gap energy, gE eV 3.339a 6.2 1.97

Effective electron mass, em 0m 0.19b (||) 0.17b (⊥ )

0.33c (||) 0.25c (⊥ )

0.11b (||) 0.10b (⊥ )

Effective heavy hole mass, hhm 0m 1.76c (||) 1.61c (⊥ )

3.53 c (||) 10.42 c (⊥ )

1.56b (||) 1.68b (⊥ )

Effective light hole mass, lhm 0m 1.76c (||) 0.14c (⊥ )

3.53 c (||) 0.24c (⊥ )

1.56b (||) 0.11b (⊥ )

Piezoelectric constant, e31 C/m2 -0.33 -0.48 -0.57 Piezoelectric constant, e33 C/m2 0.65 1.55 0.97

Spontaneous polarization, ||P d C/m2 -0.029 -0.081 -0.032

Radiative recombination coefficiente

cm3/s 4.7×10-11 1.8×10-11 5.2×10-11

Refraction index at 555 nm 2.4 2.1 2.8 Absorption coefficient at the

photon energy gEh ≈ν 105 cm-1 1 3 0.4

From M. E. Levinshtein, S. L. Rumyantsev, and M. S. Shur, Editors, “Properties of Advanced Semiconductor Materials: GaN, AlN, InN, BN, and SiGe“, John Wiley and Sons, ISBN 0-471-35827-4, New York (2001)


Nitrides: Hetero epitaxy and homoepitaxy

• Substrates• MOCVD• MBE• PALE• HVPE • Strain energy band engineering


Substrates for III-Nitride Epi

Substrate Lattice constant (Angstroms)

Thermal Conductivity W/cm-K

Thermal expansion coefficient (10-6 1/K)

GaN a = 3.189 c = 5.185

1.3 5.59 3.17

AlN a = 3.112 c = 4.982

3.2 4.2 5.3

6H SiC a = 3.08 c = 15.12

3.6 - 4.9 4.2 4.68

4H-SiC a = 3.073 c = 10.053

3.7

Sapphire a = 3.252 c = 5.213

0.5 7.5 8.5

Si a = 5.4301 1.5 3.59 GaAs a = 5.6533 0.5 6

LiGaO2, ZnO


Substrate ComparisonSubstrate Comparison

Sapphire: poor crystal structure match, large thermal expansion mismatch, poor thermal conductivity.SiC has high thermal conductivity and close lattice match in the c-plane.

But, also has: a different c-axis, relatively large thermal expansion mismatch and chemical mismatch at the interface.

GaN and AlN bulk crystals have the same crystal structure, the same crystal structure, excellent chemical match, high thermal conductivity, and the excellent chemical match, high thermal conductivity, and the same thermal expansionsame thermal expansion but are difficult to produce presently(will this change?).LEO and HVPE GaN films allow fabrication of “quasi-bulk” substrates. Temporary solution until bulk substrates become available?

From MRS Fall 2000 tutorial by M. S. Shur and L. J. Schowalter


Bulk GaN and AlN substrates have become available!

• North Coast Crystals, Inc.: Commercial Scale Production of Bulk, Polycrystalline Group III Nitrides

• Sanders, bulk nitrides (ATP)• High Pressure Research Center in Warsaw• Bulk GaN and AlN at TDI, Inc.• Sakai: Combining the ELO technology on MOVPE templates, thick GaN layers (up

to 500µm ) Samsung• Sumimoto (GaN)• Crystal IS (AlN)• NCSU (AlN)• Kansas State: sublimation (AlN)

When large area high quality AlN and GaN will become available?Which devices will emerge to take advantages of bulk substrates?


1x104

2x104

3x104

4x104

5x104

6x104

1 10 1000

2

4

6

8

10

12

14

16

18

20

22

24

Al0.13Ga0.87N : 20 nm

n-type GaN : 1 µm

Mg-doped GaN crystal

150 µm

(a)

Hal

l mob

ility

µH(c

m2 /V

s)

630 µm

10 µm

110 µm

150 µm

(b)

This work GaN/saphir [4] GaN/6H-SiC [3]

carr

ier

dens

ity n

H*1

012 (

cm-2

)

Temperature (K)

E. Frayssinet, W. Knap, P. Lorenzini, N. Grandjean, J. Massies, C. Skierbiszewski, T. Suski, I. Grzegory, S. Porowski, G. Simin, X. Hu, M.Asif Khap, M. Shur, R. Gaska, and D. Maude, Applied Physics Letters, October 16, 2000; R. Gaska, J. W. Yang, A. Osinsky, Q. Chen,M. Asif Khan, A. O. Orlov, G. L. Snider, M. S. Shur, Appl. Phys. Lett., Feb. 1999

> 60,000 cm2/V-s at low T

High 2DEG mobility for homoepitaxial GaN


GaN-based HFETs on bulk GaN substrates

Vds= +10V

0

20

40

60

80

100

120

140

160

-10 -8 -6 -4 -2 0 2

Vgs(V)

g m(m

S/m

m)

SiCbulk GaNSapphire

From M. Asif Khan and J. W. Yang, W. Knap, E. Frayssinet, X. Hu and G. Simin, P. Prystawko, M. Leszczynski, I. Grzegory, S. Porowski, R. Gaska, M. S. Shur, B. Beaumont, M. Teisseire, and G. Neu, GaN-AlGaN Heterostructure Field Effect Transistors Over Bulk GaN Substrates, Appl. Phys. Lett. 76, No. 25, pp. 3807, 3809, 19 June (2000)


GaN-based HFETs on bulk AlN substrates

0 2 4 6 8 10 120.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

-14.0

-12.0

-10.0

-8.0

-6.0

-4.0

-2.0

0.0

VG=-4, -5V

VG=-2VVG=-3V

VG=0V, 1V

VG=-4VVG=-3V

VG=-2V

VG=-1V

VG=0V

Dra

in C

urre

nt

I D

(A/m

m)

Drain Bias VDS

(V)

Gat

e Le

akag

e C

urre

nt (µA

/mm

)

X. Hu, J. Deng, N. Pala, R. Gaska, M. S. Shur, C. Q. Chen, J. Yang, S. Simin, and A. Khan, C. Rojo, L. Schowalter, AlGaN/GaN Heterostructure Field Effect Transistor on Single Crystal Bulk AlN, submitted to APL


LEO (Lateral Epitaxial Overgrowth) material

Defect free GaN

SiO2(for defect blocking)

Dislocated material

Dislocation density 109 - 1010 cm-2 for regular material104 - 107 for the LEO material


Nitrides, SiC, SiO2

• Solid-state solutions and hetero-structures based on AlN/SiC/-InN/GaN have been demonstrated.

• GaN devices on SiC substrates demonstrated superior performance

• GaN devices on Si have been demonstrated• SiO2 forms excellent interface with AlGaN*

*M. A. Khan, X. Hu, G. Simin, A. Lunev, R. Gaska and M. S. Shur, Novel AlGaN/GaN Metal-Oxide-Semiconductor Field Effect Transistor, IEEE Electron Device Letters, vo. 21, No. 2, pp. 63-65, February, 2000


Epitaxial films

• MOCVD– Lateral Epitaxial Overgrowth

• MBE• Hydride VPE

Gallium transport by chloride formation2HCl(g) + 2Ga(l)->2GaCl(g) +H2(g) T = 800 oCReaction with chloride formationGaCl(g) + NH3(g)->GaN(s) + HCl(g)+ H2(g) T = 700 oC


Nichia Two-Flow MOCVD Process for High Quality Epitaxial GaN

N2 + H2

Heater

Conical Quartz Tube IR radiation thermometer

StainlessSteel Chamber

N2 + NH3 + TMG

Substrate

Vacuum exhaust

After NakamuraRotating Susceptor


MOCVD

MOCVD reactor

Process exhaust

N2

H2

TMGa TMAl TMIn Cp2Mg

PH3 DETe/H2

3-way valve

Mass flow controller

Pressure controller

Bubbler bypass valve

Run/Vent valve


Molecular Beam Epitaxy

RHEED screenMagnets

Electron Cyclotron Resonance Cracker

Solid source

Pyrometer

N2

After Morkoc et al., J. Appl. Phys. 76 (3), p. 1363 (1991)


Pulsed Atomic Layer Epitaxy

0 1 0 2 0 3 0 4 0 5 0 6 0 7 0

- 3 . 0

- 2 . 5

- 2 . 0

- 1 . 5

- 1 . 0

- 0 . 5

0 . 0

0 . 5

1 . 0

1 . 5

2 . 0

2 . 5

T M G

T M I

N H 3

T M A

T i m e ( s e c o n d ) 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0

- 3 . 0

- 2 . 5

- 2 . 0

- 1 . 5

- 1 . 0

- 0 . 5

0 . 0

0 . 5

1 . 0

1 . 5

2 . 0

2 . 5

T M G

T M I

N H 3

T M A

T i m e ( s e c o n d )

150 repeats

GaN

Al2O3

AlInGaN (2,2,1)150

GaN

Al2O3

AlInGaN (2,2,1)150

Khan et. al. “Lattice and Energy Band Engineering in AlInGaN/GaN Heterostructure “ Appl. Phys. Lett 76, (2000) 1161.

Zhang et. al. “Pulsed atomic Layer Epitaxy of Quaternary AlInGaN Layers”Appl. Phys. Lett. 79, (2001) 925.


MOCVD AlN vs PALE AlN

sapphire

HT-Al0.2Ga0.8 N 0.2 µm

n+-Al0.2Ga0.8 N 2 µm

AlN/AlGaN SL

sapphire

PALE-AlN 0.3 µm

n+-Al0.2Ga0.8 N 2 µm

AlN/AlGaN SL

NH3

TMA

t

Conventional MOCVD

on

on

MOCVD AlN

t

TMA

NH3

PALE

on

offonoff

PALE AlN

J. P. Zhang, et.al, accepted for publication in Appl. Phys. Lett,


XRD study of MOCVD & PALE AlN

-1000 -500 0 500 1000

102

103

104

105

PALE

MOCVD

FWHM=60 arcsec=824 arcsec

Cou

nts

ω (arcsec)

experiment

simulation

PALE AlN

J. P. Zhang, et.al, accepted for publication in Appl. Phys. Lett,


STRAIN ENERGY BAND ENGINEERING QUATERNARY ALLOYS

In = 0%In = 2%

In = 4%

In = 8%∆a/a

%

Al fraction, %-1.5

-1

-0.5

0

0.5

1

0 20 40 60∆a/

a %

∆Eg = 0.25 eV∆Eg = 0.45 eV∆Eg = 0.86 eV

In=0%

In=8%

In=4%In=2%

In = 0%In = 2%

In = 4%

In = 8%∆a/a

%

Al fraction, %-1.5

-1

-0.5

0

0.5

1

0 20 40 60∆a/

a %

∆Eg = 0.25 eV∆Eg = 0.45 eV∆Eg = 0.86 eV

Al fraction, %-1.5

-1

-0.5

0

0.5

1

0 20 40 60∆a/

a %

∆Eg = 0.25 eV∆Eg = 0.45 eV∆Eg = 0.86 eV

In=0%

In=8%

In=4%In=2%

• Independent control of band- offset and Lattice Mismatch• Quantification of bulk, piezo, spontaneous polarization doping contributions

i-GaN

AlxInyGa 1-x-y N

AlN

SiC

n-GaN


SIMS and X-ray(Al- alloy composition 12%)

i-GaN

AlInxGaN

AlNSiC

n-GaN

125 126 127 128 1292 θ

In fl

ow =

75

ccm

125 126 127 128 129

(d)

(c)

In fl

ow =

50

ccm

125 126 127 128 129

(b)

In fl

ow =

25

ccm

125 126 127 128 129

(a)

In fl

ow =

0

GaN AlInGaN

X-ray (0006) peaks

In=0%

In=2%

In=1.5%

In=0.75%

Al0.10 In0.06Ga 0.84N

Electron microprobe analysis agrees with SIMS


PL and lattice constant• Lattice mismatch and band-offset vs. In- composition

ROOM TEMPERATURE PHOTOLUMINESCENCE

3.2 3.4 3.6 3.8

0.0

0.2

0.4

0.6

0.8

1.0

4

3

2

1

GaN

hνexc = 4.66 eVT = 300 K

Nor

mal

ized

PL

Inte

nsity

Photon Energy (eV)

0

.75

1.5

2

In%

0.0 0.5 1.0 1.5 2.00.10

0.15

0.20

0.25

0.30

Al - 9 %

∆Eg (

eV)

∆c (A

ngst

rom

s)

In Molar Fraction (%)

0.00

0.01

0.02

0.03

Al=12%

calculated


SURFACE AND INTERFACE QUALITYRMS versus IN

TEM AFM

0

1

2

3

4

5

6

7

8

0 0.5 1 1.5 2 2.5

In composition, %

RM

roug

hnes

s, A

(Al- alloy composition 12%)


Epitaxial Wafer

Wafer Cleaning

Typical Process Flow in GaN device fabrication

Lithography

AnnealingDielectric Deposition

Probe Contact Metallization

Mesa Etching

LithographyMetallization

multiple

Lithography


UNCLEANEDSAMPLE

CLEANEDSAMPLE

Process Flow


Etching


Metallization


Surface passivation

To dicing /packaging or on-wafer testing


Ti/Al/Ti/Au Ohmic Contacts to n-AlInGaN

0

10

20

30

40

50

-10 0 10 20 30d(µm)

R(o

hm)

AlGaN 1x10-5 ohm-cm2

AlInGaN 5x10-6 ohm-cm2

After M. Asif Khan, M. S. Shur, and R. Gaska, Strain Energy Band Engineering in AlGaInN/GaN Heterostructure Field Effect Transistors, presented at GaAs-99 Proceedings, October 4, 1999


Pd/Au Ohmic Contacts top-type GaN

•Pd (5 nm)/Au (10 nm) pads deposited with e-beam. •This thickness results in nearly 70% transparency for visible wavelengths•A 30 second RTA anneal at 400° C in an oxygen ambient •Contact resistance 1 x 10-4 Ωcm-2 at 300 K • 1.5 x 10-6Ωcm2 (at 550 K).

After A. Lunev, Vinamra Chaturvedi, Ashay Chitnis, Grigory Simin, Jinwei Yang and M. Asif KhanR. Gaska, and M. S. Shur, Low-Resistivity Pd/Au Ohmic Contacts to p-GaN for Heterostructure Bipolar Transistors and Light

Emitting Diodes, ICSRM-99, October 10-15, 1999


GaN-based Schottky Barriers

0.5

1

1.5

Bar

rier

heig

ht (

eV)

-2 -1 0 1

Xm – XGaN (eV)

After T. U. Kampen and W. Mönch, Metal Contacts on GaN, MIJ-NRS, Vol. 1, Article 4, 12/20 (1997)

Gallium Nitride Schottky Barrier Diode Operated to 500°C( Furukawa Electric )


GaN-based p-n junctions

Ohmic contacts

Light

n G a N

p - G a N

-

Ohmic contacts

Light

p

n - G a N

-

Sapphire Sapphire

G a N

After Q. Chen, M. A. Khan, C. G. Sun, and J. W. Yang, Electronics Letters, 31, p. 1781 (1995)


GaN p-n junctions on SiC substratesPt contact

p-type GaNAl contact

N-type GaNBuffer layerSiC substrate

See V. Dmitriev, MRS Internet J. Nitride Semicond. Res. 1, 29(1996).


GaN p-n junctions on LEO material

P = 1018 cm-3 N = 5x1016 cm-3

S=2x20 µm

Reverse leakage current 9x 10-7 A/cm-2 in the LEO GaNReverse leakage current 9x 10-4 A/cm-2 in the non-LEO GaN(After P. Kozodoy et al. Appl. Phys. Lett. 73(7), 975 (1998)


Band diagrams of FETs below threshold

Source Drain

Distance

Con

duct

ion

band

edg

e

Source Drain

Distance

Con

duct

ion

band

edg

e

Source Drain

Distance

Con

duct

ion

band

edg

e

Source Drain

Distance

Con

duct

ion

band

edg

e

Si GaAs

SiC GaN


Doped Channel GaN-based FET Operation at 750 oC

50 1 0

D ra in -s o u rc e vo l t a g e (V)

Dra

in C

urr

en

t (m

A/m

m)

1 0 0

20 0

0

W = 5 0 µ m L = 0 . 2 5 µ m

T = 7 5 0 o C

- 2 V- 3 V

2 V

1 V

0 V

- 1 V

After M. Kamp, GaN workshop continues the substrate search, III-Vs Review, Vol. 11, No 6, pp. 42-44 (1998)


Device Applications. Reported state-of-art performance

of III-N HFETsRF-power levels : 5...11 W/mm

Peak drain current : 1...1.5 A/mm

I-SiC/Sapphire

Pd/Ag/Au

GaN

AlN

Pd/Ag/AuAlGaN

S G D

Critical issues with III-N HFETs

Gate leakage current: 10-3-10-5 A/mm

Current collapse (RF performance degradation)

Long term stability and parameter drift


Current collapse in AlGaN/GaN HFETs:Pulsed measurements of “return current”

0

10

20

30

40

50

60

-10 -8 -6 -4 -2

Idc(VG= 0)

VG(t)

Id (return @ VG= 0)

VG= 0

Id (VG)

Current collapse

VG

A. Tarakji, G. Simin, N. Ilinskaya, X. Hu, A. Kumar, A. Koudymov, J. Zhang, and M. Asif Khan, M.S. Shur and R. Gaska, Appl. Phys. Lett., 78, N 15, pp. 2169-2171 (2001)

G. Simin, A. Koudymov, A. Tarakji , X. Hu, J. Yang and M. Asif Khan, M. S. Shur and R. Gaska APL October 15 2001

“Return” current

Current collapse

TimeVT

IDS

Time


HFET, MOSHFET, and MISHFET

-14 -12 -10 -8 -6 -4 -2 0 21x10-16

1x10-14

1x10-12

1x10-10

1x10-8

1x10-6

1x10-4

HFET

MOSHFET

MISHFET

Gat

e cu

rrent

, A

Gate voltage, V

MOSHFET - SiO2 (ε = 3.9, 100 A) MISHFET - Si3N4 (ε = 7.5,100 A)

-15 -10 -5 0

0

100

200

300

400

500

600

HFET

MISHFE

T

MOSHFET

Dra

in c

urre

nt, m

A/m

m

Gate voltage, V

I-SiC

Pd/Ag/Au

GaN

AlN

Pd/Ag/Au

AlInGaN S G D

Si3N4

X. Hu, A. Koudymov, G. Simin, J. Yang, M. Asif Khan, A. Tarakji, M. S. Shur and R. GaskaAppl. Phys. Lett, v.79, p.2832-2834 (2001)


MOSHFET (SiO2 )

I-SiC

Pd/Ag/AuGaN AlN

Pd/Ag/AuAlInGaN

S G D

SiO2

MISHFET Si3N4I-SiC

Pd/Ag/AuGaN AlN

Pd/Ag/AuAlInGaN

S G D

Si3N4

Resolving the issues: AlGaInN, gate dielectrics, InGaN channel

Reducing the gate leakage current (104 - 106 times)

AlGaN/ InGaN GaN DHFET

I-SiC

Pd/Ag/AuGaN AlN

InGaN AlInGaN

S G DSi3N4 /SiO2

I-SiC

Pd/Ag/AuGaN AlN

InGaN AlInGaN

S G D

Combining the advantagesReducing current collapse, Improving carrier confinement

MISDHFET


AlInGaN/InGaN/GaN DHFET concept: improved carrier confinement

and strain management

0 100 200 300 400-1

0

1

2

3

4

5

Ec

n

AlGaN/InGaN/GaN DHFET

Ec,

eV

Distance, A

VG:

0 -2.5 -5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

10-2

0 n, c

m -3

0 100 200 300 400-1

0

1

2

3

4

5

Ec

n

AlGaN/GaN HFET

E c, eV

Distance, A

VG: 0 -2.5 -5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

10-2

0 n, c

m -3

I-SiC

Pd/Ag/Au

GaN

AlN

InGaN (x=0.1, 50 A) AlInGaN (x=0.25, 250 A)

S G D

• Better 2DEG confinement• Constant field in the QW region• Strain compensation

G. Simin et.al. AlGaN/InGaN/GaN Double Heterostructure Field-Effect TransistorJpn. J. Appl. Phys. Vol.40 No.11A pp.L1142 - L1144 (2001)


0 2 4 6 8 10 12 140.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

VG=-8 V

VG=-6 V

VG=-4 V

VG=-2 V

VG=0 V

Cur

rent

, A/m

m

Drain Voltage, V

-16 -14 -12 -10 -8 -6 -4 -2 0 21E-3

0.01

0.1

1

Id(A

/mm

)

vg(V)

HFET DHFET

1 0 0 2 0 0 3 0 0 4 0 0 5 0 0 6 0 00 .0 1

0 .1

1

Inte

nsity

, a.u

.

G a

1 0 0 2 0 0 3 0 0 4 0 0 5 0 0 6 0 00 .0 1

0 .1

1

Inte

nsity

, a.u

.

N

1 0 0 2 0 0 3 0 0 4 0 0 5 0 0 6 0 00 .0 1

0 .1

1

Inte

nsity

, a.u

.

D i A

A l

1 0 0 2 0 0 3 0 0 4 0 0 5 0 0 6 0 00 .0 1

0 .1

1

Inte

nsity

, a.u

.

D is ta n c e , A

In

AlInGaN-InGaN-GaN DHFET characteristics

SIMS profiles


AlGaN-InGaN-GaN DHFET: Carrier confinement and current collapse reduction

-7 -6 -5 -4 -3 -2 -1 0 1 2

0.0

0.2

0.4

0.6

0.8

1.0

200OC150OC100OC

50OC25OC

200OC150OC100OC50OC25OC

Pulsed tra

nsfer c

urves

Pulsed "return" currents

Pul

sed

drai

n cu

rrent

, A/m

m

Gate pulse amplitude, V

> 1018cm-3

> 1016cm-3

> 1014cm-3

< 1014cm-3

> 1018cm-3

> 1016cm-3

> 1014cm-3

< 1014cm-3

> 1018cm-3

> 1016cm-3

> 1014cm-3

< 1014cm-3

HFE

T

> 1018cm-3

> 1016cm-3

> 1014cm-3

< 1014cm-3

> 1018cm-3

> 1016cm-3

> 1014cm-3

< 1014cm-3

> 1018cm-3

> 1016cm-3

> 1014cm-3

< 1014cm-3

DH

FET

-10 -5 0 5 10 15 20 25 300

5

10

15

20

25

30

35

~ 4

dB

G ain

Pulsed (VD S = 30 V)

CW (VD S = 25 V) Pout

6.3 W /m m

Pou

t, dbm

; Gai

n, d

B

P in, dbm


Si3N4 /AlGaN/InGaN/GaN MISDHFETDC & RF characteristics

I-SiC

Pd/Ag/AuGaN AlN

InGaN AlInGaN

S G DSi3N4

0 2 4 6 8 10 12 14 16 180.0

0.2

0.4

0.6

0.8

1.0

-14-12-10

-8-6-4

-2

VG= 0 V

I D, A

/mm

VDS, V-14 -12 -10 -8 -6 -4 -2 0 2 4

10-13

10-11

1x10-9

1x10-7

1x10-5

1x10-3

MISDHFET

DHFET

I G, A

VG, V• Low Gate leakage

current (as in MOS/MIS

HFETs)

• No current collapse (as

in DHFET)

• Stable DC and RF

performance (7.5 W/mm)

-5 0 5 10 15 20 25

10

15

20

25

30 7.5 W/mm(Pulsed, 2 GHz)

6.1 W/mm(CW, 2 GHz)

P out, d

Bm

Pin, dBm

0 2 4 6 8 10 12 14 160.00.51.01.52.02.53.03.54.04.55.0

MISDHFETCW @ 2GHz

Pou

t, W

/mm

TIME, hours


Breakdown voltage and offset gate

0.80.4 1.2 1.6 2.0

200

150

100

50

0

Gate-drain distance (A)

Bre

akdo

wn

volta

ge (V

)

From R. Gaska, Q. Chen, J. Yang, A. Osinsky, M. Asif Khan, and Michael S. Shur,AlGaN/GaN Heterostructure FETs with Offset Gate Design, Electronics Letters, 33, No. 14, pp. 1255-1257, 3 July (1997)


MOSHFET Switch

0 100 200 300 400 500 6000

5

10

15

20

- 6 V

- 3 V

0 V

+ 3 V

Vg = + 6 V

PON/OFF = 7.5 kW/mm2

R ON = 75 mOhm-mm2

Cur

rent

, A/m

m2

Drain Voltage, V

15 µm source-drain spacing

After G. Simin, X. Hu, N. Ilinskaya, A. Kumar, A. Koudymov, J. Zhang, M. Asif Khan, R. Gaska and M. S. Shur, A 7.5 kW/mm2 current switch using AlGaN/GaN Metal-Oxide-Semiconductor Heterostructure Field Effect Transistors on SiC Substrates, Electronics Letters. Vol. 36, pp. 2043 –2044, Nov. 2000


Comparison with SiC and GaN Diodes

GaN-UF

SiC-ABBGaN-UF

SiC-Purdue

GaN-UF

SiC-NCSU

SiC-RPI

GaN-Caltech

6H-SiC

4H-SiC

GaN

AlGaN-UF

AlGaN

B r e a k d o w n V o l ta g e ( V )

Sp

ec

ific

Re

sis

tan

ce

(o

hm

-cm

2)

101 102 103 10410-4

10-3

10-2

10-1

100

MG-MOSHFET

From S. J. Pearton et al.GaN Electronics for High Power, High Temperature Applications,Interface, Vol. 9, No. 2,pp. 34-39 (2,000)

MG-MOSHFET point is from G. Simin, X. Hu, N. Ilinskaya, A. Kumar, A. Koudymov, J. Zhang, M.Asif Khan, R. Gaska and M. S. Shur, A 7.5 kW/mm2 current switch using AlGaN/GaN Metal-Oxide-Semiconductor Heterostructure Field Effect Transistors on SiC Substrates (EL-2000).


Power devices –applications and ratings

10 100 10, 0001,0 0010 -2

10 0

10 2

10 3

10 1

10 -1D is p layd ri ve s

T e le c o m m u -ni c a tio ns

F a c to ryA u to m at io n

Mo to rCo n t ro l

L a m pB a l la s t

T ra c tio nHD V C

B lo c k in g vo l ta g e ( V )

PowerSupplies

Automotive

GaNregion

Cur

rent

(A)

MOSHFET

Data from B. J. Baliga, IEEE Trans., ED-43, p. 1717 (1996)


GaN Microwave Detector

From J. Lu, M. S. Shur, R. Weikle, and M. I. Dyakonov, Detection of Microwave Radiation by Electronic Fluid in AlGaN/GaN High Electron Mobility Transistors, in Proceedings of Sixteenth Biennial Conference on Advanced Concepts in High Speed Semiconductor Devices and Circuits, Ithaca, New York, Aug. 4-6 (1997), pp. 211-217


Measured Detector Responsivity

0 5 10 15 20

0

5

10

15

20(a)GaN HFET

f ( GHz )

R

( V/W

)

Measured DataCalculated (x0.25)

0.0 0.5 1.0 1.5 2.0

0

100

200

300(b)

From J. Lu, M. S. Shur, R. Weikle, and M. I. Dyakonov, Detection of Microwave Radiation by Electronic Fluid in AlGaN/GaN High Electron Mobility Transistors, in Proceedings of Sixteenth Biennial Conference on Advanced Concepts in High Speed Semiconductor Devices and Circuits, Ithaca, New York, Aug. 4-6 (1997), pp. 211-217


Photonic Nitride Devices• Solid State Lighting• UV LEDs


Importance of Solid State Lighting

• 21% of electric energy use in lighting• Half of this energy can be saved by

switching to solid-state lighting Projected savings from solid-state lighting $115 billion by year 2020

• Solid-state lighting expected to reach lifetimes exceeding 100,000 hours

• LEDs are the most efficient sources of colored light in visible spectral range.

• White phosphor-conversion LEDs surpassed incandescent lamps in performance


Benefits of LED Lighting

Data from R. Haitz, F. Kish, J. Tsao, and J. NelsonInnovation in Semiconductor Illumination: Opportunities for National Impact (2000)

0

2

4

6

8

10

12

2000 2005 2010 2015 2020 2025 2030

LED Penetration(%)

Energy Savings100TWh/yrCost Savings $10B/yr

“Low Investment Model”

An improvement of luminous efficiency by 1% may save 2 billions dollars per year.


Solid State Lighting Efficiency (lm/W)FlickersCannot be dimmedLosses in ballastNoisy

0

20

40

60

80

100

Incandescent Halogen Fluorescent White LED(2000)

White LED(2010)

2002


Cool LED Light – saving cooling costsLight and heat percentages for lighting sources

0102030405060708090

Incandescent Fluorescent LED

LightHeat


Schematic of band gap alignment in AlInGaN LEDs.

In0.23Ga0.77N

n-A

l 0.15

Ga 0.

85N

p-GaN

p-A

l 0.15

Ga 0.

85N

0.05 µm

n-GaN

p-GaN

o

In0.45Ga0.55N

p-Al

0.2G

a 0.8N

30 A

n-GaN

(a) (b)

(a) DH-based structure with two wide-band-gap cladding layers; radiative transitions occur between donor-acceptor pairs (after S.Nakamura et al., J. Appl. Phys. 76, 8189, 1994); (b) SQW structure with asymmetric confining layers; radiative transitions occur between quantum-confined levels of electrons and holes (after S.Nakamura et al., Jpn. J. Appl. Phys. 34, L1332, 1995)


Nitrides for Blue, White and UV emitters


First LED (1907)


Emissive and Electrical Characteristics

350 400 450 500 550 600 650 700

AlInGaN SQWgreen (517nm)

AlGaAs DHred (649nm)

AlGaInP DHyellow (594nm)

AlInGaN SQW blue (465nm)

AlInGaN DHblue (427nm)

Nor

mal

ized

Inte

nsity

(arb

. uni

ts)

Wavelength (nm)From A. Zukauskas, M. S. Shur and R. Gaska, Introduction to Solid State Lighting, Wiley (2002)


Current-voltage characteristics of AlGaAs, AlGaInP, and AlInGaN-based

high brightness LEDs

1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.51E-9

1E-8

1E-7

1E-6

1E-5

1E-4

1E-3

0.01

0.1

γ =2

AlGaAs DH AlInGaP DH AlInGaN DH AlInGaN SQW

Fo

rwar

d C

urre

nt (A

)

Forward Voltage (V)From A. Zukauskas, M. S. Shur and R. Gaska, Introduction to Solid State Lighting, Wiley (2002)


Chip structure of AlInGaN/Al2O3 LED(after S.Nakamura and G. Fasol, The Blue Laser Diode: GaN Based Light Emitters and Lasers, Springer, Berlin, 1997).

Sapphire Transparent Substrate

Ti/Al n-Electrode

n-GaN Contact Layer

Ni/Au p-Electrode

p-GaN Contact Layer

~100 µm

4 µm

0.15 µm

0.5 µm InGaN/AlGaN DH, SQW or MQW Structure

Transparent Metal (Au/Ni)

Buffer Layer


AlInGaN/SiC LED

n-GaN Contact Layer

Ni Back Electrode

InGaN/AlGaN DH

Au Top Electrode

p-GaN Contact Layer

n-SiC Transparent Substrate

Shorting Ring

Insulating Buffer Layer

(after J.A.Edmond et al., Proc. SPIE 3002, 2, 1997).


High power AlInGaN Flip-Chip LED

InGaN/GaN Multiple Quantum Well

Sapphire

p-GaN Contact Layer

n-GaN Contact Layer

Submount

Solder

After J. J. Wieret et al., Appl. Phys. Lett. 78, 3379, 2001.


Shaped Chips: semi-spherical

Electroluminescent Structure

Au Coating

Antireflection Coating

Hemispherical Chip

Electroluminescent StructureElectrodes

a)

b)

From A. Zukauskas, M. S. Shur and R. Gaska, Introduction to Solid State Lighting, Wiley (2002)


Light Extraction : TIP-LEDs from LumiLeDs

T o p c o n t a c t

h ig h p r e s s u re s o d iu m1 k WT I P - L E D

S t a n d a r dA lG a I n P / G a P

1

100

10

1000

P e a k w a v e le n g t h (n m )

Lu

me

n/w

att

550 600 650 700 750

m e r c u ry v a p o r 1 k Wf lu o r e s c e n t 1 W

tu n g s te n 6 0 Wh a lo g e n 3 0 W

re d f i l t e r e dtu n g s te n 6 0 W

After M.O. HOLCOMB et al. (2001), Compound Semiconductor 7, 59, 2001).


WHITE SOLID-STATE LAMP


CRI for White Light( ) ( ) ( ) ,λdλSλdλSλVK ∫∫

∞

×=0

780

380

Wlm683

Spectral Range Temperature (K) Efficacy (lm/W) General CRI

2856 17 100 4870 79 100

Full (Planckian)

6504 95 100 2856 154 100 4870 196 100

380 nm-780 nm (trimmed-Planckian) 6504 193 100

2856 334 95 4870 320 95

430 nm-660 nm (trimmed-Planckian) 6504 305 95



Optimization of White Polychromatic Semiconductor

Lamp Approach: Find the global maxima of the objective

function for different values of σ.

( ) ( ) ann RKIIF σσλλσ −+= 1,...,,,..., 11



Phase distribution for a dichromatic white lamp with the 30-nm line width of the primary sources and 4870 K color temperature

0 100 200 300 400

-60

-40

-20

0

20

380/569 nm

489/591 nm

496/635 nm

481/580 nm

450/571 nmRa

K (lm/W)(after Žukauskas et al., Appl. Phys. Lett. 80, 2002).


Optimal boundaries of the phase distribution for 4870-K white-light sources containing 2, 3, 4, and 5 primary

sources with the 30-nm line widths

320 340 360 380 400 420 440

5

10

20

304050607080

90

95

9899

99.5R

a5

4

3

2

Systems: quintichromatic quadrichromatic trichromatic dichromatic

K (lm/W)(after Žukauskas et al., Appl. Phys. Lett. 80, 2002). Crosses mark the points that are suggested for highest reasonable CRI for each number of the primary sources.


InGaN based luminescence conversion white LED

InGaN chip

Phosphor layer

(after S.Nakamura and G.Fasol, The Blue Laser Diode: GaN Based Light Emitters and Lasers, Springer, Berlin, 1997)


White light from blue emission of AlInGaN LED (465 nm) and yellow emission of cerium-doped garnet

with different peak wavelength positions

0.0 0.2 0.4 0.6 0.8 1.00.0

0.2

0.4

0.6

0.8

1.0

YAG:Ce3+

InGaN

10,000

6,0004,000

3,000

2,000

460

640700

620600

580

560

540

530520

510

500

490

480

400

y C

hrom

atic

ity C

oord

inat

e

x Chromaticity CoordinateFrom A. Zukauskas, M. S. Shur and R. Gaska, Introduction to Solid State Lighting, Wiley (2002)


MULTICHIP LED: 2 chip LEDs

Wavelength (nm)/Intensity Color Temperature

(K) 1λ /I1 2λ /I2

K (lm/W) Ra

2856 450/0.157 580/0.843 492 -13 4870 450/0.325 572/0.675 430 3.0 6504 450/0.399 569/0.601 393 9.5



Optimized spectral power distributions

400 450 500 550 600 650

K=430 lm/WRa=3

Pow

er (a

rb. u

nits

)

Wavelength (nm)

K=366 lm/WRa=85

K=332 lm/WRa=98

K=324 lm/WRa=99

2 LEDs

3 LEDs

4 LEDs

5 LEDsAfter A.Žukauskas et al., Appl. Phys. Lett. 80, 2002.



Variation of the peak wavelength with general CRI for solid-state lamps composed of 2, 3, 4, and 5

primary LEDs with the 30-nm line widths

2 5 10 20 30 40 50 60 70 80 90 95 98 99 99.5

450

500

550

600

650 2 LEDs 3 LEDs 4 LEDs 5 LEDs

Pea

k w

avel

engt

h (n

m)

Ra

(after A.Žukauskas et al., Proc. SPIE 4425, 2001)


Nichia UV LEDs

Type Product Peak Optical Forward(mm) Number Wavelength Power Output Voltage

(nm) (µW) Vf (V)Typ.

Φ5 NSHU550 375 700 3.5Φ5 NSHU590 375 700 3.5

After http://www.nichia.co.jp/product/led.html


Nichia White LEDsType Produc t Luminous Forward Direc tivity(mm) Number Intensity Voltage 2θ ½

(c d) Vf (V) (degree)Typ.

Φ3 NSPW300BS 3.2 3.6 25°Φ3 NSPW310BS 1.5 3.6 60°Φ3 NSPW312BS 2.2 3.6 35°Φ3 NSPW315BS 0.78 3.6 70°Φ5 NSPW500BS 6.4 3.6 20°Φ5 NSPW510BS 1.8 3.6 50°Φ5 NSPW515BS 0.48 3.6 70°4.6 NSPWF50BS 0.3 3.6 140/120°


Nichia Blue LEDsProduct Luminous Forward DirectivityNumber Intensity Voltage 2θ ½

(cd) Vf (V) (degree)Typ. Max.

NSPB300A 2.3 3.6 4 15°NSPB310A 1.2 3.6 4 30°NSPB320BS 0.7 3.6 4 45°NSPB500S 3.5 3.6 4 15°NSPB510S 1.5 3.6 4 30°NSPB520S 0.8 3.6 4 45°NSPB636AS 0.55 3.6 4 70°/30


Applications (for 250 nm – 340 nm)Sensing and beyond

• Environmental protection• Homeland security• Biology• Medicine• Medical sterilization• Bio-agent detection • Water and air purification• Solid-state white lighting• Short-range secure

communications• Dense data storage• Ballistic missile defense• To be emerged

Applications of U of V/RPI/SET quadrichromatic Versatile Solid-State Lamp: Phototherapy of seasonal affective disorder at Psychiatric Clinic of Vilnius University

UV-LED Based Fluorimeter with IntegratedLock-in Amplifier (after Prof. Zukauskas, U of V,Lithuania)


Existing and proposed UV LED based bio detection systems

UV-LED Based Fluorimeter with IntegratedLock-in Amplifier (after Prof. Zukauskas, U of V,Lithuania)

AnthraxBacteria

From Introduction to Biological Agent Detection Equipment for Emergency First Responders,U.S. Department of Justice Office of Justice Programs National Institute of Justice.


Medical Applications: Example• Seasonal affective disorder

affects many people (up to 10%)in the northern latitudes

• Bright white light is known to treat SAD

• The exact mechanism of treatment is not known

• Optimization of Spectral Power Distribution might help treatment

Applications of U of V/RPI/SET quadrichromatic Versatile Solid-State Lamp: Phototherapy of seasonal affective disorder at Psychiatric Clinic of Vilnius University


Multiple Quantum Well (50% Al Molar Fraction) Photoluminescence on SiC and Bulk AlN

ArF excimer laser (pulse duration 8 ns) emitting at 193 nm (6.42 eV) was used for the generation of carriers above the band gap of AlN (6.2 eV) so that both the wells and the barriers have been photoexcited. The structures were also excited selectively by 4-ns-long pulses of the fifth harmonic of Nd:YAG laser radiation at 213 nm (5.82 eV), which generates carriers only in the quantum well material.

From R. Gaska, C. Chen, J. Yang, E. Kuokstis, A. Khan, G. Tamulaitis, I. Yilmaz, M. S. Shur, J. C. Rojo, L. Schowalter, . Deep-ultraviolet emission of AlGaN/AlN quantum wells on bulk AlN, accepted at APL


AlN/AlGaN Room Temperature Photoluminescence

PL signal from MQWs on bulk AlN is approximately 28 times stronger compared to the structure grown over SiC.

PL signal from MQWs on bulk AlN forAlN/Al0.5Ga0.5N QWs with 20 nm barriers and:5 nm QWs; 2 nm QWs

1028 1029 1030 1031106

107

108

109

1010

T = 300 K

Al0.5Ga0.5N/AlN QWson bulk AlN

high-quality sample low-quality sample

Pump intensity (cm-3s-1)

Pho

tolu

min

esce

nce

Inte

nsity

(arb

. uni

ts)

240 260 280 300 320

20 nm AlN5 nm Al0.5Ga0.5N

substrate

AlN epilayerBulk AlNsubstrate

SiC substratePL In

tens

ity (a

rb. u

nits

)

Wavelength (nm)



Stimulated Emission

240 260 280 300

PL from edge @ L = 400 µm PL from edge @ L = 440 µm spontaneous PL

Lum

ines

cenc

e in

tens

ity (a

rb. u

nits

)

Wavelength (nm)

Photoluminescence spectra of Al0.5Ga0.5N/AlN MQWs deposited on bulk AlN. Solid curve represents the spectrum of spontaneous emission detected in the direction perpendicular to the sample surface; dotted and dashed curves correspond to the spectra measured from the sample edge along the direction of a 30 µm wide stripe, which length was 400 µm and 440 µm, respectively. The excitation wavelength was 213 nm.



AlInGaN-based UV LEDs on Sapphire Substrates

280 300 320 340 360 380 400 420

0 5 100

10

20ELEL

PL

EL

PLN

orm

aliz

ed in

tens

ity, a

.u.

Wavelength, nm

320nm340nm

Cur

rent

, mA

Voltage, V

305 nm

Pd/Ag/Au

Al2O3

n+-AlGaN

n-AlGaN/AlGaN (SL)

AlInGaN MQW

p-AlGaN/AlGaN (SL)

p-GaN

Ni/Au

Ti/Au

Ti/Al/Ti/Au

M. Asif Khan, Vinod Adivarahan, Jian Ping Zhang, Changqing Chen, Edmundas Kuokstis, Ashay Chitnis, Maxim Shatalov, Jin Wei Yang, Grigory Simin Stripe Geometry Ultraviolet Light Emitting Diodes at 305 nanometers using quaternary AlInGaN multiple quantum wells, Jpn. J. Appl. Phys. Vol. 40 (2001) pp. L 1308-L 1310


AlInGaN-based UV LEDs on Sapphire Substrates

Pump Current 400 mA pulsed

280 300 320 340 360 380 400 420 44010-4

10-3

10-2

10-1

100

101

102

USC square Sep 2001USC stripe Dec 2001USC square Jan 2002NTT square Sep 2001

Out

put p

ower

, mW

Wavelength, nm

square

stripeSquare+thick buffer

Improve light extraction Control current crowding

M. Shatalov, G. Simin, V. Adivarahan, A. Chitnis, S. Wu, R. Pachipulusu, K. Simin, J. P. Zhang, J. W. Yang, and M. Asif Khan . Lateral Current Crowding in Deep UV Light Emitting Diodes over Sapphire Substrates. Jpn. J. Appl. Phys. Vol. 41 (2002) pp. 5083-5087 Part 1, No. 8, August 2002


10 mW 325 nm UV LED on Sapphire

0 2 4 6 80

10

20

30

40

50

RD = 24 Ω

200 µm x 200 µm

Cu

rrent

, mA

Voltage, V

260 280 300 320 340 360 380 400 420

200 mA pulsed pumping500 ns, 10 kHz

Inte

nsity

, a.

u.

Wavelength, nm

325 nm

0 200 400 600 800 1000 12000

2

4

6

8

10

dc

pulse 500 ns, 10 kHz

Pow

er, m

WCurrent, mA

A. Chitnis, J. P. Zhang, V. Adivarahan, M. Shatalov, S. Wu, R. Pachipulusu, V. Mandavilli, and M. Asif KhanImproved performance of 325-nm emission AlGaN ultraviolet light-emitting diodes. Appl. Phys. Lett., 82, pp. 2565-2567 (2003)


260 280 300 320 340 360 380 400 420

200 mA pulsed pumping500 ns, 10 kHzIn

tens

ity, a

.u.

Wavelength, nm

285.5 nm

0 2 4 6 80

5

10

15

20

25

30

Cur

rent

, mA

Voltage, V0 20 40 60 80 100

0

2

4

6

8

10

12

14RTdc

Pow

er, µ

W

Current, mA

0 100 200 300 400 5000.00

0.05

0.10

0.15

0.20

RTpulse500 ns, 0.5%

Pow

er, m

WCurrent, mA

Rs~70-80 Ω

LT-AlN

Sapphire

n+-AlGaN buffer

SQW

p-AlGaN p+-GaN

SL

Sub-milliwatt power 285 nm Emission UV LED on Sapphire.

V. Adivarahan et al., Jpn. J. Appl. Phys. Lett., 41, L435 (2002)


285 nm Emission UV LEDLow temperature performance

0 2 4 6 80

5

10

15

20

25

30

Cur

rent

, A

Voltage, V

300 K250 K200 K150 K100 K50 K10 K

0 20 40 60 80 100 1201

10

100

200 mA

100 mA

PL

Nor

mal

ized

inte

nsity

, a.u

.

1000/T, K-1

20 mA

260 280 300 320 340 360 380

200mA500ns, 10kHz

Inte

nsity

, a.u

.

Wavelength, nm

10 K50 K100 K150 K200 K250 K300 K

A. Chitnis, R. Pachipulusu, V. Mandavilli, M. Shatalov, E. Kuokstis, J. P. Zhang, V. Adivarahan, S. Wu, G. Simin, and M. Asif Khan. Low-temperature operation of AlGaN single-quantum-well light-emitting diodes with deep ultraviolet emission at 285 nm. APL, 81, 2938-2940 (2002)


250300

350400

0200

400600

Time, ns

Inte

nsity

, a.u

.

Wavelength, nm

0 200 400 600 800 10000

1x106

2x106

3x106

4x106

5x106

I0 + ∆I exp (-t/τ), τ ~ 25 ns

285 nm peak

Inte

nsity

, a.u

.

Time, ns

0 200 400 600 800 10000

1x107

2x107

3x107

4x107

5x107

I0 - ∆I exp (-t/τ)), τ ~ 75 ns

330 nm peak

Inte

nsity

, a.u

.

Time, ns

0 10 ns100 ns300 ns600 ns

70 mA current pulse1000 ns, 20 kHz

285 nm Emission UV LEDTime resolved electroluminescence

M. Shatalov, A. Chitnis, V. Mandavilli, R. Pachipulusu, J. P. Zhang, V. Adivarahan, S. Wu, G. Simin, M. Asif Khan, G. Tamulaitis, A. Sereika, I. Yilmaz, M. S. Shur and R. Gaska, Time-resolved electroluminescence of AlGaN-based light-emitting diodes with emission at 285 nm, Appl. Phys. Lett. 82, Issue 2, pp. 167-169 (2003)


0 2 4 6 80

10

20

30

40

50

RD = 28 Ω

278 nm LED200 µm x 200 µm

Cur

rent

, mA

Voltage, V

260 280 300 320 340 360 380 400 420

200 mA pulsed pumping500 ns, 10 kHz

Inte

nsity

,a.u

Wavelength, nm

278 nm

0 200 400 600 800 10000

1

2

3

4

5

pulse500 ns, 10 kHz

dc RT

Pow

er, m

W

Current, mA

0 100 200 3000.0

0.2

0.4

Pow

er, m

W

Current, mA

Milliwatt power 278 nm UV LED on Sapphire. Modified design

J. P. Zhang, A. Chitnis, V. Adivarahan, S. Wu, V. Mandavilli, R. Pachipulusu, M. Shatalov, G. Simin, J. W. Yang, and M. Asif Khan, Milliwatt power deep ultraviolet light-emitting diodes over sapphire with emission at 278 nm, Appl. Phys. Lett. 81, 4910-4912 (2002)


Thermal and current crowding management

Square geometry Inter-digitated fingers LED arrays

0 2 4 6 8 10 12 140

10

20

30

40

50Multifinger LED

Square LEDCur

rent

, mA

Voltage, V

A. Chitnis et al., Jpn. J. Appl. Phys. Lett., 41, L320 (2002)

0 2 4 6 8 100

10

20

30

40

50

Single chip

4 x 1 array

Cur

rent

, mA

Voltage, V


278 nm / 325 nm LED comparison325 nm Emitting LED

10 mW1 A pulsed

278 nm Emitting LED

3 mW1 A pulsed

0 200 400 600 800 10000

2

4

6

8

10

12

RT

dc

pulse 500 ns, 10 kHz

Pow

er, m

W

Current, mA0 200 400 600 800 1000

0

1

2

3

pulse500 ns, 10 kHz

dc

RT

Pow

er, m

W

Current, mA

J. P. Zhang, A. Chitnis, V. Adivarahan, S. Wu, V. Mandavilli, R. Pachipulusu, M. Shatalov, G. Simin, J. W. Yang, M. Asif Khan, Milliwatt Power Deep Ultraviolet Light Emitting Diodes over Sapphire with Emission at 278 nm. APL vol. 81, No. 26, pp. 4910-4912 (2002) ; A. Chitnis, J. P. Zhang, V. Adivarahan, M. Shatalov, S. Wu, R. Pachipulusu, V. Mandavilli, M. Asif Khan. Improved performance of 325-nm emission AlGaN ultraviolet light-emitting diodes. APL vol. 82, No. 16, pp. 2565-2567 (2003)


SAW Oscillator/Photodetector

SAW

Amplifier

BASICS OF SURFACE ACOUSTIC WAVE DELAY-LINE OSCILLATOR

Phase condition

Amplitude conditionGain > Loss

πφπ mV

Lf 22=+

m - 1 m + 1m

Frequency

=

LL

VV

ff UV∆∆

Velocity change


Response to Artificial Light Sources and Sunlight

221.08 221.10 221.12 221.14 221.16-100

-80

-60

-40

-20 UV lamp Sun light Dark

Sign

al p

ower

(dB

m)

Frequency (MHz)

-5 -4 -3 -2 -1 0 1 2 3 4 5-120

-100

-80

-60

-40

-20

0

Sun and UV lamp

Sun only

Sign

al a

mpl

itude

(dB

m)

Frequency deviation (kHz)

D. Ciplys, R. Rimeika, M.S. Shur, R. Gaska, A. Sereika, J. Yang, M. Asif Khan, "Radio frequency response of GaN-based SAWoscillator to UV illumination by the Sun and man-made source", Electronics Letters, vol. 38, no. 3, pp. 134-135, 2002


SOME of LED WEB SITES

• http://www.misty.com/people/don/led.html• http://www.luxeon.com/index.html• http://ledmuseum.home.att.net/• http://www.nichia.com/• http://www.cree.com/• http://www.s-et.com• http://www.oida.org/• http://safeco2.home.att.net/laser.htm

http://www.misty.com/people/don/led.html

http://www.misty.com/people/don/led.html

http://www.luxeon.com/index.html

http://www.luxeon.com/index.html

http://ledmuseum.home.att.net/

http://ledmuseum.home.att.net/

http://www.nichia.com/

http://www.cree.com/

http://www.s-et.com/

http://www.oida.org/

http://safeco2.home.att.net/laser.htm

http://safeco2.home.att.net/laser.htm


Conclusions• Materials properties of wide band semiconductors

are superior for applications in for high power, high temperature electronics

• All device building blocks demonstrated• Record breaking microwave power performance

achieved• Strain Energy Band Engineering – Strain and Band

Offset Control using quaternary and ternary heterostructures augmented using SiO2 and Si3N4 allow us to obtain superior HFET performance

• Nitrides hold promise of solid state lighting• Nitride deep UV emitters and detectors have

been demonstrated

michael shur and asif khan - ecse @ rensselaer technology michael shur 1 and asif khan 2 ......

Documents