IRG2: Mesoscopic Narrow Gap Systems

Investigators: Doezema, McCann, Mullen, Murphy, Santos, Shi, Yang (OU); Xie (OSU); Salamo (UA); 6 postdocs/8 graduate students

Partners: Amethyst Research Inc., University of Florida, Humboldt University (Germany), Intel Corp. , Ioffe Technical Institute (Russia), NTT Basic Research Laboratories (Japan), University of Texas at Austin, Tohoku University (Japan), SUNY Albany

Motivation: Future technology needs can be addressed by nanoscale devices that exploit electron spin, quantum confinement, and ballistic transport.

IRG2: Mesoscopic Narrow Gap Systems

Mesoscopic Device Examples

1

23

4

AuShunt

Au Electrodes

InSb Mesawith

SiNx Cap

b) source drain

gate

Gate Length~500nm

metal BarrierNarrow-gap

semiconductor

Magnetic semiconductor

Magnetic Field Sensor• Working preliminary devices• Room-temperature operation• 30 nm width, diffusive transport• High electron mobility required

Spin Field-Effect Transistor• Studying spin injection and precession• Requires ballistic transport across

interfaces and through channel

Classical Non-classical

Goals of IRG-2

Improved Narrow Gap Materials Improved Narrow Gap Materials

Mesoscopic Magnetic Field SensorsMesoscopic Magnetic Field Sensors

Fundamental Studies of Spin Effects in Fundamental Studies of Spin Effects in SemiconductorsSemiconductors

Spin and Ballistic Transport DevicesSpin and Ballistic Transport Devices

Innovative Infrared DevicesInnovative Infrared Devices

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C-SPIN Advantages

Leaders in InSb materials research: MBE, device processing, transport properties

Proficiency in optics: Self-induced transparency, coherent optics, ultra-fast pump-probe

Inventor of Interband Cascade Laser for infrared applications

Mars Science Laboratory (MSL)

CHARACTERIZATION• STM, AFM• TEM, SEM• X-ray Diffraction• FTIR• Hall Effect

Mesoscopic Narrow Gap Systems

MBE GROWTH• InGaAs/AlInAs • InAs/AlSb/GaSb• InSb/AlInSb OPTICS

• Spin Lifetimes• Spin-Orbit Effects• Infrared Devices

TRANSPORT• Quantum Confined Devices• Ballistic Transport Devices• EMR and -Hall Devices

FABRICATION• Photolithography• E-beam Lithography• Reactive Ion Etching• Surface Gates

THEORY• Screened Atomic

Pseudopotentials• Spin Transport

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CHARACTERIZATION• Santos (Mishima)• Salamo• Murphy• Doezema


MBE GROWTH• Santos• Salamo• ARI collaborators

OPTICS• Yang• Salamo (Guzun)• McCann• Shi• Doezema

TRANSPORT• Murphy• Salamo (Kunets)• NTT/Tohoku collaborators

FABRICATION• Murphy• NTT/Tohoku collaborators

• Humboldt collaborators• Intel collaborators

THEORY• Mullen• Xie• Ioffe collaborator• Florida collaborator

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Strategy/Progress IRG2Growth

InSbAPL 91, 062106 (2007)

Phys Stat Sol, 2775 (2008)JCG 311, 1972 (2009)

Transport

Hall SensorsJ Mat Sci 19, 776 (2008) IEEE TED 56, 683 (2009)

Spin Lifetime

TheoryOptics

Magneto-opticsAPL 89, 021907 (2006)JVST B24, 2429 (2006)

Springer 119, 213 (2008)

Spin TransportPhysica E 34, 647 (2006)Springer 119, 35 (2008)

Interband Cascade LasersElec Lett 45, 48 (2009)

IV-VIAPL 88, 171111 (2006)

Physica E 39, 120 (2007)

TheoryPRL 101, 046804 (2008)PRB 77, 035327 (2008)PRB 78, 045302 (2008)

Infrared DevicesJAP 101, 114510 (2007)

IEEE PTL 20, 629, (2008) APL 92, 211110 (2008)

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t212p=3.5x1011cm-2

B (T)

0 2 4 6 8 10 12 14

En

erg

y (e

V)

0.00

0.01

0.02

0.03 H10d-H11d H10u-H11u H11d-H12d H11u-H12u

InGaAsAPL 91, 113515 (2007)APL 92, 222904 (2008)APL 94, 013511 (2009


Molecular Beam Epitaxy of narrow gap materialsMolecular Beam Epitaxy of narrow gap materialsSpin related experiments and associated theorySpin related experiments and associated theory– Spin-relaxation optical measurementsSpin-relaxation optical measurements– Spin-orbit transport experimentsSpin-orbit transport experiments– Theory and modeling of spin-orbit devicesTheory and modeling of spin-orbit devices

Narrow-gap electronic devicesNarrow-gap electronic devices– InGaAs-based electronic device structuresInGaAs-based electronic device structures– High-mobility hole systemsHigh-mobility hole systems

Narrow-gap photonic devicesNarrow-gap photonic devices– III-V Interband Cascade (IC) LasersIII-V Interband Cascade (IC) Lasers– IV-VI infrared and thermoelectric applicationsIV-VI infrared and thermoelectric applications

electron m*electron m* gg-factor-factor Rashba coeff., Rashba coeff.,

GaAsGaAs 0.067m0.067moo -0.5-0.5 5.2 e A5.2 e A

InIn0.530.53GaGa0.470.47AsAs 0.045m0.045moo -7-7 65 e A65 e A

InAsInAs 0.023m0.023moo -15-15 117 e A117 e A

InSbInSb 0.014m0.014moo -51-51 523 e A523 e A

III-V Semiconductors

IV-VI Semiconductors

• Band gap in mid-infrared • High thermal conductivity

Electron Mobility and Structural Defects in n-type InSb QWs

4×104

3×104

2×104

0

3.6×109

0

1.2×104

6×103

1.8×109

MT density

(/cm)TD density

(/cm2)

Mobility @

RT

(cm2/V

s)

31°Misfit dislocations

54.7°

(111) glide plane

1μm

220 Dark-field (DF) X-TEM

Record high mobility for a QW at room temperature when structural defects are minimized.

APL 91, 062106 (2007).

Santos





Spin Orbit Effects

2// zkk //kz

Bulk Inversion Asymmetry

Structural Inversion Asymmetry

Dresselhaus splitting

Rashba splitting

ηη αα

GaAsGaAs 27.6 eV 27.6 eV ÅÅ33 5.2 e 5.2 e ÅÅ22

InAsInAs 27.2 eV 27.2 eV ÅÅ33 117 e 117 e ÅÅ22

InSbInSb 760 eV 760 eV ÅÅ33 523 e 523 e ÅÅ22

Large effects predicted in narrow gap materials• Spin splitting at zero magnetic field• Spin precession• Spin-dependent ballistic trajectories

Optical Spin MeasurementsSpin TransportNMR StudiesTheory

Spin Related Experiments and Theory

Salamo (UA)Murphy, Santos, Mullen (OU)Xie (OSU)Golub (Russia)NTT Basic Research Laboratories (Japan) Tohoku University (Japan)

Optical Measurements of Spin Relaxation Salamo, Murphy, Santos

MechanismsElliot-Yafet (spin orbit)Dyakanov-Perel (inversion asymmetry)Bir-Aranov-Pikus (spin exchange with holes)Hyperfine interactions

State of the FieldGaAs extensively studiedInAs studiedInSb limited studies



Future work: Quantum Wells Confinement Energy, Confinement Asymmetry

Bulk InSb

Elliot-Yafet mechanismresponsible for spin relaxation in bulk InSb

Spin Transport MeasurementsMurphy, Santos

First observation of current focusing peaks in InSb heterostructures.

Physica E 34, 647 (2006).

Spin Transport MeasurementsMurphy, Santos

B┴B║

BT

θDoublet is related to spin.

Current Effort and Future Work: • Improved Gating with NanoTech UCSB & Penn State NanoFab• Spin Interferometers (Rings and Ring Arrays)

Physica E 34, 647 (2006).

Weak Anti-Localization MeasurementsMurphy, Santos, Golub

Good agreement with theoretical predicted values of spin-orbit coupling in InSb.

Future: study WAL as a function of gate voltage and applied strain.

Springer Proc. Phys. 119, 35 (2008).

QuickTime™ and a decompressor

are needed to see th is p icture.

Designing Spin-Orbit CouplingMullen, Murphy, Santos

SYMMETRIC ASYMMETRIC

Future Work: Design structure to maximize change in S-O with applied gate voltage.

Spin and Spin Hall TheoryXie

Proposed Device• Non-uniform Rashba effect • Spin interference• Current predicted to be ~10% spin

polarized• Device not yet realized

Spin Nernst EffectPersistent Spin Currents

PRB 77, 035327 (2008)PRB 78, 045302 (2008)





MBE growth (C-SPIN, Santos)

InxGa1-xAs/InxAl1-xAs MBE

Epilayer characterization(C-SPIN, Santos)

HRXRD, Hall effect, AFM, TEM

Epilayers for high- integration (UT Austin, Jack Lee)

HfO2

Epilayers for high- integration (SUNY Albany, Serge Oktyabrsky)

ZrO2

Gated Narrow-Gap InxGa1-xAs QWs

Epilayers for high- integration (Penn State/Cornell, Darrell Schlom)

LaAlO3

Scanning Tunneling Microscopy/Spectroscopy

(UC San Diego, Andrew Kummel)Ga2O, and In2O

8 journal articles since 2007 on ZrO2, HfO2, LaAlO3 on InxGa1-xAs

Challenges for III-V transistors• Stable & reliable gate dielectric• Integration with Si substrates• p-channel III-V FET for CMOS

Effective Mass of Holes in InSb QW

Cyclotron Resonance at 4.2K

t212b (p=3.5x1011cm-2)

Frequency (cm-1)

20 40 60 80 100 120

T(B

)/T

(0)

1.0

1.5

2.0

2.5

3.0

2.0T

7.0T

6.0T

5.0T

4.0T

3.0T

6.5T

5.5T

4.5T

3.5T

2.5T

Quantum well mh*

GaAs 0.5 mo

In0.20Ga0.80As 0.19 mo

InSb 0.04 mo

p (cm-2) mh*

2x1011 0.04 mo

3x1011 0.06 mo

5x1011 0.09mo

p-FET

n-FET

• Low-T mobility (~50,000 cm2/Vs) consistent with effective mass

• 300K mobility (700 cm2/Vs) much lower than expected

Doezema, Santos, Stanton

APS 2009

p-type InSb Quantum Well

H at 300K

(cm2/Vs)

Reference

In0.2Ga0.8As 260 R.T. Hsu et al., Appl. Phys. Lett. 66, 2864 (1995).

In0.53Ga0.48As 265 Y-J. Chen and D. Pavlidis, IEEE Trans. Elec. Dev. 39,

466 (1992).

In0.82Ga0.18As 295 A.M. Kusters et al., IEEE Trans. Elec. Dev. 40, 2164

(1993).

InSb 700 M. Edirisooriya et al., J. Cryst. Growth 311, 1972

(2009).

In0.4Ga0.6Sb 1500 B.R. Bennett et al., Appl. Phys. Lett. 91, 042104

(2007).

Ge 3100 M. Myronov, Appl. Phys. Lett. 91, 082108 (2007).

Al0.10In0.90Sb

Al0.10In0.90Sb

Al0.20In0.80Sb

Al0.20In0.80Sb

Al0.20In0.80Sb

15nm InSb well

Buffer Layer

GaAs (001) substrate

30 nm

20 nm

Be -doping

Be -doping

First realization of remotely-doped p-type InSb QWs.

Santos

Integration of InSb n-FET and Ge p-FET

BOX = Buried Oxide

BOX

Si

74Ge+

BOX

Si

O2 H2OThermal Oxide

Oxidation

HF Treatment

GexSi1-x

Oxidation

continued

Removal of thermal oxides

GexSi1-x

BOX

Si

O2 H2OThermal Oxide

BOX

Si

Thermal Oxide

BOX

Si

74Ge+

BOX

Si

O2 H2OThermal Oxide

Oxidation

HF Treatment

GexSi1-x

Oxidation

continued

Removal of thermal oxides

GexSi1-x

BOX

Si

O2 H2OThermal Oxide

BOX

Si

Thermal Oxide

GeOIn-FET p-FETGeInSb

n-FET p-FETGeInSb

Si substrateGe substrate

Ge substrate type GeOI / Si substrate typeAmethyst Research Inc.

p-type

n-type

Santos

APS 2009





Interband Cascade (IC) Laser

hv

hv

InAs/Al(In)Sbmultilayers AlSb

InAsGaInSbAlSb

AlSbGaSb

InAs/Al(In)Sbmultilayerscascade process —

»high efficiency, large output power, uniform injection over every stage, low carrier concentration, thus lower loss

interband transition —»circumvents fast phonon scattering

quantum engineering at sub-nanometer scale and Sb-based type-II QW system

»suppresses non-radiative Auger losses»allows for wide wavelength tailoring range»excellent carrier confinement because of

band-gap blocking feature

Low threshold current, high efficiency, high output power mid-IR lasers

type-II brokengap alignment

many photons per electronhv

hv

hv

hv

hv

hv

hv

Cascading

Ee

Yang, Johnson, Santos

Preliminary Results of Interband Cascade Lasers

5600 5650 5700 5750 5800 5850 59000.0

0.2

0.4

0.6

0.8

1.0

Inte

nsi

ty (

a.u

.)

Wavelength (nm)

82K136mA

100K193mA

120K301mA

140K515mA

150K696mA

CW

150mx1.86mm

A broad-area (150m x 1.9mm) device lased in continuous wave (cw) mode up to 150 K near 6 m, the longest attained, to date, for III-V interband diode lasers.

Electron. Lett. 45, 48 (2009)

Latest Results

11-stage IC laserJth~82 A/cm2, Vth~2.3V, at 84K

7.20 7.25 7.30 7.35 7.40 7.45

100K670mA

100K424mA

90K298mA

Inte

nsi

ty (

a.u

.)

Wavelength (m)

84K234mA

CW

118K1000mA

150mx1.9mm

Lower threshold current density and operating voltageLasing wavelength ~7.4 mLonger wavelengths possible

Where are we?

III-V Sb-based mid-IR diode lasers reported in literature and

3.0 3.5 4.0 4.5 5.0 5.5 6.00

100

200

300

400

JJ

ICL pulsed, cwtype-II pulsed, cwtype-I pulsed, cw

Max

imum

tem

pera

ture

(K)

Wavelength (m)

0.4 0.3

NJ

N

N

N

N

N

JJ

J

J

J

JJ

J

J

J

J

JJ

J

J

J

J

JJ

J

J

J

J

JJ

N

J

J

J

JJ

J

J

J

J

J

J

Photon energy (eV)

OU

J - JPL

N-NRL

OU- University of Oklahoma

Device fabrication and package are in a preliminary stage for ICLs

3.0 3.5 4.0 4.5 5.0 5.5 6.00

100

200

300

400

JJ

ICL pulsed, cwtype-II pulsed, cwtype-I pulsed, cw

Max

imum

tem

pera

ture

(K)

Wavelength (m)

0.4 0.3

NJ

N

N

N

N

N

JJ

J

J

J

JJ

J

J

J

J

JJ

J

J

J

J

JJ

J

J

J

J

JJ

N

J

J

J

JJ

J

J

J

J

J

J

Photon energy (eV)

OU

Our latest lasers operate up to 121 K near 7.4 m, now the longest attained to date, for III-V interband cascade lasers.

PbSe Quantum Wires for Thermoelectric Applications

• CaF2 growth on Si (110) adopts a ridge-groove morphology• Subsequent growth of PbSe produces quasi-one-dimensional structures

indicated by a 200 meV blue shift in PL • Improved thermoelectric properties predicted, based on enhanced electrical

conductivity, but reduced thermal conductivity, along wires.– TE figure of merit, ZT σ/κ, σ and κ, electrical and thermal conductivities, resp.

CaFCaF22 200 nm200 nm

[110][110]

McCann Ridge-groove CaF2 structure and subsequent PbSe growth.

Grayscale: 95 nmGrayscale: 95 nm

200 nm200 nm2 ML PbSe2 ML PbSe

[110][110]

PbSe PbSe QWRQWR

AFM of AFM of 2 ML PbSe2 ML PbSe

200 nm200 nm

[110][110]

CaFCaF22

PbSe Micro/ Nanostructures

APL 88, 171111 (2006).

SEM image and PL of a freestanding MQW microtube. Diameter 600, length 5 mm.

SEM images and PL of PbSe micro-rods.

4 μm

Physica E 39, 120 (2007).

4 μm

PbSe layersPbSe layers

BaF BaF 22 layer layer

ShiStrain in MQW causes rolling of PbSe when BaF2 layer is removed in water.

PbSe bulk PbSe

bulk

IRG2: Mesoscopic Narrow Gap Systems

Comprehensive expertise: MBE, characterization, Comprehensive expertise: MBE, characterization, fabrication, transport and optical experiments, theoryfabrication, transport and optical experiments, theory

Fundamental and technologically motivated studiesFundamental and technologically motivated studies

Devices exploit high mobility, quantum confinement, Devices exploit high mobility, quantum confinement, ballistic and spin effectsballistic and spin effects

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Strategy/Progress IRG2Growth

InSbAPL 91, 062106 (2007)

Phys Stat Sol, 2775 (2008)JCG 311, 1972 (2009)

Transport

Hall SensorsJ Mat Sci 19, 776 (2008) IEEE TED 56, 683 (2009)

Spin Lifetime

TheoryOptics

Magneto-opticsAPL 89, 021907 (2006)JVST B24, 2429 (2006)

Springer 119, 213 (2008)

Spin TransportPhysica E 34, 647 (2006)Springer 119, 35 (2008)

Interband Cascade LasersElec Lett 45, 48 (2009)

IV-VIAPL 88, 171111 (2006)

Physica E 39, 120 (2007)

TheoryPRL 101, 046804 (2008)PRB 77, 035327 (2008)PRB 78, 045302 (2008)

Infrared DevicesJAP 101, 114510 (2007)

IEEE PTL 20, 629, (2008) APL 92, 211110 (2008)

I

GG

C

B

I

GG

C

B

t212p=3.5x1011cm-2

B (T)

0 2 4 6 8 10 12 14

En

erg

y (e

V)

0.00

0.01

0.02

0.03 H10d-H11d H10u-H11u H11d-H12d H11u-H12u

InGaAsAPL 91, 113515 (2007)APL 92, 222904 (2008)APL 94, 013511 (2009

Documents

IRG2: Mesoscopic Narrow Gap Systems