IRG2: Mesoscopic Narrow Gap Systemsjohnson/MRSEC/2009-NSF-SiteVisit/...d 4×104 3×104 2×104 0...
Transcript of IRG2: Mesoscopic Narrow Gap Systemsjohnson/MRSEC/2009-NSF-SiteVisit/...d 4×104 3×104 2×104 0...
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 nanoscaledevices that exploit electron spin, quantum confinement, and ballistic transport.
IRG2: Mesoscopic Narrow Gap Systems
Mesoscopic Device Examples
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AuShunt
Au Electrodes
InSb Mesawith
SiNx Cap
b) source draingate
Gate Length~500nm
metal Barrier Narrow-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 MesoscopicMesoscopic Magnetic Field SensorsMagnetic Field SensorsFundamental Studies of Spin Effects in Fundamental Studies of Spin Effects in SemiconductorsSemiconductorsSpin and Ballistic Transport DevicesSpin and Ballistic Transport DevicesInnovative 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-probeInventor 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 µ-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
Mesoscopic Narrow Gap Systems
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
Ene
rgy
(eV
)
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
Mesoscopic Narrow Gap Systems
Molecular Beam Molecular Beam EpitaxyEpitaxy of narrow gap materialsof narrow gap materialsSpin related experiments and associated theorySpin related experiments and associated theory–– SpinSpin--relaxation optical measurementsrelaxation optical measurements–– SpinSpin--orbit transport experimentsorbit transport experiments–– Theory and modeling of spinTheory and modeling of spin--orbit devicesorbit devices
NarrowNarrow--gap electronic devicesgap electronic devices–– InGaAsInGaAs--based electronic device structuresbased electronic device structures–– HighHigh--mobility hole systemsmobility hole systems
NarrowNarrow--gap photonic devicesgap photonic devices–– IIIIII--V V InterbandInterband Cascade (IC) LasersCascade (IC) Lasers–– IVIV--VI infrared and thermoelectric applicationsVI infrared and thermoelectric applications
electron m*electron m* gg--factorfactor RashbaRashba coeffcoeff., ., αα
GaAsGaAs 0.067m0.067moo --0.50.5 5.2 e A5.2 e AInIn0.530.53GaGa0.470.47AsAs 0.045m0.045moo --77 65 e A65 e A
InAsInAs 0.023m0.023moo --1515 117 e A117 e AInSbInSb 0.014m0.014moo --5151 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
1.2×1046×103
1.8×109
MT density
(/cm)TD density
(/cm2)
Mobility @
RT
(cm2/Vs)
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
Mesoscopic Narrow Gap Systems
Molecular Beam Molecular Beam EpitaxyEpitaxy of narrow gap materialsof narrow gap materialsSpin related experiments and associated theorySpin related experiments and associated theory–– SpinSpin--relaxation optical measurementsrelaxation optical measurements–– SpinSpin--orbit transport experimentsorbit transport experiments–– Theory and modeling of spinTheory and modeling of spin--orbit devicesorbit devices
NarrowNarrow--gap electronic devicesgap electronic devices–– InGaAsInGaAs--based electronic device structuresbased electronic device structures–– HighHigh--mobility hole systemsmobility hole systems
NarrowNarrow--gap photonic devicesgap photonic devices–– IIIIII--V V InterbandInterband Cascade (IC) LasersCascade (IC) Lasers–– IVIV--VI infrared and thermoelectric applicationsVI infrared and thermoelectric applications
Spin Orbit Effects
( )2// zkkη±≈ //kzεα±=
Bulk Inversion Asymmetry Structural Inversion Asymmetry
Dresselhaussplitting
Rashbasplitting
ηη αα
GaAsGaAs 27.6 27.6 eVeV ÅÅ33 5.2 e 5.2 e ÅÅ22
InAsInAs 27.2 27.2 eVeV ÅÅ33 117 e 117 e ÅÅ22
InSbInSb 760 760 eVeV 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
Optical Measurements of Spin Relaxation Salamo, Murphy, Santos
Optical Measurements of Spin Relaxation Salamo, Murphy, Santos
Future work: Quantum Wells Confinement Energy, Confinement Asymmetry
Bulk InSb
Elliot-Yafetmechanismresponsible 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).
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)
Mesoscopic Narrow Gap Systems
Molecular Beam Molecular Beam EpitaxyEpitaxy of narrow gap materialsof narrow gap materialsSpin related experiments and associated theorySpin related experiments and associated theory–– SpinSpin--relaxation optical measurementsrelaxation optical measurements–– SpinSpin--orbit transport experimentsorbit transport experiments–– Theory and modeling of spinTheory and modeling of spin--orbit devicesorbit devices
NarrowNarrow--gap electronic devicesgap electronic devices–– InGaAsInGaAs--based electronic device structuresbased electronic device structures–– HighHigh--mobility hole systemsmobility hole systems
NarrowNarrow--gap photonic devicesgap photonic devices–– IIIIII--V V InterbandInterband Cascade (IC) LasersCascade (IC) Lasers–– IVIV--VI infrared and thermoelectric applicationsVI infrared and thermoelectric applications
MBE growth (C‐SPIN, Santos)
InxGa1‐xAs/InxAl1‐xAs MBE
Epilayer characterization(C‐SPIN, Santos)
HRXRD, Hall effect, AFM, TEM
Epilayers for high‐κ integration (UT Austin, Jack Lee)
HfO2
Epilayers for high‐κ integration (SUNY Albany, Serge Oktyabrsky)
ZrO2
Gated Narrow-Gap InxGa1-xAs QWs
Epilayers for high‐κ 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
µH 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 δ‐doping
Be δ‐doping
First realization of remotely-doped p-type InSb QWs.
Santos
Integration of InSb n-FET and Ge p-FET
BOX = Buried OxideBOX
Si
BOX
Si
GeOIn-FET p-FETGeInSb
n-FET p-FETGeInSb
Si substrateGe substrate
Ge substrate type GeOI / Si substrate typeAmethyst Research Inc.
340 360 380 400 420 4400
200
400
600
800
InSb epilayer: 2.0 µm
Growth temperature (0C)
X
-ray
rock
ing
curv
e w
idth
(arc
sec
)
two-step growth
direct growth
0 50 100 150 200 250 3000
5,000
10,000
15,000
20,000
25,000
Car
rier d
ensi
ty, n
(x10
12 c
m-2)
Hal
l mob
ility
, µ (c
m2 /V
-s)
Temperature (K)
0
2
4
6
8
p-type
n-type
Santos
APS 2009
Mesoscopic Narrow Gap Systems
Molecular Beam Molecular Beam EpitaxyEpitaxy of narrow gap materialsof narrow gap materialsSpin related experiments and associated theorySpin related experiments and associated theory–– SpinSpin--relaxation optical measurementsrelaxation optical measurements–– SpinSpin--orbit transport experimentsorbit transport experiments–– Theory and modeling of spinTheory and modeling of spin--orbit devicesorbit devices
NarrowNarrow--gap electronic devicesgap electronic devices–– InGaAsInGaAs--based electronic device structuresbased electronic device structures–– HighHigh--mobility hole systemsmobility hole systems
NarrowNarrow--gap photonic devicesgap photonic devices–– IIIIII--V V InterbandInterband Cascade (IC) LasersCascade (IC) Lasers–– IVIV--VI infrared and thermoelectric applicationsVI infrared and thermoelectric applications
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
hvhv
hvhv
hv
Cascading
Ee
Yang, Johnson, Santos
Preliminary Results of InterbandCascade Lasers
5600 5650 5700 5750 5800 5850 59000.0
0.2
0.4
0.6
0.8
1.0
Inte
nsity
(a.u
.)
Wavelength (nm)
82K136mA
100K193mA
120K301mA
140K515mA
150K696mA
CW
150µmx1.86mm
A broad-area (150µm x 1.9mm) device lased in continuous wave (cw) mode up to 150 K near 6 µm, 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
nsity
(a.u
.)
Wavelength (µm)
84K234mA
CW
118K1000mA
150µmx1.9mm
Lower threshold current density and operating voltageLasing wavelength ~7.4 µmLonger wavelengths possible
Where are we?
III-V Sb-based mid-IR diode lasersreported 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 (µm)
0.4 0.3
NJ
NN
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N
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JJ
J
J
J
JJ
J
J
J
J
JJ
J
J
J
J
JJ
J
J
J
J
JJ
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J
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JJ
J
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J
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Photon energy (eV)
OU
J - JPL
N-NRL
OU- University of Oklahoma
Device fabrication and package are in a preliminary stage for ICLs
OU
Our latest lasers operate up to 121 K near 7.4 µm, 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 2 ML PbSePbSe
[110][110]
PbSePbSeQWRQWR
AFM of AFM of 2 ML 2 ML PbSePbSe
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 PbSemicro-rods.
4 µm
Physica E 39, 120 (2007).
4 µm
PbSePbSe layerslayers
BaFBaF 22 layerlayer
ShiStrain in MQW causes rolling of PbSe when BaF2 layer is removed in water.
PbSebulk 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, theoryFundamental and technologically motivated studiesFundamental and technologically motivated studiesDevices 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)
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t212p=3.5x1011cm-2
B (T)
0 2 4 6 8 10 12 14
Ene
rgy
(eV
)
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