IRG-2: Nanoscale Interface and Magneto-electronic Studies

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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.
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Mesoscopic Device Examples
Non-classical
Classical

• 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

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Goals of IRG-2

• Improved Narrow Gap Materials
• Mesoscopic Magnetic Field Sensors
• Fundamental Studies of Spin Effects in
  Semiconductors
• Spin and Ballistic Transport Devices
• Innovative 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)
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Mesoscopic Narrow Gap Systems
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Mesoscopic Narrow Gap Systems
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Strategy/Progress IRG2
Transport
Optics
Growth
Theory
InSb APL 91, 062106 (2007) Phys Stat Sol, 2775
(2008) JCG 311, 1972 (2009)
Theory PRL 101, 046804 (2008) PRB 77, 035327
(2008) PRB 78, 045302 (2008)
Spin Lifetime
Spin Transport Physica E 34, 647 (2006) Springer
119, 35 (2008)
Interband Cascade Lasers Elec Lett 45, 48 (2009)
InGaAs APL 91, 113515 (2007) APL 92, 222904
(2008) APL 94, 013511 (2009
Magneto-optics APL 89, 021907 (2006) JVST B24,
2429 (2006) Springer 119, 213 (2008)
Hall Sensors J Mat Sci 19, 776 (2008) IEEE TED
56, 683 (2009)
Infrared Devices JAP 101, 114510 (2007) IEEE PTL
20, 629, (2008) APL 92, 211110 (2008)
IV-VI APL 88, 171111 (2006) Physica E 39, 120
(2007)
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Mesoscopic Narrow Gap Systems

• Molecular Beam Epitaxy of narrow gap materials
• Spin related experiments and associated theory
• Spin-relaxation optical measurements
• Spin-orbit transport experiments
• Theory and modeling of spin-orbit devices
• Narrow-gap electronic devices
• InGaAs-based electronic device structures
• High-mobility hole systems
• Narrow-gap photonic devices
• III-V Interband Cascade (IC) Lasers
• IV-VI infrared and thermoelectric applications

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III-V Semiconductors
electron m g-factor Rashba coeff., a
GaAs 0.067mo -0.5 5.2 e A
In0.53Ga0.47As 0.045mo -7 65 e A
InAs 0.023mo -15 117 e A
InSb 0.014mo -51 523 e A
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IV-VI Semiconductors

• Band gap in mid-infrared
• High thermal conductivity

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Electron Mobility and Structural Defects in
n-type InSb QWs
Santos
Record high mobility for a QW at room temperature
when structural defects are minimized.
APL 91, 062106 (2007).
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Mesoscopic Narrow Gap Systems

• Molecular Beam Epitaxy of narrow gap materials
• Spin related experiments and associated theory
• Spin-relaxation optical measurements
• Spin-orbit transport experiments
• Theory and modeling of spin-orbit devices
• Narrow-gap electronic devices
• InGaAs-based electronic device structures
• High-mobility hole systems
• Narrow-gap photonic devices
• III-V Interband Cascade (IC) Lasers
• IV-VI infrared and thermoelectric applications

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Spin Orbit Effects
Bulk Inversion Asymmetry
Structural Inversion Asymmetry
Rashba splitting
Dresselhaus splitting
? a
GaAs 27.6 eV Å3 5.2 e Å2
InAs 27.2 eV Å3 117 e Å2
InSb 760 eV Å3 523 e Å2

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

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Spin Related Experiments and Theory
Salamo (UA) Murphy, Santos, Mullen (OU) Xie
(OSU) Golub (Russia) NTT Basic Research
Laboratories (Japan) Tohoku University (Japan)
Optical Spin Measurements Spin Transport NMR
Studies Theory
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Optical Measurements of Spin Relaxation
Salamo, Murphy, Santos
Mechanisms Elliot-Yafet (spin orbit) Dyakanov-Pe
rel (inversion asymmetry) Bir-Aranov-Pikus (spin
exchange with holes) Hyperfine
interactions State of the Field GaAs
extensively studied InAs studied InSb limited
studies
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Optical Measurements of Spin Relaxation
Salamo, Murphy, Santos
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Optical Measurements of Spin Relaxation
Salamo, Murphy, Santos
Bulk InSb
Elliot-Yafet mechanism responsible for spin
relaxation in bulk InSb
Future work Quantum Wells Confinement
Energy, Confinement Asymmetry
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Spin Transport Measurements
Murphy, Santos
First observation of current focusing peaks in
InSb heterostructures.
Physica E 34, 647 (2006).
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Spin Transport Measurements
Murphy, Santos
Doublet 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).
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Weak Anti-Localization Measurements
Murphy, 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).
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Designing Spin-Orbit Coupling
Mullen, Murphy, Santos
ASYMMETRIC
SYMMETRIC
Future Work Design structure to maximize change
in S-O with applied gate voltage.
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Spin and Spin Hall Theory
Xie

• Proposed Device
• Non-uniform Rashba effect
• Spin interference
• Current predicted to be 10 spin polarized
• Device not yet realized

Spin Nernst Effect Persistent Spin Currents
PRB 77, 035327 (2008) PRB 78, 045302 (2008)
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Mesoscopic Narrow Gap Systems

• Molecular Beam Epitaxy of narrow gap materials
• Spin related experiments and associated theory
• Spin-relaxation optical measurements
• Spin-orbit transport experiments
• Theory and modeling of spin-orbit devices
• Narrow-gap electronic devices
• InGaAs-based electronic device structures
• High-mobility hole systems
• Narrow-gap photonic devices
• III-V Interband Cascade (IC) Lasers
• IV-VI infrared and thermoelectric applications

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Gated Narrow-Gap InxGa1-xAs QWs
Epilayers for high-k integration (UT Austin,
Jack Lee) HfO2
Epilayers for high-k integration (Penn
State/Cornell, Darrell Schlom) LaAlO3
Epilayers for high-k integration (SUNY Albany,
Serge Oktyabrsky) ZrO2

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

MBE growth (C-SPIN, Santos) InxGa1-xAs/InxAl1-xAs
MBE
Epilayer characterization (C-SPIN, Santos) HRXRD,
Hall effect, AFM, TEM
Scanning Tunneling Microscopy/Spectroscopy (UC
San Diego, Andrew Kummel) Ga2O, and In2O
8 journal articles since 2007 on ZrO2, HfO2,
LaAlO3 on InxGa1-xAs
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Effective Mass of Holes in InSb QW
Doezema, Santos, Stanton
p (cm-2) mh
2x1011 0.04 mo
3x1011 0.06 mo
5x1011 0.09mo
Quantum well mh
GaAs 0.5 mo
In0.20Ga0.80As 0.19 mo
InSb ?0.04 mo

• Low-T mobility (50,000 cm2/Vs) consistent with
  effective mass
• 300K mobility (700 cm2/Vs) much lower than
  expected

Cyclotron Resonance at 4.2K
APS 2009
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p-type InSb Quantum Well
Santos
mH 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).

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

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Integration of InSb n-FET and Ge p-FET
Santos
Ge
Ge
InSb
InSb
p-FET
p-FET
GeOI
n-FET
n-FET
BOX Buried Oxide
Ge substrate
Si substrate
Ge substrate type
GeOI / Si substrate type
Amethyst Research Inc.
p-type
n-type
APS 2009
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Mesoscopic Narrow Gap Systems

• Molecular Beam Epitaxy of narrow gap materials
• Spin related experiments and associated theory
• Spin-relaxation optical measurements
• Spin-orbit transport experiments
• Theory and modeling of spin-orbit devices
• Narrow-gap electronic devices
• InGaAs-based electronic device structures
• High-mobility hole systems
• Narrow-gap photonic devices
• III-V Interband Cascade (IC) Lasers
• IV-VI infrared and thermoelectric applications

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Interband Cascade (IC) Laser
Yang, Johnson, Santos
type-II broken gap alignment

• cascade 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
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Preliminary Results of Interband Cascade Lasers
A broad-area (150mm x 1.9mm) device lased in
continuous wave (cw) mode up to 150 K near 6 mm,
the longest attained, to date, for III-V
interband diode lasers.
Electron. Lett. 45, 48 (2009)
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Latest Results
11-stage IC laser Jth82 A/cm2, Vth2.3V, at 84K

• Lower threshold current density and operating
  voltage
• Lasing wavelength 7.4 mm
• Longer wavelengths possible

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Where are we?
J - JPL
N-NRL
III-V Sb-based mid-IR diode lasers
reported in literature and
OU- University of Oklahoma
Device fabrication and package are in a
preliminary stage for ICLs
Our latest lasers operate up to 121 K near 7.4
mm, now the longest attained to date, for III-V
interband cascade lasers.
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PbSe Quantum Wires for Thermoelectric Applications
McCann Ridge-groove CaF2 structure and subsequent
PbSe growth.
AFM of 2 ML PbSe
Grayscale 95 nm

• 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 ? s/?, s and ?,
  electrical and thermal conductivities, resp.

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PbSe Micro/ Nanostructures
Shi Strain in MQW causes rolling of PbSe when
BaF2 layer is removed in water.
PbSe layers
BaF 2 layer
PbSe bulk
SEM image and PL of a freestanding MQW
microtube. Diameter 600, length 5 mm.
SEM images and PL of PbSe micro-rods.
APL 88, 171111 (2006).
Physica E 39, 120 (2007).
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IRG2 Mesoscopic Narrow Gap Systems

• Comprehensive expertise MBE, characterization,
  fabrication, transport and optical experiments,
  theory
• Fundamental and technologically motivated studies
• Devices exploit high mobility, quantum
  confinement, ballistic and spin effects

36
Strategy/Progress IRG2
Transport
Optics
Growth
Theory
InSb APL 91, 062106 (2007) Phys Stat Sol, 2775
(2008) JCG 311, 1972 (2009)
Theory PRL 101, 046804 (2008) PRB 77, 035327
(2008) PRB 78, 045302 (2008)
Spin Lifetime
Spin Transport Physica E 34, 647 (2006) Springer
119, 35 (2008)
Interband Cascade Lasers Elec Lett 45, 48 (2009)
InGaAs APL 91, 113515 (2007) APL 92, 222904
(2008) APL 94, 013511 (2009
Magneto-optics APL 89, 021907 (2006) JVST B24,
2429 (2006) Springer 119, 213 (2008)
Hall Sensors J Mat Sci 19, 776 (2008) IEEE TED
56, 683 (2009)
Infrared Devices JAP 101, 114510 (2007) IEEE PTL
20, 629, (2008) APL 92, 211110 (2008)
IV-VI APL 88, 171111 (2006) Physica E 39, 120
(2007)