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Georgios Katsaros – Aussois 2010
Self-assembled SiGe single hole transistors
G. Katsaros1, P. Spathis1, M. Stoffel2, F. Fournel3, M. Mongillo1, V. Bouchiat4,F. Lefloch1, A. Rastelli2, O. G. Schmidt2 and S. De Franceschi1
1CEA Grenoble, LaTEQS Laboratory,France 2IFW-Dresden, Germany3CEA Grenoble, LETI, France 4CNRS-Grenoble, Neél Institute, France
Georgios Katsaros – Laboratoire de Transport Electronique Quantique et Supraconductivité
Si (001)
Lattice-mismatched SK-growth. E.g.
Ge/Si(001)
Wetting layer (WL)formation
Spontaneous formation of 3D
islands
Ge
Ge Competition: elastic energy relaxation vs surface energy
The Stranski-Krastanow growth mode
Georgios Katsaros – Laboratoire de Transport Electronique Quantique et Supraconductivité
The Ge/Si(001) System
50x32x7 nm3 50x50x7 nm3
50x50x10 nm3
110x110x27 nm3
Georgios Katsaros – Laboratoire de Transport Electronique Quantique et Supraconductivité
Why are SiGe self-assembled quantum dots interesting?Nominally pure Ge islands contain Si
• Ge content bigger close to the apex of the islands
• Si content increases the higher the growth temperature
•Strain relaxation towards the apex of the islands
G.K. et al.,Phys. Rev. B 72, 195320 (2005)
PhD Thesis, Konstanz 2006 T. U. Schülli et al.
Phys. Rev. Lett. 90, 066105 (2003)
Georgios Katsaros – Laboratoire de Transport Electronique Quantique et Supraconductivité
Controlling the position of SK quantum dots
SK quantum dots localize on nanoscale grooves
G. K. et al., Phys. Rev. Lett. 101, 096103 (2008)
PhD Thesis Konstanz 2006
Georgios Katsaros – Laboratoire de Transport Electronique Quantique et Supraconductivité
O.G. Schmidt Group, IFW Dresden
Controlling the position of SK quantum dots
Growth on patterned substrates
Georgios Katsaros – Laboratoire de Transport Electronique Quantique et Supraconductivité
Hole quantum confinement in a SiGe quantum-dot transistor
Si t
unne
l bar
rier
Met
also
urce
con
tact
Ge
quan
tum
dot
Met
aldr
ain
cont
act
Si t
unne
l bar
rier
QUALITATIVE BAND DIAGRAM
Georgios Katsaros – Laboratoire de Transport Electronique Quantique et Supraconductivité
State of the art for p-type SiGe nanostructures
Lu et al., PNAS 102, 0504581102 (2005)
Hu et al., Nat. Nanotechn. 2, 622 (2007)Xiang et al., Nat. Nanotechn. 1,
208 (2006)
Georgios Katsaros – Laboratoire de Transport Electronique Quantique et Supraconductivité
State of the art for p-type SiGe nanostructures
Roddaro et al., PRL 186802 (2008)
Small dots g ~ 2
Georgios Katsaros – Laboratoire de Transport Electronique Quantique et Supraconductivité
C)
Single-hole transport in weakly coupled devices
Georgios Katsaros – Laboratoire de Transport Electronique Quantique et Supraconductivité
C)
Single-hole transport in weakly coupled devices
Coulomb blockade conductance peaks
Georgios Katsaros – Laboratoire de Transport Electronique Quantique et Supraconductivité
Low-temperature single-hole transport
Excitation lines(Energy-level spacing of a few meV due to size confinement
in the SiGe island)
Georgios Katsaros – Laboratoire de Transport Electronique Quantique et Supraconductivité
Zeeman splitting of quantum-dot hole statesDirect tunneling spectroscopy
G.K. et al., Nature Nanotechnology 5, 458 (2010)
Georgios Katsaros – Laboratoire de Transport Electronique Quantique et Supraconductivité
Haendel et al., PRL 96, 086403 (2006)
g=6k
g=2k
g~0
g=4k
Composition dependentLuttinger parameter k:
Ge: -3.37Si: 0.42
60% Ge: -0.30880%Ge -1.153
Band Structure of SiGe
Fraj et al.,Semiconductor Science
and Technology 23, 085006 (2008).Fraj et al.,
J. Appl. Phys. 102, 053703 (2007).
Zeeman: Hz ~ -2kμBB·J
Georgios Katsaros – Laboratoire de Transport Electronique Quantique et Supraconductivité
Haendel et al., PRL 96, 086403 (2006)
g=6k
g=2k
g~0
g=4k
Composition dependentLuttinger parameter k:
Ge: -3.37Si: 0.42
60% Ge: -0.30880%Ge -1.153
Band Structure of SiGe
Fraj et al.,Semiconductor Science
and Technology 23, 085006 (2008).Fraj et al.,
J. Appl. Phys. 102, 053703 (2007).
Nenashev et al.,Phys. Rev. B 67,205301 (2003)
Zeeman: Hz ~ -2kμBB·J
Georgios Katsaros – Laboratoire de Transport Electronique Quantique et Supraconductivité
Sequential Spin filling
8 T 7 T 6 T 5 TVsd
Vg
N-1N+1 N
Georgios Katsaros – Laboratoire de Transport Electronique Quantique et Supraconductivité
Sequential Spin filling
8 T 7 T 6 T 5 TVsd
Vg
N-1N+1 N
8 T 7 T 6 T 5 T
Georgios Katsaros – Laboratoire de Transport Electronique Quantique et Supraconductivité
Can be used for spectroscopy [De Franceschi et al, PRL 86, 878 (2001)]
Resolution determined by temperatureand not by life-time broadening!
Inelastic cotunneling (strong coupling)
Flat ‘featurelless’ differential conductance within coulomb diamond
⇓
Georgios Katsaros – Laboratoire de Transport Electronique Quantique et Supraconductivité
eV = δ
Can be used for spectroscopy [De Franceschi et al, PRL 86, 878 (2001)]
δ
N+1 N N-1
Vsd
Vg
Resolution determined by temperatureand not by life-time broadening!
Inelastic cotunneling (strong coupling)
Step in differential conductance
⇓
Georgios Katsaros – Laboratoire de Transport Electronique Quantique et Supraconductivité
Zeeman splitting measured by spin flip inelastic cotunneling
Georgios Katsaros – Laboratoire de Transport Electronique Quantique et Supraconductivité
Zeeman splitting measured by spin flip inelastic cotunneling
Georgios Katsaros – Laboratoire de Transport Electronique Quantique et Supraconductivité
Summary of g-factor results
Georgios Katsaros – Laboratoire de Transport Electronique Quantique et Supraconductivité
Measuring the spin-orbit coupling strength
Georgios Katsaros – Laboratoire de Transport Electronique Quantique et Supraconductivité
Measuring the spin-orbit coupling strength
Georgios Katsaros – Laboratoire de Transport Electronique Quantique et Supraconductivité
Measuring the spin-orbit coupling strength
Georgios Katsaros – Laboratoire de Transport Electronique Quantique et Supraconductivité
Measuring the spin-orbit coupling strength
N. Roch et al., Nature 453, 633 (2008)
Georgios Katsaros – Laboratoire de Transport Electronique Quantique et Supraconductivité
Measuring the spin-orbit coupling strength
Georgios Katsaros – Laboratoire de Transport Electronique Quantique et Supraconductivité
Measuring the spin-orbit coupling strength
Georgios Katsaros – Laboratoire de Transport Electronique Quantique et Supraconductivité
Measuring the spin-orbit coupling strength
G. K. et al., Nature Nanotechnology 5, 458 (2010)
Georgios Katsaros – Laboratoire de Transport Electronique Quantique et Supraconductivité
Measuring the spin-orbit coupling strength
G. K. et al., Nature Nanotechnology 5, 458 (2010)
Georgios Katsaros – Laboratoire de Transport Electronique Quantique et Supraconductivité
Summary
• First realization of three terminal devices based on SiGe self-assembled nanocrystals
• Low temperature measurements indicate strongly anisotropic hole g-factors
• Tunable spin-orbit coupling strength is demonstrated
Outlook