self-assembled sige single hole transistors · pdf filegeorgios katsaros – laboratoire...

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


The Ge/Si(001) System

50x32x7 nm3 50x50x7 nm3

50x50x10 nm3

110x110x27 nm3


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)


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


O.G. Schmidt Group, IFW Dresden

Controlling the position of SK quantum dots

Growth on patterned substrates


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


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)


State of the art for p-type SiGe nanostructures

Roddaro et al., PRL 186802 (2008)

Small dots g ~ 2


C)

Single-hole transport in weakly coupled devices


C)

Single-hole transport in weakly coupled devices

Coulomb blockade conductance peaks


Low-temperature single-hole transport

Excitation lines(Energy-level spacing of a few meV due to size confinement

in the SiGe island)


Zeeman splitting of quantum-dot hole statesDirect tunneling spectroscopy

G.K. et al., Nature Nanotechnology 5, 458 (2010)


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


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


Sequential Spin filling

8 T 7 T 6 T 5 TVsd

Vg

N-1N+1 N


Sequential Spin filling

8 T 7 T 6 T 5 TVsd

Vg

N-1N+1 N

8 T 7 T 6 T 5 T


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

⇓


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

⇓


Zeeman splitting measured by spin flip inelastic cotunneling


Summary of g-factor results


Measuring the spin-orbit coupling strength



N. Roch et al., Nature 453, 633 (2008)



G. K. et al., Nature Nanotechnology 5, 458 (2010)


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

self-assembled sige single hole transistors · pdf filegeorgios katsaros – laboratoire...

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