Silicon Based Heterostructures for Nano and Optoelectronics

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Silicon Based Heterostructures for Nano- and
Optoelectronics

• A.V.Dvurechenskii

630090, Novosibirsk dvurech_at_isp.nsc.ru www.isp.nsc
.ru
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Future Prospect of Si/Ge Heterostructures for
Nano- and Optoelectronics
SiGe
D.J. Paul, Semicond. Sci. Technol. 19, R75R108
(2004)
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Advantages of Quantum dots nanostructure

• increased sensitivity to normally incident light
  (as a result of breaking of the polarization
  selection rules, so eliminating the need for
  reflectors, gratings or optocouplers)
• expected large photoelectric gain associated with
  a reduced capture probability of photoexcited
  carriers (due to suppression of electron-phonon
  scattering)
• small thermal generation rate and, hence, small
  dark current (resulted from zero-dimensional
  character of the electronic spectrum that
  renders a much improved signal-to-noise ratio and
  allows to increase the operation temperature of
  the detectors).
• possibility of the narrow-band detection due to
  discreteness of the density of states.

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Ge/Si quantum dots
Dense array of QDs

• Size of commonly used pyramidal shape QDs
• 1.5 nm height
• 15 nm
  base
• Size dispertion 10-20,
• Density 3?1011 cm-2

TEM image of Ge QDs in Si 6 monolayer Ge
deposition
Geometrical model of Ge in S
A.I. Yakimov, A.V. Dvurechenskii, A.I. Nikiforov.
J. Nano- and Optoelectronics. 2006, v.1, ? 2,
119-175.
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Electron configuration and optical transition in
Ge/Si quantum dot structures.
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Quantum efficiency of Ge/Si p-i-n
waveguide photodiode
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How to increase efficiency of absorbsion/luminesce
nce

• Two necessary conditions
• 1) to ensure strong electron localization in Si
  In this case the interband optical transitions
  will direct in wave vector space, because the
  average momentum of electron in Si conduction
  band and hole in Ge will be zero
• 2) to ensure the overlapping as much as possible
  of electron and hole wave functions, and
  consequently to provide possibility of direct
  interband optical transitions in real space.

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Enhanced oscillator strength of interband
transitions in coupled Ge/Si quantum dots
Oscillator strength of double quantum dots
relative to oscillator strength of single
quantum dot.
Yakimov A.I., Bloshkin A.V., Dvurechenskii A.V.
Appl. Phys. Lett., 93,132105 (2008)
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Stark effect in type-I and type-II QDs

• Type-II QDs (Ge/Si)

• Type-I QDs (InAs/GaAs)

electron
electron
EC
Si Ge Si
EC
F
GaAs InAs GaAs
EV
hole
hole
EV
z
z
ze
zh
ze
zh
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p-i-n diode under reverse bias
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Photocurrent spectra vs applied reverse bias
A.I.Yakimov, A.V.Dvurechenskii, A.I.Nikiforov,
V.V.Ulyanov, A.G.Milekhin, A.O.Govorov,
S.Schulze, and D.R.T. Zahn. Phys. Rev. B, 2003,
67, ? 12, 125318.
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• Photocurrent spectra

• Transition energies as a function of electric
  field

As expected for a system with built-in dipole
moments, the Stark shift for both transitions
appears to be linear!
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Ece??Vg , ?Vg1,1 V, Ec43,3 meV
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Spin blockade in conductivity through array of
quantum dots
Experiment idea
Ge Si Ge Si Ge Si Ge Si Ge
Si Ge
?lt1 ?1 ?gt1
There is no need for spin flip
There is need for spin flip, probability of
tunneling is less by two order of value
There is no need for spin flip
Spin polarization by external magnetic field
leads to increasing of magnetoresistance at ??1.
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Spin blockade in conductivity through array of
quantum dots
Sketch of measured structure
Vgate
SiO2
Al
Al
NA1016 cm-3
?-Si(B)
Ge QDs
Si (001) substrate
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Spin blockade in conductivity through array of
quantum dots
Magnetoresistance dependence versus gate voltage
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The Si-based nanoheterostructures with high
mobility of electrons and holes in the
two-dimensional channel for high-frequency
transistors and high-speed integrated devices
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New generation of Automated Compact MBE-CBE
Installation Katun 100 industrial focused,
very convenient in operation
Installation depending on directions of its use
can consist of the several specialized vacuum
chambers chambers of a loading - unloading of
plates substrates (2 cartridges on 7 plates in
diameter of 102 mm) chambers epitaxial growth of
elementary semiconductors (Si, Ge), metal,
dielectric layers are supplied with electron beam
evaporators, gas and plasma sources of molecular
beams chambers for grovth of ?3?5, A3N and ?2?6
semiconductor compounds can contain up to 12
molecular sources, including ventille type for
antimony, phosphorus and arsenic.
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Two-chamber installation Katun 100
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Conclusion

• Germanium-silicon low-dimensional
  nanoheterostructures represent very promising new
  material for device applications.
• The experimental results open the door
• for progress of innovation in the field of
  application of the nanostructures in
  silicon-based nanoelectronic, infrared detectors
  and solar cells.

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Thank you for attention