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2011-1 Special Topics in Optical Communications. Towards population inversion of electrically pumped Er ions sensitized by Si nanoclusters. O. Jambois , Optics Express, 2010. Jeong -Min Lee ( [email protected] ) High-Speed Circuits and Systems LAB.

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towards population inversion of electrically pumped er ions sensitized by si nanoclusters
2011-1 Special Topics in Optical Communications

Towards population inversion of electrically pumped Er ions sensitized by Si nanoclusters

O. Jambois, Optics Express, 2010

Jeong-Min Lee

([email protected])

High-Speed Circuits and Systems LAB.

contents
2011-1 Special Topics in Optical CommunicationsContents
  • Abstract
  • Introduction
  • Conduction mechanisms and power efficiency
  • Inverted fraction of Er ions
  • Conclusion

High-Speed Circuits and Systems LAB.

abstract
2011-1 Special Topics in Optical CommunicationsAbstract
  • The estimation of the inverted Er fraction in a system of Er doped silicon oxide sensitized by Si nanoclusters
  • Electroluminescence: obtained from the sensitized Er with power efficiency: 10-2 %
  • 20 % of the total Er concentration: inverted in the best device(one order of mag. higher than optical pumping)

High-Speed Circuits and Systems LAB.

introduction
2011-1 Special Topics in Optical CommunicationsIntroduction
  • Key challenges of Si photonics:
    • Realization of an efficient Si-based light source
      • Various Si nanocluster (Si-ncl)-based materials using quantum confinement effects in Si  Light emitting diode
    • Realization of a Si-based injection laser
      • The system of Er-doped silica sensitized by Si-ncl (1.55um is important for telecom applications and absorption minimum)
  • The improvement in Er excitation thanks to Si-ncl sensitization:
    • Broadband absorption spectrum of the Si-ncl
    • The effective cross section of the system is increased three or four orders of magnitude

High-Speed Circuits and Systems LAB.

introduction1
2011-1 Special Topics in Optical CommunicationsIntroduction
  • A principal limitation of the material:
    • A small proportion of Er ions are coupled to Si-ncls
    • Optical pumping: high fluxes are required to achieve population inversion

 Pumping the Si-nclelectrically the excitation cross section is increased by two orders of magnitude from that achieved using optical pumping

  • Preparation of active layers of Er-doped SRSO:
    • Magnetron co-sputtering of three confocal cathodes, SiO2, Er2O3 and Si, under a pure Ar plasma
    • Annealing at 900°C for 30 minutes
    • Electroluminescence was measured using conventional MOS structure
    • Gate electrode: n-type polycrystalline silicon , thickness(200nm), area(2.56x10-4cm2)

High-Speed Circuits and Systems LAB.

conduction mechanism and power efficient
2011-1 Special Topics in Optical CommunicationsConduction mechanism and power efficient
  • Current density-electric field characteristics:
  • The current on applied voltage is dependant on characteristic of dielectrics
  • Poole-Frenkel-type mechanism:

High-Speed Circuits and Systems LAB.

conduction mechanism and power efficient1
2011-1 Special Topics in Optical CommunicationsConduction mechanism and power efficient
  • Electroluminescence spectra of layer C352:
  • Electroluminescence at 1.54 μm was observed for both devices
    • Applied Voltage: -30 V
    • Carrier flux: 3.4x1016 q.cm-2s-1
  • PL was pumped with the 476 nm line of Ar laser
  • ηPE: The ratio between emitted optical power and electrical power input  1.3x10-2 %
  • ηEQE=ηPE x eV/ћω : The external quantum efficiency  0.4 %

High-Speed Circuits and Systems LAB.

inverted fraction of er ions
2011-1 Special Topics in Optical CommunicationsInverted fraction of Er ions
  • From the estimation of the optical power  Estimate the number of Er ions in the first excited state

 The number of Er ions in the first excited state:

      • Τrad: the Er radiative life time
      • S: the emission area
      • d: the thickness of the active layer
  • Difficult to estimate the radiative time:
    • Presence of the Si-ncl due to the Purcell effect
    • Nanocluster size
    • Er-to-nanocluster separation

High-Speed Circuits and Systems LAB.

inverted fraction of er ions1
2011-1 Special Topics in Optical CommunicationsInverted fraction of Er ions
  • Si-ncl size and/or density are higher  shorter-radiative time
  • Estimate fraction of the light
    • Total internal reflection inside the active layer
    • Back reflection from the back electrode
    • 12 % of the emitted light is able to leave the top electrode

High-Speed Circuits and Systems LAB.

inverted fraction of er ions2
2011-1 Special Topics in Optical CommunicationsInverted fraction of Er ions
  • At low flux: the population of the first excited state increase linearly with electron flux
  • At higher flux: saturation is observed for both devices
  • The first time that the inversion level has been estimated for electrical pumping
  • For optical pumping, high fluxes are necessary to reach
  • Flux increases  rise time decreases

High-Speed Circuits and Systems LAB.

inverted fraction of er ions3
2011-1 Special Topics in Optical CommunicationsInverted fraction of Er ions
  • Observe a sublinear evolution of the reciprocal rise time with flux  main mechanism for Er excitation is through Si-ncl
  • Conduction mechanism: Si-ncl play a dominant role in charge transport
  • Electrical pumping: excitation of almost all the coupled Er
  • Further works:
  • Optimize thin layers for electrical pumping
  • Analysis of the dynamics of the system is underway

High-Speed Circuits and Systems LAB.

inverted fraction of er ions4
2011-1 Special Topics in Optical CommunicationsInverted fraction of Er ions
  • EL rise and decay time are observed to be non-exponential
  • Time-resolved EL for C352 with increasing charge flux:

High-Speed Circuits and Systems LAB.

conclusion
2011-1 Special Topics in Optical CommunicationsConclusion
  • Significant development in Si photonics for the realization of a Si-based optical source by demonstrating an increased fraction of inverted Er ions
  • The benefits of using electrical pumping to reach high values of inversion
  • A power efficiency(ηPE) of 10−2% is reported, corresponding to an external quantum efficiency(ηEQE) of 0.4%

High-Speed Circuits and Systems LAB.

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