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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 ( minlj@tera.yonsei.ac.kr ) High-Speed Circuits and Systems LAB.

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

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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

(minlj@tera.yonsei.ac.kr)

High-Speed Circuits and Systems LAB.


Contents

2011-1 Special Topics in Optical Communications

Contents

  • 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 Communications

Abstract

  • 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.


Si nanocrystal

2011-1 Special Topics in Optical Communications

Si nanocrystal

High-Speed Circuits and Systems LAB.


Si nanocrystal and erbium ion

2011-1 Special Topics in Optical Communications

Si nanocrystal and Erbium ion

High-Speed Circuits and Systems LAB.


Introduction

2011-1 Special Topics in Optical Communications

Introduction

  • 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 Communications

Introduction

  • 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 Communications

Conduction 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 Communications

Conduction 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 Communications

Inverted 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 Communications

    Inverted 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 Communications

    Inverted 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 Communications

    Inverted 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 Communications

    Inverted 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 Communications

    Conclusion

    • 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.


    Thank you for listening

    2011-1 Special Topics in Optical Communications

    Thank you for listening

    Jeong-Min Lee

    (minlj@tera.yonsei.ac.kr)

    High-Speed Circuits and Systems


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