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

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

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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.

2011-1 Special Topics in Optical Communications

- Abstract
- Introduction
- Conduction mechanisms and power efficiency
- Inverted fraction of Er ions
- Conclusion

High-Speed Circuits and Systems LAB.

2011-1 Special Topics in Optical Communications

- 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.

2011-1 Special Topics in Optical Communications

High-Speed Circuits and Systems LAB.

2011-1 Special Topics in Optical Communications

High-Speed Circuits and Systems LAB.

2011-1 Special Topics in Optical Communications

- 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)

- Realization of an efficient Si-based light source
- 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.

2011-1 Special Topics in Optical Communications

- 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.

2011-1 Special Topics in Optical Communications

- 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.

2011-1 Special Topics in Optical Communications

- 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.

2011-1 Special Topics in Optical Communications

- 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

- Presence of the Si-ncl due to the Purcell effect
- Nanocluster size
- Er-to-nanocluster separation

High-Speed Circuits and Systems LAB.

2011-1 Special Topics in Optical Communications

- 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.

2011-1 Special Topics in Optical Communications

- 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.

2011-1 Special Topics in Optical Communications

- 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.

2011-1 Special Topics in Optical Communications

- 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.

2011-1 Special Topics in Optical Communications

- 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.

2011-1 Special Topics in Optical Communications

Thank you for listening

Jeong-Min Lee

(minlj@tera.yonsei.ac.kr)

High-Speed Circuits and Systems