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OPTICAL CONTROL AND TUNING OF THERMAL-PIEZORESISTIVE SELFSUSTAINED OSCILLATORS
Author: Harris J. Hall, Luda Wang, J. Scott Bunch,
Siavash Pourkamali, and Victor M. Bright
Reporter: 朱家君Date: 2015/4/14
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Outline
• Introduction• Theory• Experiment• Results (A3 and C6)• Conclusion
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Introduction• Electrically driven thermal-piezoresistive self-sustained
oscillators
• Optical control (HeNe, 632nm wavelength)
→ tune frequency
→ on/off control
• Photoexcitation of charge carriers
→ piezoresistive coefficient change
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Device (A3, n-type SOI)
in-plane longitudinal mode
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Theory • Motional conductance:
(E: temperature dependent)
• Photoexcitation of carriers → silicon’s resistivity ↓
HeNe energy (~1.96 eV) > extrinsic (~0.15 eV)
and intrinsic (~1.12 eV)• Illumination ↑ , IDC ↑ , power dissipation changed,
Joule heating changed in turn, steady-state temperature
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Piezoresistance factor P(N,T)• Piezoresistive coefficient:
1. Total carrier concentration from excited carriers ↑
2. Steady-state temperature changes
• Piezoresistive coefficient ↓
→ gm ↓
→ not satisfied gmRA < -1
→ finally shutoff
carrier concentration
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Experiment
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Results (C6, DC=31.61V)
DC current Peak frequency
(1D Lorentzian profile)
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Results (C6, DC=31.61V)
V(AC, max) Oscillation off/on
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• Photoexcitation of carriers
→ device resistance ↓
→ DC power dissipation in turn ↓
→ temperature ↓
→ stiffens the Young’s modulus
→ frequency ↑.
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Results (A3, DC=37.96V)
carrier excitation saturation limit → scattering loss mechanisms to dominate and cause an increase in electrical resistance
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Conclusion• This work demonstrates thermal-piezoresistive oscillators
can be frequency tuned and controllably quenched using continuous wave HeNe illumination of the structure.
• It is predicated upon direct influence of the piezoresistivity of the material.
• This method of control potentially offers a unique way of integrating these devices with on-chip photonic circuitry.
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END
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Application