Optical control and tuning of thermal piezoresistive selfsustained oscillators

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

Outline

• Introduction• Theory• Experiment• Results (A3 and C6)• Conclusion

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

Device (A3, n-type SOI)

in-plane longitudinal mode

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

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

Experiment

Results (C6, DC=31.61V)

DC current Peak frequency

(1D Lorentzian profile)

Results (C6, DC=31.61V)

V(AC, max) Oscillation off/on

• Photoexcitation of carriers

→ device resistance ↓

→ DC power dissipation in turn ↓

→ temperature ↓

→ stiffens the Young’s modulus

→ frequency ↑.

Results (A3, DC=37.96V)

carrier excitation saturation limit → scattering loss mechanisms to dominate and cause an increase in electrical resistance

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.

END

Application