Design, fabrication and characterization of a suspended heterostructure

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Leduc, Vincent Louis Philippe
NEMS , Displacement sensing , 2DEG , Piezoelectricity , GaAs
This thesis presents the design and theoretical modeling of an aluminum gallium arsenide/gallium arsenide heterostructure from which suspended nanoscale mechanical resonators with embedded two-dimensional electron gas (2DEG) can be made. The mechanical characteristics of the resonator and the piezoelectric actuation scheme are investigated using finite-element modeling. For a 836 nm-long, 250 nm-wide and 164 nm-thick beam with gold electrodes on top, out-of-plane flexural vibrations are verified to be piezoelectrically excited at the beam's fundamental frequency of 925.6 MHz. Fabrication recipes for the making of ohmic contacts to the 2DEG, Hall bars and suspended structures are developed using the designed crystal structure. Electrical properties of the 2DEG are evaluated in both large, unsuspended structures as well as in sub-micron size suspended structures. It is found that the 2DEG has a reasonable electron density of 7.04E11 cm^-2 and electron mobility of 1.72E5 cm^2/(V s).
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