2GHz gallium arsenide bulk acoustic wave resonators fabricated using sol-gel technology

This paper reports on the deposition of ferroelectric lead titanate thin films on metallized GaAs substrates intended for use as bulk acoustic wave (BAW) resonators using the technique of sol-gel. The films were prepared using a new sol-gel route based on 1,3 propanediol solvent which gives a tenfold thickness increase over conventional methods using toxic methoxyethanol. Films about 1gm thick which are suitable for 2GHz operation have been grown in a single deposition. Highly homogeneous, crystalline fllms are produced at low sintering temperatures and short holding times using rapid thermal annealing. The relative permittivity of the films at lMHz is estimated to be about 21 and hysteresis measurements reveal spontaneous polarization and coercive field values of 17¿C/cm2 and 0.7MV/m respectively.