ISSN:
1089-7550
Source:
AIP Digital Archive
Topics:
Physics
Notes:
The composite resonator consists of a uniform thin layer etched in a small well-defined region of a semiconductor wafer to form a diaphragm, upon which is deposited a thin piezoelectric film along with the electrodes to form a resonant region directly on the wafer. Although the composite resonator, which operates in an essentially thickness-extensional mode, can be constructed to employ energy trapping, almost all existing experimental work in the literature is for the case when trapping is not present. All previous analytical work expressly ignores radiation into the bulk semiconductor except one treatment, which unrealistically ignores the junction between the etched diaphragm and the bulk semiconductor. In this work an analysis of the composite resonator driven into essentially thickness-extensional vibrations by the application of a voltage to strip electrodes is performed. The analysis includes all radiating plate waves in the thick portion of the semiconductor. The solution consists of a sum of terms satisfying all differential equations and boundary conditions on major surfaces exactly and uses the appropriate variational principle of linear piezoelectricity to satisfy the remaining conditions approximately. For the case of the aluminum–nitride film on gallium arsenide the Q is calculated for both the configuration in which the film ends at the edges of the electrodes and in which it continues to the edges of the etched diaphragm when trapping is not present and for the latter configuration when trapping is present. The calculations show that when trapping is not present the Q is a very rapidly varying function of the ratio of the composite resonator thickness to the wafer thickness and that the range of variation is very large, i.e., between one and two orders of magnitude. The calculations also reveal that when trapping is present the Q is always much larger and its range of variation much smaller than when trapping is not present.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.337183
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