Surface Acoustic Surface Acoustic Wave Devices on Wave Devices on

NitridesNitridesWu BinWu Bin

EE598 Wide Bandgap SemiconductorsInstructor: Dr. Huili(Grace) XingDepartment of Electrical EngineeringUniversity of Notre Dame

OutlineOutline

IntroductionIntroduction Surface Acoustic Wave (SAW) deSurface Acoustic Wave (SAW) de

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Surface acoustic waves (SAW) is the general name for the waves that propagate at the surface of solids, whose displacement amplitudes undergo exponential decay beneath this surface, similar to the ones that propagate on the water surface. Typically almost all of the energy is localized within a depth of two wavelengths. The SAW industry uses mainly Rayleigh waves, which are named after Lord Rayleigh.

For applications in electronics, the piezoelectric effect is used to convert electrical energy into acoustic wave energy and vice versa. Information carried by the surface acoustic waves along the surface of a crystal substrate may be processed during propagation. The most common processing techniques involve either the time delay of the signal, which depends on the geometry of the device and the acoustic velocity, or the amplitude of the signal which can be varied or "weighted" by controlling the efficiency of the piezoelectric transduction.

What Is SAW and How It Works-- A very brief description

The Interdigital Transducer (IDT)The IDT comprises two sets of interpenetrating metallic electrodes fabricated photolithographically on the surface of a piezoelectric substrate.A typical SAW device contains two such IDTs,one as input transducer, the other as output transducer to convert the SAW back to the electrical domain, e.g. delay or filtering.

Some IDT Designs

Some More IDT Designs

SAW Device As Bandpass FilterSAW Device As Bandpass Filter

mms

sm

SAW

ms

sm

EM

GHzf

f

f

3103101

3000

3.0101

103

1

69

9

8

0

00

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Simple Calculation Simple Calculation Considering The Merit of Considering The Merit of

SAW DevicesSAW Devices

Small SAW DevicesSmall SAW Devices

Small SAW DevicesSmall SAW Devices

SAW Device As SensorSAW Device As Sensor

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TT

cc

mm

0

1

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m is mass, c is stiffness, is dielectric constant, is surface conductivity, T is the temperature, and p is the pressure.

SAW Device As SensorSAW Device As Sensor

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