United Technologies Corporation

Donald E Cullen

William J Tanski

Thomas W Grudkowski

Sears W Merritt

Emilio J Branciforte

Robert N Sacks

Meyer Gilden

Robert A Wagner

Roger D Carroll

Gerald Meltz

Thomas M Reeder

Gary K Montress

A heterojunction acoustic charge transport device (HACT) having a charge transport channel 39 which is sandwiched between upper and lower charge confinement layers, 14,20, has the charge transport channel 39 made of a Strained Layer Superlattice (SLS) comprising alternating deep-well semiconductor layers 40, that provide a deep quantum well depth, and strain relief layers 42 that provide strain relief to prevent dislocations from occurring due to lattice mismatches between the InGaAs layers within the channel 39 and the charge confinement layers 14,20, thereby allowing the overall thickness of the channel 39 to be at least as wide as conventional HACT devices that use a GaAs channel. The strain relief layers 42 may be narrowly sized to allow tunneling of electrons across the entire channel 39 thereby allowing the charge to move as a single group, or alternatively, widely sized to provide separate isolated channels thereby allowing the charge to move in separate groups. Both embodiments provide increased quantum well depth in the channel 39 over conventional HACT devices.

Increased well depth hact using a strained layer superlattice

A HACT device which propagates charge packets 21 along a charge transport channel 17 by a surface acoustic wave (SAW) 14 is provided with an interdigital electrode grid 30 disposed on the upper surface of the HACT, near the charge transport channel 17, having electrodes 30 spaced a distance of one-half wavelength of the SAW. A hold voltage Vh is applied across alternating electrodes to store (i.e., stop and hold) each charge packet. When a charge packet is to be released, the hold voltage Vh is removed and the electrodes 30 are shorted together or alternatively connected through a maximum allowable impedance, thereby allowing each charge packet 21 to be stored and released by the device without having the electrodes 30 absorb the SAW electric fields. Because the electrodes 30 are spaced one-half a SAW wavelength apart, the HACT memory can store each and every charge packet 21, thereby providing a Nyquist bandwidth device. Furthermore, the electrodes 30 are made thin to reduce mechanical absorption of the SAW by the electrodes.

Nyquist frequency bandwidth hact memory

A heterostructure acoustic charge transport (HACT) device having a number of signal tap electrodes has revealed unexpected insensitivity to electrode spacing and unexpected sensitivity to electrode width. Spacing of one SAW wavelength between consecutive electrodes and an electrode width of .lambda./20 are preferred.

HACT electrode configuration

An acoustic charge transport device having a number of signal tap electrodes has revealed unexpected insensitivity to electrode spacing and unexpected sensitivity to electrode width. Spacing of one-half SAW wavelength between consecutive electrodes and an electrode width of .lambda./20 are preferred for low frequency response.

Act electrode configuration for linear readout

A simplified heterostructure charge transport device has a GaAs transport layer that is the top layer of the device, deposited on an (Al,Ga) As barrier layer for vertical confinement of charge packets. Confinement at the top surface is provided by pinning of the conduction band surface states.

Surface channel hact

A separated substrate acoustic charge transport device includes a surface acoustic wave (SAW) element fabricated on a piezoelectric substrate and an acoustic charge transport element fabricated on a separate semiconducting substrate. The substrates are separated by a small gap such that the evanescent electric field associated with the propagating SAW wave extends into a transport channel in the acoustic charge transport element to provide for longitudinal charge confinement and transport along the transport channel.

Separated substrate acoustic charge transport device

An accelerometer includes a cantilevered pieozelectric beam mounted to a surface inside a fluid filled chassis with a proof mass attached to the beam's free end. Surface skimming bulk wave delay lines are mounted on opposing major surfaces of the beam and are responsive to strain induced therein by acceleration of the proof mass.

Surface skimming bulk acoustic wave accelerometer

Acoustic Wave Devices comprise lithium niobate substrates 6, 22 having the principal plane cut at zero degrees and 128.degree., respectively, with respect to the Y crystallographic axis thereof, propagating in the X direction, with amorphous silicon dioxide surface layers of 0.42 and 1.24 wavelengths, respectively.

Environmentally stable lithium niobate acoustic wave devices

A surface acoustic wave (SAW) pressure sensor is mechanically supported within a vacuum sealing structure by a cylindrical metal sleeve which isolates the SAW sensor substrate from induced thermal strain resulting from temperature cycling of the structure, and which provides for a fluid conduit through the vacuum environment from the sensor diaphragm to an orifice formed through the wall of the structure.

Surface acoustic wave (SAW) pressure sensor structure

A strain isolation technique for a surface acoustic wave (SAW) device having a piezoelectric SAW substrate is disclosed. A cut in the surface of the piezoelectric SAW substrate forms an isolated surface region where active SAW signal propagation occurs. The cut prevents undesirable surface strains from affecting SAW signal propagation in the isolated region.

Strain relief technique for surface acoustic wave devices

A dual range accelerometer includes a mass 10 supported on a cantilevered beam 12, there being stops 70, 71 such that for low accelerations the beam acts as a cantilever and for high accelerations, one of the stops causes the beam to flex as a beam supported at both ends. Surface acoustic wave devices 17, 46 provide a signal having a frequency which is a function of strain in the beam 12, thereby to detect accelerations in two different ranges.

Dual range, cantilevered mass accelerometer

An accelerometer comprising a mass 10 supported on a piezoelectric cantilevered beam 12 with SAW resonators 17, 46 disposed on the surface of the beam includes cover plates 66, 68 over the SAW resonators and sealed to the beam by seals 70, 72 which may be rigid (glass frit) or soft (filled polyimid).

Fluid damped saw accelerometer

A surface acoustic wave (SAW) device having a substrate of desired material is vacuum encapsulated in a structure fabricated from the same material as that comprising the substrate.

Vacuum encapsulation for surface acoustic wave (SAW) devices

A diaphragm formed in a substrate and having a piezoelectric surface includes a first surface acoustic wave (SAW) delay line disposed on said surface and connected in an oscillator circuit for a significant frequency sensitivity to surface strain of said diaphragm, and a second, similar oscillator with the SAW delay line thereof connected for a significant frequency sensitivity to surface strain of the diaphragm opposite in sense to that of the first oscillator, and a mixer for providing the difference in the frequencies of the two oscillators, whereby the overall sensitivity to strain is enhanced, while at the same time the sensitivity to temperature variations is reduced significantly through subtractive combination.

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Manchester, CT, United States of America

Donald E Cullen