Abstract: Group III-V nitride films are fabricated on mesas patterned either on substrates such as sapphire substrates, or on mesas patterned on group III-V nitride layers grown on substrates. The mesas provide reduced area surfaces for epitaxially growing group III-V nitride films, to reduce thermal film stresses in the films to reduce cracking. The surfaces of the mesas on which the films are grown are dimensioned and oriented to reduce the number of thin film crack planes that can grow on the mesas. Further cracking reduction in the films can be achieved by thinning the substrate to form membranes. The reduced substrate thickness at the membranes reduces the thermal expansion mismatch tensile stress in the films. The mesas can reduce or eliminate the occurrence of cracks in GaN or AlGaN epitaxial films grown on the mesas, for percentages of aluminum in the AlGaN films of up to about 18%.

Abstract: This invention relates to a multiple wavelength laser structure, and more particularly, to a multiple wavelength laser array structure fabricated by flip-chip bonding from laser structures on two different substrates. A side by side red/IR laser structure is flip-chip bonded to a blue laser structure to form a red/blue/IR hybrid integrated laser structure.

Abstract: An ultrasonic transducer and its method of fabrication wherein bonding between an impedance matching layer on one side of a piezoelectric layer and a support layer on the other side of the piezoelectric material is made by providing onto each material a smooth, thin gold film on the smooth surfaces of the layers which are to be in contact with one another in the assembled transducer. The layers are bonded to each other by the gold films under moderate temperature and pressure to form the transducer. Sawing of the impedance matching and piezoelectric layers into a plurality of parallel transducers attached to the support layer forms an array.

Abstract: An ultrasonic transducer and its method of fabrication wherein bonding between an impedance matching layer on one side of a piezoelectric layer and a support layer on the other side of the piezoelectric material is made by providing onto each material a smooth, thin gold film on the smooth surfaces of the layers which are to be in contact with one another in the assembled transducer. The layers are bonded to each other by the gold films under moderate temperature and pressure to form the transducer. Sawing of the impedance matching and piezoelectric layers into a plurality of parallel transducers attached to the support layer forms an array.

Abstract: A surface acoustic wave (SAW) device is provided with short-term and long-term stability by recessing the electrode structure into the surface of the piezoelectric crystal of the device. In addition, the surface is passivated with the silicon polymer, and a cover of the same crystalline material is placed above the electrode structure to prevent absorption of impurities into the surface from the atmosphere. The passivation is believed to reduce the effect of thermal agitation of the bonds of the crystal lattice structure, and thereby prevent the making and breaking of chemical bonds with hydroxyl ions that may have been entrapped from the atmosphere. The SAW device is particularly useful in the construction of stable oscillator circuits wherein the passivation provides improved short-term frequency stability and the cover provides long-term frequency stability.

Abstract: A reflective grating for a surface acoustic wave device is formed of interleaved sets of contiguous metal strips deposited on the surface of the device. The metal in one set of the strips has a density greater than that of the acoustic propagating medium of the device while the metal of the second set of strips has a density essentially equal to that of the acoustic propagating medium of the device. Typically, a piezoelectric material such as a crystal of quartz or a crystal of lithium niobate is utilized as the base material of the device with the grating being formed of an overlay of alternating strips of gold and aluminum.

Abstract: Surface acoustic wave devices are disclosed which have enhanced reflectivity gratings with conductive stripes between grooves in the substrate or conductive stripes within the grooves. For lithium niobate substrates, aluminum stripes coupled together and positioned between grooves or unconnected and positioned within the grooves are preferred. For quartz substrates, gold stripes within the grooves are used. Methods for fabricating such structures are also disclosed.