Raytheon

About: Raytheon is a company organization based out in Waltham, Massachusetts, United States. It is known for research contribution in the topics: Signal & Antenna (radio). The organization has 15290 authors who have published 18973 publications receiving 300052 citations.

Infrared absorption behavior in CdZnTe substrates

Abstract: Infrared (IR) optical transmission measurements of polished CdZnTe wafers can provide useful information about excess impurities, stoichiometry, and inhomogeneities (precipitates and inclusions). We have investigated the IR transmission behavior of Cd0.96Zn0.04Te between 8 m and 20 m at room temperature. The measurements were made before and after thermal treatments involving control of the Cd and Zn overpressures, which served to minimize the Cd (cation) vacancy population. Our results support the polar optical phonon scattering theory of Jensen, according to which the absorption in donor dominated CdZnTe varies asm with m=3. For material dominated by acceptors, we show that the theoretical absorption by inter-valence band transitions can be approximated by a similar power law with exponent m=1, and that Cd-vacancy dominated wafers are in reasonable agreement with this. We find some wafers in which the asgrown condition exhibits partial compensation of impurity donors by Cd vacancy acceptors, and demonstrate removal of the compensation by annealing to fill the vacancies. In a separate group of wafers, we find that an observed increase in absorption occurring during growth of a HgCdTe layer by liquid phase epitaxy can be explained in terms of an increase in Cd vacancies caused by diffusion of Cd to Te precipitates. This effect can be reversed by annealing in Cd−Zn vapor, which fills vacancies and eliminates some precipitates. Impurity concentrations were measured by glow discharge mass spectrometry (GDMS).

Carbon-doped base GaAs/AlGaAs heterojunction bipolar transistor grown by metalorganic chemical vapor deposition using carbon tetrachloride as a dopant source

Abstract: Carbon tetrachloride (CCl4) has been used as a carbon doping source for the base region of a GaAs/AlGaAs Npn heterojunction bipolar transistor (HBT) grown by low‐pressure metalorganic chemical vapor deposition (MOCVD). Transistors were fabricated and characterized for dc current gain, emitter‐base junction ideality factor, base contact resistance, and external base resistance. Microwave characterization by S‐parameter measurement was performed to determine the common emitter current gain and maximum available gain as a function of frequency. Transistors with the base contact area self‐aligned to a 3×10 μm emitter finger had a dc current gain as high as 50, an emitter‐base junction ideality factor of n=1.2, and a current gain cutoff frequency of ft=26 GHz. Transistors of equal emitter area without self‐alignment exhibited dc current gain as high as 86, n=1.2, and ft=20 GHz. A base contact resistance of Rc=2.85×10−6 Ω cm2 and an external base sheet resistance of Rs=533.4 Ω/⧠ were measured. These preliminary...

Engine mount system for a turbofan gas turbine engine

Abstract: A gas turbine engine according to an exemplary aspect of the present invention includes a gear train defined along an engine centerline axis, and a spool along the engine centerline axis which drives the gear train, the spool includes a low stage count low pressure turbine.

Three-dimensional component stacking using high density multichip interconnect decals and three-bond daisy-chained wedge bonds

Abstract: A three-dimensional circuit structure that interconnects an integrated circuit chip, along with additional active devices and passive components to a substrate by way of a high density multichip interconnect decal disposed on the integrated circuit chip. The three-dimensional circuit structure thus comprises the substrate, an integrated circuit attached to the top of the substrate, and the high density multichip interconnect decal attached to the integrated circuit. One or more passive components and relatively small active devices are attached to the top of the high density multichip interconnect decal. A plurality of three-bond, daisy-chained wedge bonds are used to interconnect the active devices and passive components to the substrate by way of the HDMI decal. Each wedge bond comprises a wire that initiates at an HDMI decal bond pad, an intermediate stitch bond at an integrated circuit bond pad, and terminates at a substrate bond pad.