Infrared detectors fabricated from Hg1−xCdxTe typically operate in the 60 to 160 K range. The temperature dependence of the atomic structure of HgCdTe may influence device performance. We present the first detailed study of the x-ray diffraction lattice parameters of molecular-beam epitaxy grown Hg1−xCdxTe epilayers between 15 and 300 K. The epilayers were grown on (100) oriented CdTe substrates, and varied in thickness (6 to 11-μm) and composition (x=0–0.172). The (400) reflection was measured to determine the lattice parameter a⊥ normal to the film. HgTe (x=0) exhibited normal lattice contraction (α=4.7×10−6±0.3 K−1 at 300 K), with a minimum in a⊥ at 60 K, and an expansion of a⊥ below 60 K. In addition to showing a minimum in a⊥ at 60 K, some of the Hg1−xCdxTe (x≠0) epilayers (10 μm thick) exhibited anomalous behavior with varying degrees of thermal hysteresis in a⊥. The average contraction of a⊥ for these epilayers from 300 to 60 K is 0.006 Å. This is compared with results we have obtained from a temperature dependent extended x-ray absorption fine structure study of these HgCdTe epilayers: whereas HgTe exhibited a normal thermal contraction of the Hg–Te bond length consistent with the lattice parameter results, in the HgCdTe epilayers this bond contracts 0.02 to 0.03 Å on cooling from 300 to 10 K. We also present lattice parameter measurements for a thin cap layer of CdTe on HgCdTe. An increase of 0.0134 Å in a⊥ relative to the bulk was observed for a 1000 Å layer of CdTe on HgCdTe at 300 K.
The magnetic properties of transition-metal–rich Fe-Co-Al films prepared by sputtering from a hollow cathode ring segmented target have been studied as a function of transition-metal composition as well as differing sputtering parameters such as substrate temperature. The major new results observed are high values of the saturation moment for series of samples with (Fe79Co21)100−xAlx for x=0–25. The saturation magnetization 4πMs observed at x=0 is 29.2±2.6 kG. This measured value was in agreement with extrapolations based on data for x=10–25.
Integrated circuit (IC) modules have been developed for a multichannel Ka-band receiver. The modules include a MMICcompatible mixer/lF amplifier and a MIC LO-distribulion network. Four mixer/lF modules have been integrated with the LO network and other components to form a multichannel receiver prototype. This work is an important step toward the realization of a new generation of compact lowcost receivers for airborne and ground-based applications.
SUMMARYMMlCcompa'dble and MIC modules have been developed for a new generation of Ka-band (26 to 40 GHz) multichannel low-cost receivers. The modules developed were: (1) an integrated quasimonolithic dc-biased low-loss mixer with a two-stage 2 to 6 GHz FET amplifier and (2) a MIC LO-distribution network. Four mixer/lF modules have been integratedwith the LO network and other components to form a multichannel receiver prototype. Figure 1 shows the mixer, which was designed and tested prior to integration with the IF amplifier. To minimize the development turnaround time, quasimonolithic construction was utilized, wherein beam-lead diodes are bonded to a GaAs chip containing monolithic lumped and distributed elements. For low-noise wide-band operation, the mixer incorporates low-parasitic GaAs in-house devices [l]. As in a related design 121, the IF output circuit is an RFlLO band-reject filter. (Relative to the conventional low-pass approach, the band-reject filter avoids the re-entry problems associated with multioctave microwave/mm-wave applications.) Mixer measurements, conducted with only 2 mW of LO drive, showed that the
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