DC-2 GHz low loss cryogenic InAs/AlSb HEMT switch
A DC-2 GHz InAs/AlSb HEMT MMIC single pole double throw (SPDT) switch designed for cryogenic temperature has been fabricated and characterized. This switch is suitable for low RF power applications that require low insertion loss and high isolation. At 2 GHz, the SPDT switch demonstrated a typical low insertion loss of 0.7 dB at 300K and 0.3 dB at 90K. The isolation is greater than 40dB for both temperatures. These results demonstrate the outstanding potential of ABCS HEMT technology for low loss SPDT switches for cryogenic temperature.
Metamorphic AlSb/InAs HEMT for low-power, high-speed electronics
Metamorphic high electron mobility transistors (HEMT) on GaAs substrates, with InAs channels and 0.1-/spl mu/m metal gates, have demonstrated 5 to 10 times lower power dissipation for equivalent f/sub T/ over conventional InAlAs/InGaAs lattice-matched HEMTs and MHEMTs. Our AlSb/InAs HEMT's exhibit transconductances higher than 1S/mm at drain biases as low as 0.2 V, while maintaining measured f/sub T/ results greater than 200 GHz and f/sub MAX/ results approaching 200 GHz. We have achieved low power X-band MMIC low-noise amplifiers with greater than 7 dB/stage peak gain from 12-14 GHz and 6 mW/stage DC power dissipation.
Silica in Soils1
Publisher Summary Silica in free and combined forms is a dominant component of the solid material of many soils, and dissolved silica is commonly a major solute of soil solutions. Breakdown of primary silicates, translocation of silica in solution, and deposition of secondary silica-containing substances are involved in the development of soils. Ions essential for the growth of plants are released to the soil solution as silicates weather, and these ions may be held against leaching at exchange sites on other silicates. Silica is absorbed in appreciable quantities by some plants and is returned to the surface of the soil as the plants decay. The nature and transformations of silica and silicates in soil are, thus, fundamental to an understanding of many aspects of soil and plant sciences.