Journal
IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES
Volume 64, Issue 10, Pages 3139-3150Publisher
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
DOI: 10.1109/TMTT.2016.2598168
Keywords
Cryogenic low-noise amplifier (LNA); high electron-mobility transistor (HEMT); monolithic microwave integrated circuit (MMIC); small-signal model; stability
Categories
Funding
- Fraunhofer IAF and MPIfR within the Project mHEMT Prozess-Optimierung fur niedrigstes Eigenrauschen bei kryogenen Temperaturen
- Fraunhofer-Gesellschaft
- Max-Planck-Gesellschaft
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An investigation of metamorphic high electron mobility transistor stability at cryogenic temperature is presented in this paper. Unlike in the case of two-finger transistors, the measurements of cooled four-finger devices with large gate widths exhibit unstable behavior in the form of steps in the current-voltage characteristics, discontinuities in the transconductance, and reduced gain. This unstable behavior has hampered the reliable realization of low-noise amplifiers for cryogenic applications. We study different gate-width devices with a multiport transistor model, allowing the separation of gate and drain feeder structures from the active part of the transistor. The simulation reveals the presence of resonances in the frequency region of several hundreds of gigahertz. We demonstrate that the resonances disappear when an air bridge is placed across the fingers of the drain feeder structure, and confirm the stabilizing effect of the air bridge both on device and circuit level by cryogenic measurements.
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