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T-shaped gate formation is a major processing step in the fabrication of high-performance field-effect transistor FET-based III-V devices. Traditional bilayer or trilayer E-beam lithography methods using PMMA/(PMMA&PMAA) copolymers are high-cost options which also lack the required critical dimension control for manufacturing. Lithography methods that use only a single layer of PMMA for the formation of T-shaped gate stem, and routine I-line resist lithography for the tee-top, i.e., hybrid T-shaped gates, have been developed and extensively used in manufacturing. This approach has also been extended to the fabrication of deep submicron T-shaped gates using all I-line optical lithography. Both chemical shrinks and chromeless phase-shift resolution enhancement techniques have been investigated.Index Terms-Field-effect transistor, GaAs, T-shaped gate.

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High quality Josephson tunnel junctions have been fabricated whose tunneling barrier is polycrystalline germanium chemically vapor deposited on a NbN base electrode and covered by a Nb counterelectrode. These junctions have excellent characteristics for device applications: values of Vm (the product of the critical current and the subgap resistance measured at 2 mV and 4.2 K) ranging between 35–48 mV, ideal threshold curves, a steep current rise at the gap voltage, and Josephson current densities from 100 to 1100 A/cm2.