Prospects of Terahertz Transistors with the Topological Semimetal Cadmium Arsenide

Electronic devices that operate at terahertz frequencies will require new materials that exhibit higher carrier velocities than traditional semiconductors. Calculations show that cadmium arsenide, a 3D topological (Dirac) semimetal, is an excellent candidate for field effect transistors that operate at frequencies above 1 THz. Moreover, such transistors have unique advantages that are enabled by the properties of Dirac electrons. These include predictions of an unprecedented linearity of the transconductance and cutoff frequencies over a large operating range and cutoff frequencies that remain above 1 THz at carrier densities as low as 10 11 cm −2 . The calculations are underpinned by measurements of devices with cadmium arsenide channels. Extremely low contact resistances (<2 × 10 −9 Ω cm 2 ), high electron velocities (>7 × 10 5 m s −1 ), and unprecedentedly large current densities (up to 10 A mm −1 ) are demonstrated. Current modulation (>50%) and transconductance already achieved in the early transistors show the potential for large (>10 ×) improvements by reducing interface trap densities. The results demonstrate the significant potential of topological semimetals for high‐speed transistors operating in the THz regime and open up new opportunities for next‐generation RF circuits.