Prospects of Terahertz Transistors with the Topological Semimetal Cadmium Arsenide

Abstract

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 1011 cm−2. The calculations are underpinned by measurements of devices with cadmium arsenide channels. Extremely low contact resistances (<2 × 10−9 Ω cm2), high electron velocities (>7 × 105 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.

Thickness-independent transport in thin (001)-oriented cadmium arsenide films

“…As a sanity check, note that a difference in frequency of 20 T suggests that the quantity E F i ≈ (60 meV) 2 , assuming v F = 5 × 10 5 m/s [19]. This is indeed what is observed in Fig.…”

“…A future direction for future research lies in dual-gated devices, which can disentangle tuning of the carrier density from that of i . That research will be enabled by optimization 035435-8 of the capping layer, gate dielectric [19,28], and device design, and is a critical step toward realizing the quantum spin Hall insulator state in cadmium arsenide.…”

Pressure-induced reconstructive phase transition inCd3As2

“…Recently, topologically protected states have also been observed in thin films of Cd 3 As 2 [10][11][12]. Thus, Cd 3 As 2 is currently being explored for technological applications based on the topological properties, e.g., for optical switches, electronic devices operating at frequencies in the terahertz regime, and high-sensitivity photodetectors [13][14][15]. In addition, Cd 3 As 2 is a prime candidate for applications based on the large magnetoresistance, room-temperature chiral charge pumping, thermoelectric properties, and possible topological superconductivity [16][17][18][19][20].…”

Topological Materials for Functional Optoelectronic Devices

“…[37] As a result, Cd 3 As 2 channel FETs exhibit extreme high current density. [27,37] It should be noted that although 3D TDSs do not have a bulk bandgap, recent studies indicate that the Dirac nodes become gapped in extremely thin (below 60 nm) films. [44][45][46] Shoron et al have demonstrated ambipolar transport in MBE grown Cd 3 As 2 channel FETs at low temperature, as shown in Figure 3i,j.…”