Guest Editorial for the special issue on devices and circuits for millimeter‐wave and THz applications

Abstract

Wireless communication, precision guidance, imaging, internet of things, and biomedical applications in the millimeter-wave and THz bands promise new functionalities that cannot be provided by present systems. Different from present design methods, new design methods are required to support the development of high-performance millimeterwave and THz band devices and systems. These new design methods should incorporate new materials, advanced processing and technologies, and can accurately account for multi-physics coupling effects. This special issue collects 32 papers including 20 papers on active device modeling, nine papers on passive device and circuit modeling and design techniques, and three papers on emerging system applications.Active devices for state-of-the-art millimeter-wave and THz systems discussed in this special issue include Indium phosphide (InP) heterojunction bipolar transistors (HBTs), Indium Gallium Phosphide (InGaP)/Gallium arsenide (GaAs) HBTs, Gallium nitride (GaN) high electron mobility transistors (HEMTs), GaAs HEMTs, complementary metal oxide silicon (CMOS) transistors, and electric vacuum devices. The discussion covers the important device features of high frequency, high power, low noise, and high efficiency. As the frequency goes up to the millimeter-wave and THz bands, advanced physical-based or SPICE-like equivalent circuit and compact models are needed. As a solid-state device, InP transistor can operate at a very high frequency by taking advantages of extremely high electron mobility. Zhang et al 1 presented a review on the compact modeling of InP HBTs for THz integrated circuits. Useful improvements made for HBTs are reported on the analysis of intrinsic base resistances by Chen et al, 2 on large-signal models by Hu et al, 3 on the determination of cutoff and maximum oscillation frequencies by Zhang and Gao, 4 and on the thermal resistance calculation by Wang et al. 5 Due to a high breakthrough voltage and saturation velocity, GaN HEMTs is very promising for millimeter-wave solid-state power amplifiers. Chen et al 6 reported an improved quasi-physics zone division large-signal model to account for electro-thermal effects, which is valid for the ambient temperature range of 245 to 390 K. Physical parameters' effects, reliable parameter extraction, and dynamic thermal impedance extraction for the equivalent circuit models of GaN HEMTs are discussed by Mi et al, 7 Chen et al, 8 and Wang et al, 9 respectively. The modeling of emerging devices is also presented by Chen et al 10 for GaN-on-diamond HEMTs and Zhang et al 11 for AlGaN/GaN fin-shaped HEMTs, which may be interesting for next generation devices. Accurate modeling of transistors' noise performance is important for low-noise applications. Jarndal et al 12 developed a noise model for GaN HEMTs and Caddemi et al 13 reported an improved scalable parameter extraction method for GaAs HEMTs. CMOS transistor is very competitive in millimeter-wave and THz circuits due to its mature process. Bashir et al 14 presented a scalable small-...