Si, SiGe, InP, III-N, and p-diamond FETs and HBTs for sub-terahertz and terahertz applications

Abstract

InGaAs and GaN HEMTs, InP and SiGe HBTs, and Si MOS demonstrated an efficient detection of terahertz (THz) radiation. The detection mechanism is the rectification of the decaying oscillations of plasma waves. These devices have been also used for homodyne and heterodyne detection, frequency mixing, and for the detection of THz pulses. A high detection speed, a wide dynamic range, and the sensitivity to the sign of the THz electric field make them very attractive for applications in the THz time resolved and time-domain spectroscopy. InP-based and SiGe HBTs have also demonstrated the THz operation. The missing link to revolutionizing the THz electronics is the lack of efficient and powerful THz electronic sources. The Dyakonov-Shur and plasmonic boom instabilities - the proposed mechanisms of generating THz radiation by FETs - require the resonant excitation of the plasma waves, i.e. very short device sizes and high materials and interface quality. The feature sizes of 7 nm and 5 nm of the current and emerging generations of Si CMOS are considerably smaller than the 15 to 30 nm mean free path in Si at room temperature. Ballistic transport in such nanoscale FETs should enable the resonant plasma wave regimes. GaN-based FETs, with extremely high sheet carrier densities and, as a consequence, with higher plasma frequencies, should demonstrate even better performance. The materials properties of p-diamond make it a promising candidate for plasmonic THz sources. New device designs - plasmonic crystals - using multiple resonant sections should improve coupling and increase power.