Assessment of THz Performance for a Lateral SiGe HBT on SOI With a Laterally Graded Base

This paper presents a simulation-based assessment of the design, characteristics, and feasibility of a lateral SiGe heterojunction bipolar transistor with a graded base on a silicon on insulator. A device was created with a focus on integration with the CMOS process, THz f
_T
/f
_max
, and low-power dissipation. These characteristics are achieved with an ultrathin base width of 22 nm, grading of the base, and modification of standard doping profiles. In TCAD simulations, the n-p-n device has a unity gain cutoff frequency (f
_T
) of 1.2 THz and maximum oscillation frequency (f
_max
) of 2 THz. The p-n-p of the same design has f
_T
of 900 GHz and f
_max
of 1.8 THz. Additional Monte Carlo plots that show electron velocity and carrier densities across the length of the device, and a discussion on ballistic effects in the proposed devices are presented. To demonstrate the feasibility of the device, a possible process flow for fabrication is also summarized.