Virtual-Source-Based Self-Consistent Current and Charge FET Models: From Ballistic to Drift-Diffusion Velocity-Saturation Operation

Abstract

A simple analytical FET channel charge partitioning model valid under ballistic and quasi-ballistic transport conditions is developed. With this model, the virtual-source (VS) based charge-based transport compact model is extended to include self-consistent analytical channel charge partitioning models for quasi- and fully-ballistic conditions, with continuous current and charges and their derivatives. Drift-diffusion with or without velocity-saturation transport conditions are also comprehended with adaptations of existing-literature models, and the resulting terminal charges and capacitances are compared with those assuming ballistic operation. With only a limited number of physically meaningful parameters, the extended VS compact model forms an ideal platform for the exploration of the dynamic behavior of current and future FET devices. The simple model is validated here by comparison with experimental data from a well-characterized industry 45-nm metal/high-k complementary metal-oxide-semiconductor including parasitic elements using a Verilog-A implementation to simulate ring oscillators. It is also validated by comparison with S-parameter-derived capacitances of near-ballistic III-V high-electron mobility transistors. In both cases, the effects of different assumed transport conditions on the dynamic device behavior are explored.