Boundary Regions and Their Contribution to Current Spreading in Grounded Gate Nmosts

Abstract

3-D-TCAD results are presented showing current density profiles for triggered GGNmosts with substantial, and with minimal, drain ballast resistance. That same variation is repeated on two more GGNmosts with reduced source ballast resistance, which reduces the electron–hole current ratio. The simulated current density profiles fill only part of the device, while in the complementary part of the device no current flows. Between these parts, boundary regions exist in which the current density decreases from its peak value to zero. The width of these boundary regions is set by carrier diffusion, and can therefore not be arbitrarily small. As this article shows, the result is that the boundary regions can contribute to GGNmost current spreading. Moreover, the boundary regions can exist in a stable manner over time, and this article shows the physical mechanism by which this happens. Finally, this article shows how boundary regions manifest themselves in TLP ${I}$ ( ${V}$ )-curves: features relating to boundary regions are identified in TLP ${I}$ ( ${V}$ )-curves simulated by 3-D-TCAD, and then replicated in measured TLP ${I}$ ( ${V}$ )-curves. Bottom line is that boundary regions can help spread current in a GGNmost.