How to model intrinsic semiconductor in Sentaurus TCAD for ISFET simulation.

Hello, I am trying to model intricsic semiconductor for ISFET that can mimic the properties of electrolyte medium. I saw various literature on pH sensing ISFET doing this. But I need help with the coding.

What is ISFET?
(ISFET is not a standard abbreviation, in IC design, manufacturing, or semiconductor device areas).

In TCAD, just set the doping level at a low level (e.g. 1e10 cm-3), and you will get an intrinsic semiconductor.

Thank you. I wanted to mean Ion-Sensitive FET.