Simulations

The following simulations were performed using Microtec 3.0 (student version). The simulations use the default Lombardi mobility model parameters. The other transistor parameters were chosen to match as well as possible the n-channel transistor used in the appendix to Chapter 5 (nominally a 3 um channel length, 12 um channel width device fabricated in a 0.5 um MOSIS process). The following parameters (taken from the SPICE model) were used:

substrate doping = 1.1*10¹⁷

oxide thickness 98 A

interface state density 7*10¹¹

threshold adjust (p type) chosen to yield correct threshold voltage

 

The simulations are

doping concentration (log scale)

channel potential as a function of drain voltage

drain current as a function of drain voltage (VG=1 V to VG=3 V)

subthreshold current (VD = 3.3 V)

electron concentration (log scale) for different bias conditions (VG=3 V)

VG = 0 V, VD = 0 V

VG = 3 V, VD = 0 V

VG = 3 V, VD = 2 V

VG = 3 V, VD = 2.5 V

VG = 3 V, VD = 3 V

Note that as no "tuning" was done, it is not surprising that the subthreshold slope and the drain current in saturation do not match exactly!