go atlas
mesh space.mult=1.0
#
x.mesh loc=0.00 spac=0.01
x.mesh loc=0.20 spac=0.0001
x.mesh loc=0.25 spac=0.01
x.mesh loc=0.30 spac=0.0001
x.mesh loc=0.40 spac=0.01
x.mesh loc=0.5 spac=0.01
#
y.mesh loc=0.00 spac=0.001
y.mesh loc=0.002 spac=0.001
y.mesh loc=0.005 spac=0.001
y.mesh loc=0.035 spac=0.01
y.mesh loc=0.065 spac=0.15
#
region num=1 material= Air x.min=0 y.min=0
region num=2 material= SiO2 x.min=0.2 x.max=0.3 y.min = 0.002 y.max=0.005
region num=3 material= silicon x.min=0 x.max=0.2 y.min =0.005 y.max=0.035
region num=4 material= silicon x.min=0.2 x.max=0.3 y.min =0.005 y.max=0.035
region num=5 material= silicon x.min=0.3 x.max=0.5 y.min =0.005 y.max=0.035
region num=6 material= silicon x.min=0 x.max=0.5 y.min =0.035 y.max=0.065
#
electrode name= gate x.min=0.2 x.max=0.3 y.min =0.0 y.max=0.002
electrode name= source x.min=0 x.max=0.1 y.min =0.002 y.max=0.005
electrode name= drain x.min=0.4 x.max=0.5 y.min =0.002 y.max=0.005
#
doping uniform concentration= 1E13 p.type region=6
doping uniform concentration= 1E20 n.type region=3
doping uniform concentration=1E13 p.type region=4
doping uniform concentration=1E20 n.type region=5
#
contact name= gate n.poly
inter qf=3e10 y.max=0.005
contact name= source
contact name= drain
#
models cvt srh print
#
#output val.band con.band qfn qfp e.field j.electron j.hole j.conduction j.total ex.field ey.field flowline e.mobility h.mobility qss e.temp h.temp j.disp band.param charge
#
Method gummel newton
Solve init
#Solve prev
#Solve vdrain=0
#Solve vdrain=0.1
#Solve vdrain=0.5
Solve vdrain=1.5
#Solve vdrain=2
#Ramp the gate
#
Log outf=100nm_Vt_output.log master
Solve vgate=0 vstep=0.25 vfinal=3 name=gate
save outf=100nm_Vt_output.str
#plot result
tonyplot 100nm_Vt_output.log
#tonyplot 100nm_Vt_output.str
#extract device parameter
extract name="vt"(xintercept(maxslope(curve(abs(v."gate"),abs(i."drain")))) \
- abs(ave(v."drain"))/2.0)
#
quit
In this code, there is no direct definition of the threshold voltage (Vt). Therefore, it is not possible to determine why the threshold voltage is negative or positive based on this code alone.
In general, the threshold voltage of a MOSFET can be positive or negative, depending on the type of MOSFET (n-channel or p-channel) and the doping concentrations in the device. For an n-channel MOSFET, the threshold voltage is typically negative, while for a p-channel MOSFET, it is typically positive. The polarity of the threshold voltage can also depend on the doping concentrations in the device.
To determine the polarity of the threshold voltage in a specific MOSFET device, you would need to analyze the doping concentrations and the type of MOSFET being used.
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