求助silvaco的带宽，仿出来的带宽图形不对

370127099

下面是程序：
go atlas
mesh
#
x.m l=0.0 spacing=1
x.m l=3.0 spacing=0.8
x.m l=7.0 spacing=0.5
x.m l=17.0 spacing=0.5
x.m l=20.0 spacing=0.8
x.m l=24.0 spacing=1
#
y.m l=0.0 spacing=1
y.m l=0.3 spacing=0.05
y.m l=1.0 spacing=0.5
y.m l=1.6 spacing=0.5
y.m l=5.0 spacing=1

region num=1 material=silicon x.min=0.0 x.max=24 y.min=0.0 y.max=5.0
region num=2 sio2 x.min=0.0 x.max=1.0 y.min=0.0 y.max=1.0
region num=3 sio2 x.min=3.0 x.max=4.0 y.min=0.0 y.max=1.0
region num=4 sio2 x.min=6.0 x.max=7.0 y.min=0.0 y.max=1.0
region num=5 sio2 x.min=17.0 x.max=18.0 y.min=0.0 y.max=1.0
region num=6 sio2 x.min=20.0 x.max=21.0 y.min=0.0 y.max=1.0
region num=7 sio2 x.min=23.0 x.max=24.0 y.min=0.0 y.max=1.0

electrode name=anode x.min=11.5 length=1 y.min=-0.5 y.max=0.0
electrode name=cathode x.min=4.5 length=1 y.min=-0.5 y.max=0.0
electrode name=cathode x.min=18.5 length=1 y.min=-0.5 y.max=0.0

#....p-epi doping
doping uniform p.type conc=5e15
#....nw doping
doping uniform n.type conc=1.56e17 x.min=3.5 x.max=20.5 y.min=0.0   y.max=1.56
#....p+ dopi
doping uniform p.type conc=5.5e19 x.min=7.0 x.max=17.0 y.min=0.0   y.max=0.3
#....n+ doping
doping uniform n.type conc=5e19 x.min=4.0 x.max=6.0 y.min=0.0 y.max=0.3
doping uniform n.type conc=5e19 x.min=18.0 x.max=20.0 y.min=0.0 y.max=0.3
save outf=apd.str

models srh optr fldmob auger bgn
impact selb
method newton trap maxtrap=10
contact name=anode

output con.band val.band flowlines
beam num=1 angle=90 x.ori=12 y.ori=-1.0 wavelength=0.6  b1=0.1
solve init
solve vanode=-0.5 vstep=-1 vfinal=-9.9 name=anode
#solve vstep=-0.2 vfinal=-10.5 name=anode
#solve vstep=-0.02 vfinal=-10.5 name=anode
#solve vstep=-0.01 vfinal=-10.55 name=anode
log off

log outf=apd.log gains s.params inport=anode outport=cathode

solve vbase=0.7 ac freq=10 fstep=2 mult.f nfstep=10
solve ac freq=1e4 fstep=1e4 nfstep=8
solve ac freq=1e5 fstep=1e5 nfstep=8
solve ac freq=1e6 fstep=1e6 nfstep=8
solve ac freq=1e7 fstep=1e7 nfstep=8
solve ac freq=1e8 fstep=1e8 nfstep=8
solve ac freq=1e9 fstep=1e9 nfstep=8

log off
tonyplot apd.log -set apd.set
quit
tonyplot apd.str

软件的警告：
Warning: Calculated gain GUmax is negative.This condition usually arises when contact resistances are specified.  Consider using  parasitics specified on the LOG statement.

370127099

宽带仿真图