heterojunction bipolar transistor

 code:-

go atlas

mesh  space.mult=1.0

# 

x.mesh loc=0.00 spac=0.25

x.mesh loc=2.00 spac=0.25

x.mesh loc=3.00 spac=0.2

x.mesh loc=4.00 spac=0.2

#

y.mesh loc=0.00 spac=0.03

y.mesh loc=0.15 spac=0.005

y.mesh loc=0.20 spac=0.015

y.mesh loc=0.25 spac=0.01

y.mesh loc=0.50 spac=0.05

y.mesh loc=0.75 spac=0.01

y.mesh loc=0.90 spac=0.03

#

#

region num=1 material=GaAs y.min=0.75

region num=2 material=GaAs y.min=0.25 y.max=0.75

region num=3 material=AlGaAs y.max=0.0 x.comp=0.3 \

 grad.34=0.15   

region num=4 material=GaAs y.min=0.15 y.max=0.25  

region num=5 material=SiO2 y.max=0.15 x.max=3.0

#

elec num=1  name=emitter x.min=3.0 x.max=4.0 y.min=0.0 y.max=0.0

elec num=2  name=base    x.min=0.0 x.max=2.0 y.min=0.15 y.max=0.15

elec num=3  name=collector bot 

#

doping uniform region=1 n.type conc=2.e17

doping uniform region=2 n.type conc=5.e16

doping uniform region=3 n.type conc=2.e17

doping uniform region=4 p.type conc=2.e18

#

material taun0=1.e-9 taup0=1.e-9 

material material=AlGaAs mun=2200 mup=350 

model  srh fldmob   print  optr  

model material=GaAs conmob evsatmod=1 

#

solve init

save outf=hbt.str

tonyplot  hbt.str 

method gummel newton trap  vsatmod.inc=0.01 

solve

solve local vcollector=2.0

log outf=hbt.log 

solve vbase=0.025

solve vbase=0.1

method  newton  autonr trap vsatmod.inc=0.01 itlim=50

solve vbase=0.2 vstep=0.1 name=base vfinal=1.4

solve vbase=1.45 vstep=0.025 name=base vfinal=1.5

tonyplot hbt.log 

quit

result:-