# 9: Physics of Semiconductor Devices¶

## Example number 9.1, Page number 9.14¶

In :
#importing modules
import math
from __future__ import division

#Variable declaration
h=6.62*10**-34;     #planck's constant(J sec)
c=3*10**8;     #velocity of light(m/sec)
Eg=1.43*1.6*10**-19;    #energy gap(J)

#Calculation

#Result
print "wavelength of radiation is",round(lamda,3),"micro m"

wavelength of radiation is 0.868 micro m


## Example number 9.2, Page number 9.28¶

In :
#importing modules
import math
from __future__ import division

#Variable declaration
d=5*10**-6;     #thickness(m)
Dc=3.4*10**-3;    #diffusion coefficient(m**2 S-1)

#Calculation
tow_diff=d**2/(2*Dc);     #time taken(s)

#Result
print "time taken is",round(tow_diff*10**9,1),"*10**-9 s"

time taken is 3.7 *10**-9 s


## Example number 9.3, Page number 9.28¶

In :
#importing modules
import math
from __future__ import division

#Variable declaration
w=5*10**-6;     #thickness(m)
vsat=10**5;     #velocity(m/s)

#Calculation
tow_drift=w/vsat;     #transit time(s)

#Result
print "transit time is",tow_drift,"s"

transit time is 5e-11 s


## Example number 9.4, Page number 9.29¶

In :
#importing modules
import math
from __future__ import division

#Variable declaration
A=10**-6;     #area(m**2)
e=1.6*10**-19;     #charge(coulomb)
Nd=10**21;     #electron concentration(m**-3)
epsilonr=11.7;
epsilon0=8.85*10**-12;
V=10;    #potential(V)
RL=50;   #resistance(ohm)

#Calculation
Cj=(A/2)*math.sqrt(2*e*epsilonr*epsilon0*Nd/V);      #diode capacitance(F)
delta_fel=1/(2*math.pi*RL*Cj);    #frequency bandwidth(Hz)

#Result
print "diode capacitance is",round(Cj*10**12,1),"pF"
print "frequency bandwidth is",int(delta_fel*10**-6),"MHz"
print "answer varies due to rounding off errors"

diode capacitance is 28.8 pF
frequency bandwidth is 110 MHz
answer varies due to rounding off errors