# Chapter 12 : Semiconductor Physics¶

## Example number 1, Page number 228¶

In [1]:
#importing modules
import math
from __future__ import division

#Variable declaration
ni=2.5*10**19          #intrinsic concentration
myun=0.40              #mobility of electrons
myup=0.25              #mobility of holes
e=1.6*10**-19

#Calculations
sigmai=ni*e*(myun+myup) #conductivity of intrinsic semiconductor
rhoi=1/sigmai

#Result
print"Resistivity =",round(rhoi,4),"ohm-m"

Resistivity = 0.3846 ohm-m


## Example number 2, Page number 228¶

In [2]:
#importing modules
import math
from __future__ import division

#Variable declaration
myun=0.36              #mobility of electrons
myup=0.14              #mobility of holes
e=1.6*10**-19
rhoi=2.2               #resistivity

#Calculations
ni=1/(rhoi*e*(myun+myup))/10**18

#Result
print"Intrinsic concentration= %1.2f*10**18 m**-3" %ni

Intrinsic concentration= 5.68*10**18 m**-3


## Example number 3, Page number 228¶

In [3]:
#importing modules
import math
from __future__ import division

#Variable declaration
myun=0.39              #mobility of electrons
myup=0.21              #mobility of holes
ni=2.5*10**19          #intrinsic concentration
e=1.6*10**-19

#Calculations
sigmai=ni*e*(myun+myup) #conductivity of intrinsic semiconductor
rhoi=1/sigmai

#Result
print"Conductivity = %1.1f" %sigmai,"ohm**-1-m**-1"
print"resistivity= %1.2f" %rhoi,"ohm-m"                #the answer provided in the textbook is incorrect

Conductivity = 2.4 ohm**-1-m**-1
resistivity= 0.42 ohm-m


## Example number 4, Page number 228¶

In [4]:
#importing modules
import math
from __future__ import division

#Variable declaration
Eg=0.8                 #Energy gap width
T=300
m=9.1*10**-31          #mass of electron
k=1.38*10**-23
h=6.63*10**-34

#Calculations
ni=2*((2*22*m*k*T)/(7*h**2))**(3/2)*math.exp((-Eg*1.6*10**-19)/(2*k*T))/10**18

#Result
print"concentration of intrinsic charge= %1.2f*10**18 /m**3" %ni #the answer provided in the textbook is incorrect

concentration of intrinsic charge= 4.83*10**18 /m**3


## Example number 5, Page number 229¶

In [5]:
#importing modules
import math
from __future__ import division

#Variable declaration
RH=3.22*10**-4         #Hall coefficient
rho=9.0*10**-3
e=1.6*10**-19

#Calculations
p=1/(RH*e)/10**21
myup=RH/rho

#Result
print"hole concentration= %1.1f*10**21 m**-3"  %p
print"mobility of holes= %1.4f m**2 V**-1 s**-1" %myup

hole concentration= 19.4*10**21 m**-3
mobility of holes= 0.0358 m**2 V**-1 s**-1


## Example number 6, Page number 229¶

In [6]:
#importing modules
import math
from __future__ import division

#Variable declaration
RH=3.66*10**-4         #Hall coefficient
t=10**-3               #thickness
I=1                    #current
B=0.5                  #magnetic induction

#Calculations
VH=(RH*I*B)/t

#Result
print"Hall voltage VH= %1.3f" %VH,"V"

Hall voltage VH= 0.183 V


## Example number 7, Page number 300¶

In [7]:
#importing modules
import math
from __future__ import division

#Variable declaration
RH=7.5*10**-5         #Hall coefficient
sigma=200              #conductivity
e=1.6*10**-19          #electron charge

#Calculations
n=1/(e*RH)/10**22
myu=sigma*RH

#Result
print"charge density= %1.2f*10**22 /m**3" %n
print"mobility= %0.3f m**2 V**-1 s**-1" %myu

charge density= 8.33*10**22 /m**3
mobility= 0.015 m**2 V**-1 s**-1