effective mass and classification of semiconductor

1. Course: Electronic Devices
paper code: EC301
Course Coordinator: Arpan Deyasi
Department of Electronics and Communication Engineering
RCC Institute of Information Technology
Kolkata, India
7/28/2020 1Arpan Deyasi, EC301, RCCIIT

2. Classification of material based on band diagram
V.B
C.B
V.B
C.B
F.R~1eV
V.B
C.B
F.R~10eV
7/28/2020 2Arpan Deyasi, EC301, RCCIIT

3. Classification of Semiconductor based on band position
k
E
k
E
Direct bandgap Indirect bandgap
Ex: GaAs Ex: Sihν
Δk=0 Δk≠0
hν
7/28/2020 3Arpan Deyasi, EC301, RCCIIT

4. Classification of Semiconductor based on
position of Fermi-level
EC
EV
EFI
EF
EC
EV
EFI
EF
n- nondegenerate
p- nondegenerate
EC
EV
EFI
EF
n- degenerate
EC
EV
EFI
EF
p- degenerate
7/28/2020 4Arpan Deyasi, EC301, RCCIIT

5. Expression of Effective mass
g
d
v
dk
ω
=
g
d E
v
dk
 
=  
 
1
g
dE
v
dk
=

7/28/2020 5Arpan Deyasi, EC301, RCCIIT

6. Expression of Effective mass
Gain in electron energy ext gdE F v dt=
1
ext
g
dE
F
v dt
=
1
1
ext
dE dE
F
dk dt
−
 
=  
 
7/28/2020 6Arpan Deyasi, EC301, RCCIIT

7. Expression of Effective mass
ext
dk dE
F
dE dt
= 
ext
dk
F
dt
= 
acceleration
gdv
a
dt
=
7/28/2020 7Arpan Deyasi, EC301, RCCIIT

8. Expression of Effective mass
1d dE
a
dt dk
 
=  
 
1d dE dk
a
dk dk dt
 
=  
 
2
2
1 d E dk
a
dk dt
=

7/28/2020 8Arpan Deyasi, EC301, RCCIIT

9. Expression of Effective mass
* extF
m
a
=
*
2
2
1
dk
dt
m
d E dk
dk dt
 
 
 =
  
  
  


7/28/2020 9Arpan Deyasi, EC301, RCCIIT

10. Expression of Effective mass
2
*
2
2
m
d E
dk
=

E
k
7/28/2020 10Arpan Deyasi, EC301, RCCIIT

11. Concept of Hole
*cond
c
qE
a
m
−
=
*val
v
qE
a
m
−
=
− *val
v
qE
a
m
=
mv*>mc
* &
acond & aval are oppositely directed
7/28/2020 11Arpan Deyasi, EC301, RCCIIT