Transcript 슬라이드 제목 없음

 P-N Junction Diodes 
How do they work?
(postponing the math)
Chap. 5.2
p-n Junction Diode
p-Type Material
n-Type Material
p-n Junction
p-n Junction Diode
 p-n Junction
p-Type Material
n-Type Material
p-n Junction
p-Type Material
n-Type Material
 A p-n junction diode is made by forming a p-type region of
material directly next to a n-type region.
p-n Junction Diode
 p-n Junction
p-Type Material
n-Type Material
ND - NA
ND
x
NA
p-n Junction
p-n Junction Diode
 In regions far away from the “junction” the band diagram
EC
EC
EF
Ei
Ei
EF
EV
EV
p-Type Material
n-Type Material
p-n Junction Diode
 But when the device has no external applied forces, no current
can flow. Thus, the Fermi-level must be flat!
 We can then fill in the junction region of the band diagram as:
EC
EC
EF
Ei
Ei
EF
EV
EV
p-Type Material
n-Type Material
p-n Junction Diode
 But when the device has no external applied forces, no current
can flow. Thus, the Fermi-level must be flat!
 We can then fill in the junction region of the band diagram as:
EC
EC
Ei
EF
EF
Ei
EV
EV
p-Type Material
n-Type Material
p-n Junction Diode
 Built-in-potential
p-Type Material
n-Type Material
EC
- qVBI
Ei
EF
EC
EF
Ei
EV
EV
Electrostatic Potential
V
1
( EC  Eref )
q
VBI Built-in-potential
x
p-n Junction Diode
 Built-in-potential
Electrostatic Potential
V
1
( EC  Eref )
q
VBI Built-in-potential
x
 Electric Field
Electric Field
E
dV
dx
x
p-n Junction Diode
 Poisson’s Equation
Charge Density   q( p  n  N  N )
D
A
(NOT Resistivity)
Electric Field
 E  

KS 0
Relative Permittivity
of Semiconductor
(r)
dE


dx
KS 0
Permittivity of free space
in 1-dimension
p-n Junction Diode
 Built-in-potential
Electric Field
dV
E
dx
x
 Charge Density
Charge Density
dE
  KS 0
dx
qND
+
-
+
-
qNA
+
x
p-n Junction Diode
Energy

1
q

dV
dx
Potential
Electrical Field
KS 0
Charge Density
dE
dx
p
n
As +
Bh+
e–
M
Metallurgical Junction
E0
Neutral p-region
M
E (x)
Neutral n-region
-Wp
0
-Wn
x
–Eo
V (x)
M
Wp
Vo
Space charge region
Wn
lo g (n ), lo g (p )
p po
x
n no
P E (x)
ni
eVo
p no
npo
x
x = 0
 net
Hole
o Potential Energy PE (x)
x
M
Electron Potential Energy PE (x)
eN d
– Wp
x
Wn
-e N a
–eVo
p-n Junction Principles