TEORI DASAR HUBUNGAN SEMIKONDUKTOR

Hamzah Afandi, Antonius Irianto danBetty Savitri

Source: Millman, Jacob, Grabel, Arvin, Microelectronics, Mc. Graw Hill Int. Ed., 1994.

Robert Boylestad, Louis Nashelsky Sixth Edition; Prentice Hall,1997.

Review: Semiconductor Properties Variation– Intrisic Concentration vs Temperature:

– Mobility vs Temperature: ; mn=2.5, mp=2.7

(100<T<400K)

– Mobility vs Electric Field intensity:

kTEi

GTAn /30

2 0

mT 0

21

0 nnnn 0 1

0 nn ~ 107 cm/s

103 V/cm 104 V/cm

Review: Currents in semiconductor

• Drift Current: )pn pq(nJ

pn pnq

Drill:

Calculate the conductivity of an extrinsic semiconductor with donor atom’s concentration of 1016 atom/cm3 (at 300K)!

10

.

.

1045.1

475

15002

2

xni

sVcm

p

sVcm

n

REVIEW: The Physics of Electronics

Carrier’s Concentration in extrinsic Semiconductor

pn = ni2

nNpN AD

D

2i

D N

n pNn ;

Mass-Action Law

Charge Density should maintain electric neutrality of crystal

For n-type semiconductor, NA = 0; thus:

A

2i

A N

n nNp ; For p-type semiconductor, ND = 0; thus:

Review: Currents in semiconductor

• Diffusion Current:

2pp A/m dp/dx D q -J

Concentration

xx0 x1

p(x0)

p(x1)

dx

dp

Jp

Dp = Diffusion Constant of Carrier

Einstein Relationship between D and

Tn

n

p

p VDD

VT

q

kTVT 11600

Review: Currents in semiconductor

• Total Current:

)2ppp (A/m dp/dx D q -pqJ

Concentration

xx0 x1

p(x0)

p(x1)

dx

dp

Jp

)2nnn (A/m dn/dx D q nqJ

Review: Graded semiconductor

dp/dx D q -pqJ ppp

Concentration

xx1 x2

p(x1)

p(x2)

dx

dp

V21

p1 p2

Jp = 0; in open circuited steady state condition

dx

dp

pV

dx

dV

mVdx

dp

pV

dp/dx Vq -pq0

VD

T

T

Tpp

Tpp

1

)/(1

)(ln

1

2

121

2

1

2

1

Vp

pVV

pdp

VdV

T

x

x

T

x

x

pn JUNCTION DIODE

Hamzah Afandi, Antonius Irianto danBetty Savitri

Source: Millman, Jacob, Grabel, Arvin, Microelectronics, Mc. Graw Hill Int. Ed., 1994.

Open Circuited Junction

p type n type

Semiconductors Semiconductors

ElectronsHoles

neutral neutral

Open Circuited JunctionJunction Formation

p type n type

Junction

Depletion RegionSpace Charged Region

Open Circuited JunctionJunction Formation

p type n type

Charge Density (V)

Depletion RegionSpace Charged Region

-Wp Wn

Open Circuited JunctionJunction Formation

p type n type Field Intensity ()

Depletion RegionSpace Charged Region

-Wp Wn

')'(

)( dxxv

xx

Wp

E

Open Circuited JunctionJunction Formation

p type n type Electrostatic Potential (V)

Depletion RegionSpace Charged Region

-Wp Wn

V = 0

V0

')'()(V dxxxx

Wp

E

Open Circuited JunctionJunction Formation

p type n type

Potential Barrier of electrons(V)

Depletion RegionSpace Charged Region

-Wp Wn

V = 0V0

Closed Circuited JunctionForward Biased pn Junction

p type n type

Depletion RegionSpace Charged Region

Closed Circuited JunctionForward Biased pn Junction

p type n type

Depletion RegionSpace Charged Region

Closed Circuited JunctionReverse Biased pn Junction

p type n type

Depletion RegionSpace Charged Region

Closed Circuited JunctionReverse Biased pn Junction

p type n type

Depletion RegionSpace Charged Region

Closed Circuited JunctionReverse Biased pn Junction

p type n type

Depletion RegionSpace Charged Region

VOLT-AMPERE CHARACTERISTIC

(A) 1

T

DV

V

SD II

ID

VD

IS (A Scale)

V-VZ

Cut-inOffest

Turn-onBreakdown

= 2 (Si) = 1.5 (Ge)

Diode Circuit Analysis: Load-Line Concept

ID

VD

+

_VAA

R

VD

ID+

_

QIDQ

VDQ VAA

VAA /R

Solve for:VAA = 3 VR = 2 K

(A) 110.5 507

mV

V

D

D

I

CALCULATIONEXAMPLES

Given in class