ee130/230a discussion 4

EE130/230A Discussion 4

Peng Zheng

Illumination of a Semiconductor with Light

EE130/230A Fall 2013

(Refer to Discussion 3.)

Schottky Contact Energy Band Diagrams:

EE130/230A Fall 2013

Ideal M-S Contact: FM > FS, n-type

FF MBn

Band diagram instantly after contact formation:

Equilibrium band diagram:Schottky Barrier Height:

EE130/230A Fall 2013

qVbi = FBn– (Ec – EF)FB

W

n

Ideal M-S Contact: FM < FS, n-type

EE130/230A Fall 2013

Band diagram instantly after contact formation:

Equilibrium band diagram:

Ideal M-S Contact: FM < FS, p-type

MBp FF GE

Band diagram instantly after contact formation:

Equilibrium band diagram:Schottky Barrier Height:

EE130/230A Fall 2013

qVbi = FBp– (EF – Ev)FB

W

p-typesemiconductor

FBp

EE130/230A Fall 2013

Ideal M-S Contact: FM > FS, p-typep-typesemiconductor

Equilibrium band diagram:

Band diagram instantly after contact formation:

Summary

EFEc

Ev

EF

Ec

EvEF

Ev

EF

EcEv

R.F. Pierret, Semiconductor Fundamentals, p. 481

EE130/230A Fall 2013

)(2

D

Abis

qNVVW

)(2

A

biAs

qNVVW

WAC s /

For rectifying contacts:

small-signal capacitance

Schottky Contact to p-type Silicon with NA = 1016 cm-3 and FBp = 0.4 eV, VA=0V

EE130/230A Fall 2013

Schottky Contact to p-type Silicon with NA = 1016 cm-3 and FBp = 0.4 eV, VA=0V

EE130/230A Fall 2013

W0.52 μm

qVbi = FBp– (EF – Ev)FB

p-type SiM

Ev

EF

Ec

Eo

FM=4.77 eVcSi=4.05 eV

0.195 eV0.4eV=FBp

Schottky Contact to p-type Silicon with NA = 1016 cm-3 and FBp = 0.4 eV, VA=-0.2V

EE130/230A Fall 2013

Once Vbi and NA are known, FBp can be determined:

22

)(21AqNVV

C sA

Abi

A

VBpFBVFBpbi ln)(

NNkTEEqV FF

Using C-V Data to Determine FB

Abi

sA

AbiA

s

ss

VVqNA

VVqN

AWAC

22

EE130/230A Fall 2013

2

1C

AV

Good luck to Quiz 1