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EE130/230A Discussion 5. Peng Zheng. Current Flow in a Schottky Diode. EE130/230A Fall 2013. Current Flow. FORWARD BIAS. Current is determined by majority-carrier flow across the M-S junction: Under forward bias, majority-carrier diffusion from the semiconductor into the metal dominates

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Current flow in a schottky diode
Current Flow in a SchottkyDiode

EE130/230A Fall 2013


Current flow
Current Flow

FORWARD BIAS

  • Current is determined by majority-carrier flow across the M-S junction:

    • Under forward bias, majority-carrier diffusion from the semiconductor into the metal dominates

    • Under reverse bias, majority-carrier diffusion from the metal into the semiconductor dominates

REVERSE BIAS

R.F. Pierret, Semiconductor Fundamentals, Fig. 14.3

EE130/230A Fall 2013

Lecture 8, Slide 3


Practical ohmic contact
Practical Ohmic Contact

Band Diagram for VA0

Equilibrium Band Diagram

q(Vbi-VA)

qVbiFBn

EFM

EFM

Ec, EFS

Ec, EFS

Ev

Ev

If the depletion width is sufficiently narrow (<10 nm for silicon), then carriers can quantum-mechanically tunnel through the Schottky/potential barrier in each direction, so that the contact becomes practically ohmic.  This is the case when the semiconductor is degenerately doped.  Since current flows relatively easily through an ohmic contact, the applied bias across an ohmic contact is very small in practice

EE130/230A Fall 2013

Lecture 8, Slide 4


Pn junction electrostatics
PN Junction Electrostatics

EE130/230A Fall 2013


Fermi level applets
Fermi level applets

  • http://jas.eng.buffalo.edu/


Electrostatics step junction
Electrostatics (Step Junction)

Band diagram:

Electrostatic potential:

Electric field:

Charge density:

R.F. Pierret, Semiconductor Fundamentals, Figure 5.4

EE130/230A Fall 2013

Lecture 9, Slide 7


Effect of applied voltage
Effect of Applied Voltage

R.F. Pierret, Semiconductor Fundamentals, Figure 5.11

EE130/230A Fall 2013

Lecture 9, Slide 8


A silicon step junction maintained at T = 300K under equilibrium conditions has a p-side doping of NA = 11016 cm-3 and n-side doping of ND = 11015 cm-3

EE130/230A Fall 2013


A silicon step junction maintained at T = 300K under equilibrium conditions has a p-side doping of NA = 11016 cm-3 and n-side doping of ND = 11015 cm-3

EE130/230A Fall 2013


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