ECE 875: Electronic Devices

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ECE 875Electronic Devices

• Prof. Virginia Ayres
• Electrical Computer Engineering
• Michigan State University
• ayresv_at_msu.edu

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Lecture 23, 10 Mar 14
Chp 03 metal-semiconductor junction Currents I
-V / J-V measurements discussion of part b (not
assigned) in Pr. 3.08 on board to introduce
thermionic emission model for I-V (or
J-V) Thermionic emission model where from
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Pr. 3.08
Use X 1/1010
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Thermionic emission model for J
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Lecture 23, 10 Mar 14
Chp 03 metal-semiconductor junction Currents I
-V / J-V measurements discussion of part b (not
assigned) in Pr. 3.08 on board to introduce
thermionic emission model for I-V (or
J-V) Thermionic emission model where from
VM Ayres, ECE875, S14
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Width Height
Barrier width versus height maximally
affect different types of transport which are
energy-dependant
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1. Thermionic emission (enough energy compared
with height qfBn is critical)
Dotted line Both 1. and 2. can be going on at
the same time
2. Tunnelling (WD is critical)
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3. Jrec
4. diffusion of electrons 5. diffusion of holes
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4. diffusion of electrons
5. diffusion of holes
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Thermionic emission model for transport
enough energy above EC compared with barrier
height qfn is critical
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Start
Need to put dn in terms of vx
EC
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N(E) 3D
f(E) hot non-degenerate
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So far dn is now in terms of dv
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v is 3D e- moving in any direction. Still need
to pick out the transport direction in x
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See next slide for helpful integrals
Note that k kB 1.38 x 10-23 J/K
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Requirement on the KE/velocity in the transport
direction x
You need to re-write the contact potential in
terms of the barrier height
Are you done? No.
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Current density from metal into semiconductor
Note current direction is going the other
way. No bias on metal side V 0
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Total Thermionic Current density
JTE J s-gtm J m-gts
JTE
JTE-sat
JTE-sat
Now you are done.