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ECE 875: Electronic Devices

ECE 875: Electronic Devices. Prof. Virginia Ayres Electrical & Computer Engineering Michigan State University ayresv@msu.edu. Lecture 23, 10 Mar 14. Chp 03: metal-semiconductor junction Currents:

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ECE 875: Electronic Devices

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  1. ECE 875:Electronic Devices Prof. Virginia Ayres Electrical & Computer Engineering Michigan State University ayresv@msu.edu

  2. 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

  3. Pr. 3.08: Use: X 1/1010 VM Ayres, ECE875, S14

  4. Thermionic emission model for J VM Ayres, ECE875, S14

  5. 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

  6. Width Height Barrier width versus height maximally affect different types of transport which are energy-dependant VM Ayres, ECE875, S14

  7. 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) VM Ayres, ECE875, S14

  8. 3. Jrec 4. diffusion of electrons 5. diffusion of holes VM Ayres, ECE875, S14

  9. 4. diffusion of electrons 5. diffusion of holes VM Ayres, ECE875, S14

  10. Thermionic emission model for transport: enough energy above EC compared with barrier height qfn is critical VM Ayres, ECE875, S14

  11. Start: Need to put dn in terms of vx EC

  12. N(E): 3D f(E): “hot”: non-degenerate

  13. So far: dn is now in terms of dv

  14. v is 3D: e- moving in any direction. Still need to pick out the transport direction in x

  15. See next slide for helpful integrals Note that k = kB = 1.38 x 10-23 J/K

  16. 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.

  17. Current density from metal into semiconductor: Note: current direction is going the other way. No bias on metal side: V = 0

  18. Total Thermionic Current density: JTE = J s->m + J m->s JTE = = {JTE-sat} JTE-sat = Now you are done.

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