1 / 27

ECE 875: Electronic Devices

This lecture discusses the metal-insulator-semiconductor junction, focusing on the behavior of n-channel and p-channel devices in different substrates. The capacitances and voltage requirements are also explored.

rosettaj
Download Presentation

ECE 875: Electronic Devices

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


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

  2. Lecture 29, 24 Mar 14 • Chp 04: metal-insulator-semiconductor junction: GATES • Q, E , V/y: WD , Vi • Capacitances VM Ayres, ECE875, S14

  3. Lec 26: p-type Si Use energy band diagram to find: Electron concentration in channel V requirements: battery = $ E –field/Vi across the insulator: breakdown not good VM Ayres, ECE875, S14

  4. 2 Or nn0 Or nn0 Or pp0/nn0 3: @ ys for known condition 1. Know substrate doping NA or ND VM Ayres, ECE875, S14

  5. From Lec 26-27 example: Known condition: n-channel in p-substrate: VM Ayres, ECE875, S14

  6. From Lec 27 example: Known condition: p-channel in n-substrate:

  7. Have: values for ys and Qs : Therefore have potential drop across the dielectric: Vi = |Qs| d ei Makes sense to evaluate this in strong inversion/accumulation Therefore have battery V

  8. Example: is this an n-channel or p-channel device?

  9. Answer: is this an n-channel in p-substrate (NA)

  10. Lec 26: p-type Si Use energy band diagram to find: Electron concentration in channel V requirements: battery = $ E –field/Vi across the insulator: breakdown not good VM Ayres, ECE875, S14

  11. Qs = Qn + Qdepletion = Qn + q (NA or ND) WD

  12. Qs = Qn + Qdepletion = Qn + q (NA or ND) WD

  13. Lecture 29, 24 Mar 14 • Chp 04: metal-insulator-semiconductor junction: GATES • Q, E , V/y: WD , Vi • Capacitances VM Ayres, ECE875, S14

  14. ON to OFF: n-channel in a p-substrate: VM Ayres, ECE875, S14

  15. OFF to ON: n-channel in a p-substrate: ON: Strong inversion Going OFF: intrinsic OFF: Strong accumulation Going OFF: Flatband VM Ayres, ECE875, S14

  16. Fig 07: n-channel in p-substrate: ON OFF C / Ci VM Ayres, ECE875, S14

  17. Fig. 07 shows all behaviors. Complication: C-V curves depend on frequency of voltage sweep. Gate voltage: Sweeping Vgate for example ± 4 Volts over and over to turn the channel OFF and ON: binary logic Low: 1- 1 kHz Intermediate: 1 kHz - 1 MHz High: > 1 MHz VM Ayres, ECE875, S14

  18. Start: Low frequency C-V curves VM Ayres, ECE875, S14

  19. Example: what values are easiest to determine experimentally? VM Ayres, ECE875, S14

  20. Answer: @OFF, @ON and minimum Example: Why so? Answer: compare to slide 18, works for now VM Ayres, ECE875, S14

  21. Note that Qn can be big number Units = C/cm2 E (x) = constant || plate capacitor Ci E (x) = distributed capacitor CD = dQs/dys Total C: Ci and CD are in series VM Ayres, ECE875, S14

  22. VM Ayres, ECE875, S14

  23. CD = dQs/dys = large neglect C ≈ Ci Also true in strong inversion VM Ayres, ECE875, S14

  24. Can normalize curve to Ci I will continue with experimental readings in F/cm2. Fancy C means Farads/Area. OFF ON 1.0 C / Ci VM Ayres, ECE875, S14

  25. OFF ON 2.0 1.73 1.0 C (x 10-7 F/cm2) 0.5 C-V curve for an n-channel in a p-type Si block Low frequency curve: 1 Hz Ci= eie0 d Units: F/cm2 VM Ayres, ECE875, S14

  26. Important: Use C-V reading to experimentally solve for the gate oxide thickness d: Ci= eie0 => d = eie0 dCi OFF ON 2.0 1.73 1.0 C (x 10-7 F/cm2) 0.5 C-V curve for an n-channel in a p-type Si block Low frequency curve: 1 Hz VM Ayres, ECE875, S14

  27. Next: Cmin is easy to identify on the experimental curve: VM Ayres, ECE875, S14

More Related