1 / 36

ECE 875: Electronic Devices

ECE 875: Electronic Devices. Prof. Virginia Ayres Electrical & Computer Engineering Michigan State University ayresv@msu.edu. Lecture 18, 19 Feb 14. Chp. 02: pn junction: C-V curves: About Pr. 2.02 Mixed linearly graded and abrupt pn junction: About Pr. 2.03 More about the Debye length.

scave
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 18, 19 Feb 14 • Chp. 02: pn junction: • C-V curves: About Pr. 2.02 • Mixed linearly graded and abrupt pn junction: About Pr. 2.03 • More about the Debye length VM Ayres, ECE875, S14

  3. VM Ayres, ECE875, S14

  4. Epitaxial layer: layer grown in front: n-layer grown on the p+ substrate “…formed IN an n-type epitaxial layer” As grown n-type epitaxial layer p+ substrate VM Ayres, ECE875, S14

  5. “…depletion capacitance ….formed IN an n-type epitaxial layer” means formation of a depletion region WD = WDp + WDn As grown n-type epitaxial layer p+ substrate VM Ayres, ECE875, S14 WDn = ? WDp = 0.07 mm

  6. Find the thickness of the depletion region WDn formed in the n-type epitaxial layer As grown n-type epitaxial layer p+ substrate VM Ayres, ECE875, S14 WDn = ? WDp = 0.07 mm

  7. Find the thickness of the depletion region WDn formed in the n-type epitaxial layer Under which bias condition? Vext = Reverse: -1 V As grown n-type epitaxial layer p+ substrate Equilibrium: 0 V Forward: + 0.95 V VM Ayres, ECE875, S14 WDn = ? WDp = 0.07 mm

  8. Find the thickness of the depletion region WDn formed in the n-type epitaxial layer Under bias condition: Vrev = -1 V, for which WD is biggest. Given WDp-max = 0.07 mm. Find WDn-max Vext = Reverse: -1 V As grown n-type epitaxial layer p+ substrate Equilibrium: 0 V Forward: + 0.95 V VM Ayres, ECE875, S14 WDn = ? WDp = 0.07 mm

  9. Two ways to finish: use Method 01: VM Ayres, ECE875, S14

  10. Use intercept:i VM Ayres, ECE875, S14

  11. Use slope VM Ayres, ECE875, S14

  12. Watch out for Units: VM Ayres, ECE875, S14

  13. VM Ayres, ECE875, S14

  14. Lecture 18, 19 Feb 14 • Chp. 02: pn junction: • C-V curves: About Pr. 2.02 • Mixed linearly graded and abrupt pn junction: About Pr. 2.03 • More about the Debye length VM Ayres, ECE875, S14

  15. VM Ayres, ECE875, S14

  16. For mixed type pn doping, find: WD ybi Emax NA-(x) and ND+(x) E (x) VM Ayres, ECE875, S14

  17. For mixed type pn doping, find: WD ybi Emax NA-(x) and ND+(x) E (x) 2nd easiest to find: Easiest to find: VM Ayres, ECE875, S14

  18. D D VM Ayres, ECE875, S14

  19. Find Emax “as if”: Solve for Em VM Ayres, ECE875, S14

  20. Next step: VM Ayres, ECE875, S14

  21. Relation of Emax to WDn “as if”: VM Ayres, ECE875, S14 Use Em. Solve for WDn

  22. For mixed type pn doping, find: WD ybi Emax NA-(x) and ND+(x) E (x) ✔ 2nd easiest to find: ✔ Easiest to find: VM Ayres, ECE875, S14

  23. For mixed type pn doping, find: WD ybi Emax NA-(x) and ND+(x) E (x) Find potential drop on p-side using correct yi(x) formula for linearly graded Find potential drop on n-side using correct yi(x) formula for linearly graded ybi = potential drop on p-side + potential drop on n-side ✔ ✔ VM Ayres, ECE875, S14

  24. For mixed type pn doping, find: WD ybi Emax NA-(x) and ND+(x) E (x) ✔ ✔ ✔ What do you expect the E (x) plot to look like? VM Ayres, ECE875, S14

  25. VM Ayres, ECE875, S14

  26. For mixed type pn doping, find: WD ybi Emax NA-(x) and ND+(x) E (x) ✔ ✔ ✔ What do you expect the doping(x) plot to look like? VM Ayres, ECE875, S14

  27. VM Ayres, ECE875, S14

  28. Lecture 18, 19 Feb 14 • Chp. 02: pn junction: • C-V curves: About Pr. 2.02 • Mixed linearly graded and abrupt pn junction: About Pr. 2.03 • More about the Debye length VM Ayres, ECE875, S14

  29. Debye length: p+n example on spring 2012 Midterm: VM Ayres, ECE875, S14

  30. Debye length: p+n example on spring 2012 Midterm: NA- NA- ND+ ND+ ND+ NA- NA- NA- NA- NA- NA- ND+ ND+ ND+ NA- NA- NA- NA- NA- NA- ND+ ND+ ND+ NA- NA- NA- NA- NA- NA- ND+ ND+ ND+ NA- NA- NA- NA- NA- NA- ND+ ND+ ND+ NA- NA- NA- NA- VM Ayres, ECE875, S14

  31. Debye length: p+n example on spring 2012 Midterm: LD = 41.2 nm NA- NA- ND+ ND+ ND+ NA- NA- NA- NA- NA- NA- ND+ ND+ ND+ NA- NA- NA- NA- NA- NA- ND+ ND+ ND+ NA- NA- NA- NA- NA- NA- ND+ ND+ ND+ NA- NA- NA- NA- NA- NA- ND+ ND+ ND+ NA- NA- NA- NA- VM Ayres, ECE875, S14

  32. Debye length LD pos-neg shielding length: “Debye shielding” LD = 41.2 nm NA- ND+ NA- ND+ NA- ND+ NA- ND+ NA- ND+ VM Ayres, ECE875, S14

  33. In Sze abrupt pn junction calculations for E (x) and yi(x): r Q+/WDn Area= ND+ Single type of charge. This is outside LD. NA- NA- ND+ ND+ ND+ NA- NA- NA- NA- NA- NA- ND+ ND+ ND+ NA- NA- NA- NA- NA- NA- ND+ ND+ ND+ NA- NA- NA- NA- NA- NA- ND+ ND+ ND+ NA- NA- NA- NA- NA- NA- ND+ ND+ ND+ NA- NA- NA- NA- VM Ayres, ECE875, S14

  34. Will see Debye shielding length LD again: Chp. 03: metal-semiconductor interface: develops special charge layer to achieve shielding Chp. 04 & Chp. 06: metal-insulator-semiconductor interface develops inversion layer (gate/channel region in a transistor) during operation VM Ayres, ECE875, S14

  35. Will see Debye shielding length LD again: Chp. 04, Fig. 4: Inversion region: e-s  surface charge Qs formed in a p-side VM Ayres, ECE875, S14

  36. Will see Debye shielding length LD again: Chp. 04, fig.4: Where: VM Ayres, ECE875, S14

More Related