1 / 19

ECE 875: Electronic Devices

ECE 875: Electronic Devices. Prof. Virginia Ayres Electrical & Computer Engineering Michigan State University ayresv@msu.edu. Lecture 31, 28 Mar 14. Chp 04: metal-insulator-semiconductor junction: GATES Capacitances: Low frequency voltage sweep: 1 Hz to 1KHz

vern
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 31, 28 Mar 14 • Chp 04: metal-insulator-semiconductor junction: GATES • Capacitances: Low frequency voltage sweep: 1 Hz to 1KHz • High frequency voltage sweep: > 1Mz • - slow ramp: Pr. 4.06 • - fast ramp VM Ayres, ECE875, S14

  3. C-V curves and Frequencies: • Use 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 • Vgate: Slow ramp • Vgate: Fast ramp ON/OFF cycles per sec “counting” charge per sec applied to gate VM Ayres, ECE875, S14

  4. C-V curves for n-channel in p-substrate: ON OFF Low Intermediate C / Ci High + slow ramp High + fast ramp VM Ayres, ECE875, S14

  5. What looks different in the readout: flat line in Vfor and Cmin shift ON OFF Low C / Ci Cmin High + slow ramp C’min V’min = VT Vmin VM Ayres, ECE875, S14

  6. Low frequency C-V: You know the experimental values in the circles. Therefore it’s easy to get a number for Cdmin Cmin = Ci CDmin CDmin = CminCi Ci + Cmin Ci + CDmin VM Ayres, ECE875, S14

  7. Low frequency C-V: Low: 1- 1 kHz: develop (ON) and later remove (=> OFF) a full inversion layer and a full depletion region VM Ayres, ECE875, S14

  8. High frequency + slow ramp: > 1 MHz: develop and later remove a full depletion region charge qNAWD. But e-’s don’t have time to form a full inversion layer at the surface Fig. 8, (b) VM Ayres, ECE875, S14

  9. High frequency + slow ramp: simpler: C’Dmin = es /WDmax  So total capacitance C’min is: C’min = Ci C’Dmin Ci + C’Dmin VM Ayres, ECE875, S14

  10. Low frequency High frequency, Slow ramp WDmax is bigger Qn smaller VM Ayres, ECE875, S14

  11. High frequency + slow ramp: WDmax From strong inversion up to thermal energy Have been finding WD = WDm at the start of inversion with ys = 2 kT/q ln (NA/ni). But (Qs, ys) can be bigger VM Ayres, ECE875, S14

  12. High frequency + slow ramp: WDmax: VM Ayres, ECE875, S14

  13. Assume that Pr. 4.06  the high frequency- slow ramp condition VM Ayres, ECE875, S14

  14. Low frequency High frequency, Slow ramp High frequency, Fast ramp WDmax is bigger WDmax is biggest Qn layer; no time to form at all Qn smaller Qn biggest VM Ayres, ECE875, S14

  15. High frequency + fast ramp: during ON: No Qn and big WDmax: “driven into deep depletion” VM Ayres, ECE875, S14

  16. CD Qs region ys (@x = 0) Ci across insulator region VM Ayres, ECE875, S14

  17. VM Ayres, ECE875, S14

  18. ys VGate

  19. Iterate Pr. 3.9 until donor concentration ND-nth – ND-(nth+1) = 0.01 x 1016 cm-3

More Related