1 / 23

P-N Junctions – Equilibrium

P-N Junctions – Equilibrium. N. P. W. V appl = 0. V bi = (kT/q)ln(N A N D /n i 2 ). W = 2k s e 0 V bi (N A +N D )/q(N A N D ). V bi. E F. P-N Junctions – Forward Bias. N. P. W. -. +. V appl > 0. V bi = (kT/q)ln(N A N D /n i 2 ).

zaina
Download Presentation

P-N Junctions – Equilibrium

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. P-N Junctions – Equilibrium N P W Vappl = 0 Vbi = (kT/q)ln(NAND/ni2) W = 2kse0Vbi(NA+ND)/q(NAND) Vbi EF ECE 663

  2. P-N Junctions – Forward Bias N P W - + Vappl > 0 Vbi = (kT/q)ln(NAND/ni2) W = 2kse0(Vbi-Vappl)NA+ND)/q(NAND) Vbi-Vappl EFp EFn EFn - EFp = qVappl in QNR ECE 663

  3. P-N Junctions – Reverse Bias N P W - + Vappl < 0 Vbi = (kT/q)ln(NAND/ni2) W = 2kse0(Vbi+Vappl)NA+ND)/q(NAND) Vbi+Vappl EFp EFn EFn - EFp = -qVappl in QNR ECE 663

  4. Voltage variation r x E x V x

  5. Equilibrium: Forward and Reverse Currents cancel ECE 663

  6. Forward Bias: Reverse thermionic flow increases nie(EFn-Ei)/kT + Forward Bias - ECE 663

  7. Reverse Bias: Forward currents win - Reverse Bias + ECE 663

  8. I-V Curve for Ideal Diode ECE 663

  9. Ideal P-N Junction Diode Assumptions: • Steady-State conditions • Non-degenerate doping • One-dimensional • Low Level Injection • Only drift, diffusion,thermal R-G (no photons) ECE 663

  10. Ideal P-N Junction Diode x' x ∂2Dpn ∂2Dnp Dpn Dnp DP - = 0 DN - = 0 ∂x2 ∂x’2 tP tN ECE 663

  11. Boundary Conditions x np = ni2(eFn-Fp) np = ni2eqV/kTin QNR regions ∂2Dpn Dpn DP - = 0 ∂x2 tP ECE 663

  12. Condition in the Depletion Region x' x ECE 663

  13. Condition in the Depletion Region x' x Jp Jn ∂DpN ∂DnP ∂DnP No RG ≈ -qDP ≈ qDN ≈ -qDN Jp Jn ∂x ∂x ∂x’ ECE 663

  14. Condition in the Depletion Region x' x J Jp Jn Jp(xn) Jp Jn Jn(-xp) = Jn(xn) J = Jn(-xp) + Jp(xn) ECE 663

  15. Minority Carrier Diffusion Equations – n side QNR Boundary Conditions: ECE 663

  16. Solution Use continuity equation to find current density at edge of depletion x=xn ECE 663

  17. For the p-side Boundary Conditions: - Current Density from continuity equation ECE 663

  18. Total Diode Current Ideal diode equation or Shockley Equation ECE 663

  19. Saturation Current Density ECE 663

  20. Forward Bias Larger by eqV/kT ECE 663

  21. Reverse Bias Smaller by eqV/kT ECE 663

  22. Ideal Diode I-V characteristic ECE 663

  23. Real Diode I-V characteristic ECE 663

More Related