ECE 875: Electronic Devices

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

2. Lecture 17, 17 Feb 14 • Chp. 02: pn junction: • Abrupt pn junction • Linearly graded pn junction • Both: Experimental measurements: C-V curves • Examples VM Ayres, ECE875, S14

3. Remember this sequence in real research: find: • Charge Q and charge density r • Electric field E • Potential y • Energy barrier q y • Depletion region WD or equivalent local region • C-V • I-V

4. Abrupt junction: Q and r = Constant values E (x) yi(x) q yi(x)

5. An experimental measure for the Abrupt junction: C-V curve: VM Ayres, ECE875, S14

6. Example: HW05: Sze Pr. 2.02(a) find the slope and set up the calculation for N(b) find the intercept and set up the calculation for ybi Slope ~ 1/N: V = Vbattery

7. Realistic experimental result: VM Ayres, ECE875, S14

8. Example:

9. Linearly graded junction: power of x raised by 1: Achieve by co-doping Q and r = linear = Constant x x = a x E (x) yi(x) q yi(x)

10. Linearly graded junction: power of x raised by 1: r = linear = Constant “a” x x

11. An experimental measure for the linearly graded junction: C-V curve: Missing 2kT/q in (38) intercept Experimentally sweep this slope VM Ayres, ECE875, S14

12. Example:

13. Excel (below) or Matlab:

15. Answer: And given: it is an abrupt p+n junction

16. Example:

17. Slope Intercept

18. Slope:

20. Given: p+n: N =

21. Intercept

22. Answer: 6 properties:

23. Given: p+n: WD

27. What is LD: the Debye length:

28. Debye length:

29. Debye length: 1. working definition of a good abrupt junction 2. watch out for circumstances that can create a small depletion width WD < LD

30. In Example: ✔

31. Lecture 17, 17 Feb 14 • Chp. 02: pn junction: • Abrupt pn junction • Linearly graded pn junction • Both: Experimental measurements: C-V curves • Examples VM Ayres, ECE875, S14

32. Linearly graded junction: power of x raised by 1: Achieve by co-doping Q and r = linear = Constant x x = a x E (x) yi(x) q yi(x)

33. Steps 1-3:

34. E –field = E (x), and Emax:

35. Potential yi(x), and ybi:

36. An experimental measure for the linearly graded junction: C-V curve: Missing 2kT/q in (38) intercept Experimentally sweep this slope VM Ayres, ECE875, S14