1. EE 5340 Semiconductor Device Theory Lecture 19 – Spring 2011 Professor Ronald L. Carter ronc@uta.edu http://www.uta.edu/ronc

2. ©rlc L19-31Mar20112 Test 2 – Tuesday 05Apr11 11 AM Room 129 ERB Covering Lectures 11 to19 Open book - 1 legal text or ref., only. You may write notes in your book. Calculator allowed A cover sheet will be included with full instructions. For examples see http://www.uta.edu/ronc/5340/tests/.

3. npn BJT currents in the forward active region ©RLC ©rlc L19-31Mar20113 I C = J C A C I B =-(I E +I C ) J nE J nC I E = -J E A E J RB =J nE -J nC J pE J GC J RE J pC

4. ©rlc L19-31Mar20114 E current equations mode npn BJT (w/o gen/rec)

5. ©rlc L19-31Mar20115 C current equations in npn BJT (w/o gen/rec)

6. ©rlc L19-31Mar20116 Ebers-Moll Model (Neglecting G-R curr) (Fig. 9.30*) -J E A E =I E J C A C =I C

7. ©rlc L19-31Mar2011 Source of Ebers-Moll Equations (E) 7

8. ©rlc L19-31Mar2011 Source of Ebers-Moll Equations (C) 8

9. ©rlc L19-31Mar2011 E-M model equations 9

10. ©rlc L19-31Mar2011 Fig. 9.30* -J E A E = I E J C A C = I C E B C RIRRIR FIFFIF Ebers-Moll Model (Neglecting G-R curr) 10

11. ©rlc L19-31Mar2011 E-M linking current model 11

12. ©rlc L19-31Mar201112 E-M linking current model (cont)

13. ©rlc L19-31Mar2011 E-M linking current model (cont) 13

14. ©rlc L19-31Mar201114 More non-ideal effects in BJTs  Base-width modulation (FA: x B changes with changes in V BC )  Current crowding in 2-dim base High-level injection (minority carriers g.t. dopant - especially in the base). Emitter Bandgap narrowing (N E ~ density of states at cond. band. edge) Junction breakdown at BC junction

15. ©rlc L19-31Mar201115 Recombination/Generation Currents (FA)

16. ©rlc L19-31Mar201116 FA npn figure of merit – emitter efficiency

17. ©rlc L19-31Mar201117 FA npn figure of merit – base transport factor

18. ©rlc L19-31Mar201118 FA npn figure of merit – recombination factor

19. ©rlc L19-31Mar201119 Common base current gain,  F TT 

20. ©rlc L19-31Mar201120 Common base current gain,  F (continued)

21. ©rlc L19-31Mar201121 Common emitter current gain,  F

22. ©rlc L19-31Mar2011 Common base current gain,  F (cont.) 22

23. ©rlc L19-31Mar2011 Common emitter current gain,  F 23

24. ©rlc L19-31Mar2011 References * Semiconductor Physics and Devices, 2nd ed., by Neamen, Irwin, Boston, 1997. **Device Electronics for Integrated Circuits, 2nd ed., by Muller and Kamins, John Wiley, New York, 1986. 24