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半導體量測技術 Semiconductor Materials and Device Characterization

半導體量測技術 Semiconductor Materials and Device Characterization Topic 6: charge pumping technique and HS experiment Instructor: Dr. Yi-Mu Lee Department of Electronic Engineering National United University. Topics: Ch. 6 in D. K. Schroder. Charge pumping method (p. 379)

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半導體量測技術 Semiconductor Materials and Device Characterization

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  1. 半導體量測技術 Semiconductor Materials and Device Characterization Topic 6: charge pumping technique and HS experiment Instructor: Dr. Yi-Mu Lee Department of Electronic Engineering National United University

  2. Topics: Ch. 6 in D. K. Schroder • Charge pumping method (p. 379) • Haynes-Shockley experiment (time of flight) • Photoelectric effect (time of flight) • Introduction to mobility • Presentation: 12/29 = 3 students 01/05 = 5 students • Final exam: (3:00pm~5:30pm)

  3. Charge pumping (CP) method

  4. Step-1

  5. Step-2

  6. Step-3

  7. Good for small-size device:

  8. Variable base mode:

  9. The Haynes-Shockley Experiment (1/2) 1951, Bell Labs independent measurement of minority carrier mobility () and diffusion coefficient (D) basic principles - field applied to semiconductor bar -narrow pulse, high concentration of minority carriers generated -pulse drifts due to (time to drift a fixed distance  mobility

  10. Haynes-Shockley Exp. (2/2) • Minority Carrier: • generation by laser pulse • diffusion due to nonuniform concentration • drift by E-field • recombination to remove the excess carriers

  11. -pulse spreads due to diffusion ( diffusion coefficient) In Fig. 4-18 (n-type material n0 >> p0) -pulse of holes generated at t=0 - - -pulse of holes drift indirection -pulse monitored at x = L; drift velocity Vd is

  12. H-S Pulse Spreading consider diffusion without drift or recombination  Eq (13b) or (4-33b) (p. 418):

  13. Note that  the amplitude decreases w/ time  the pulse width increased w/ time

  14. pulse width = full width @ 1/e pts.  for a fixed peak height , the pulse width x can be found (21)(4-45) where td is the time corresponding to the pulse spread x  (21)  , or (22)(4-46)

  15. Example 4-6 n-type Ge is used in a Haynes-Schockley experiment. The length of the Ge bar is 1 cm, the probes are spaced 0.95 cm apart.  battery voltage is 2.0 V  td = 0.25 ms  pulse width t (oscilloscope) = 117 s Find p and Dp (and check agreement w/ the Einstein relations

  16. so

  17. Homework 6 in D. K. Schroder: • 6.4 • 6.5 • 6.6 • Review: • P. 531~536 (Fig. 8.16) • P. 540~551 (mobility) • Interesting website: http://jas.eng.buffalo.edu/education/semicon/diffusion/diffusion.html

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