1. ECE 874: Physical Electronics
Prof. Virginia Ayres
Electrical & Computer Engineering
Michigan State University

2. Lecture 26, 27 Nov 12 Chp. 05: Recombination-Generation Processes
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3. baseline situation W
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4. Reverse biassed pn junction:
Ideally in depletion region W: p = n = 0
(always do have thermally generated ni/pi but internal field E in W continuously sweeps them out)
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5. New stuff in the picture: the effect of light
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6. Effect of shining light on reverse biassed pn junction:
In depletion region W: p = n ≠ 0
In depletion region W: p = n = large
In depletion region W:
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7. xpp
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11. Lecture 26, 27 Nov 12 Chp. 06: Currents
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12. General assuming capture/emission coefficients don’t change much from equilibrium values:
Steady state:
(5.24)
Equilibrium:
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13. Now include the ordinary mechanisms that can change n and p: drift currents and diffusion currents
And anything else!
drift
diffusion
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14. Now include the ordinary mechanisms that can change n and p: drift currents and diffusion currents
And anything else!
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15. Now include the ordinary mechanisms that can change n and p: drift currents and diffusion currents
And anything else!
6.1: review of drift
6.2: review of diffusion
6.3: list of equations for dn/dt, dp/dt and J’s – no new material
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16. Hw06 Prs. 6.3 and 6.4: Diffusion: diff diff
A diffusion current happens anytime you have a spatial variation in the concentrations of n or p
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17. Example problem: from Pr. 6.4:
Put a red box around any region where n-type ness changes: dn/dx
Put a blue box around any region where p-type ness changes: dp/dx -L
-L/2
L/2 L
VM Ayres, ECE874, F12

18. Example problem: from Pr. 6.4:
Put a red box around any region where n-type ness changes: dn/dx
Put a blue box around any region where p-type ness changes: dp/dx -L
-L/2
L/2 L
VM Ayres, ECE874, F12

19. Example problem: from Pr. 6.4:
hole
VM Ayres, ECE874, F12 -L
-L/2
L/2 L

20. VM Ayres, ECE874, F12

21. VM Ayres, ECE874, F12