ece 874: physical electronics

ECE 874:Physical Electronics

Prof. Virginia AyresElectrical & Computer EngineeringMichigan State [email protected]

VM Ayres, ECE874, F12

Lecture 26, 27 Nov 12

Chp. 05: Recombination-Generation Processes


baseline situation

W


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)


New stuff in the picture: the effect of light


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:


xpp


Lecture 26, 27 Nov 12

Chp. 06: Currents


General assuming capture/emission coefficients don’t change much from equilibrium values:

(5.24)

Steady state:

Equilibrium:

0


Now include the ordinary mechanisms that can change n and p:drift currents and diffusion currents

And anything else!

drift diffusion



And anything else!



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


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


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 0 L/2 L



Put a red box around any region where n-type ness changes: dn/dx

-L -L/2 0 L/2 L

Put a blue box around any region where p-type ness changes: dp/dx



hole

-L -L/2 0 L/2 L

ece 874: physical electronics

Documents

ntype ness changes

ptype ness changes

concentrations of n

largein depletion region

diffusion currentsand

drift currents

blue box

red box