Steady state excess carrier - Semiconductor

1. Nov 19, 2015

kidsasd987

Steady state of semiconductor w.r.t excess carrier.

1. If we shine photons on semiconductor and then turn the light off, semiconductor is not under the steady state condition. (it is under transient state since excess carrier concentration is decreasing)

2. If we shine photons for a long time, then it will reach steady state. (generation=recombination)

2. Nov 19, 2015

Staff: Mentor

Technically, those are statements, not questions... Is this for schoolwork?

3. Nov 19, 2015

kidsasd987

Sorry. I forgot to add a sentence.

"Please confirm if these statements are true, and if not please tell me why."

4. Nov 19, 2015

Staff: Mentor

What is the context of these questions?

5. Nov 19, 2015

kidsasd987

please check this video from 1:06:41 to 1:07:48.

So, the whole ppt is about excess carrier genearation and continuity equation.
But if we find the solution for 1st order ode, delta n(t) is a exponential function and its derivative is also exponential.

if delta n(t) is at steady state, its time derivative must be 0. so, I assume that the first statement is true.

Last edited: Nov 19, 2015
6. Nov 19, 2015

kidsasd987

2nd satement is a bit confusing.

(2.9.9)
(2.9.10)

(2.9.11)
(2.9.12)

generation rate - recombination = 0 (difussion ->recombination)
therefore, delta n and delta p are constant values, hence steady state.

* is the steady state concentration delta n (or delta p) dependent on the intensity and frequency of light that we shine onto semiconductor?

Last edited: Nov 19, 2015