# stuck between the problem

#### bhuvanesh

Aug 29, 2013
201
question : find intrinsic carrier concentration at T=200k for silicon (in cm^-3).
Answer is attached.In that why is that (200/300)^3 is added there.my only hope is this forum.Thank you

#### Attachments

• _20150122_025819.JPG
27.7 KB · Views: 108

#### davenn

Moderator
Sep 5, 2009
14,142
there is no attachment

#### bhuvanesh

Aug 29, 2013
201
sorry,i have attached now

#### Arouse1973

Dec 18, 2013
5,178
question : find intrinsic carrier concentration at T=200k for silicon (in cm^-3).
Answer is attached.In that why is that (200/300)^3 is added there.my only hope is this forum.Thank you

Are you seriously trying to teach yourself semiconductor physics?

#### Ratch

Mar 10, 2013
1,098
question : find intrinsic carrier concentration at T=200k for silicon (in cm^-3).
Answer is attached.In that why is that (200/300)^3 is added there.my only hope is this forum.Thank you

Nc and Nv have temperature parameters that are raised to the 3/2 power. If the temperature ratios are moved outside the exponent brackets, then the temperature ratios have to be raised to the third power to compensate for the move.

Ratch

#### bhuvanesh

Aug 29, 2013
201
Nc and Nv have temperature parameters that are raised to the 3/2 power. If the temperature ratios are moved outside the exponent brackets, then the temperature ratios have to be raised to the third power to compensate for the move.

Why we need to move temperature outside the exponential.i have solved this in my way say weather it is right or wrong with explanation .Thank you

#### Attachments

• IMG_20150126_073127162.jpg
52.4 KB · Views: 132

#### Ratch

Mar 10, 2013
1,098
Why we need to move temperature outside the exponential.i have solved this in my way say weather it is right or wrong with explanation .Thank you

Nv and Nc have their temperature parameters inside a term raised to the 3/2 power. You don't need to take those temperatures outside the radical, but if you do, you have to compensate for their removal. The solution seems to have elected to move the temperature parameter to the outside the radical. Therefore, the temperature term has to be raised to the third power to compensate for the movement.

Ratch

#### bhuvanesh

Aug 29, 2013
201
sire i dont understand what do you saying here ,where it is raised to 3/2.its raised to power 3.

#### Ratch

Mar 10, 2013
1,098
sire i dont understand what do you saying here ,where it is raised to 3/2.its raised to power 3.

What book are you using? Doesn't it have the formula shown in the attachment? When Nv and Nc are multiplied together, the "2" in the denominator is cancelled and "3" remains.

Ratch

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