Increase in doping concentrations resulting in a decrease in mobility?

[theBEAST]

Homework Statement

So in one of our practice problems it states that as we increase the doping concentrations, the result will be a decrease in mobility.

However, I thought that when you increase doping concentrations, there will be a higher concentration of carriers available for conduction and thus the conductivity increases. So this should result in an increase in mobility? Also, when they say doping concentrations, it can either be p or n type dopants right?

 

[ehild]

Homework Statement

So in one of our practice problems it states that as we increase the doping concentrations, the result will be a decrease in mobility.

However, I thought that when you increase doping concentrations, there will be a higher concentration of carriers available for conduction and thus the conductivity increases. So this should result in an increase in mobility? Also, when they say doping concentrations, it can either be p or n type dopants right?

The conductivity increases, but the mobility decreases. The conductivity is proportional to the concentration of free carriers, about equal to the doping concentration; and also proportional to the mobility. But the mobility decreases with the doping, as the free carriers collide with the impurities more frequently, so the drift velocity decreases.

ehild

 

[theBEAST]

The conductivity increases, but the mobility decreases. The conductivity is proportional to the concentration of free carriers, about equal to the doping concentration; and also proportional to the mobility. But the mobility decreases with the doping, as the free carriers collide with the impurities more frequently, so the drift velocity decreases.

ehild

Oh wow, that's actually pretty cool, thanks!

 

[ehild]

You are welcome

ehild