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

 

[HalfLostAndSearching]

I can explain the relationship between doping concentrations and mobility in semiconductors. Doping is the process of intentionally adding impurities to a semiconductor material in order to alter its electrical properties. When we increase doping concentrations, we are essentially increasing the number of impurities in the material.

Now, the mobility of a material refers to the ease with which charge carriers (electrons or holes) can move through it. In a doped semiconductor, the charge carriers are either electrons or holes, depending on the type of dopant used. When we increase the doping concentrations, we are essentially increasing the number of charge carriers in the material.

However, as the doping concentration increases, the distance between these charge carriers decreases, leading to more collisions between them. These collisions hinder the movement of charge carriers and result in a decrease in mobility. So, while the number of charge carriers increases with higher doping concentrations, the mobility decreases due to increased collisions.

It is also important to note that doping concentrations can refer to both p-type and n-type dopants. In both cases, an increase in doping concentrations will result in a decrease in mobility due to increased collisions between charge carriers.

In summary, while an increase in doping concentrations does lead to an increase in the number of charge carriers available for conduction, it also results in a decrease in the mobility of these charge carriers due to increased collisions. This is why an increase in doping concentrations can result in a decrease in mobility.