Question

Explain what a diffusion current is. How is the diffusion constant related to the electron mobility?

Answer 1

Answer and Explanation:

Diffusion current can be defined as the current that flows as a result of diffusion of charge carriers in a semiconductor device as a result of difference in the concentration of holes and electrons in the both the regions (p and n) of the semiconductor device.

Depletion region of p-n junction is dominated by diffusion current.

The diffusion constant is directly proportional to the electron mobility and is given by the expression:

`D_(c) = \Gamma ^(2) \mu ^(2) \tau`

where,

`D_(c)` = Diffusion coefficient

`\mu` = electron mobility

`\tau` = time of correlation

Therefore, other parameters being constant (say):

`D_(c)` is directly propotional to
`\mu ^(2)`