Question

The impurity levels of a doped semiconductor are 30 me V below the conduction band. Determine whether the semiconductor is n-type or p-type. At the room temperature thermal collisons occur as a result of which the extra electron loosely bound to the impurity ion gets an amount of emergy kT [where k is Boltzmann constant `=8.62xx10^(-5) eV//K]` and hence this electron can jump into conduction band. What is the value of T?

Answer 1

The separation of impurity energy level from conduction band is less in case of n-type semiconductor and more in case of p-type semiconductor. As energy separation of impurity level `=30xx10^(-3)eV` is much smaller than energy gap of pure semiconductor `(~~1eV)`, therefore, the doped semiconductor is n-type.
Here, `E_(g)=30xx10^(-3)eV=kT`
or `T=(30xx10^(-3))/k=(30xx10^(-3))/(8.62xx10^(-5))=348K`