Question $1.$

a$)$ Draw the full electronic configuration of Chromium $($atomic number $=24).$

$[4$ Marks$]$

b$)$ A $25$ mm silicon slab is doped with the following doping profile:

Nd $=1015+1016$X $($where X is in cm$).$

i$)$ Calculate the electric field from the point A $($XA $=1$ mm$)$ to the point B $($XB $=3$ mm$),$ at

room temperature.

$[8$ Marks$]$

ii$)$ If we increase the temperature to $400$ K$.$ Which will be the new electric field between

point A and point B$?$

$[4$ Marks$]$

c$)$ A GaAs sample has been doped in such a way that the effective density of states in the valence

band and conduction band are $=8\mathrm{.}310203$ and $=9\mathrm{.}510173.$ The

temperature is $=300,$ you can assume the Fermi energy is $0\mathrm{.}3$ below the conduction

band and GaAs bandgap is $1\mathrm{.}42.$ Calculate:

i$)$ Concentration of electrons

$[5$ Marks$]$

ii$)$ Concentration of holes

$[4$ Marks$]$

$[$TOTAL: $25$ marks$]$