Question

The number of silicon atoms per m3 is 5 x 1028. This is doped simultaneously with 5 x 1022 atoms per m3 of Arsenic and 5 x 1020 per m3 atoms of Indium. Calculate the number of electrons and holes. Given that n. = 1.5 x 1016 m-3. Is the material n-type or p-type?

Answer 1

Arsenic is donor, where as indium is acceptor impurity. Here, number of donor atoms added,
ND = 5 × 1022m3and number of acceptor atoms added,
NA= 5 × 1020 m-3
Therefore, number of free electrons created, n = ND= 5 x1022and number of holes created, nh = NA= 5 x 1020.
Now, ne > nh
Therefore, net number of free electrons created
n‘e = n - nh = 5 x 1022 - 5 x 1020
= 4.95 x 1022m-3
Also, net number of holes created,

As (n_e^1 > n_h^1) the resulting material is n-type semiconductor.