Correct Answer - Option 1 : Silicon atoms act as p-type dopants in Arsenic sites and n-type dopants in Gallium sites
Concept:
If the substituting atom gives one extra electron in the outermost shell then n-type semiconductor is formed. If substituting atom has one electron less in the outermost shell then p-type semiconductor is formed.
Si → 4e- in the outermost shell
Ga → 3e- in the outermost shell
As → 5e- in the outermost shell
Application:
Note: Here, GaAs is doped with Silicon. So, Silicon is the substituting atom.
For Arsenic sites, Silicon will act as a p-type dopant as it has 1 electron less than Arsenic in its outermost shell.
And for Gallium sites, Silicon will act a n-type dopant as it has 1 electron more than Gallium in its outermost shell.
Si → Ga → 1e- extra → n-type
Si → As → 1e- less → p-type