Step 1: Understanding the Question:
To create an n-type semiconductor from group 14 Silicon ($Si$), we need to add a dopant that has more valence electrons than $Si$.
Step 2: Detailed Explanation:
1. Silicon ($Si$) has 4 valence electrons.
2. An n-type (negative type) semiconductor requires extra electrons. This is achieved by doping with group 15 elements (pentavalent).
3. Arsenic (As) belongs to group 15 and has 5 valence electrons. When it replaces a $Si$ atom, 4 electrons form bonds, and the 5th electron becomes free, contributing to conductivity.
4. Boron (B), Gallium (Ga), and Indium (In) belong to group 13 (trivalent). They create "holes", leading to p-type semiconductors.
Step 4: Final Answer:
Arsenic (As) is used to obtain an n-type semiconductor.