Silicon, with 4 Valence Electrons, Is the Most Widely Used

Multiple Choice

Silicon, with 4 valence electrons, is the most widely used material for photovoltaic devices even though it is only a semiconductor. You can improve the conductivity with dopants. Which of these elements would best serve to create an n-type semiconductor when added to silicon?

A) B
B) C
C) Ge
D) P
E) Both a and b