Semiconductor doping and conductivity

Question

Why is the conductivity of Si dopped with P and As much bigger than the conductivity of Si dopped with In and P?

Answer 1

I presume you mean doped with (P,As) vs (P,In), that is both together. And I assume you are comparing similar concentrations.

In that case, note that both P and As are donors, so both will add carriers to the conduction band. In contrast, In is an acceptor, so it will counteract the P resulting in a lower carrier concentration (compensation).