Heres the question: A sample of pure silicon, which has four valence electrons is doped with gallium, which has three valence electrons, to give a concentration of 10^23 m^-3. a. Is the material n-type or p-type? b. If the electron mobility is 0.14 m^2/Vs and the hole mobility is 0.05 m^2/Vs, what is the conductivity? I know this is a p-type, just want to make sure. And the equation for conductivity is conductivity = (number denisty)*(electron charge)*(mobility), but I don't know how to incorporate electron and hole mobility into this. An explanation and working out on how you solve this question especially part b) would really be helpful. Thanks.