1. What is the equilibrium concentration of electrons and holes in an n-type silicon at T=21.2°C (n_i = 1.0x10¹⁰cm^-3) in which N_DD=4x10¹⁰cm^-3 and are all ionized, and N_AA=0? How much error is introduced if the intrinsic electron is neglected?

2. A homogeneously doped n-type Si at 21.2°C (n₁-=1.00x10¹⁰cm^-3) has N_DD= 1.25X10¹⁵cm^-3 donors and N_AA=0.25x10¹⁵cm^-3 acceptors, all of which are ionized. At some instance of time, for example t=13:00, the carrier concentrations were found to be N=1.25x10¹⁵cm^-3 and P=0.25x10¹⁵cm^-3 and were uniform over the entire volume of the crystal.

(a) Is the crystal electrically neutral at P-13:00?

(b) Why is the crystal not at thermodynamic equilibrium at t=13:00 and back up your answer quantitatively?