Assume that carrier screening from impurity electrons will make the impurity bound state disappear by disregarding the one-electron per one-impurity difficulty (the idea of screening by the electron density fluctuation rather than by individual electron).
(a) How will the theoretical N versus 1/T be modified at the higher temperature ranges in a sample that has 1020 phosphorus/cm3?
Next, assume that there are two groups of electrons with concentrations N1 cr and N21, then the N2 bound states will be screened out by the N1 electrons when their concentration N1 reaches Ncr.
(b) How does the presence of the second group of electrons affect the N versus 1/T curve?