Silicon crystallizes in the diamond structure with a lattice constant a 5.43a a) how many atoms does the cubic elementary cell contain? b) phosphorus atoms incorporated on si sites act as donors. calculate the ionization energy of such a donor impurity within the framework of the simple hydrogenic model (dielectric constant esi 12). c) calculate the radius ro of the first bohr orbital. what is the probability d) discuss the validity of the hydrogenic model and explain its shortcom- e) at what impurity concentration does interaction between the donor cen- of finding the electron in its ground state within a sphere of radius 2ro? how many si atoms are located within such a sphere? ings ters become important? the related impurity band conductivity is as- sumed to correspond to an average donor separation of 4ro 0.