[填空题]
For an arsenic donor atom/iqt17/x q,lpg za 4fs in a doped silicon semiconductor, assume that theo 6iszu5gk49d "extra" electron moves in a Bohr orbit about the arsenic ion. For6oui5 dksg z49 this electron in the ground state, take into account the dielectric constant $ K = 12 $ of the Si lattice (which represents the weakening of the Coulomb force due to all the other atoms or ions in the lattice), and estimate
(a) the binding energy, E = eV
(b) the orbit radius for this extra electron. r = nm
