Follow the same procedure as in Problem 19 to find the binding energy E0 for the first B...

Follow the same procedure as in Problem 19 to find the binding energy E₀ for the first Bohr orbit of the extra electron in silicon. Comment on the result.

Consider what happens when silicon is doped with arsenic. Suppose that the extra, weakly bound electron from arsenic moves in the first Bohr orbit in a silicon atom. The first Bohr orbit has a radius of

Because of the effects of screening, it is necessary to replace ε₀ with the electric permittivity  = 11.7 for silicon).

(a) Compute the effective Bohr radius for this electron.

(b) Compare your result with the lattice spacing in silicon, about 0.235 nm, and comment on the result.