A) \[10.0\,eV\]
B) \[1.0\,eV\]
C) \[0.1\,eV\]
D) \[0.001\,eV\]
Correct Answer: C
Solution :
When donor impurity (+5 valence) added to a pure silicon (+4 valence), the +5 valence donor atom sits in the place of + 4 valence silicon atom. So it has a net additional + 1 electronic charge. The four valence electron form covalent bond and get fixed in the lattice. The fifth electron (with net ? 1 electronic charge) can be approximated to revolve around + 1 additional charge. The situation is like the hydrogen atom for which energy is given by \[E=-\frac{13.6}{{{n}^{2}}}eV\]. For the case of hydrogen, the permittivity was taken as e0. However, if the medium has a permittivity er, relative to e0, then \[E=-\frac{13.6}{\varepsilon _{r}^{2}{{n}^{2}}}eV\] For Si, er = 12 and for n = 1, \[E\tilde{}0.1\,eV\]
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