1.

The typical ionisation energy of a donor in silicon is

Answer»

`10. 0 eV`
`1.0 eV`
`0.1 eV`
`0.001 eV`

SOLUTION :When donor impurity (`+5` valence) added to a pure silicon (`+4` valence), the `+5` valence donor ATOM sits in the PLACE fo `+4` valence silicon atom. So it has a net additional `+1` electronic charge. The four valence electron from covelent bond and get fixed in the lattice. The fifth electron (with net `-1` electronic additional charge. The situation is like the hydrogen atom for which energy is given by `E=13.6/(n^(2)) eV`. for the case of hydrogen, the permitivity was teken as `epsilon_(0)`. however, if the MEDUIM has a permittivity `epsilon_(r)`, relative to `epsilon_(0)`,then `E=-13.6/(epsilon_(r)^(2)) eV`
For `Si,epsilon_(r) =12` and for `n=1,E=0.1 eV`


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