In the case of N-type germanium semiconductor the energy required to detach fifth electron from the donor atom is :
0.01 eV
In an N-type semiconductor a pentavalent donor atom (phosphorus, arsenic or antimony) forms four covalent bonds with its neighbours, and its fifth valence electron is only loosely bound to the donor ion. Because this electron moves inside a crystal of high dielectric constant and with a reduced effective mass, its binding energy is far smaller than the ionisation energy of a free atom.
A hydrogen-like estimate \(E_d \approx 13.6\,\text{eV}\times\dfrac{m^*/m_0}{\varepsilon_r^2}\) gives only a few hundredths of an electron-volt. Germanium has a large relative permittivity (about 16) and a small electron effective mass, so its donor ionisation energy is about 0.01 eV. This is far below the germanium band gap and below kT (about 0.026 eV) at room temperature, so practically every donor in germanium is ionised at room temperature.
0.05 eV is the typical donor ionisation energy in silicon, whose smaller permittivity binds the fifth electron more strongly, so it does not apply to germanium. 0.25 eV is far too large for a shallow donor, and 0.70 eV is close to the full band gap of germanium, the energy needed to create an electron–hole pair rather than to free a donor electron.
0.01 eV option is correct.
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.................... is a client server application that identifies each host on the internet with a unique user-friendly name.
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Codes:
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