Question

When a semiconducting material is doped with an impurity, new acceptor levels are created. In a particular thermal collision, a valence electron receives an energy equal to 2kT and just reaches one of the acceptor levels. Assuming that the energy of the electron was at the top edge of the valence band and that the temperature T is equal to 300 K, find the energy of the acceptor levels above the valence band.

Answer 1

Explanation:

• On top of the valence band, the electron is located before the thermal excitation.
• In the acceptor level, the electron was present after the thermal excitation.
• This shows that the energy gap between the acceptor level and the valence band is equal to the electron absorbed energy in thermal excitation. So,  
• 2kT = Energy gap between the acceptor level and the valence band

$\Rightarrow \mathrm{E}=2 \times 1.38 \times 10-23 \times 300$

$\Rightarrow E=(2 \times 1.38 \times 3) \times 10-21 J$

$\Rightarrow E=5.175 \times 10-2 \mathrm{eV}$

$\Rightarrow \mathrm{E}=51.75 \mathrm{meV}$