First slide

Types of semiconductors

Question

When a semi-conducting material is doped with an impurity, new acceptor levels are created. In a particular thermal collision, a valence electron receives an energy equal to 2 kT (k = Boltzmann Constant, T = Absolute Temperature) and just reaches one of the acceptor levels. Assuming that the energy of the electron was at the top edge of valence band and the temperature T is equal to 300 K . Find the energy of acceptor levels above the valence band.

Moderate

A

52 meV
B

41 meV
C

30 meV
D

25 meV

Solution

Given : 2 kT = Energy gap between acceptor hand and valency band
$∴ E = 2 \times 1.38 \times 10^{- 23} \times 300 [k = B o l t z m a n n C o n s \tan t]$
$E = (2 \times 1.38 \times 3) \times 10^{- 21} J$
$= (\frac{6 \times 1.38}{1.6}) \times \frac{10^{- 21}}{10^{- 19}} e V$
$= 5.175 \times 10^{- 2} e V = 5.175 \times 10^{1} m e V ≃ 52 m e V$

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