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Physics Question on Semiconductor electronics: materials, devices and simple circuits

An n-type semiconductor is formed

A

when germanium crystal is doped with an impurity containing 3 valence electrons

B

when germanium crystal is doped with an impurity containing 5 valence electrons

C

from pure germanium

D

from pure silicon

Answer

when germanium crystal is doped with an impurity containing 5 valence electrons

Explanation

Solution

Pentavalent impurity atom i.e., atoms having 5 valence electrons such as antimony (Sb) or arsenic (As), when added to a pure semiconductor, produce excess of free electrons i.e., donor electrons to the semiconductor. For this reason, pentavalent impurity atoms are called donor impurity atom. The semiconductor so produced is called n-type extrinsic semiconductor So the corresponding wavelength is equal to,     λ=hcE=6.67×10−34×3×1081.5×1.6×10−19 \, \, \, \, \lambda=\frac{hc}{E} =\frac{6.67 \times 10^{-34} \times 3 \times 10^{8}}{1.5 \times 1.6 \times 10^{-19}}        =8.3375×10−26×1019=8337.5A˚ \, \, \, \, \, \, \, =8.3375 \times 10^{-26} \times 10^{19} =8337.5 \mathring{A}