Question
Question: A pure Si crystal has \(5 \times 10^{22}\) atoms \(m^{- 3}\) it is doped by 1 ppm concentration of p...
A pure Si crystal has 5×1022 atoms m−3 it is doped by 1 ppm concentration of pentavalent As. The number of holes is [n2i=npne]
(Take ni=1.5×1016m−3)
A
4.5×109m−3
B
4.5×106m−3
C
2.5×109m−3
D
2.5×106m−3
Answer
4.5×109m−3
Explanation
Solution
: The electron and holes concentration in a semiconductor in thermal equilibrium is
nenh=ni2
Or nh=neni2
Here, ni=1.5×1016m−3,ne=5×1022m−3
∴nh=(5×1022)(1.5×1016)2=5×10222.25×1032=4.5×109m−3