NCERT Class XII Chapter
Semiconductor Electronics
Questions With Solutions
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Question : 13
Total: 19
In an intrinsic semiconductor the energy gap E g n i n i n 0 ( −
) n 0
k B 10 − 5 K − 1
Solution:
Conductivity is given by
σ = e (n e µ e + n h µ h
For intrinsic semiconductorn e n h n i
Also mobility of holes (µ h µ e
So, conductivity σ =e n e µ e
Temperature dependence of intrinsic carrier concentration
n i n 0 e ( −
)
So, conductivity, σ =e n i µ e e µ e n 0 e ( −
)
wheree µ e n 0 σ 0
Hence , σ =σ 0 e ( −
)
Conductivity at 600 K,σ 1 σ 0 e (
)
Conductivity at 300 K,σ 2 σ 0 e (
)
Dividing (i) and (ii)
e − [
−
] e +
[
]
e 11.6 10 5
So,σ ( 600 K ) 10 5 σ ( 300 K )
Conductivity increases rapidly with the rise of temperature.
σ = e (
For intrinsic semiconductor
Also mobility of holes (
So, conductivity σ =
Temperature dependence of intrinsic carrier concentration
So, conductivity, σ =
where
Hence , σ =
Conductivity at 600 K,
Conductivity at 300 K,
Dividing (i) and (ii)
So,
Conductivity increases rapidly with the rise of temperature.
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