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Carbon, silicon and germanium have four valence electrons each. At room temeprature which one of the following statements is most appropriate?
(a)The number of free electrons for conduction is significant only in Si and Ge but small in C.
(b)The number of free conduction electrons is significant in C but small in Si and Ge.
(c)The number of free conduction electrons is negligibly small in all the three.
(d)The number of free electrons for conduction is significant in all the three.

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Important Questions on Semiconductor Electronics: Materials, Devices and Simple Circuits
EASY
12th Uttar Pradesh Board
IMPORTANT
Identify the property which is not a characteristics for a semiconductor,

EASY
12th Uttar Pradesh Board
IMPORTANT
What is an intrinsic semiconductor?

MEDIUM
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IMPORTANT
Determine the conductivity and resistivity of pure germanium at assuming that at this temperature the concentration of germanium is The electron and hole mobilities are and respectively. Take, .

MEDIUM
12th Uttar Pradesh Board
IMPORTANT
A sample of germanium is doped to the extent of donor atoms per cm3 and acceptor atoms per . The resistivity of pure germanium at the temperature of the sample is Find the total conduction current density due to an applied electric field of The electron and hole mobilities are given to be and respectively. Take, .

MEDIUM
12th Uttar Pradesh Board
IMPORTANT
The energy gap in germanium is Compare the intrinsic conductivity of germanium at and . Take

MEDIUM
12th Uttar Pradesh Board
IMPORTANT
In an intrinsic semiconductor the energy gap is . Its hole mobility is much smaller than electron mobility and independent of temperature. What is the ratio between conductivity at and that at ? Assume that the temperature dependence of intrinsic carrier concentration is given by where is a constant.

MEDIUM
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The energy gap of a semiconductor is The maximum wavelength at which it starts energy absorption will be

EASY
12th Uttar Pradesh Board
IMPORTANT
and are conduction band, valence band and forbidden energy gap, respectively, for a solid. If lattice constant increases, then
