Tag: properties of solids

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Multiple choice chemistry solid state electrical and magnetic properties of solids impurity defects properties of solids

In a n-type semiconductor, which of the following statements is true?

  1. Electrons are majority carriers and trivalent atoms are dopants.

  2. Electrons are minority carriers and pentavalent atoms are dopants.

  3. Holes are minority carriers and pentavalent atoms are dopants.

  4. Holes are majority carriers and trivalent atoms are dopants.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The n-type semiconductor can be produced  by doping impurity atoms of valence 5 i.e, pentavalent atoms like phosphorous and so electrons are majority charge carriers and Holes are minority charge carriers.

So correct answer is option C.

Multiple choice chemistry solid state electrical and magnetic properties of solids impurity defects properties of solids

With which one of the following elements silicon should be doped so as to give p-type of semiconductor?

  1. Selenium

  2. Boron

  3. Germanium

  4. Arsenic
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The n-type semiconductors are obtained when $Si$ or $Ge$ are doped with elements of group 15, eg, Arsenic $(As)$, while p-type semiconductors are obtained when $Si$ or $Ge$ are doped with traces of group 13 , ie Indium $(In)$ , Boron $(B)$.

So the correct option is $B$.

Multiple choice chemistry solid state electrical and magnetic properties of solids impurity defects properties of solids

Which of the following statement is true about semiconductors?

  1. Impurity of lower group creates $n-$type semiconductors
  2. Impurity of higher group creates $p-$type semiconductors

  3. extrinsic semiconductors are formed by doping impurity

  4. Intrinsic semiconductors become conductors when temperature is raised
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

An extrinsic semiconductor is one that has been doped; during manufacture of the semiconductor crystal a trace element or chemical called a doping agent has been incorporated chemically into the crystal, for the purpose of giving it different electrical properties than the pure semiconductor crystal.

So, option $C$ is correct.

Multiple choice chemistry solid state electrical and magnetic properties of solids impurity defects properties of solids

Which of the following is true about the charge acquired by $p-$type semiconductors?

  1. Positive

  2. Neutral

  3. Negative
  4. Depends on concentration of $p$ impurity
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

$p-$type semiconductors have a larger hole concentration than electron concentration. In p-type semiconductors, holes are the majority carriers and electrons are the minority carriers. $p-$type semiconductors are created by doping an intrinsic semiconductor with acceptor impurities. A common $p-$type dopant for silicon is boron or gallium. There will be no charge on the semiconductor.

So, correct answer is option $B$.

Multiple choice chemistry solid state electrical and magnetic properties of solids impurity defects properties of solids

Which of the following oxides behaves as conductor or insulator depending upon temperature?

  1. $TiO$
  2. $SiO _2$
  3. $TiO _3$
  4. $MgO$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

$TiO _{ 3 }$ behaves as conductor or insulator depending on temperature because of variation of energy gap between valence band and conduction band with the variation of temperature.

So, correct answer is option $C$. 

Multiple choice chemistry solid state electrical and magnetic properties of solids impurity defects properties of solids

To get a $n-$type semiconductor from silicon, it should be doped with a substance with valence _______.

  1. 2

  2. 1

  3. 3

  4. 5
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

An $n-$type semiconductor is made by adding a small amount of a Group-V element such as phosphorous ($P$) or arsenic ($As$) to the intrinsic semiconductor. Group-V elements have five valence electrons per atom.

So, correct answer is option $D$.

Multiple choice chemistry solid state electrical and magnetic properties of solids impurity defects properties of solids

Statement-I  The conductance through electrons is called n-type conduction and if through positive semi holes it is called p-type conduction.

Statement-II  Doping involves the preparation of semiconductor by the addition of impurities in the intrinsic semiconductor.

  1. Statement-I is correct but Statement-II is wrong

  2. Statement-I is wrong but Statement-II is correct

  3. Both Statement-I and Statement-II are correct and Statement-II is correct explanation of Statement-I

  4. Both Statement-I and Statement-II are correct but Statement-II is not correct explanation of Statement-I
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The conductance through electrons is called n-type conduction and if through positive semiholes, it is called p-type conduction.
Doping involves preparation of semi-conductors by the presence of impurities in the intrinsic semiconductor.With donor impurities, we get n-type semi-conductors and with acceptor impurities, we get p-type semi-conductors.

Thus, the explanation provided was inadequate.