Assertion : Conductivity of silicon increases by doping it with group-15 elements.
Reason : Doping means introduction of small amount of impurities like P, As or Bi into the pure crystal.
Assertion : Conductivity of silicon increases by doping it with group-15 elements.
Reason : Doping means introduction of small amount of impurities like P, As or Bi into the pure crystal.
Reason : Doping means introduction of small amount of impurities like P, As or Bi into the pure crystal.
A
If both assertion and reason are true and reason is the correct explanation of assertion
B
If both assertion and reason are true but reason is not the correct explanation of assertion
C
If assertion is true but reason is false
D
If both assertion and reason are false.
Text Solution
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The correct Answer is:
B
When a silicon crystal is doped with a group- 15 elements, such as P, As, Sb or Bi the structure of the crystal lattice is left unchanged but an occasional atom with five valence electrons occupies a site that would normally be occupied by a silicon atom. The foreign atom uses four of its. electrons in covalent bonding but the remaining fifth electron becomes delocalised and is thus free to contribute to electrical conduction.
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There is an increase in conductivity when Silicon is doped with Phosphorous. Give reason.
Doping mens introduction of small amount of impurities like phosphorus , arsenic or boron into the pure crystal . In pure silicon , ther are four valenices used in bonding with other four adjacent silicon crystal is doped with a group -15 element ( with five valence electron ) such as P, As , or Bi , the structure of the crystal lattic remains unchanged . Out of the five valence electron of group -15 doped element four element are used in normal covalent bonding with silicon while fiffth electron is delcoasiled and thus conducts electricity Doping a silicon crystal with a group -13 element (with three valence electrons ) such as B, Al, Ga or In products a semiconductor with three electrons in in dopant . The place where fourth electron is missing is called an electron vacancy or hole . Such hole can move throught the crystal like a positive charge giving rise conduction of electricity. Silicon that has been dopend with group - 15 elements is called :
Doping mens introduction of small amount of impurities like phosphorus , arsenic or boron into the pure crystal . In pure silicon , ther are four valenices used in bonding with other four adjacent silicon crystal is doped with a group -15 element ( with five valence electron ) such as P, As , or Bi , the structure of the crystal lattic remains unchanged . Out of the five valence electron of group -15 doped element four element are used in normal covalent bonding with silicon while fiffth electron is delcoasiled and thus conducts electricity Doping a silicon crystal with a group -13 element (with three valence electrons ) such as B, Al, Ga or In products a semiconductor with three electrons in in dopant . The place where fourth electron is missing is called an electron vacancy or hole . Such hole can move throught the crystal like a positive charge giving rise conduction of electricity. Silicon that has been dopend with group - 13 elements is called :
Assertion: The conductivity of an intrinsic semiconductor depends on its temperature. Reason The conductivity of an intrinsic semiconductor is slightly higher than that of a lightly doped p-type semiconductor.
Doping mens introduction of small amount of impurities like phosphorus , arsenic or boron into the pure crystal . In pure silicon , ther are four valenices used in bonding with other four adjacent silicon crystal is doped with a group -15 element ( with five valence electron ) such as P, As , or Bi , the structure of the crystal lattic remains unchanged . Out of the five valence electron of group -15 doped element four element are used in normal covalent bonding with silicon while fiffth electron is delcoasiled and thus conducts electricity Doping a silicon crystal with a group -13 element (with three valence electrons ) such as B, Al, Ga or In products a semiconductor with three electrons in in dopant . The place where fourth electron is missing is called an electron vacancy or hole . Such hole can move throught the crystal like a positive charge giving rise conduction of electricity. No. of valene electrons in silicon are :
In a ideal crystal there nust be regular repeating arrangement of the constuting particles and its entropy must be zero at absolute zero at absolute zero temperature. However, it is impossible to obtain an ideal crystal and it suffers from certain defects called imperfections. In pure crystal these defects arise either due to disorder or dislocation of the movement of the particles even at absolute zero temperature. Such defect increases with rise in temperature. In addition ti this, certain defects arise due to the pressure of some impurities. Such defects not only modify the existing properties of the crystalline solid but also impart certain new characteritics to them. In pure crystal, e.g, silicon or germanium at 0K, the electrons are prsent in fully occupied lowest energy states and are not xpected to conduct any electricity. However at temperature above 0K, some electron leave their bonds and become free to move in the crystal lattice, giving rise to and become free to move in the crystal lattice, giving rise to electrical conductivity. The electron deficient bonds, called holes (+vely charged) and thermally mobile electrons move in opposite direction under the electric field. Stoichiometric ppoint defects include (a) Schottky defects, which arise due to missing of both cations and anions from their lattice sites without disturbing the stoichiometry and (b) Frenked defects, which arise due to misplacement of certian ions in the crystal lattice. The former defect gives rise to no change of density. Another type of defects are non-stoichometry defects where the cetions and anion are not present in the stoichiometry ratio. In metal excess defect, metal ions or positive ions are in excess as compared to anions of non-metals stoichiometrycally. On the other hand in metal deficiency defect, the cations are in lesser proportion than stoichiometric value. Since the crystal is neutral electrically, the balance of charge is maintained by free electrons or extra positive charges. The metal excess defects gives rise to conduction of electricity due to the presence of free electrons. Also crystals having metal excess defects are paramagnetic and coloured due to the presence of electrons in the anion vacancies. Impurity defects arise when some foreign atoms are present at the lattice sites in place of the host atoms or at the vacant interstitial sites. When 15 group elements like P or are doped into Si or Ge, the added impurity atoms occupy the lattice sites forming four covalent bonds with 4 Si/Ge atoms leaving an extra electron free to move. Such a crystal is said to be n-type semi conductor because the conduction of electricity is due to movement of extra unbounded electrons. If doping of a covalent crystal of 14 group elements are caused by addition of small amounts of elements are caused by addition of small amounts of elements of group 13, e.g, Al or Ga with three valence electrons, one covalent bond formed will be electron deficient and acts as a positive hole. The presence of such holes in the crystal leads to electrical conductivity and the the crystal is said to be p-type semiconductor. The type of semiconduction shown by crystal capable of showing Schottky defect, will be :
In a ideal crystal there nust be regular repeating arrangement of the constuting particles and its entropy must be zero at absolute zero at absolute zero temperature. However, it is impossible to obtain an ideal crystal and it suffers from certain defects called imperfections. In pure crystal these defects arise either due to disorder or dislocation of the movement of the particles even at absolute zero temperature. Such defect increases with rise in temperature. In addition ti this, certain defects arise due to the pressure of some impurities. Such defects not only modify the existing properties of the crystalline solid but also impart certain new characteritics to them. In pure crystal, e.g, silicon or germanium at 0K, the electrons are prsent in fully occupied lowest energy states and are not xpected to conduct any electricity. However at temperature above 0K, some electron leave their bonds and become free to move in the crystal lattice, giving rise to and become free to move in the crystal lattice, giving rise to electrical conductivity. The electron deficient bonds, called holes (+vely charged) and thermally mobile electrons move in opposite direction under the electric field. Stoichiometric ppoint defects include (a) Schottky defects, which arise due to missing of both cations and anions from their lattice sites without disturbing the stoichiometry and (b) Frenked defects, which arise due to misplacement of certian ions in the crystal lattice. The former defect gives rise to no change of density. Another type of defects are non-stoichometry defects where the cetions and anion are not present in the stoichiometry ratio. In metal excess defect, metal ions or positive ions are in excess as compared to anions of non-metals stoichiometrycally. On the other hand in metal deficiency defect, the cations are in lesser proportion than stoichiometric value. Since the crystal is neutral electrically, the balance of charge is maintained by free electrons or extra positive charges. The metal excess defects gives rise to conduction of electricity due to the presence of free electrons. Also crystals having metal excess defects are paramagnetic and coloured due to the presence of electrons in the anion vacancies. Impurity defects arise when some foreign atoms are present at the lattice sites in place of the host atoms or at the vacant interstitial sites. When 15 group elements like P or are doped into Si or Ge, the added impurity atoms occupy the lattice sites forming four covalent bonds with 4 Si/Ge atoms leaving an extra electron free to move. Such a crystal is said to be n-type semi conductor because the conduction of electricity is due to movement of extra unbounded electrons. If doping of a covalent crystal of 14 group elements are caused by addition of small amounts of elements are caused by addition of small amounts of elements of group 13, e.g, Al or Ga with three valence electrons, one covalent bond formed will be electron deficient and acts as a positive hole. The presence of such holes in the crystal leads to electrical conductivity and the the crystal is said to be p-type semiconductor. In the crystal of Fe_(0.93) O, the percentage of Fe(III) will be:
In a ideal crystal there nust be regular repeating arrangement of the constuting particles and its entropy must be zero at absolute zero at absolute zero temperature. However, it is impossible to obtain an ideal crystal and it suffers from certain defects called imperfections. In pure crystal these defects arise either due to disorder or dislocation of the movement of the particles even at absolute zero temperature. Such defect increases with rise in temperature. In addition ti this, certain defects arise due to the pressure of some impurities. Such defects not only modify the existing properties of the crystalline solid but also impart certain new characteritics to them. In pure crystal, e.g, silicon or germanium at 0K, the electrons are prsent in fully occupied lowest energy states and are not xpected to conduct any electricity. However at temperature above 0K, some electron leave their bonds and become free to move in the crystal lattice, giving rise to and become free to move in the crystal lattice, giving rise to electrical conductivity. The electron deficient bonds, called holes (+vely charged) and thermally mobile electrons move in opposite direction under the electric field. Stoichiometric ppoint defects include (a) Schottky defects, which arise due to missing of both cations and anions from their lattice sites without disturbing the stoichiometry and (b) Frenked defects, which arise due to misplacement of certian ions in the crystal lattice. The former defect gives rise to no change of density. Another type of defects are non-stoichometry defects where the cetions and anion are not present in the stoichiometry ratio. In metal excess defect, metal ions or positive ions are in excess as compared to anions of non-metals stoichiometrycally. On the other hand in metal deficiency defect, the cations are in lesser proportion than stoichiometric value. Since the crystal is neutral electrically, the balance of charge is maintained by free electrons or extra positive charges. The metal excess defects gives rise to conduction of electricity due to the presence of free electrons. Also crystals having metal excess defects are paramagnetic and coloured due to the presence of electrons in the anion vacancies. Impurity defects arise when some foreign atoms are present at the lattice sites in place of the host atoms or at the vacant interstitial sites. When 15 group elements like P or are doped into Si or Ge, the added impurity atoms occupy the lattice sites forming four covalent bonds with 4 Si/Ge atoms leaving an extra electron free to move. Such a crystal is said to be n-type semi conductor because the conduction of electricity is due to movement of extra unbounded electrons. If doping of a covalent crystal of 14 group elements are caused by addition of small amounts of elements are caused by addition of small amounts of elements of group 13, e.g, Al or Ga with three valence electrons, one covalent bond formed will be electron deficient and acts as a positive hole. The presence of such holes in the crystal leads to electrical conductivity and the the crystal is said to be p-type semiconductor. Which of the following statements is correct about the conduction of electricity in pure crystal of silicon at room temperature?
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