Conductivity and Charge Carriers in Semiconductors

The video tutorial explains the concept of conductivity in semiconductors, contrasting it with metals. It covers the role of electric fields, drift velocity, and mobility in determining conductivity. The tutorial also discusses the differences in mobility between electrons and holes, and derives the formula for conductivity in semiconductors. A numerical problem is solved to find the intrinsic conductivity of pure germanium, illustrating the application of the concepts discussed.

What distinguishes semiconductors from metals in terms of charge carriers?

• Semiconductors have only electrons as charge carriers.

• Metals have only holes as charge carriers.

• Metals have both electrons and holes as charge carriers.

• Semiconductors have both electrons and holes as charge carriers.

What is the relationship between drift velocity and electric field intensity?

• Drift velocity is independent of electric field intensity.

• Drift velocity is directly proportional to electric field intensity.

• Drift velocity is equal to electric field intensity.

• Drift velocity is inversely proportional to electric field intensity.

What is the unit of mobility?

• Volt per meter

• Meter per second

• Ohm meter

• Meter square per volt second

How is current density related to conductivity in semiconductors?

• Current density is equal to conductivity.

• Current density is independent of conductivity.

• Current density is directly proportional to conductivity.

• Current density is inversely proportional to conductivity.

What is the charge of an electron?

• 1.6 x 10^9 Coulomb

• 1.6 x 10^19 Coulomb

• 1.6 x 10^-9 Coulomb

• 1.6 x 10^-19 Coulomb

How does the effective mass of a hole compare to that of an electron?

• The effective mass of a hole is less than that of an electron.

• The effective mass of a hole is equal to that of an electron.

• The effective mass of a hole is greater than that of an electron.

• The effective mass of a hole is not related to that of an electron.

What is the formula for conductivity in semiconductors?

• σ = nμn + pμp

• σ = nμnE + pμpE

• σ = nμnE - pμpE

• σ = nμn - pμp

What is the mobility of free electrons in pure germanium?

• 0.48 meter square per volt second

• 0.28 meter square per volt second

• 0.18 meter square per volt second

• 0.38 meter square per volt second

What is the intrinsic concentration of charge carriers in pure germanium?

• 2.5 x 10^19 per meter cube

• 2.5 x 10^-19 per meter cube

• 2.5 x 10^9 per meter cube

• 2.5 x 10^-9 per meter cube

What is the calculated intrinsic conductivity of pure germanium?

• 2.24 ohm meter^-2

• 2.24 ohm meter^2

• 2.24 ohm meter^-1

• 2.24 ohm meter