semiconductor unit-1

The intrinsic carrier density is 1.5 × 10^16 m^-3 . If the mobility of electron and hole are 0.13 and 0.05 m^2 v^-1 s^-1 . Calculate the conductivity

• 4.32 × 10^-4 ohm^-1 m^-1

• 4.60 × 10^-5 ohm^-1 m^-1

• 5.00 × 10^6 ohm^-1 m^-1

• 2.24 × 10^3 ohm^-1 m^-1

In a forward bias P-N junction diode which of the following is correct

• It has high resistance

• Current flow due to minority charge carrier

• Current flowing through diode is small

• It has low resistance

Which of the following is a characteristics of a zener diode?

• It consist in forward bias only

• It has a sharp breakdown voltage in reverse bias

• It has high forward voltage drop

• It is not used for voltage regulation

Applications of zener diode are

1. 1. voltage regulater

2. 2. for meter protection

3.rectifier

4.signal diode in communication circuit

5.reference diode in transister circuit

• 1,2,4

• only 2 and 4

• 1,2,5

• only1

In a Semiconductor the number density of intrinsic charge carriers at 27℃ is 1.5 × 10^16 m^-3 . If the semiconductor is doped with an impurity atom then the hole density increase to 4.5 × 10^22 m^-3 . The electron density in the doped semiconductor is

• 5 × 10^9 m^-3

• 6 × 10^9 m^-3

• 0.05 × 10^9 m^-3

• 0.5 × 10^-11 m^-3

In which semiconductor electrons are majority charge carriers and holes are minority charge carriers

• Intrinsic semiconductor

• P-Type

• Extrinsic semiconductor

• N-type

In which breakdown mechanism the electric field is weak or not strong enough and why

• In field ionaisation, due to lightly doped junction

• In impact ionaisation, due to lightly doped junction

• In field ionaisation, collision of electron and host atom

• In impact ionaisation, due to collision

Which material is commonly used for making semiconductor?

• SILICON

• ALUMINIUM

• COPPER

• INDIUM

A Light Emitting Diode (LED) is fabricated using Gallium semi-conducting material whose band gap is 1.42 eV  Then the wavelength of light emitted from the LED is

• 1243nm

• 975nm

• 875nm

• 1400nm

In a semiconductor no. of electron are 3 × 10^15 m^3  and no. of holes are 3.5 × 10^16 m^3 . If the mobility of electron and holes are 18 × 10^-3 m^2/Vs and 20 × 10^-4 m^2/Vs . Then calculate the conductivity of semiconductor.

• 1.984 × 10^-5 ohm^-1 m^-1

• 19.84 × 10^-5 ohm^-1 m^-1

• 29.18 × 10^-4 ohm^-1 m^-1

• 2.918 × 10^-4 ohm^-1 m^-1