Semiconductor Physics MCQ

Que.31 As per Hall effect, if any specimen carrying a current I is placed in a transverse magnetic field B, then an electric field E is induced in the specimen in the direction

• (a) parallel to I
• (b) perpendicular to B and parallel to I
• (c) parallel to I and B
• (d) perpendicular to both I and B

Que.32 Which of the following quantities cannot be measured/determined using the Hall effect?

• (a) Type of semiconductor (p or n)
• (b) Mobility of charge carriers
• (c) Diffusion constant
• (d) Carrier concentration

Que.33 The minimum energy of a photon required for intrinsic excitation is equal to

• (a) the energy of the bottom of the conduction band
• (b) the energy of the top of the valence band
• (c) forbidden gap energy
• (d) Fermi energy

Que.34 Atomic number of silicon is

• (a) 12
• (b) 13
• (c) 14
• (d) 15

Que.35 When donor atoms are added to the semi-conductor,

• (a) Increases the energy band gap of the semiconductor
• (b) Decreases the energy band gap of the semiconductor
• (c) Introduces a new narrow band gap near the conductor band
• (d) Introduces a new discrete energy level below the conduction band

Que.36 The diffusion length for holes Lp, is the

• (a) Average distance which an injected hole travels before recombining with an electron
• (b) Maximum distance travelled by a hole before recombining with an electron
• (c) Length of the region in which diffusion takes places
• (d) Minimum distance travelled by a hole before it recombines with an electron

Que.37 Doping intrinsic Silicon with Arsenic as an impurity

• (a) Only increases the conductivity of Silicon by increasing the number of free electrons available
• (b) Produces a semiconductor in which the charge carriers are predominantly electrons but holes are also present
• (c) Produces a semiconductor in which the charge carriers are predominantly holes but free electrons also present
• (d) Produces a semiconductor in which the charge carriers contain a nearly equal number of electrons and holes

Que.38 Hall effect is useful for the measurement of a semiconductor’s

• (a) mobility, carrier, concentration and temperature.
• (b) type (n-type or p-type), conductivity and temperature.
• (c) type (n-type or p-type), mobility and carrier concentration.
• (d) mobility, conductivity and temperature.

Que.39 Medium doping in Silicon and Germanium corresponds to the impurity of the order of

• (a) 1 part in 10⁶
• (b) 1 part in 10⁵
• (c) 1 part in 10⁴
• (d) 1 part in 10⁸

Que.40 An electric field is applied to a semiconductor. Let the number of charge carriers is n and the average drift speed be v. If the temperature is increased then

• (a) both n and v will increase
• (b) n will increase but v will decrease
• (c) v will increase but n will decrease
• (d) both n and v will decrease