# Semiconductor Physics MCQ

Que.11 Consider a semiconductor bar having a square cross-section. Assume that holes drift in the positive x-direction and magnetic field is applied perpendicular to the direction in which holes drift. The sample will show

• (a) a negative resistance in the positive y-direction
• (b) a positive voltage in the positive y-direction
• (c) a negative voltage in the positive y-direction
• (d) a magnetic field in the positive y-direction

Answer: (c) a negative voltage in the positive y-direction

Que.12 A semiconductor specimen of thickness d, width w, and carrying current I is placed in a magnetic field B to develop Hall voltage VH a direction perpendicular to I and B. VH is NOT proportional to

• (a) B
• (b) I
• (c) 1/w
• (d) 1/d

Que.13 The correct sequence of the following materials in the increasing order of conductivity is

• (a) Silicon doped with boron – Silver – Aluminium – Intrinsic silicon
• (b) Intrinsic silicon – Aluminium – Silver – Silicon doped with boron
• (c) Aluminium – Intrinsic silicon – Silicon doped with boron – Silver
• (d) Intrinsic silicon – Silicon doped with boron – Aluminium – Silver

Answer:(d) Intrinsic silicon – Silicon doped with boron – Aluminium – Silver

Que.14 Even though carbon is in the IV group of the Periodic Table, is not used as a semiconductor because it has

• (a) High dielectric constant
• (b) Large energy gap > 5 eV
• (c) Low-temperature coefficient
• (d) Low thermal conductivity

Answer: (b) Large energy gap > 5 eV

Que.15 Silicon and Germanium are not suitable for the fabrication of laser diodes because:

• (a) Their absorption coefficients are very high
• (b) Their emission coefficients are very low
• (c) They have a direct band gap
• (d) They have an indirect band gap

Answer: (d) They have an indirect band gap

Que.16 The mobility of electrons in a semiconductor is defined as the

• (a) Diffusion velocity per unit electric field
• (b) Diffusion velocity per unit magnetic field
• (c) Drift velocity per unit magnetic field
• (d) Drift velocity per unit electric field

Answer: (d) Drift velocity per unit electric field

Que.17 Which one of the following statements is correct in respect of the use of Direct Gap (DG) and Indirect Gap (IG) semiconductors in the fabrication of Light Emitting diode?

• (a) Both DG and IG semiconductors are suitable
• (b) Only DG semiconductor is suitable
• (c) DG semiconductor is suitable and some IG materials having proper dopants are also used
• (d) only IG semiconductors are suitable

Answer: (c) DG semiconductor is suitable and some IG materials having proper dopants are also used

Que.18 Mobility is defined as

• (a) diffusion velocity per unit field
• (b) drift velocity per unit field
• (c) displacement per unit field
• (d) number of free electrons/number of bound electrons

Answer: (b) drift velocity per unit field

Que.19 In addition to conduction, which one of the following mechanisms can account for the Transport of charges in a semiconductor (not ordinarily encountered in metals)?

• (a) E.M.F. generated within the body of the semiconductor
• (b) Mutual attraction between charges
• (c) Mutual repulsion between charges
• (d) Diffusion

Que.20 For a semiconductor, the conductivity is a function of the products of the number of charge carriers and their mobilities. As a result, if the temperature of a slab of intrinsic silicon increases, how does its conductivity vary?

• (a) Decreases
• (b) Increases as a non-linear variation
• (c) Remains unaffected
• (d) Increases or decreases depending upon the rise in temperature

Answer: (b) Increases as a non-linear variation

Hello friends, my name is Trupal Bhavsar, I am the Writer and Founder of this blog. I am Electronics Engineer(2014 pass out), Currently working as Junior Telecom Officer(B.S.N.L.) also I do Project Development, PCB designing and Teaching of Electronics Subjects.

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