Chapter Exam

Chapter-14 Semiconductor Electronics: Materials — Online MCQ Test

Q: Which of the following is an intrinsic semiconductor?

Answer: A. Pure silicon — An intrinsic semiconductor is a pure semiconductor material without any doping impurities. Pure silicon is the classic example of an intrinsic semiconductor.

Q: What is the valence electron configuration of silicon?

Answer: B. 3s²3p² — Silicon has atomic number 14 with electron configuration [Ne]3s²3p², giving it 4 valence electrons, which makes it a Group 14 element suitable for semiconductor applications.

Q: When a pentavalent impurity atom replaces a silicon atom in the crystal lattice, the extra electron becomes a ___.

Answer: C. Free charge carrier — The extra electron from a pentavalent dopant becomes a free charge carrier that contributes to conduction. This electron is loosely bound and easily excited into the conduction band.

PHYSICS · CLASS 12 INTER II YEAR · Andhra State Board

Practice Chapter-14 Semiconductor Electronics: Materials with a free chapter-wise online MCQ test for Andhra State Board CLASS 12 INTER II YEAR PHYSICS. This chapter covers: Devices and Simple Circuits. AI-generated questions from basic to board-exam level, with instant results and explanations.

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Chapter-14 Semiconductor Electronics: Materials — Important Questions & Answers (FAQ)

Frequently asked questions from Andhra State Board CLASS 12 INTER II YEAR PHYSICS — Chapter-14 Semiconductor Electronics: Materials, with answers and explanations. These are sample questions; the exam has its own separate question set.

Which of the following is an intrinsic semiconductor?

A. Pure silicon ✓
B. Doped germanium
C. n-type silicon
D. p-type germanium

Answer: A. Pure silicon
An intrinsic semiconductor is a pure semiconductor material without any doping impurities. Pure silicon is the classic example of an intrinsic semiconductor.

What is the valence electron configuration of silicon?

A. 3s²3p¹
B. 3s²3p² ✓
C. 3s²3p³
D. 3s²3p⁴

Answer: B. 3s²3p²
Silicon has atomic number 14 with electron configuration [Ne]3s²3p², giving it 4 valence electrons, which makes it a Group 14 element suitable for semiconductor applications.

When a pentavalent impurity atom replaces a silicon atom in the crystal lattice, the extra electron becomes a ___.

A. Hole
B. Donor level
C. Free charge carrier ✓
D. Forbidden band

Answer: C. Free charge carrier
The extra electron from a pentavalent dopant becomes a free charge carrier that contributes to conduction. This electron is loosely bound and easily excited into the conduction band.

A semiconductor device operates most efficiently when ___.

A. Doping concentration is extremely high (>10²⁰ cm⁻³)
B. The material is perfectly intrinsic with zero doping
C. Doping concentration is controlled at an optimal level ✓
D. Temperature is maintained at absolute zero

Answer: C. Doping concentration is controlled at an optimal level
Optimal doping concentration balances charge carrier density and mobility. Too much doping increases scattering and reduces mobility, while too little doping provides insufficient carriers for desired conductivity.

Why are wide band gap semiconductors like GaN and SiC preferred for high-power, high-temperature applications compared to silicon?

A. They have lower thermal conductivity
B. They can withstand higher electric fields before breakdown and have lower leakage currents at high temperatures ✓
C. They are cheaper than silicon
D. They have higher electron mobility at room temperature

Answer: B. They can withstand higher electric fields before breakdown and have lower leakage currents at high temperatures
Wide band gap semiconductors (GaN: 3.4 eV, SiC: 3.2 eV vs Si: 1.1 eV) can sustain higher electric fields before avalanche breakdown and generate far fewer thermal carriers at elevated temperatures, enabling superior high-power and high-temperature performance.