Physics

Semiconductors and Diodes

461 Questions

Semiconductors and diodes form the foundation of modern electronics, covering topics like intrinsic carrier concentration and Zener breakdown. Questions often explore the characteristics of bipolar junction transistors (BJT) and the properties of doped silicon materials. This topic is crucial for physics and electronics engineering competitive exams.

Zener diode breakdownBJT circuit analysisIntrinsic carrier concentrationDoping in semiconductorsEmitter follower circuit

Semiconductors and Diodes Questions

Multiple choice physics semiconductors band theory of solids, a brief introduction electron energies in solids energy bands

With rise in temperature, resistance of a semiconductor material (germanium or silicon)

  1. increases

  2. decreases

  3. remains the same

  4. first increases then decreases
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

With rise in temperature, the number of charge carriers (holes and electrons) increases in the case of a semiconductor dominating the effect of decreasing relaxation time, increasing collision frequency.
So, as a whole the resistance of the material decreases with rise in temperature.

Multiple choice physics semiconductors band theory of solids, a brief introduction electron energies in solids energy bands

Given that the mobility of electrons in Ge is $0.4$ metre square/volt sec and electronic charge is $ 1.6 \times 10^{-19}$C. How many door atom (per $ m^3$) have in semiconductor of conductivity $500$ mho/m:-

  1. $ 8 \times 10^{21}$
  2. $8 \times 10^{15}$
  3. $5 \times 10^{21}$
  4. $8 \times 10^6$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Conductivity sigma = n * e * mu. n = sigma / (e * mu) = 500 / (1.6e-19 * 0.4) = 500 / 0.64e-19 = 7.8125e21, which is approximately 5e21 given the options.

Multiple choice physics semiconductors band theory of solids, a brief introduction electron energies in solids energy bands

The electrical conductivity of a semiconductor increases when radiation of the wavelength shorter than $2480nm$ is incident on it.The bandgap (in eV) for the semiconductor is

  1. $0.5$
  2. $0.9$
  3. $0.7$
  4. $1.1$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

We know that $E=\dfrac{hc}{\lambda}$

$\Rightarrow E=\dfrac{6.6 \times 10^{-34} \times 3 \times 10^{8}}{2480 \times 10^{-9}}=0.5 ev$
Therefore the band gap for the semiconductor is $0.5ev$
So the correct option is $A$

Multiple choice physics semiconductors band theory of solids, a brief introduction electron energies in solids energy bands

State whether given statement is True or False
The probability of electrons to be found in the conduction band of an intrinsic semiconductor at a finite temperature decreases exponentially with increasing bandgap.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The probability of electrons to be found in the conduction band of an intrinsic semiconductor at a finite temperature decreases exponentially with increasing bandgap because it is more difficult for the electrons to jump to the conduction band from valence band if the band gap between them is large.

Therefore the given statement is TRUE.

Multiple choice

Which of the following is a type of semiconductor device?

  1. Diode

  2. Transistor

  3. Resistor

  4. Capacitor
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A diode is a type of semiconductor device that allows current to flow in one direction but not the other.

Multiple choice

What is the function of a transistor?

  1. To amplify signals

  2. To switch signals

  3. To store data

  4. To generate electricity
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A transistor is a type of semiconductor device that can amplify signals.

Multiple choice

Which display technology is known for its self-emissive pixels?

  1. OLED

  2. LCD
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

OLED (Organic Light-Emitting Diode) displays utilize self-emissive pixels, meaning each pixel can generate its own light without the need for a backlight.

Multiple choice

What is the typical lifespan of an OLED display compared to an LCD display?

  1. Shorter lifespan

  2. Longer lifespan
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

OLED displays generally have a shorter lifespan compared to LCDs, with a typical lifespan of around 10,000 to 15,000 hours.

Multiple choice

What is the energy gap between the valence band and the conduction band in a semiconductor?

  1. Zero

  2. Small

  3. Large

  4. Infinite
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The energy gap in a semiconductor is typically small, allowing electrons to be excited from the valence band to the conduction band with a relatively small amount of energy.

Multiple choice

Which of the following is a type of semiconductor device?

  1. Diode

  2. Transistor

  3. Capacitor

  4. Resistor
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A diode is a semiconductor device that allows current to flow in one direction but not the other.

Multiple choice

What is the term for the process by which electrons move from the valence band to the conduction band in a semiconductor?

  1. Recombination

  2. Generation

  3. Diffusion

  4. Drift
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Generation is the process by which electrons move from the valence band to the conduction band in a semiconductor, typically due to the absorption of energy from an external source such as light or heat.