Physics

Semiconductors and Diodes

457 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

The energy gap $E _G$ of a semi-conductor decreases with rise in temperature.

  1. True

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

As the temperature is increased, the thermal energy to the electron within the semiconductor material also increases. Therefore, now lower energy is required to break the bond. This reduction in Bond energy also reduces the band gap. So, the band gap of a semiconductor decreases with increasing temperature.

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

The energy of radiation emitted by $LED$ is :

  1. greater than the band gap of the semiconductor used

  2. always less than the band gap of the semiconductor used.

  3. always equal to the band gap of the semiconductor used.

  4. equal to the or less than the band gap of the semiconductor used
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

In an LED, photons are emitted when electrons drop from the conduction band to the valence band. The energy of the emitted photon is approximately equal to or slightly less than the band gap energy.

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.