Worksheet: Semiconductor Diodes

In this worksheet, we will practice model a semiconductor diode as a junction between n type and p type doped semiconductors.

Q1:

The diagram shows a p–n junction in a circuit. The positively charged side of the junction’s depletion region is shown in red, and the negatively charged side is shown in blue. Is the junction forward biased or reverse biased?

  • AForward biased
  • BReverse biased

Q2:

The diagram shows a p–n junction in a series circuit. The positively charged side of the junction’s depletion region is shown in red, and the negatively charged side is shown in blue. When the battery terminal connections are reversed, does the resistance of the circuit greatly decrease, greatly increase, or stay approximately the same?

  • AResistance stays approximately the same.
  • BResistance greatly decreases.
  • CResistance greatly increases.

Q3:

In a PN junction, both free electrons and vacancies can diffuse through the junction, as shown in the diagram.

Toward which side of the junction is the direction of the net diffusion current?

  • AThe p-side
  • BThe n-side

In which of the following regions is the concentration of free electrons greatest?

  • AThe p-side
  • BAt the middle of the junction
  • CThe n-side

In which of the following regions is the concentration of vacancies greatest?

  • AThe n-side
  • BThe p-side
  • CAt the middle of the junction

In which of the following regions is the concentration of both free electrons and vacancies smallest?

  • AAt the middle of the junction
  • BThe p-side
  • CThe n-side

Q4:

The graph shows the variation in the current through a p–n junction with the external voltage applied across the junction. The graph contains a region where the current is nearly zero. Does this region correspond to the p–n junction being forward biased or reverse biased?

  • AReverse biased
  • BForward biased

Q5:

Each of the following diagrams shows a p–n junction. The charged sides of the junction’s depletion region are shown in red and blue. The junction is shown under conditions of forward bias, reverse bias, and zero bias. Which bias shown correctly represents zero bias?

  • A
  • B
  • C

Q6:

Each of the following diagrams shows a p–n junction. The charged sides of the junction’s depletion region are shown in red and blue. The junction is shown under conditions of forward bias, reverse bias, and zero bias. Which bias shown correctly represents reverse bias?

  • A
  • B
  • C

Q7:

The diagram shows a p–n junction. The charged sides of the junction’s depletion region are shown in red and blue. The junction is initially not biased. Which of the following diagrams correctly shows how the charge distribution of the depletion region changes when the junction is reverse biased?

  • A
  • B
  • C
  • D
  • E

Q8:

In a PN junction, there are different densities of donor ions and acceptor ions on either side of the depletion region of the junction. Which color line most correctly represents the variation in the magnitude of the electric field along the length of the junction?

  • AThe pink line
  • BThe orange line
  • CThe green line
  • DThe blue line
  • EThe purple line

Q9:

The diagram shows a lattice of silicon atoms in a semiconductor. The left side of the lattice has been doped with donor atoms. This is called the n-side. The right side of the lattice has been doped with acceptor atoms. This side of the lattice is called the p-side. The regions on either side of the dividing line are of equal size and the ion concentration is the same on both sides. The semiconductor is at thermal equilibrium.

Toward which side of the lattice will free electrons tend to move by diffusion?

  • AThe p-side
  • BThe n-side

Toward which side of the lattice will holes tend to move by diffusion?

  • AThe n-side
  • BThe p-side

Q10:

In a PN junction, an electric field is produced in the depletion region due to the different concentrations of donor ions and acceptor ions on either side of the depletion region. The electric field produces a current called the drift current, 𝐼drift.

Which of the directions shown most correctly represents the direction of the electric field produced in the depletion region?

  • AI
  • BII

Is the net current produced by the electric field in the depletion region in the same direction as the diffusion current or in the opposite direction?

  • ASame direction
  • BOpposite direction

The current through a PN junction consists of the diffusion current 𝐼di and the drift current 𝐼drift. At equilibrium, what is the relationship between the magnitude of 𝐼di and that of 𝐼drift?

  • A𝐼<𝐼didrift
  • B𝐼>𝐼didrift
  • C𝐼=𝐼didrift

Q11:

The diagram shows a lattice of silicon atoms in a semiconductor. The left side of the lattice has been doped with donor ions. This is called the n-side. The right side of the lattice has been doped with acceptor ions. This side of the lattice is called the p-side. The regions on either side of the dividing line are of equal size and the ion concentration is the same on both sides. The semiconductor is at thermal equilibrium.

What is the ratio of free electrons on the n-side to vacancies on the p-side?

What is the difference between the net relative electronic charge in the two regions?

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